Polymer Blends Research Papers

RepRapable Recyclebot: Open source 3-D printable extruder for converting plastic to 3-D printing filament

In order to assist researchers explore the full potential of distributed recycling of post-consumer polymer waste, this article describes a recyclebot, which is a waste plastic extruder capable of making commercial quality 3-D printing... more

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Current research on the blends of natural and synthetic polymers as new biomaterials: Review

by Alina Sionkowska

2011, Progress in Polymer Science

This review reports recent advances in the field of the blends of natural and synthetic polymers as new biomaterials. These materials have attracted both academic, and, for several blends, industrial attention because they exhibit... more

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Review Article: Recycling of Polystyrene

by Maharana Tungabidya

2007, Polymer-plastics Technology and Engineering

Recycling of polystyrene can be done by mechanical, chemical, and thermal methods. High impact polystyrene is a promising material for mechanical recycling since its properties are not extremely affected even after multiple processing of... more

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Superabsorbent hydrogels based on cellulose for smart swelling and controllable delivery

by bo duan

2010, European Polymer Journal

Novel superabsorbent hydrogels were prepared successfully from carboxymethylcellulose sodium (CMC) and cellulose in the NaOH/urea aqueous system by using epichlorohydrin (ECH) as cross-linker. The structure and morphology of the hydrogels... more

Fig. 2. Photographs of GEL91: (a) original hydrogel, (b) swollen hydrogel, (c) dried hydrogel and (d) hydrogel after swelling in NaCl solution for a week.

Fig. 1. Proposed mechanism for cross-linking reaction of ECH with cellulose and CMC. Reaction conditions and chemical composition of the cellulose/CMC hydrogels. Table 1

Fig. 3. FT-IR spectra of cellulose/CMC hydrogels: (a) cellulose hydrogel, (b) GEL64, (c) GEL73, (d) GEL82 and (e) GEL91. Fig. 3 shows the FT-IR spectra of cellulose/CMC hydro- gels. The broad absorption bands of the hydrogels at 3300-3500 cm7! were assigned to stretching of the large number of hydroxyl groups on the backbone. The asym- metric and symmetric stretching vibration of CH2 was evi- denced by the appearance of the absorption peaks at 2930 cm7! and 2860 cm~!. Compared with the cellulose hydrogel without CMC (see Fig. 3a), the band observed at 1600 cm~! and 1420 cm! in the cellulose/CMC hydrogel can be attributed to COO™ stretching and bending, respec-

Fig. 4. TG and DTG curves of CMC, cellulose, cellulose/CMC mixture and GEL55. The influence of the carboxymethylcellulose composi- tion on the swelling ratio of cellulose/CMC hydrogels in distilled water at 37°C is shown in Fig. 6. The samples exhibited high equilibrium swelling ratio, indicating all of the samples were superabsorbent hydrogels. As expected, the equilibrium swelling ratio of the cellulose/CMC hydro- gels increased rapidly with an increase in the CMC con- tents. This confirmed further that highly hydrophilic carboxyl group of CMC could absorb a lot of water to en- hance the space in the hydrogels. In the other hand, cellu- lose/NaOH/urea aqueous solution could form irreversible gelation by heating [39], thus physical cross-linking in cellulose also played an important role in the formation

Fig. 7. Effects of simulated biological solutions on swelling ratio of the cellulose/CMC hydrogels at 37 °C.

Fig. 5. SEM images of the cross-sections of the cellulose/CMC hydrogels.

of hydogels. So, the entanglements of cellulose chains through hydrogen bonds could occur easily in solutions of high cellulose concentration, leading to the decrease of the equilibrium swelling ratio with an increase of cellulose content. The maximum swelling ratio of the hydrogels was more than 1000, which was clearly higher than that pre- pared from cellulose derivative [32]. It is important for biodegradable materials to have high swelling ratio for wide application in the biomedical field. Fig. 6. Equilibrium swelling ratio of the cellulose/CMC hydrogels after immersing in distilled water for a week, as a function of the composition of CMC and cellulose at 25 °C.

Fig. 8. Effects of inorganic salt concentration on swelling ratio of the cellulose/CMC hydrogels: (a) NaCl, (b) CaCl. The effect of salt concentration on the swelling ratio of the cellulose/CMC hydrogels is given in Fig. 8. In NaCl solu- tion (Fig. 8a), the swelling ratio of hydrogels decreased with an increase of the ionic strength of the solution. The hydrogels with higher CMC contents exhibited more signif- icant decline of swelling ratio with the increase of the NaCl concentration. In CaClz aqueous solution, the swelling ratio decreased quickly because of the higher cationic charge of CaCl, in comparison with NaCl, in accord with the Donnan equilibrium theory. In this case, the distinction in the con- centration of mobile ions between the hydrogel and solu- Fig. 10 displays the reswelling behaviors of the dried cellulose/CMC hydrogels in distilled water at 37°C. The reswelling capabilities of the hydrogels decreased with the increasing CMC content. The water uptake of dried GEL55 reached 91%, whereas that of dried GEL91 exhibited a low value of 19%. These results indicated that it was more difficult for the higher swelling ratio samples to reach their

Fig. 11. In vitro percent cumulative release of BSA from GEL55, GEL73 and GEL91 in PBS (pH 7.4) at 37 °C. Superabsorbent hydrogels were fabricated successfully from CMC and cellulose in NaOH/urea aqueous solution by cross-linking with ECH. The superabsorbent mechanism could be described as that the stiff cellulose molecules acted as the strong backbone of the network structure for keeping appearance of the hydrogels including a lot of water, and the highly hydrophilic CMC contributed to the higher swelling ratio. The experimental results proved that the cellulose/CMC hydrogels exhibited superabsorbent capacity and high equilibrium swelling ratio, which could be improved by changing the amount of CMC. The hydro-

Fig. 10. Reswelling kinetic of the cellulose/CMC hydrogels in distilled water at 37 °C. The in vitro release profiles of BSA from GEL91, GEL73 and GEL55 in a phosphate buffered solution (PBS pH 7.4) are shown in Fig. 11. There was a typical biphasic release pattern, namely a burst release followed by a slower sus- tained release. Initially, fast release of BSA was observed, especially in GEL91 in which more than 70% of BSA was re- leased within the first 10h, owing to the surface loaded BSA in hydrogel. The cumulative release percents of GEL55 and GEL73 were less than that of GEL91 during the same period of time. This result indicated that bigger pores of GEL91 induced faster release of BSA. Beyond the

Fig. 9. Deswelling kinetics of cellulose/CMC hydrogels in 0.1 M NaCl solution at 37 °C.

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Journal - Characterization of Edible Film from mixture of tapioca, chitosen, glycerin and extract mangosteen rind (Garciniae mangostana) for malang apple (Malus domestika) packaging

by Putri aswanti hasanah

Have performed research on the utilization of edible film from mixture of tapioca, chitosen, glycerin and extract mangosteen rind (Garciniae mangostana) for malang apple (Malus domestika) packaging. The process of making edible film was... more

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Polyvinyl chloride-based blends

by Daniela RUSU and

2003, Handbook of Polymer Blends and Composites

The extraordinary growth in the use of plastics in the last century is in response to a growing world population, with its increasing demands for more food, better health care, improved housing and numerous cheaper and abundant consumer... more

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Degradation and aging of polymer blends I. Thermomechanical and thermal degradation

by Stanislav Nešpůrek

1999, Polymer Degradation and Stability

The commercial importance of polymer blends implies interest in knowledge of their degradation behaviour under environmental stresses. Processes accompanying thermomechanical and thermal degradation of blends of commodity polymers are... more

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Improving performance of polyvinyl acetate (PVA) as a binder for wood by combination with melamine based adhesives

by Alireza Kaboorani

2011, International Journal of Adhesion and Adhesives

In this study blending PVA with MUF and MF was evaluated as an approach to enhance the performance of PVA towards water and elevated temperatures. MF and MUF were added to PVA at different proportions: 15%, 30%, 50%, 70% and 100%. Blends... more

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Melt rheology of polymer blends from melt flow index

by Dr Aroon Shenoy

1984, A. V. Shenoy, D. R. Saini, V. M. Nadkarni

Polymer blends have received a lot of attention in recent years due to the possibility of getting compounds with novel and/or different properties through proper marriage of the properties of the respective mono-components. The flow... more

FIGURE 1 Possible viscosity-composition relationships for polymer blends

FIGURE 2 Melt Flow Index variation with blend composition for high density polyethylene/polypropylene blend at 190°C

FIGURE 7 Coalesced curve for polypropylene-high density polyethylene blend at test load condition of 2.16 kg

FIGURE 8 Coalesced curve for high density polyethylene-polymethylmethacrylate blend at test load condition of 2.16 kg

FIGURE 9 Coalesced curve for polystyrene—polymethyimethacrylate blend at test load condition of 5 kg

FIGURE 10 Coalesced curve for polystyrene-polyacetal blend at test load condi- tion of 5.00 kg

FIGURE 11 Coalesced curve for polymethylmethacrylate—polyacetal blend at test load condition of 3.8 kg

number of commercial thermoplastic blends such as polyphenylene oxide/polystyrene, acrylonitrile butadiene styrene/polycarbonate, polyvinyl chloride/polymethylmethacrylate etc. currently in use as summarized in Table I.' In polymer blends, the individual polymers are chemically different and do not form covalent bonds as in copolymers. The blends are often characterised by their phase behaviour as being either miscible or immiscible. Certain blends are completely miscible and form a single phase while others form domains rich in one polymer dispersed within the matrix of the second polymeric component. The degree of thermodynamic com- patibility? between the individual components of blend have impli- cations in rheology and processing due to the possibilities of phase separation with increasing incompatibility. During polymer processing operations like extrusion, injection malding etc the molten nolymer hlend is snhiected to a series of

Investigations on the rheological properties of polymer blends

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Advances in forward osmosis membranes: Altering the sub-layer structure via recent fabrication and chemical modification approaches

by Dr.Wafa Ali

The forward osmosis process has obtained renewed interest nowadays and it might become an alternative solution for many industrial applications to meet the current and future requirements for potable water. The FO process depends on the... more

Fig. 1. A schematic diagram of a commercial FO-TFC membrane. Reproduced with permission from [116]. Copyright 2017 Elsevier. Considerations, such as low water quality in a single stage [3], draw solution properties, reverse salt flux [5] and the choice of an ideal FO membrane are critical for the development of the FO desalination system [11]. A wide range of membranes have been used for the FO process in both flat sheet and hollow fibre configurations including cellulose acetate (CA), cellulose triacetate (CTA), thin film composite (TFC), and bio-mimetic membranes [13]. Amongst FO membranes, the cellulosic membrane has been employed widely for the FO process; however, it suffers low selectivity, is prone to biological attack and chemical hydrolysis [14]. Thereafter, desalination researchers focused on unique TFC-FO membranes for the FO system because of excellent Phase inversion is the most important and successful technique used for the preparation of flat sheet and hollow fibre FO membranes. It involves mixing a polymer with solvent and casting of the polymer suspension on a support layer. The next step is the immersion pre- cipitation of this support layer which could be described as soaking a polymer solution in a non-solvent coagulant bath [21]. In addition to this process, a dry-jet wet spinning process was also used to fabricate a hollow fibre substrate [22]. It consists of preparing a polymer dope which was extruded by a spinneret at a volume rate that was fixed by a gear pump. Subsequently, it was subjected to an air gap followed by a soaking in a coagulation bath. Electro-spinning is another technique used for the formation of fibrous polymer in various configurations and functions. It has been employed to fabricate flat sheet and hollow fibre membranes. It involves applying a high electrical field to a polymer

Fig. 2. Showing the typical FO system which operates under osmotic pressure difference using seawater feed, NaCl draw solute and FO membrane. Adapted with permission from [127]. Copyright 2012 Elsevier. This osmotic pressure (st) is influenced by the draw solute con- centration and its temperature [46]. Accordingly, the osmotic pressure

which can be re-expressed as follows [10]: Fig. 3. The most important properties for selecting the ideal membrane for osmosis process.

In summary, other players in the market include Porifera, Toray and Aquaporin. The TFC membranes performed better than cellulosic membranes because of higher tolerance to pH ranges from 2 to 11 and were stable at a temperature over 60°C. As mentioned previously, it exhibited higher water permeability and can tolerate the process con- ditions of pressure retarded osmosis (PRO) [77]. In contrast, the two stages of preparation result in higher cost and there is a challenge in performance outperformed the commercial HTI-CTA mem- branes.1.16LMH using DI water and salt rejection of 94.1% using 50 mM NaCl feed in RO mode [11]. However, the sub-layer is thick and the structural parameter (492 um) needs optimization. Moreover, re- cent TFC-HTI membranes included a mesh-embedded sub-layer was synthesized. It exhibited 2 folds higher water flux (1.4LMH) than commercial CA membrane but lower salt rejection of 92% [16]. The sub-layer thickness is double CA and it had a high S value of 533 um. In addition, a flat sheet TFC made of both spongy skin and a finger-like structure produced a structural parameter of 670-710 um. This may decrease the tortuosity, yielding to quite low ICP impact [29]. The water flux was higher than 12 LMH as compared to commercial CTA membrane (5LMH) and a brackish water RO membrane (0.78 LMH) using 10mM NaCl FS and 0.5M NaCl DS. It appears that the straight finger-like pore structure is more significant than the sponge-like structure to mitigate the ICP. Presently, a hollow fibre membrane Fig. 4. (a) a schematic illustration of Layer by Layer process. Adapted with permission from [87]. Copyright 2011 American Chemical Society

Fig. 5. (a) schematic diagram of the preparation to make a membrane with vertical pores. (b, c, d) SEM micrographs of TFC membrane showing vertical pores having open structure in both sides of sub-layer creating spongy structure. Adapted with permission from Liang et al. [105]. Copyright 2017 Elsevier.

The electro-spinning process produces polymeric fibres with a dia- meter between 5 and 500 nm and less than several micrometers, a small pore size and large surface area [107,108]. The scaffold-like nanofibres can be transformed to more porous with interconnected pores to obtain low tortuosity and S value [109]. Compared to PI technique, this structure can be obtained easily by the electro-spinning method [110,111]. The morphologies, orientation of prepared nanofibre, dif- ferent diameters and aspect ratio can be fulfilled by controlling the environment conditions, the solution viscosity, the flow rate of the Fig. 6. a, b, c, d represents TFC membrane embedded polyacrylonitrile (PAN)/cellulose acetate (CA) blended nanofibres mat that synthesized in DMF at various weight ratios: (a) PAN, CA 2/8, (b) PAN/CA 5/5, (c) PAN/CA 8/2, (d) pure PAN. (e-f) Cross-sectional SEM image of TFC membranes embedded nanofibrous PAN layer. Adapted with permission from Bui and McCutcheon [113]. Copyright 2012 American Chemical Society. Liang et al. [105] proposed using the PI combined bidirectional freezing process to tailor the PVDF substrate of a TFC membrane. It was chosen to make a substrate with vertically oriented pores in the sub- layer. The preparation process is illustrated in Fig. 5(a) so the polymer solution was added into a mould made of two stainless steel and glass plates [106]. Then the thickness was tailored perfectly and the mould was located in a water bath with various temperatures. Next, it was soaked vertically in an extraction solvent to obtain the membrane containing vertical pores. The newly developed FO membrane showed a nodular structure on the top and its porosity was estimated at 74%. It can be seen from Fig. 5(b) that the pores were formed vertically with a pore size of about 1.8 um. It can be observed that pores have an open shape in the bottom and top sides, as well as a spongy structure in the

Fig. 7. (a) The synthesis process of carboxylated polysulfone (CPSF). (b) A comparison between the pristine PSf and CPSf in terms of microstructure. It is shown a spongy-like structure in the CPSf support layer. Adapted with permission from [149]. Copyright 2013 Elsevier. In Zhong et al.'s [145] study, interfacial polymerization was adopted to prepare PPSU-TFC based hollow fibre membrane. It was found that the sulfonation preparation greatly influenced the membrane micro- structure. This is because nonsulfonated membrane formed a macro- void-free structure caused by quick de-mixing while the modified sub- strate (1.5mol% sPPSU) displayed a sponge-like structure. The structural parameter was dropped to 1.63x10°*m from 7.46 x 107*m for a pristine PPSU membrane. This allows more ef- fective water diffusion within the membrane resulting in higher water permeability of 1.99LMH, reduced salt passage of 0.0399LMH and acceptable salt rejection of 90.9% against DI water and 1000 ppm NaCl in RO mode. When Widjojo et al. [144] used sPPSU mixed with different past, the sulfonation process was used to functionalize polysulfone polymer to obtain a high hydrophilicity, produce the desired macro- voids, open pore structures and to enhance rejection of organics [141,142], leading to improved water fluxes in forward osmosis sys- tems. In one study exploring the impacts of a sulfonated copolymer composed of PES and PPSU when blended with polyethersulfone (PESU E6020P) in a TFC membrane, it was found that the higher concentra- tion of the sulfonated polymer in the substrate lead to lower surface roughness [143]. When 50 wt% sulfonated material was embedded in the support layer, a more favourable sponge-like structure free of macrovoids was formed. The porosity and pore size increased due to slow de-mixing in the phase inversion compared to pure PESU. The structural parameter exhibited a low value of 3.24 x 107~*m when increasing the amount of sulfonated polymer and therefore reduced ICP effects. Another advantage of this modification was the formation of a high permeable active layer on the substrate. In addition to this, the effect of directly sulfonated polymer with various sulfonation degrees on the morphology, mechanical properties and performance were in- vestigated. It is important to note that the greatest water permeability approached 0.73LMH for 50wt% sulfonated polymer embedded membrane as compared to pristine PESU membrane because of im- proved hydrophilicity. The salt rejection and solute permeability almost remained the same when using 400 ppm NaCl solution in RO experi- ment. monomers to fabricate the support layer, the thickness of both the non- sulfonated and sulfonated polymers was in the range of 35-50 um. The sulfonated support layer was hydrophilic and had a sponge-like struc- ture compared to the non-sulfonated sample with macrovoids only. A reduction in the ICP and a good wettability of the sub-layer were ob- servable. When the polymer contained 2.5mol% of 4,4’-Di- chlorodiphenyl sulfone, the membrane displayed very low water per- meability of 3.23 LMH and salt passage of 1.05 LMH against DI water and 400 ppm NaCl feeds in RO filtration. In contrast, the pristine membrane showed water permeability of 12.53 and higher salt passage of 5.78 LMH. Interestingly, the salt rejection of the developed mem- brane was improved of about 84.1% versus the pristine membrane (81.7%).

Several modification procedures have also been used to improve the FO membrane properties. The chemical modification involves the ad- dition of a chemical modifier which adheres strongly to the surface by the covalent bonding providing chemical stability [173]. One of its advantages is providing low severe effects of ICP in the support layer and improving the water permeation [16]. For example, the separation

Fig. 9. (a) A schematic diagram demonstrating the synthesis procedure of CaCO3-coated PES support layer of TFC-FO membrane. (b) Micrograph images showing the PES top surfa (a—c). Adapted from Liu et al. [200]. Copyright 2016 Nature/Scientific reports. to provide the negative charges. Then, PI was formed on the top surface followed by the mineral coating on the inner surface substrate. The PES/PAAS5 appeared rough after the alternative immersion procedure which indicated effective CaCO3 coating as can be seen in Fig. 9(b). This coating enabled an effective hydrophilicity via the electrostatic interaction. This means the interaction between Ca?* and carboxylate groups of PAA accelerated the nucleation of Ca?* on the pore surface followed by an interaction with CO; ? to form the coating on the substrate [200,14]. Additionally, the mineral coating contributed to a little decline in the water permeability when using DI water in RO experiment. This decrease caused by the swelling issue of PAA leading to contraction and pore blocking. However, it was useful in removing An alternative hydrophilization procedure is the bio-mineral coating of CaCO; on the PES substrate to improve wettability, which decreases the S value and ICP effects in TFC-FO membrane [200]. This coating was used for other polymeric membranes in previous studies [14,201,202]. It can provide the substrate with the required hydro- philicity because it can be connected to water through strong ionic hydrogen bonding. A PES sub-layer was exposed to bio-mineral (CaCO3) coating to cover the inner surface of this layer [200]. In Fig. 9(a), the three stages for the preparation of the mineral coating are described. First, the polyacrylic acid (PAA) deposited into PES polymer

Fig. 10. (a) A diagram presenting the modification procedure to form AqpZ-incorporated SLB forward osmosis (FO) membrane. The PSf substrate (gray) was treated with PDA an followed by the deposition of the amide bonded DOPE SLB (orange). (b) SEM micrographs show the asymmetrical structure with flat surface of the modified support layer. The SLB fille the gaps on the PDA-coated PSf membrane successfully. Adapted with permission from [206]. Copyright 2015 The Royal Society of Chemistry. Currently, the water channel protein aquaporin is used in fabri- cating FO membrane to facilitate water transport through the mem- brane [80]. A wide range of research has been carried out using dif- ferent procedures to form aquaporin incorporated membranes [80,90,203-205]. Scientists are interested in aquaporin due to its ef- fective performance. This was attained with the preferential water Additionally, a novel strategy was developed to form stable aqua- porin based biomimetic membranes with excellent FO performance [206]. This strategy is described in Fig. 10, it involved applying PDA coating on the PSf substrate and the deposition of proteoliposomes and

The forward osmosis process has obtained renewed interest nowadays and it might become an alternative so- lution for many industrial applications to meet the current and future requirements for potable water. The FO process depends on the osmotic pressure gradient between a high salinity draw solute and low salinity feed solution across a semi-permeable membrane to extract pure water. Despite the potential advantages of FO, there are some technical drawbacks that hinder FO application for water desalination. One of the most significant critical challenges is the need for membrane compatible with the FO process. To improve FO desalination feasibility, membrane development is required to obtain maximum water permeability and minimum reverse solute flux over long-term operations. Therefore, this review starts by demonstrating the fundamentals and membrane development over the years. Fabrication modifications for the support layer of FO membranes and the crucial challenges of the FO process are summarized. Recent trends of the chemical modifications of the bulk and substrate are discussed. The advantages and disadvantages of the modifications on the FO membrane productivity are also addressed. Finally, concluding with future perspectives. Keywords: Forward osmosis Desalination Chemical modifications Membrane fabrication Support layer Synthetic polymer Nanotechnology * Centre for Water Advanced Technologies and Environmental Research (CWATER), College of Engineering, Swansea University, Fabian Way, Swansea SA1 8EN, UK > College of Engineering, University of Sharjah, P.O. Box 27272, Sharjah, United Arab Emirates Wafa Ali Suwaileh*, Daniel James Johnson“, Sarper Sarp*, Nidal Hilal**

Table 1 (continued) synthesized with double active layers on PES a sub-layer [76]. The sub- layer contained a dense and porous finger-like macrovoid structure, and S value was of 996 um. In this case, the outer selective layer successfully minimized the ICP and fouling into the sub-layer against real waste- water brine. This new membrane had acceptable mechanical strength for hydraulic pressure over 20 bar and superior fouling resistance. An excellent water permeability of 1.5 LMH and a very low salt perme- ability of 0.02 LMH and a salt rejection of 94.2% were recorded using DI water and 1000 ppm NaCl FS respectively.

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Effect of percentage of short fibers removed from cotton during spinning on the properties of dyed polyester/cotton-blended knitted fabrics

by Tanveer Hussain

The aim of this study was to assess the effect of the percentage of short cotton fibers removed during spinning on the properties of dyed polyester/cotton-blended knitted fabrics. Combing of cotton fibers was done at 12% and 18% short... more

Table 3. AFIS parameters of combed cottons.

Table 2. Properties of raw cotton fibers CIM-443.

Table 1. Properties of polyester fibers.

Table 4. Properties of yarns with different short fiber removal (noil%). Table 5. MINITAB™ analysis of variance output for 19.68 tex (Ne, 30) PES/Co yarns.

yarns are given in Tables 6 and 7, respectively. Table 8 gives the color difference values of knitted samples dyed in three different colors. MINITAB™ ANOVA output for fabric weight and bursting strength is given in Table 9. It is evident from the results that there is no significant difference in the weight and _ bursting strength of knitted fabrics containing cotton combed at two different percentage of short fiber removal. Simi- larly, it is also clear from Tables 6, 7, and 8 that there is no significant difference in shade (DE < 0.5) and other physical characteristics in the dyed knitted fabrics due to difference in noil%. Conclusions

Table 6. Physical properties of knitted fabric samples.

Table 8. Color difference values of knitted samples dyed in different colours.

Table 7. Color fastness properties of knitted fabric samples after dyeing.

Table 9. MINITAB™ analysis of variance out put for fabric weight and bursting strength.

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Rheological Properties of Polymers: Structure and Morphology of Molten Polymer Blends

by Adesola Adegbola

2011, Materials Sciences and …

The article reviews a brief literature on the rheological properties of polymer melts and blends. Experimental results on polymer blends are summarized. Technically, vital types of multi-phase polymers such as compounds and blends are... more

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Chitosan: A Natural Antimicrobial Agent- A Review

by Shakeel Ahmed

Chitosan is the second most abundant natural polymer after cellulose in the world; primarily composed of glucosamine and N-acetyl glucosamine residues with a 1, 4-β-linkage. Chitosan is considered as most promising materials for future... more

Figure 1. Showing extraction of chitin and chitosan from different sources Sources: Chitosan was first discovered by Rouget in 1859 during boiling of chitin in a concentrated potassium hydroxide solution, which resulted in deacetylation of chitin. It was formely named by hoppe Seyler in 1894[124].

digestive systems, as well as insect’s external structure and some fungi. It is also found in the iridophores (reflective material) of both eyes and epidermis of cephalopods and arthropods of phylum Mollusca and the epidermal cuticle of the vertebrates. Paralipophrys trigloides’s epidermal cuticle is also chitinous in nature [31, 32]. Shell wastes of shrimp, lobsters, crabs and krill are the main commercial sources of chitin. Therefore, we can say that chitin is not only present in invertebrates but is also present in vertebrates. Types: There are three forms of chitin viz a, B, and y chitin. The a-form is composed of polysaccharide strands aligned in alternating antiparallel fashion which is mainly obtained from crab and shrimp. a—Chitin is the most abundant one; the anti-parallel arrangement in a-chitin gives rise to strong hydrogen bonding and consequently makes it more stable. The rarer B-chitin is composed of parallel strands of polysaccharides, it is found in association with proteins in squid pens [33, 34] and in the tubes synthesized by pogonophoran and vestimetiferan worms [35, 36]. Both a and B chitin are commercially available. B- form can be converted into a-form form, but reverse is not possible[119-121]. The y-form of chitin contains two parallel and one anti-parallel strands of chitin [37]. Use of lithium thiocyanate leads to conversion of y-chitin into a-chitin [122]. The chains are associated with one another by very strong hydrogen bonding between the amide groups and carbonyl groups of the adjuncted chain. Hydrogen linkages are responsible for the great insolubility of chains in water and for the formation of fibrils.

Physico-chemical characteristics: Chitin is a structural biopolymer, which has a role similar to that of collagen in the higher animals and cellulose in terrestrial plants [38-40]. Plants produce cellulose in their cell walls and insects and crustaceans produce chitin in their shells [41, 42]. Cellulose and Chitosan provide structural integrity and protection to plants and animals, respectively and share very similar structure.[43, 44] The only difference between structure of chitosan and cellulose is the amine (NH2) group at position C-2 of chitosan instead of the hydroxyl (-OH) group found in cellulose(Figure. 4). Thus, chitosan is a biopolymer which consists of N-acetyl-2-amino-2-deoxy-D- glucopyranose and 2-amino-2-deoxy-D-glucopyranose, where the repeating units are linked by B-(1—4)- glycosidic bonds [45]. After purification, chitosan has a rigid crystalline structure through inter-molecular and intra-molecular hydrogen bonding and show polymorphism. However, unlike plant fiber, chitosan possesses net ionic positive charges, which give it the ability to chemically bind with negatively charged fats, lipids, cholesterol, metal ions, proteins, and macromolecules, etc. [46]. In this respect, chitin and chitosan have attained increasing commercial interest as suitable resource materials due to their excellent

Table 1: Application of chitosan and its derivatives in different areas [94,125]

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Perspectives of Polymer Blends on Industrial Design

by gio Barrera

This paper will review the important developments in the field of polymer blends. The subject of polymer blends has been one of the most prolific areas in polymer science and technology in the past five decades judging from publications... more

Only nucleation and growth can occur in the metastable region. Spinodal decomposition is best observed by crossing through the critical point in o the unstab region. In some cases, spinodal decomposition may result if such that nucleation of phase separation does no occur. In ad e region without crossing the metastable the metastable region is rapidly crossed dition to the observations by McMaster, another early study of spinodal decomposition was reported by Nishi et al. [60]. At the later stages of phase separation, the di fferences in t hese two processes become less obvious as phase coalescence occurs (referred to as Ostwald ripening by McMaster). Spinodal decomposition 1... ....% 8g Qa eg a i: ee: a oe ee, ey ee ee, ee ee en, ; ee

Table 1. Comparison of Phase Separation Processes. The relationship of these processes to the phase diagram is shown in Figure 1.

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Tailor-Made Distribution of Nanoparticles in Blend Structure toward Outstanding Electromagnetic Interference Shielding

by Sourav Biswas

Engineering blend structure with tailor-made distribution of nano-particles is the prime requisite to obtain materials with extraordinary properties. Herein, a unique strategy of distributing nanoparticles in different phases of a blend... more

Engineering blend structure with tailor-made distribution of nano-particles is the prime requisite to obtain materials with extraordinary properties. Herein, a unique strategy of distributing nanoparticles in different phases of a blend structure has resulted in >99% blocking of incoming electromagnetic (EM) radiation. This is accomplished by designing a ternary polymer blend structure using polycarbonate (PC), poly(vinylidene fluoride) (PVDF), and poly(methyl meth-acrylate) (PMMA) to simultaneously improve the structural, electrical, and electromagnetic interference shielding (EMI). The blend structure was made conducting by preferentially localizing the multi-wall nanotubes (MWNTs) in the PVDF phase. By taking advantage of " π−π stacking " MWNTs was noncovalently modified with an imidazolium based ionic liquid (IL). Interestingly, the enhanced dispersion of IL-MWNTs in PVDF improved the electrical conductivity of the blends significantly. While one key requisite to attenuate EM radiation (i.e., electrical conductivity) was achieved using MWNTs, the magnetic properties of the blend structure was tuned by introducing barium ferrite (BaFe) nanoparticles, which can interact with the incoming EM radiation. By suitably modifying the surface of BaFe nanoparticles, we can tailor their localization under the macroscopic processing condition. The precise localization of BaFe nanoparticles in the PC phase, due to nucleophilic substitution reaction, and the MWNTs in the PVDF phase not only improved the conductivity but also facilitated in absorption of the incoming microwave radiation due to synergetic effect from MWNT and BaFe. The shielding effectiveness (SE) was measured in X and K u band, and an enhanced SE of −37 dB was noted at 18 GHz frequency. PMMA, which acted as an interfacial modifier in PC/PVDF blends further, resulting in a significant enhancement in the mechanical properties besides retaining high SE. This study opens a new avenue in designing mechanically strong microwave absorbers with a suitable combination of materials.

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Processable conductive graphene/polyethylene nanocomposites: Effects of graphene dispersion and polyethylene blending with oxidized polyethylene on rheology and microstructure

by Muhammad Z Iqbal

Poor dispersion of graphene in non-polar polymer matrices creates composites with limited applications. A method to improve the dispersion of graphene in polyethylene (PE) via blending PE with oxidized PE (OPE) is examined. Graphene was... more

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Studies on thermal degradation and flame retardant behavior of the sisal fiber reinforced unsaturated polyester toughened epoxy nanocomposites

by Paluvai Nagarjuna Reddy

2015, Wiley

Unsaturated polyester (UP) toughened nanocomposites were prepared using both sisal fibers and montmorillonite clays. The effect of fibers and Cloisite 30B (C30B) nanoclays on the mechanical properties, thermal stability, flame retardant,... more

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Recent developments in polyurethane-based conducting composites

by James Njuguna

2000, Journal of Materials Science

Polyurethane-based conducting composites with polyaniline, polythiophene or polypyrrole are in the class of modern macromolecular materials that combine the toughness and elasticity of polyurethane matrix with conductivity of... more

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Injection stretch blow moulding process of reactive extruded recycled PET and virgin PET blends

by Dumitru Pavel

2005, European Polymer Journal

Reactive extruded recycled PET (RER-PET) was blended with virgin PET in order to find optimum composition for producing bottles using injection stretch blow moulding (ISBM) process. Two variables were investigated namely, RER-PET... more

Fig. 1. Central composite rotatable design for two variables.

Fig. 2. Central composite rotatable design for x; and x variables.

Fig. 3. RER-PET and virgin PET blends [v] (dl g7').

Fig. 4. Weight in grams of RER-PET and virgin PET blend’s bottles as a function of RER-PET and PMDA concentrations.

Fig. 6. Trans conformational effect of RER-PET and virgin PET blended bottles at 1337 cm7! absorbance as a function of RER-PET and PMDA concentrations. bottles that weighed less than 19.57 g showed high trans conformation or orientation. 3.5. Dichroic ratio

The dichroic ratio investigations were carried out using the FTIR absorbance of the carbonyl group per- pendicular-polarized band at 1729 cm~' wavenumber [19]. Since the band at 1729 cm™! is sensitive to perpen- dicular polarization, low dichroic ratio values would mean high orientation and vice versa.

Fig. 7. Dichroic ratio of RER-PET and virgin PET blends bottles at 1729 cm™! absorbance band as a function of RER- PET and PMDA concentrations.

Fig. 8. Burst pressure (bar) of RER-PET and virgin PET blend’s bottles as a function of RER-PET and PMDA concentrations.

Fig. 9. Top load strength (N) of RER-PET and virgin PET blend’s bottles as a function of RER-PET and PMDA concentrations. Top load test is one of the standard and significant tests that give information about the ability of plastic bottles to uphold an axial load [3,26]. Fig. 9 shows the top load strength of RER-PET and virgin PET blends bottle in response to different RER-PET and PMDA concentrations. Top load strength results showed that the highest value of 564 N placed within a contour curve of 550 N that is located at 0.02-0.07 wt.% PMDA con- centrations and 28-32 wt.% RER-PET concentrations. The minimum top load of 414.N, placed within contour curve of 420 N, corresponds to the high PMDA concen- tration region of 0.28—-0.3 wt.% and RER-PET concen- tration of 48-52 wt.% RER-PET bottles top load strength depends on both the RER-PET and PMDA concentrations. The blends bottles top load strength de- creases with increasing PMDA concentration as clearly

Fig. 10. Drop impact failure (%) of RER-PET and virgin PET blend’s bottles as a function of RER-PET and PMDA concentrations. The blends bottle drop impact failure increased with increasing RER-PET concentrations as shown in Fig. 10, however, at RER-PET concentrations of between 70 and 80wt.%, bottles drop failure rate

Fig. 12. Bottle weight loss (%) vs. time for different PMDA values at 50 wt.% RER-PET concentration. F. Awaja, D. Pavel | European Polymer Journal 41 (2005) 2614-2634

Fig. 13. Bottle weight loss (%) vs. time for different RER-PET concentration at constant PMDA concentration of 0.15 wt.%.

Fig. 14. Carbonation loss (%) RER-PET and virgin PET blend’s bottles as a function of RER-PET and PMDA concentrations.

Fig. 16. FTIR absorbance vs. time at 4990 cm! band for CO; filled bottles. regions of trans-crystalline, trans-amorphous and gauche-amorphous reported by some researchers [9,15] might explain the relationship between carbonation loss and trans conformation intensity. Carbonation is lost not only through the gauche-amorphous phase but also through the trans-amorphous phase. A comparison between Figs. 14 and 4 indicates that RER-PET bottles’ carbonation loss is not clearly related to bottles average weight. RER-PET blends bottles carbonation loss has no clear dependency on the dichroic ratio as shown from a comparison between Figs. 14 and 7. Fig. 15 shows the RER-PET and virgin PET blends bottles absorbance of CO, over the duration of the experiment. The three RER-PET blended samples are at different PMDA concentrations and a constant RER-PET concentration of 50 wt.%. The CO, absor- bance of a virgin PET sample is also shown for compar- ison. CO, absorbance decreases linearly with time. Since CO, mostly permeates through the sidewalls of the bot- tles, CO, permeation is linear with time and does not de- pend on CO, molecules concentration in the bulk material of the sidewalls.

Fig. 15. FTIR absorbance vs. time at 4990 cm! band for CO; filled bottles.

Fig. 17. FTIR absorbance of virgin PET bottle for the carbonation loss test. Bottle optical clarity showed dependence on both RER-PET and PMDA at different concentrations. There is a strong interaction between the two variables. However, the effect of PMDA concentration can be found at RER-PET concentrations between 20 and 30 wt.% in which increasing PMDA concentrations result in an increase in clarity. At RER-PET concentra- tion of 50-68 wt.%, the increase in PMDA concentra- tion results in a decrease in bottle clarity. In other RER-PET concentration regions of 30-50 wt.% and 68-80 wt.%, PMDA concentration showed no effect on clarity. The dispersed PMDA molecules did not affect the light scattering although having a different refractive index. As part of the PMDA effect, clarity decreases with increasing RER-PET concentration. Decreases in clarity may also be attributed to the fact that RER- PET contains coloring contaminants, which slightly affect light transmission and reduce clarity. PET bottle optical clarity is an important property that can be decisive for the suitability of RER-PET material usage for packaging liquid products. Fig. 19 shows the blends RER-PET and virgin PET blends bot- tles clarity in response to different RER-PET and PMDA concentrations. The RER-PET and virgin PET blend’s bottle with the highest clarity value of 88.5% is

Fig. 19. Clarity (%) of RER-PET and virgin PET blends bottles as a function of RER-PET and PMDA concentrations. It was reported that clarity is affected by biaxial orien- tation during the blow moulding stage. Biaxial orienta-

Fig. 18. FTIR absorbance of RER-PET and virgin PET blends (sample no. 7) bottle for the carbonation loss test.

* CV is the carboxyl groups content and CVh is the hydroxyl groups content. Properties of virgin PET and POSTC-PET flakes Table 1

(Panel A) Coded values vs. real values (Panel B) experimental set

* Rear barrel temperature for the original setting is 275 °C. ISBM fixed parameters Table 3

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Biodegradation and thermal decomposition of poly(lactic acid)-based materials reinforced by hydrophilic fillers

by Parveen Sangwan

2010, Polymer Degradation and Stability

The effect of hydrophilic fillers (starch and wood-flour) on the degradation and decomposition of poly (lactic acid) (PLA) based materials was investigated. Biodegradation was evaluated by composting under controlled conditions in... more

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Provided for non-commercial research and education use Not for reproduction, distribution or commercial use.

Fig. 1. Rate of biodegradation of PLA/starch, PLA/wood-flour and cellulose samples under aerobic composting conditions. E. Petinakis et al. / Polymer Degradation and Stability 95 (2010) 1704—1707

Fig. 3. Thermal decomposition of PLA/starch blends evaluated by TGA at a heating rate of 20 °C/min. Fig. 4 shows the thermal decomposition of PLA/wood-flour composites measured by TGA. Similar to starch, the processes of dehydration and carbon burning can be clearly observed at about 150 and 450 °C, respectively. It was noted that a “shoulder” occurred from 250 °C to 350 °C and a large decomposition peak for the pure wood-flour. Previous studies [27,28] have shown that the “shoulder” peak can be attributed to decomposition of hemicellulose and slower decomposition of lignin, and the large

Fig. 2. SEM morphologies of the specimen after partial biodegradation in composting testing (A and a are PLA 90/starch 10 blend; B and b are PLA 90/WF 10 composite)

Fig. 4. Thermal decomposition of PLA/wood-flour composites evaluated by TGA at a heating rate of 20 °C/min. Fig. 5 shows a p lot of filler content vs. decomposition temper- ature for PLA/starch blends and PLA/wood-flour composites. It is seen that the decomposition temperatures of PLA/starch blends are lower than that of PLA/wood-flour composites. It has been noted that the decomposition temperature of starch (322 °C) is lower than that of wood -flour (355 °C). When starch decomposes it produces some small polar molecules, and it has previously been reported [29—33] that various gaseous emissions such as CO, CO2, H20, CHy, C2H4 and CH20 could be detected by FTIR. It is highly likely these molecu PLA in a similar fas a decrease in the d decomposition tem could be used to ex es could break down the polyester chain of the hion to break down by hydrolysis, resulting in ecomposition temperature of PLA. The lower perature of starch as compared to wood-flour plain the lower decomposition temperature of PLA in the blends with starch.

E. Petinakis et al. / Polymer Degradation and Stability 95 (2010) 1704—170; Fig. 5. A plot of filler content vs. decomposition temperature for PLA/starch blends anc PLA/wood-flour composites.

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Influence of accelerator type on properties of NR/EPDM blends

by Chakrit Sirisinha and

2007, Polymer Testing

The effect of accelerator type on processability and mechanical properties of 60/40 natural rubber/ethylene propylene diene monomer (NR/EPDM) blend was investigated. Three groups of commercial accelerators were selected, i.e., sulfenamide... more

Fig. 1. The relationship between swelling ratio and accelerator type. The relationship between the swelling ratio and accelerator type is illustrated in Fig. 1. As it is widely accepted that the swelling ratio is inversely proportional to crosslink density, with reference to the crosslink density results determined indirectly from the torque difference data, the swelling ratio should theoretically be in the following order: TBBS<TMTD<MBTS<MBT. Surprisingly, in spite of its lower crosslink density, the TMTD- cured blend possesses a similar degree of swelling resistance to the TBBS-cured blend. This is thought to arise from the highly crosslinked continuous NR phase restricting the solvent swelling.

Fig. 2. Effect of accelerator type on rebound resilience of the blends.

Compounding formulation (Haake Rheomix 3000p). The mixing conditions were set as follows: fill factor = 0.7, initial chamber temperature = 60°C, ro or speed =40rpm and mixing time = 9min. After mixing, the compounds were sheeted out on a LRM150). Measuremen (ML1+4 @ 125°C) was ISO 289 using a Mooney viscometer two-roll mill (Labtech of Mooney viscosity carried out according to TechPro viscTECH + ). The cure c haracteristics, e.g., scorch time (¢,2) and optimum cure time (¢,90) including minimum torque (M_,) and maximum torq were determined using a moving die r (TechPro MD +) at 160° was reported earlier that the torque d ue (My) heometer 6502. It ifference C following ISO (My—M_) is directly proportional to the degree of crosslinking, therefore it is employed here to indirectly represent the blend vulcanizates [13]. crosslink density of the

Effect of accelerator type on Mooney viscosity and cure characteristics of the blends Table 2

Effect of accelerator type on dynamic properties of the blends Table 3 imparts the NR phase with higher crosslink density than MBTS. labile 5 illustrates the eftect of accelerator type on dynamic properties of the blend. The results clearly reveal that the storage moduli (E’) of TMTD-cured and TBBS-cured blends are relatively high com- pared to those of MBTS-cured and MBT-cured blends. As it is widely accepted that the storage modulus is directly proportional to the degree of elasticity, and thus crosslink density, a sensible explanation for such finding is therefore given by the greater degree o [D and TBBS. A reverse trend is observed for TM] crosslinking imparted by damping factor (tan 6) results, i.c., MBT and MBTS give com blends wit pared with 7 h relatively high damping factor, [MTD and TBBS. As the damping factor is inversely proportional to the degree of crosslinking, the results again confirm that both TM] [D and TBBS give the blends a greater degree of crosslinking than MBTS and MBT.

Effect of accelerator type on mechanical properties of the blends Table 4 Compared to TMTD, TBBS gives a_ better balance of crosslink density in each phase of the blend (it gives higher crosslink density in the EPDM phase). The TBBS-cured blend therefore possesses higher tensile and tear strengths than the TMTD- cured blend. It is surprising to find that, even hough the MBTS-cured blend possesses a relatively ow total crosslink density, its tensile strength is comparable with that of TBBS-cured blend. The high tensile strength of MBTS-cured blend is hought to arise from the ability of MBTS to give sufficiently high cure level in the EPDM phase. As both MBT-cured and MBTS-cured blends possess relatively low total crosslink density, their tear strengths are relatively high compared to those of TBBS-cured and TMTD-cured blends.

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Polylactic acid/polypropylene polyblend fibers for better resistance to degradation

by Narendra Reddy

2008, Polymer Degradation and Stability

Polyblend fibers were produced from five ratios of polylactic acid/polypropylene (PLA/PP) in an effort to improve the resistance to hydrolysis and biodegradation, and to improve the dyeability of PLA. The inherent limitations of PLA such... more

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Novel superabsorbent cellulose-based hydrogels crosslinked with citric acid

by Demitri L

2008, Journal of Applied Polymer Science

This work is focused on the preparation of new environmentally friendly hydrogels derived from cellulose and hence originating from renewable resources and characterized by biodegradable properties. Two cellulose derivatives, sodium... more

Scheme 1 Possible crosslinking reaction mechanism of citric acid with cellulose.

Figure 2. DSC curing thermograms of CMCNa (a); HEC (b); and CMCNa/HEC (3/1) hydrogel (3.75% of CA) (c). DSC analysis of neat CMCNa and HEC powders are reported in Figure 2. The peak in the first scan indicates that some water is still absorbed in the polymers. Above 100°C, a possible degradation peak of CMCNa is detected. Both CMCNa and HEC show a thermal stability below 100°C.

Figure 1 DSC curing thermogram of citric acid.

Figure 3 FTIR spectra of citric acid (CA) (a); A10 reaction mixture before heating (b); A10 reaction mixture after 5 h of heating (c); B10 reaction mixture before heating (d); and B10 reaction mixture after 6.5 h of heating (e).

Figure 6 Carbonyl band area ratio (1738 cm !/1590 cm’) of reactions B10 (@) and B20 (M) at different reac- tion times. Figure 6 shows peak area ratio A;/A2 of HEC polymer when the reaction is performed at 80°C with 20% of CA or 10% of CA. The anhydride band intensity increase from 0 to 0.098 when the reaction time increase from 0 h to 6.5 h, but drop to 0 when the reaction time reaches 24 h. The B20 reaction (Fig. 6, Ml) follows exactly the same trend providing a maximum of 0.079 value at 5 h. Assuming that the crosslinking mechanism is the same described for CMCNa, the anhydrification and esterification reac- tions appear superimposed in this case. Therefore, HEC polymer shows a single peak in Figure 6. This latter result was in accordance with conclusion of Xie and Liu.”* They studied the degree of substitu- tion, as evaluation of crosslinking esterification, on starch thermally reacted with CA at different reac- tion time and found a maximum after few hours.

Figure 5 Carbonyl band area ratio (1738 cm '/1590 cm’) of reaction A10 at different reaction times.

Figure 4 Carbonyl band area ratio (1738 cm '/1590 cm~’) of reaction A20 at different reaction times.

Figure 7 FTIR spectra of C10 reaction mixture before heating (a); C10 reaction mixture after 8 h of heating (b); C10 reaction mixture after 13 h of heating (c); C20 reaction mixture before heating (d); C20 reaction mixture after 8 h of heating; (e) and C20 reaction mixture after 13 h of heat- ing (f). Finally, to complete this study, polymer mixtures of CMCNa and HEC were crosslinked. CMCNa has carboxylic groups in its structure that increase the volume variation process in solution. A preliminary attempt to follow the reaction pathway was failed. Probably the reaction systems considered are too complex having many different reaction centers. FTIR spectra of C10 reaction registered before (Curve a), after 8 h (Curve b), and after 13 h (Curve c) of heating are compared in Figure 7. Figure 7 (Curves d-f) shows similar spectra but referred to reaction sample C20. Moreover, it is worth noting that when polymer mixtures are used (C10 and C20) a broad signal appears at about 1715 cm‘ (see spec- tra 7a and 7d), especially when a higher CA concen- tration is used in the reaction. In fact, with 20% of

Figure 8 Equilibrium swelling ratio versus reaction time of CMCNa polymer with 10% w/w (M™) or 20% w/w (@) of CA crosslinker concentration (both samples were dried under vacuum at 30°C for 24 h and then reacted at 80°C).

Figure 10 Equilibrium swelling ratio versus reaction time of CMCNa/HEC weight ratio 3/1 mixture with 10% w/w (HM) or 20% w/w (®) of CA crosslinker concentration (bott samples were dried under vacuum at 30°C for 24 h and then reacted at 80°C).

Figure 11 Equilibrium swelling ratio versus reaction time of CMCNa/HEC weight ratio 3/1 mixture with 1.75% w/w (A), 2.75% w/w (Mf) or 3.75% w/w (®) of CA cross- linker concentration (all samples were dried under vacuum at 30°C for 24 h and then reacted at 80°C).

Figure 9 Equilibrium swelling ratio versus reaction time of HEC polymer with 10% w/w (M) or 20% w/w (@) of CA crosslinker concentration (both samples were dried under vacuum at 30°C for 24 h and then reacted at 80°C).

Samples Composition ‘Used for Each Crosslinking Reaction Performed at 80°C

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Formulation and curing characteristics of EPDM/NR and EPDM/SBR polyblends used in metallic surfaces rubber lining

by Payam Zahedi

2009, Journal of Applied Polymer Science

In this work, a new elastomeric liner was introduced to protect the metal surfaces of storage tanks against corroding materials in petrochemical industries. This new liner was prepared on the basis of EPDM/NR and EPDM/SBR compounds. The... more

Figure 1 Typical disassembled test cell for chemical re- sistance testing of rubber tank lining.

Figure 2 Cure curves for (a) SBR/NR, (b) EPDM/NR, and (c) EPDM/SBR before modification in the curing system. As can be seen in Figure 2(a), the optimum cure time (too) for sample SBR/NR (50/50) was about 6 min. This value at tog for SBR/NR was less than too EPDM/NR [Fig. 2(b)] and EPDM/SBR [Fig. 2(c)]. The reason for this difference is due to fewer num- bers of unsaturated bonds in EPDM compared with SBR. Consequently, a higher rate of network forma- tion between the double bonds and sulfur in SBR is observed. On the other hand, because the degree of unsaturation in SBR is less than NR, the values of too and scorch time (t,) for EPDM/NR relative to

Figure 3 Cure curves for SBR/NR (50/50), EPDM/NR (70/30), and EPDM/SBR (70/30) after modification in the curing system. Table V shows qualitative test results for cracking, blistering, permeability, and adhesion strength of the rubber liner to metallic surface. Cracking and blister- ing test observations for EPDM/NR (70/30), EPDM/ SBR (70/30), and SBR/NR (50/50) were negative and here was a smooth surface with out any cracking and blistering effects. As was explained in penetra- ion tests of liquid and vapors of caustic solution, only EPDM/NR samples are affected by penetration due to a more flexible structure and a softer surface because of more double bonds and free movements of elastomeric chains, which are not bonded by sulfur cross-links. Evaluation tests related to the strength of he rubber layer bonded to metallic surface by using heat activated binding adhesive, Chemosil X6025, show that for all three samples, the adhesive forms suitable bonds between the surfaces of rubber layer with the metal surface. The activation of these bonds for the cure system at 140°C is resistant to caustic liquids and vapors and there is no penetration between the rubber layer—metallic surface and no cor- rosion was observed at the metallic surface.

Recipes for SBR/NR, EPDMI/NR, and EPDM/SBR Polyblends TABLE II

Accelerators Used for the Curing System of the Samples TABLE I The cure time of the samples was selected accord- ing to ASTM D 2084 by using a rheometer 100 (Hyundai). The cure curves were obtained at 140°C for these samples.

Mechanical Properties of the Samples Before and After Immersion in HCl Solution * Minus sign is due to properties decrement after HCl immersion compared to the properties before HCl immersion.

The Mechanical Properties of the Samples After Modifications in the Curing System TABLE IV ZDEC, a third accelerator, tetramethylthiuram disul- fide (TMTD), which is from the thiuram group, was used. The reason for using three different types of accelerators was to get a synergism effect for increasing the cure rate.’*’” In the optimum formu- lation, 1.5 phr MBT, 1.5 phr ZDEC, and 1.8 phr TMTD were used. One of the objectives of this work was to increase the efficiency of the curing system and reduce the tog for EPDM/NR and EPDM/SBR polyblend samples. Normally, TMTD gives a higher rate of curing and reinforcing effect on cross-links.”° samples. Comparing the mechanical properties of the samples under investigation, we can conclude that EPDM/SBR (70/30) samples have similar and acceptable properties to SBR/NR (50/50).

+: observed; —: not observed. The Qualitative Observation After Immersing the Samples in Caustic Solution TABLE V

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Stabilization effect of lignin in polypropylene and recycled polypropylene

by Adriana Kovalcik (previous name Gregorova)

2005, Polymer Degradation and Stability

The influence of lignin on the oxidative stability of polypropylene (PP) and recycled polypropylene (recPP) plaques has been examined by differential scanning calorimetry under non-isothermal conditions. Lignin was used as a dry powder in... more

Fig. 2. Concentration dependences of the onset oxidation temperatures for individual heating rates MH: 6 = 1 Kmin™', O:6=3Kmin|, a: 6=5Kmin', V: 6=7Kmin', @: 6=10Kmin', DC: 6=15Kmin—. From Eq. (3) it is obvious that if the value of PF is greater than one, the additive has a stabilizing effect on he polymer. In Figs. 3—5, the protection factor of PP and recPP stabilized with lignin and/or Irganox 1010 is plotted as a function of temperature. Figs. 3 and 4 show he dependences of PF on temperature for the PP and recPP samples stabilized with various concentrations of ignin. These dependences exhibit increasing tendency with decreasing temperature and with the increasing content of lignin. Dependences of PFs on temperature for the samples stabilized with Irganox 1010 and with he mixture of Irganox 1010 and lignin are depicted in Fig. 5. It is obvious that the stabilization of recPP by

Fig. 1. Experimental and fitted dependences of the onset oxidation temperatures on the heating rates for polypropylene stabilized with lignin in various concentration.

Fig. 3. Dependences of protection factor on temperature for lignin ir PP.

Fig. 4. Dependence of protection factor on temperature for lignin in recPP.

Fig. 5. Dependence of PP protection factor on temperature for Irganox 1010 and lignin.

Fig. 6. Dependence of VST on lignin content in PP and recPP.

VST of PP and recPP stabilized with Irganox 1010 and lignin Table 4

Kinetic parameters A, B and their standard deviations Table 2

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Biocomposites based on lignin and plasticized poly (L‐lactic acid)

by Md Arifur Rahman

Journal of Applied …

In this research work, biocomposites based on a ternary system containing softwood Kraft lignin (Indulin AT), poly-L-lactic acid (PLLA) and polyethylene glycol (PEG) have been developed. Two binary systems based on PLLA/PEG and... more

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Ellipsometric determination of Flory-Huggins interaction parameters in solution

by Georg Krausch

2004

We have used spectroscopic ellipsometry to determine the Flory-Huggins parameters in thin films of polystyrene, poly(2vinyl pyridine), and poly(tert butyl methacrylate) swollen in controlled atmosphere of various common solvents. From the... more

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The Effect of Filler Loading on Curing and Mechanical Properties of Natural Rubber/recycled Rubber Powder Blends

by razif nordin (Dr.)

2005, International Journal of Polymeric Materials

... Rubber World, : May, 25; 9. Rodriguez, EL 1988. Polym. Eng. Sci., 28: 1455 [CROSSREF] [CrossRef], [Web of Science ®]; 10. Tipana, M. and Kale, DD 1997. Rubb. Chem. Technol., 70: 815 [CrossRef], [Web of Science ®]; 11. Ismail, H.,... more

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Potential of blend of kappa-carrageenan and cellulose derivatives forgreen polymer electrolyte application

by MOHD SAIFUL ASMAL RANI and

tIn this study, new biopolymer blend based on kappa-carrageenan and cellulose derivatives were pre-pared using solution casting technique. The cellulose derivative, carboxymethyl cellulose was producedfrom cellulose extracted from kenaf... more

Fig. 1a. FTIR spectra for k-carrageenan and CMKC powder.

Fig. 1b. FTIR spectra for cellulose and CMCE.

Fig. 2. Cross-sectional SEM images of k-carrageenan, CMKC, cellulose and CMCE.

Fig. 3b. XRD spectra of cellulose and CMCE powder. Fig. 3a. XRD spectra of k-carrageenan and CMKC powder.

Fig. 4. FTIR spectra of CMKC/CMCE blend films.

Fig. 5. Cross-sectional SEM images of pure CMKC, CMCE and CMKC/CMCE blend films. S. Rudhziah et al. / Industrial Crops and Products xxx (2015) xxx-xxx

S. Rudhziah et al. / Industrial Crops and Products xxx (2015) xxx-xxx Fig. 6. Tan 6 curves versus temperature for BO, B2, B4 and B5.

Fig. 7. (a) Variation of log conductivity of CMKC/CMCE blend as a function of CMCE concentration, (b) H* conduction mechanism and intermolecular interaction in CMKC/CMCE blend, (c) impedance plot for CMCK/CMCE (B4) blend film and (d) model of equivalent circuit.

The compositions and designations of the CMKC/CMCE (wt%) blendfilms. Table 1 a few hours to form homogenous solution. The solution was then poured into Petri dishes and allowed to dry at room temperature for 2 weeks to obtain free standing films. The free standing films obtained were kept in a desiccator for further drying. The proce- dure was repeated to obtain other blends with CMKC:CMCE ratios of 60:40, 70:30, 80:20 and 90:10. The weight percentage of CMCE added to CMKC was calculated using the following equation;

Elemental data of k-carrageenan, cellulose and their derivatives. Table 2

Glass transition temperatures for CMKC, CMCE and CMKC/CMCE blend films. Table 3 band at 926 cm~! of CMKC/CMCE film is observed to decrease with addition of CMCE from 10 to 40 wt%. The peak shifts seen for all the blends suggest that the intermolecular interaction has occurred between the two component polymers (Wu et al., 2012).

Mechanical properties of CMKC, CMCE and CMKC/CMCE blend films. sile strength of the blend films improved with the increase of CMCE contents and reached a maximum point of 15.15 MPa at 40 wt% of CMCE content. The enhancement of TS of the blend films might be attributed to the hydrogen bonding interaction between CMKC and CMCE and improvement of intermolecular interaction between the two polymers (Wu et al., 2012).

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Role of ITO and PEDOT:PSS in stability/degradation of polymer:fullerene bulk heterojunctions solar cells

by MIHAELA RUSU

2010, Solar Energy Materials and Solar Cells

a b s t r a c t Two polymers:fullerene bulk heterojunction solar cells: [(I) poly[2-methoxy-5-(3,7-dimethyloctyloxy)]-1,4-phenylenevinylene (MDMO-PPV): methanofullerene phenyl-C 61 -butyric-acid-methyl-ester ([60]PCBM) and (II)... more

Fig. 1. Organic solar cells architecture. Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate )— Baytron PH (PEDOT:PSS) was purchased from Baytron and deposited without any dilution by spin coating on glass or ITO covered pattern glass. For obtaining polymer:fullerene blends poly[2-methoxy-5-(3,7-dimethyloctyloxy)]-1,4-phenylenevinylene

Fig. 2. J-V curves of solar cells under AM 1.5 illumination at an irradiation intensity of 100 mW/cm7: (a) P3HT:PCBM blend and (b) MDMO-PPV:PCBM blend. Table 1 summarizes the photovoltaic parameters of the investigated cells at AM 1.5, 100 mW/cm? illumination. The Vo¢ is the open circuit voltage, J,. the density of short-circuit current. As indicative values, for cell 1, the fill factor was about 0.36 for a device having an cathode area of 0.32 cm”. The power conversion efficiency for pristine cells was about 1.02% without taking into account the mismatch factor. This value corresponds to current values obtained for non-annealed cells of this type [19]. The aluminium cathode surface area was 0.32 cm?.

Fig. 4. J-V characteristics for ITO free solar cells: (a) P3HT:PCBM blend and (b) MDMO-PPV:PCBM blend with different surface area of cathode

Fig. 3. Band energy diagram for (a) P3HT:PCBM blend and (b) MDMO-PPV:PCBM blend solar cells with ITO/PEDOT:PSS and Al as electrodes. We noticed a surface size effect for both types of cells (Fig. 4). We attributed the small difference between curves for cells with the “same” area to the shadow effect arising from evaporation through a mask of the top electrode.

Fig. 5. Comparison between J-V characteristics of the two free ITO cells (S=0.32 cm?). Surface size effect was put in evidence also by other authors 24-26] for other types of cells. A similar behaviour is observed: the V,,. is the same for cells with different cathode areas, but the

Fig. 7. J-V characteristics evolution with ageing for (a) PEDOT:PSS/P3HT:PCBM/LiF/Al cell and (b) PEDOT:PSS/MDMO-PPV:PCBM/LiF/Al cell Fig. 6. Current flow for a cell having an active area larger than collecting cathode surface area. According to this (especially, for the calculation of power conversion efficiency), if we compare cells with different surfaces area, mismatching correction should be taken into account. In this The correct value of short-circuit current density J§, could be found either using a mask (so limiting the irradiation to cathode area); or by measuring the values Js} and JS? for two cells with known cathode radii (r and R), calculating the dimension d, from Eq. (2) and then calculating J§c.

Device performance of P3HT-PCBM, MDMO-PPV:PCBM solar cell with ITO or/and PEDOT:PSS as transparent electrode without thermal annealing, under AM. 1.5 100 mW/cm? illumination; pristine and after 40 days ageing in open atmosphere.

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Preparation, characterization and antibacterial properties of cyanoethylchitosan/cellulose acetate polymer blended films

by Hassan Ibrahim and

2011, Carbohydrate Polymers

Modification of chitosan (CS) by means of blending with other polymers is a convenient method to improve its physical properties for practical utilization. The similarity of cellulose and chitosan in primary structures might facilitate... more

It is clear from Table 1 that keeping the aqueous sodium hydrox- ide concentration in the filter cake between 6 and 10% is quite proper to activate the double bonds of acrylonitrile to facilitate its addition on the hydroxyl groups of chitosan. Sodium hydroxide concentration <6% is not enough to activate the double bonds, while concentration >10% is enough to acti- vate the double bonds and to attack the nitrile groups to yield amide and/or carboxyl groups (Hebeish & Khalil, 1988; Sharma, Kumar, & Soni, 2003). The results of solubility confirm this result where a DS <1.2 is not enough to open the structure and the material swells only while at a DS 1.20-1.23 the structure is open enough to let the material dissolve in DMF. Increasing the sodium hydroxide concentration above 10% will facilitate the hydrolyzing attack of NaOH on the CN group to convert it to -CONH> and/or -COOH which are capable of closing the structure again by hydro- gen bonding.

Fig. 1. FTIR spectra of CA film (a), CA:CECS blended films 80:20 (b), 60:40 (c), 40:60 (d), 20:80 (e) and CECS film (f).

Fig. 2. TGA for CECS/CA polymer blends. Chitosan, a cationic antibacterial agent, has been widely used, particularly for wound dressing, and the target site of the cationic biocides is the cell envelope of bacteria. The mechanism of antibac- terial activities of chitosan that the amino group of chitosan is bound to surface components of the bacteria and then inhibits Table 4 shows the antibacterial activity (MIC and MBC) of the chitosan and its derivative CECS, according to the two-fold broth tube dilution method, on S. aureus and E. coli as described in Section

their growth was developed (Papineau, Hoover, Knorr, & Farkas, 1991; Sudharshan, Hoover, & Knorr, 1992). They thought that at lower concentration chitosan may have bound to the neg- atively charged bacterial surface to disturb the cell membrane and cause cell death due to leakage of intracellular components (Zheng, Zhu, & Sun, 2000), at high concentration, chitosan may have additionally coated the bacterial surface to prevent leakage of intracellular components as well as to impede mass transfer across the cell barrier (Helander, Nurmiaho, Ahvenainen, & Roller, 2001).

Experimental conditions used: [chitosan], 5 gm; [acrylonitrile], 25 ml in vapour phase; reaction period, 3h; [NaOH] 6%; wet pick-up of mother liquor of NaOH reaches 100%. Effect of the sodium hydroxide concentration and reaction period on DS of resultant cyanoethylchitosan and its solubility in DMF. Table 1

FTIR absorption bands in CA/CECS blends.

Percent nitrogen content, tensile strength and elongation yield% of CA/CECS and Viscose/CMCS blended films.

MIC and MBC values found for Chitosan, Cyanoethylchitosan. Table 4

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Thermoplastic polyolefin based polymer – blend-layered double hydroxide nanocomposites

by Tapas Kuila

2008, Composites Science and Technology

Layered double hydroxides (LDHs) are a new class of promising nanomaterials which improve the physicochemical properties of the polymer matrix. The present work deals with the preparation of nanocomposites of ethylene vinyl acetate... more

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AN INTRODUCTION TO BASALT ROCK FIBER AND COMPARATIVE ANALYSIS OF ENGINEERING PROPERTIES OF BRF AND OTHER NATURAL COMPOSITES

by Piyush Sharma

Basalt is a common extrusive volcanic rock. An inert rock found worldwide, basalt is the generic term for solidified volcanic lava. Safe and abundant, basalt rock has long been known for its thermal properties, strength and durability. It... more

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Mechanical and thermo-chemical properties of wood-flour/polypropylene blends

by Alireza Ashori

2010, Polymer Bulletin

The main objective of this research was to study the potential of waste polypropylene and waste wood for making wood plastic composites (WPCs). The effects of nanoclay (NC), microcrystalline cellulose (MCC), and coupling agent (MAPP) on... more

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New fire-protective intumescent coatings for wood

by Ryszard Kozłowski

2008, Journal of Applied Polymer Science

Polyurethane coatings are highly flammable, and because of their widespread applications on different substrates (wood, steel, and building materials), there is a need to increase their fire-safety properties. Intumescent additives... more

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Utilization of corn fibers and luffa peels for extraction of pollutants from water

by Suresh Valiyaveettil

Corn fibers and luffa peels were evaluated for removing toxic heavy metal ions and dissolved organic dyes from water. Fresh peels were pretreated to remove all soluble components before using them for extraction studies. Presence of eOH... more

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Effect of percentage of short fibers removed from cotton during spinning on the properties of dyed polyester/cotton‐blended knitted fabrics

by tanveer hussain

2011, Journal of the Textile Institute

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Effects of LDPE and glycerol contents and compounding on the microstructure and properties of starch composite films

by Pratik Bhandari

2010, Carbohydrate Polymers

Fig. 1. Effects of compounding and LDPE content on the surface morphology of composite films plasticized with 25% glycerol and consist of (a) 95S:5PE-P, (b) 95S:5PE-NF (c) 90S:10PE-P, (d) 90S:10PE-NP, (e) 85S:15PE-P, (f) 85S:15PE-NP (S, corn starch; PE, polyethylene; P, compounding; NP, no compounding).

Fig. 2. Effect of glycerol content on the surface morphology of compounded films (a) 25% and (b) 35%. The additional peaks at 21.6° and 23.8° were attributed to that of LDPE (Matzions et al., 2001). types of composites manifested crystalline starch-related peaks at 26 angles of 13.3°, 17.4°, 18.7° and 20.0°, which largely resembled a ‘B’-type structure. Thus, the native ‘A’-type crystalline structure of starch was lost after extrusion. The development of ‘B’-type lattice structure could be attributed to the fast recrystallization of amy- lose or the outer chains of amylopectin, or both, in the presence

Fig. 3. X-ray patterns of (a) 95% S+5% PE+25% G-P, (b) 95% S+5% PE+ 35% G-P, (c) 85% S+15% PE+25% G-P, (d) 85% S+15% PE+ 35% G-P, (e) 85% S+ 15% PE+25%G and (f) 85% S+15% PE+ 35% G composite films (S, corn starch; PE, polyethylene; G, glycerol; P, compounding).

Fig. 4. FTIR spectra of (a) LDPE, (b) native corn starch, (c) starch-glycerol film and (d) starch-LDPE composite film.

Fig. 5. FTIR spectra showing the effect of compounding on composite films contain- ing (a) 95% S+5% PE+25% G, (b) 95% S+5% PE+ 25% G-P, (c) 85% S+ 15% PE+25%G and (d) 85% $+ 15% PE+25% G-P (S, corn starch; PE, polyethylene; G, glycerol; P, compounding).

Means with the same letter within a column are not significantly different (P>0.05) by Duncan’s multiple range test; P, compounding Tensile and water vapor permeability properties of starch-LDPE composites. Table 1

Thermal properties of starch-LDPE composites. P, compounding. Table 2

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Barrier properties of biodegradable composite films based on kappa-carrageenan/pectin blends and mica flakes

by Vitor Alves

2010, Carbohydrate Polymers

In this work, the enhancement of the barrier properties to water vapour and gases (CO 2 and O 2 ) of a polymeric matrix composed by kappa-carrageenan and pectin (66.7% kappa-carrageenan), with the inclusion of mica flakes, was studied.... more

Fig. 1. Scanning Electron Microscopy pictures of the films cross section: (a) 5% mica, (b) 10% mica, (c) 20% mica. The measured water flux for the different experimental condi- tions is presented in Fig. 3. The relative values obtained are in accordance with the driving forces imposed, since higher values

Fig. 2. Experimental moisture sorption isotherms of kappa-carrageenan/pectin films with different amounts of mica flakes: (Ml) 0% , (1) 5%, (A) 10% and (O) 20% (mass of mica per mass of dry polymer); the respective fitted GAB curves (lines) and GAB parameters (inserted table). The sorption isotherm of isolated mica flakes is also presented (@).

Fig. 4. Water vapour pressure profiles on the films boundary layers and water concentration inside the films for both driving forces: (a) 100.0-10.8 %RH and (b) 75.4-60.5 %RH. Fig. 3. Water vapour flux as a function of mica content for two driving forces: 100.0-10.8 %RH (filled symbols) and 75.4-60.5 %RH (opened symbols).

Fig. 5. Water vapour permeability as a function of mica content. P/Pp represents the normalized WVP values. When the 75.4-60.5 (%RH) difference was used, both film sur- faces where in contact with a relatively high water activity. As a re- sult, the film is hydrated throughout the entire water diffusion path. On the contrary, when the 100-10.8 (%RH) driving force is applied, even though one of the surfaces is in contact with an atmosphere with a high water activity, the other surface is exposed to an almost dry environment (Fig. 4). Therefore, there is a high water concentration gradient through the film thickness, limiting the plasticizing effect, and part of the polymeric matrix maintains its tightly packed network structure which contributes to hinder water transport. A similar behaviour was obtained by Mauer, Smith, & Labuza, 2000, with f-casein films tested using two driving forces: 53-11 (%RH) and 76-53 (%RH). A higher WVP was observed with the later driving force (2.9 x 10-'! mol m/m?s Pa) when compared to that measured with the 53-11 %RH difference (1.0 x 10-1! mol m/m? s Pa).

Fig. 6. Effective diffusion coefficient of water through the films as a function of mica content. D/Do represents the normalized Dey values. The measured permeability to carbon dioxide and oxygen as a function of the mica content is presented in Fig. 7. The values ob-

Water sorption coefficients in both sides of the films for the driving forces studied (the errors associated to the S values are below 5.2%). Table 1

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Suppression of Skin−Core Structure in Injection-Molded Polymer Parts by in Situ Incorporation of a Microfibrillar Network

by D. Byelov

2006, Macromolecules

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Characterization of polyhydroxybutyrate-hydroxyvalerate (PHB-HV)/maize starch blend films

by Kelen Reis

2008, Journal of Food Engineering

Blends of polyhydroxybutyrate-hydroxyvalerate (PHB-HV) with maize starch at starch contents of 0%, 20%, 30%, 40% and 50% were prepared by casting. The morphological and molecular properties were investigated by using Fourier transform... more

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Influence of accelerator type on properties of NR/EPDM blends

by Chakrit Sirisinha

2007, Polymer Testing

The effect of accelerator type on processability and mechanical properties of 60/40 natural rubber/ethylene propylene diene monomer (NR/EPDM) blend was investigated. Three groups of commercial accelerators were selected, i.e., sulfenamide... more

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Melt Mixing of Ethylene/Butyl Acrylate/Glycidyl Methacrylate Terpolymers with LDPE and PET

by Aida Benhamida and

2009, Macromolecular Materials and Engineering

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Glass transition temperatures in binary polymer blends

by Witold Brostow

2009, Journal of Polymer Science Part B: …

Knowledge of the glass transition temperatures (T g s) as function of composition reflects miscibility (or lack of it) and is decisive for virtually all properties of polymer-based materials. In this article, we analyze single... more

Figure 1. Compositional variation of blend T, for miscible binary polymer mix- tures, which obey or are very close to the ideal mass-additivity behavior (PTA + PVME and PECH + PHB) and blends that exhibit departure from it (PS + PPE- 3100 and PTT + PET).

Figure 2. Compositional variation of blend T, for the miscible polymer blend PVE + PI. The deviation from linearity plot is shown in the insert.

Figure 3. Linear fitting of the dependence between the principal parameter of the proposed equation, ao, and the parameters of (a) the Gordon-Taylor, ker, or (b) the Jenckel-Heusch equation, 6 [b = ap(Tgo — T,,1)]. The data in these plots involve miscible binary polymer blends for which parameter az is zero. Note that for blends with a; 4 0, the ratio ao(Tg2 — Tz1) is also nearly equal to b. The errors in the values are comparable to the size of the symbols unless other- wise indicated.

Figure 4. Compositional variation of blend T for the miscible polymer blends of (a) PEI + PBI and (b) PMMA + CAP. In each case, the deviation from line- arity plot is shown in the insert.

Figure 5. Compositional variation of T, for the mis- cible polymer blends PxaMS + PCHMA. rFarameter dg 1S zero 1n the alorementioned examples of polymer mixtures, in agreement with the assumed moderate complexity of their behav- ior. Nevertheless, there exist interesting cases of “anomalous” changes in the dynamics of mixtures with components of nearly equal T,. The intrigu- ing behavior involves either positive! >? or nega- tive’ departures from the mass-additivity rule, which are accompanied by blend T,s not interme- diate to those of the blend components. In an attempt to explain this phenomenon several sce- narios have been invoked; for example, either changes in volume due to blending (i.e., positive or negative excess volume), changes in the inter- molecular constraints, or nonrandom mixing. No matter the cause, this anomaly produces signifi- cant positive or negative values for az. Character- istic examples provide the miscible blends of poly(«-methyl styrene) (PaMS) with poly(cyclo- hexyl methacrylate) (PCHMA)*? and of PECH with PVME,” in which the 7, of some blends is above the highest neat component value (T',2). For example, in the PxaMS + PCHMA system (Fig. 5), the ao, b, and kgr values strongly depart from the linear ag versus kay and 6b versus ao dependences established by the data included in Figure 3. This behavior is consonant with the dis- tinctly nonzero value of our third parameter. Note that in this case also, the proposed equation

Figure 6. Comparison of the compositional variation of the glass transition temper- atures observed in miscible blends of PVME with (a) PVPh, (b) P2CS, and (c) PS. An unusual plot (observed only in PVME + PVPh) of the T,-deviation from the weighted-average blend T, is shown in the insert.

Figure 7. Compositional variation of blend T, for the miscible PMMA + PVPh polymer blend. The plot of the deviation from linearity is shown in the insert.

Journal of Polymer Science: Part B: Polymer Physics DOI 10.1002/polb

Figure 9. (a) Compositional variation of T, data (@) of Miwa et al.’* for PVME + PoCIS blends. (b) Effec- tive Ts (Ml) of components versus gpymr. Explanation in text.

“The weight fraction of the semicrystalline component in a blend, above which its partial crystallization appears, is indicated. Table 1. Mixture Information and Curve-Fitting Results for the Parameters Incorporated in Eq 7*

“The values are determined applying eqs 1, 4, and 7 to experimental data for 11 representative systems with a range of dynamic heterogeneities (AT,’s between ~10 aad 200 K). > PHB, PCL and PC are the Semicrystalline components. Table 2. Comparison of the R? Values and the Reduced y-Square 77/DoF Values

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Polyethylene polyurethane blends for improved paint adhesion (Progress in Organic Coatings 2011;72(3):492-497)

by Jie Song

Polyolefins have low free surface energy that prevents good wettability of adhesives or paint emulsions to their surface. This work shows that adhesion of olefin block copolymers (OBC) to a polyurethane-based paint can be significantly... more

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Crystal structure and electrical properties of gadolinia doped bismuth oxide nanoceramic powders

by Prof.Dr. İbrahim USLU

A novel method of fabrication of gadolinia doped bismuth oxide nanoceramic via the sol-gel technique is reported. Their thermal, structural and morphological properties are described by measurements of Differential Thermal... more

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Tuning the microwave absorption through engineered nanostructures in co-continuous polymer blends

by Sourav Biswas

Herein, we report tailor-made properties by dispersing nanostructured materials in a co-continuous polymer blend (PVDF/ABS) that is capable of shielding electromagnetic (EM) radiation. To accomplish this, lossy materials were employed... more

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Properties and recyclability of thermoplastic elastomer prepared from natural rubber powder (NRP) and high density polyethylene (HDPE)

by Chakrit Sirisinha and

2010, Polymer Testing

Preparation of thermoplastic natural rubber (TPNR) was carried out by blending high density polyethylene (HDPE) with natural rubber powder (NRP) obtained from spray drying of pre-vulcanized natural rubber latex. The blend ratio of... more

Fig. 1. SEM micrographs of the NRP at different magnifications (a) x 1,000 and (b) x 10,000. TPNRs were prepared by blending NRP with HDPE in a laboratory-sized internal mixer (Brabender Plasticorder High ammonia natural rubber latex (HA-grade) was obtained from Thai rubber latex corporation (Thailand) PCL. Zinc oxide was supplied by Univenture PCL. Potassium hydroxide and ammonia solution were supplied by Bang trading 1992 (Thailand), Co., Ltd. Wingstay L was obtained from DKSH Co., Ltd. Zinc diethyldithiocarbamate and sulfur were supplied by Reliance Technochem (Flexsys) Thailand

Fig. 2. Plot of complex viscosity versus angular frequency of the TPNRs.

Fig. 4. Stress-strain curves of the TPNRs.

Fig. 3. Storage modulus (G’) as a function of angular frequency of the TPNRs.

Fig. 6. Tension set and compression set of the TPNRs. Fig. 5. Relationship between degree of crystallinity of HDPE and blend ratio. The effect of blend ratio on tensile properties, hardness and tear strength of the TPNRs is summarized in Table 2. Unlike the results reported by Nakason et al. [9], the tensile strength tends to increase gradually with increasing NRP/ HDPE ratio. The explanation is given by the phenomenon of strain-induced crystallization, as previously mentioned. It should be noted that the addition of NRP into HDPE matrix could interfere with the degree of crystallinity in HDPE. The The influence of blend ratio on tension set and compression set is depicted in Fig. 6. With increasing NRP content, significant improvement of elasticity is achieved as clearly observed from the continuous reductions in both tension set and compression set. Again, the improved elasticity is attributed mainly to the combination of the

Fig. 7. SEM micrographs of the TPNRs prepared from various blend ratios (a) 60/40, (b) 70/30, (c) 80/20 and (d) 90/10.

Fig. 8. Effect of recycling cycle on tension set of the TPNRs.

* phr: parts per hundred of rubber Formulation of the pre-vulcanized natural rubber latex. Table 1

Mechanical properties of NRP/HDPE at various blend ratios. Table 2

Mechanical properties of the virgin and the recycled TPNRs. Table 3

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On the Surface Free Energy of PVC/EVA Polymer Blends: Comparison of Different Calculation Methods

by Marie-Caroline Michalski

1998, Journal of Colloid and Interface Science

The surface free energy of polymeric films of polyvinylchloride (PVC) ؉ poly(ethylene-co-vinylacetate) (EVA) blends was calculated using the van Oss treatment (Lifshitz and electron donorelectron acceptor components of surface free... more

FIG. 1. Total surface free energy of PVC, EVA, and their blends, using Geo,, (@), Geo, (O), DA,, considering (yg,)"? > 0 (a), DA, considering (yéyv)"? > 0 (A), DA,, considering (yé,)"? < 0 (Mp, and DA, considering (yéy)"? < 0 (C) as calculation methods. Della Volpe and Siboni (23) have highlighted that the choice of the liquid triplet was very important for the consistency of results in the donor-acceptor approach. Therefore, to check whether the negative square root problem that we encountered was not an artefact due to the test liquids chosen (the com- monly used water/glycerol/diiodomethane), we have solved the DA, approach with all the possible liquid triplets (Annex 4). We have found that negative square roots arose regardless the triplet chosen, which confirms this anomaly. We should also

FIG. 2. Square root of the electron donor (— ) and electron acceptor ( - - ) parameters of the surface free energy of PVC, EVA, and their blends, using DA,, (mb and DA, (C) as calculation methods. Another way to handle the negative (gy)? values would be to consider them as an artefact and simply assume that they should be zero. This treatment was suggested by Good (20) for the handling of very small positive values (in the order of 0.05 mJ m “). This would mean that the donor-acceptor component of all nolymer and blends would vanish. However, in our case, the negative values are not small enough to be considered as zero, nor are they similar enough: (ygy)"? decreases from

FIG. 3. Apolar surface free energy component of PVC, EVA, and their blends, using Geo,, (@), Geo, (O), DA, (A), and DA, (A) as calculation methods. We can also observe a greater difference between Geo,, and Geo, methods than between DA, and DAs With the donor- acceptor methods DA,,, or DA,, both Yev W and yey have similar values (Figs. 3 and 4). Therefore, the total surface free energy

FIG.4. Nondispersive/donor- acceptor surface free energy components of PVC, EVA, and their blends, using Geo,, (@), Geo, (OC), DA, considering (yey)? > 0 (a), DA, considering (yg,,)"? > 0 (A), DA,, considering (yg,)"” < 0 (mp, and DA, considering (yg) < 0 (C) as calculation methods. Solid Apolarity

FIG. 5. Plot used to determine EVA (—LI—) and PVC (:::O--:-) surface free energy components with the Geo,, calculation method.

FIG. 6. Apolarity fraction of PVC, EVA, and their blends, using Geo,, (@), Geo, (©), DA,, considering (yg) > 0 (a), and DA, considering (yey)? > 0 (A) as calculation methods.

Contact angle (°)* of Standard Liquids on EVA, PVC, and Their Blends * Average value reported with the corresponding standard deviation. > Value measured in the present study. ° From Ref. (23). TABLE 2

Surface Tension Components (mN m~') of Standard Liquids Used in This Study, from Ref. (20) * Used to solve Geo,, and Geo, methods. > Used to solve DA,, and DA, methods. ° By convention, from Ref. (22).

Surface Free Energy of PVC, Its Apolar (Dispersive/Lifshitz- van der Waals) Component and A polarity Fraction (x? = y4y/ysy; xtW = y&W/yoy), According to Different Calculation Methods, Compared with Literature Values TABLE 3

Nondispersive and Donor- Acceptor Surface Free Energy Components (mJ m~7) of PVC According to Different Calculation Methods, Compared with Literature Values TABLE 4

Nondispersive and Electron Donor- Electron Acceptor Surface Free Energy Components (mJ m~2) of PVC + EVA Blends According to Different Calculation Methods

Surface Free Energy (mJ m~7) of PVC + EVA Blends According to Different Calculation Methods

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