Polymer Degradation

This study investigated the influence of iron concentration on the thermodynamic properties of syndiotactic polypropylene (sPP)/iron composites in the melt phase in a series of samples with varying iron content, ranging from 0 to 10% with a step of 2%. The HYSYS software was used to estimate molecular weight, critical temperature (T c), critical volume (V c), and eccentricity (E c). The results showed that all these properties changed as the iron content varied. The findings of this study confirmed that iron concentration has an impact on the mechanical and chain dynamic (microscopic) properties of polymer composites.

Oxygen: definition of the element specified to the periodic table, structure and characteristics. Fire: definition. Triangle of fire: Heat, Oxygen and Fuel. Classes A, B, C, D, E, F of fire. Interaction fire-oxygen: Oxygen does not react for itself, needs combustion and release heat energy. How foam extinguish a flame: process and types of foams. Detach oxygen from fire: split thermal chemical reactors, electric discharges, catalysts, deoxygenation, the oxygen reduction reaction, electrochemical method. Conclusions: stablish elements and halogens to detach oxygen from fire like Bromines, Fluorines. Secondly find out a foam-some active in the market-to isolate the flame from the environment (oxygen)

A BSTRA CT Nylon 6,6 polymers o[" different degrees of polymerisation have been characterised by ultra-violet (uv) absorption, fluorescence and phosphorescence emission spectroscopy, viscosiO' number and amine end-group balance and the data related to their subsequent thermal and photo-chemical stabilities. The latter, determined by the percentage change in viscosity number, clearly shows that in both cases polymer stability is markedly influenced by the final stages q(polymerisation under both steam and nitrogen atmospheres, the latter being the most detrimental. During both 0[ these processes the molecular weight increases, as indicated h)' an increase in viscosity number, as does the concentration O]~fluorescent andphosphorescent impurities and products absorbing uv at 294 nm. Extraction o['some q['these species hy 2-propanol results in a marked improvement in polymer photostability, implicating the involvement o[" these chromophores in initiation q[" photo-oxidation. Thermal degradation at 120C confirms the presence O[two types ~f.fluoreseent species. The.first is reactive, rapidly diffhses out ~ff the polymer and is associated with cyclic ~, fl-unsaturated carbonyl compounds; the second is non-volatile in-chain in O'pe, increases in concentration and is associated with ~-ketoimide structures. However, whilst correlations between the presence of light absorbing~luminescent carbonyl species is evident to 77

The studies on wollastonite reinforced recycled ABS (Acrylonitrile butadiene styrene) composites were investigated. Powder-based wollastonite with a particle size of 13 microns was mixed with recycled Acrylonitrile butadiene styrene in various proportions of wt.%. Recycled ABS was homogeneously mixed and composite was prepared using a twin-screw extruder and it was pelletized. specimens were prepared using the injection moulding process and mechanical properties like tensile strength as per ASTM D638 was carried out and the results were compared with the properties of recycled ABS. It was found that the recycled ABS with 10%,20%,30%,40% of wollastonite improved the tensile modulus and as well as fall in tensile strength and elongation at break.

Throughout its lifecycle, poly(ethylene terephthalate) (PET) undergoes significant degradation from long-term ultraviolet (UV) exposure, moisture, and shear forces, with these effects intensified during mechanical recycling. To characterize molecular degradation, PET samples subjected to UV aging in dry, marine, and freshwater environments, as well as diverse shear rates (90-450 s-1) are investigated using rheological analysis. Rheological analysis effectively distinguishes competing PET degradation effects under UV exposure from shear effects, highlighting crosslinking in dry conditions and hydrolytic chain scission under aqueous environments. Under shear, virgin PET shows an upshift in molecular weight (Mw) due to crosslinking reactions, while recycled PET experiences a drastic reduction in Mw owing to chain scission. When virgin PET goes through even a single shear-processing cycle, its crystallite size decreases by 70%, increasing crystallinity and releasing volatile by-products including aldehydes, acids, and alkanes that further compromise its recyclability. This study reveals that both UV and shear degradation significantly impair the mechanical properties of PET by reducing tensile strength and elongation at break by 55% and 99%, respectively. Linking degradation history to crystallization and mechanical behavior provides molecular-level insights.

The development of starch films containing natural antioxidants is one alternative of active packaging. Starch is a well-studied natural biopolymer that can be used for the development of biodegradable films because it presents a low cost, is easy to obtain and presents good ability to form films. Hibiscus sabdariffa, commonly known as hibiscus, roselle or red sorrel, is an annual herbaceous sub shrub that contains many types of biocompounds, including organic and phenolic acids. The aim of the present work was to determine the influence of electron beam irradiation on potato starch film containing hibiscus extract. The aqueous hibiscus solution was prepared by boiling for 3 min 1% w/ml dehydrated hibiscus flowers in 500 ml deionized water. The film forming solution was prepared by casting (5% potato starch, 3% glycerol as plasticizer and the hibiscus solution) and irradiated in a 1.5 MeV electron beam accelerator Dynamitron II (Radiation Dynamics Inc.), with doses of 0, 20, 40 and ...

Degradation of polyvinyl polymers (polyvinyl formal, polyvinyl alcohol, and polyvinyl acetate) by highenergy heavy ions was analysed with in situ mass spectrometry and infrared spectroscopy. Both at room temperature and at cryogenic temperature, the polymers are severely damaged by scission of side chains and the polymer backbone, releasing a large number of molecular fragments. Correlation of structural analysis of the damaged polymer and mass analysis of its volatile fragments gives plausible reaction mechanisms for the ion induced degradation. These are compared to thermal degradation. The differences found between the two degradation processes are due to the non-equilibrium character of the ion based process with its high electronic excitation and ionisation. The results are of practical relevance for applications of the polymers in devices of particle accelerators and space vehicles.

The production of an innovative, high-performance graphene-based polymer nanocomposite using cost-effective techniques was pursued in this study. Well-dispersed and uniformly distributed graphene platelets within a polymer matrix, with strong interfacial bonding between the platelets and the matrix, provided an optimal nanocomposite system for industrial interest. This study reports on the reinforcement of high molecular weight multimodal-high-density polyethylene reinforced by a microwave-induced plasma graphene, using melt intercalation. The tailored process included designing a suitable screw configuration, paired with coordinating extruder conditions and blending techniques. This enabled the polymer to sufficiently degrade, predominantly through thermomechanical-degradation, as well as thermo-oxidative degradation, which subsequently created a suitable medium for the graphene sheets to disperse readily and distribute evenly within the polymer matrix. Different microscopy techniq...

Increasing concern exists today about the preservation of our ecological systems. Most of today's synthetic polymers are produced from petrochemicals and are not biodegradable. The bio-based biodegradable products have raised great interest to apply in the Industrial applications. Bio-polymers are the polymer that is developed from living beings. The materials prepared from single biopolymer are shown under performance properties towards numerous industrial applications. It is worthwhile to explore the biopolymer composites to acquire desired qualities by blending the chosen biopolymers with required additives. Moreover, the bio-polymers have efficiency in conjugation with numerous additives, it is easy to obtain the properties of engineering materials in these composites. The mechanical properties are studied for series of biopolymer composites are prepared by blending of Carboxy Methyl Cellulose (CMC) with Poly Vinyl Alcohol (PVA).

The annual plastic production in Indonesia has exceeded 4.6 million tons and accumulated in the aquatic system. Polyethylene terephthalate (PET) and Polypropylene (PP) are the most widely used plastics in manufacture of packaging, fibres, and drinking bottles, etc. The degradation of these plastics to micro sizes leads to environmental threats, especially when the micro plastics interact with fresh water microorganism such as microalgae. Therefore, the study on the interaction between micro plastics and microorganisms is really important. The aim of this study was to evaluate the impact of microplastics on the growth of microalgae Spirulina sp and also to evaluate the contribution of microalgae Spirulina sp to the plastic degradation. The interaction between microalgae and microplastics was evaluated in a 1 L glass bioreactor contained microalgae Spirulina sp and PP and PET microplastics with the size of 1 mm at various concentrations (150 mg/500 mL, 250/500 mL and 275 mg/500 mL) for 112 days. The results showed that the tensile strength of micro plastic PET decreased by 0.9939 MPa/day while PP decreased by 0.1977 MPa/day. The EDX analysis of microplastics showed that the decreasing carbon in PET (48.61%) was higher as compared to PP (36.7%). FTIR analysis of Spirulina sp cells showed that the CO 2 evolution of cells imposed by PET microplastic was higher than imposed by PP. The growth rate of Spirulina sp applied by micro plastic was lower than the control and the increase of microplastic concentration significantly reduced the growth rate of algae by 75%. This research concluded that biodegradation has important role in the degradation process of plastic.

Facile synthesis of multifunctional organic/ inorganic materials is gaining importance. Present study deals with single step synthesis of PLLA/ZnO nanocomposite by ZnO nanoparticles catalyzed ring opening polymerization of L-lactide. The PLLA/ZnO nanocomposites with different ZnO concentrations were prepared and characterized by FT-IR, XRD, TEM, SEM, DSC, TGA, GPC, 13 C NMR and 1 H NMR etc. Uniform dispersion of ZnO nanoparticles of size 2-10 nm was achieved without any surface modification of the nanoparticles. The results showed that the as-synthesized PLLA/ZnO nanocomposites possessed thermal properties different from PLLA/ZnO nanocomposites synthesized by other techniques. The synthesized nanocomposite also showed excellent photochemical properties which were analyzed by studying decomposition of methylene blue dye.

Urea-formaldehyde (UF) resins are widely used over the world as an adhesive, principally in the civil construction, but its use leads to formaldehyde emissions when exposed to higher temperatures. In this way, the aim of this study was to evaluate the partial replacement of adhesives made of UF resin by sulfonated Kraft lignin, up to 30 mass%, and study its effects on the mechanism and on the kinetic/thermodynamic parameters of the thermal degradation, as well as on the thermal stability of the UF resin through thermogravimetric analysis and using isoconversional methods. The results showed that the lignin addition to the UF resin was beneficial, as there was synergy between the materials and verification of enhancement of thermal stability. Aside from the changes in the thermal behavior, the probable reduction of the emission of formaldehyde in the second step of degradation of the UF resin was also observed. These results indicate that the lignin can be used as a potential material to partially replace the UF resin.

ABSTRACTRadiation-induced modifications in polymeric materials are briefly reviewed. The attention is paid to the effect of ionizing radiation on the mechanical properties of polymers. The competition between several parallel degradation processes in the harsh conditions of the space environment is analyzed. The need for a complex analysis of the effect of polymeric materials in simulated space environments is demonstrated.

The effect of stainless steel, glass, zirconium and titanium enamel surfaces on the thermal and photooxidative toughening mechanism of dehydrated castor oil films deposited on these surfaces was investigated using different analytical and spectroscopic methods. The conjugated and non-conjugated double bonds were identified and quantified using both Raman spectroscopy and 1D and 2D NMR spectroscopy. The disappearance of the double bonds in thermally oxidised oil-on-surface films was shown to be concomitant with the formation of hydroperoxides (determined by iodometric titration). The type of the surface had a major effect on the rate of thermal oxidation of the oil, but all of the surfaces examined had resulted in a significantly higher rate of oxidation compared to that of the neat oil. The highest effect was exhibited by the stainless steel surface followed by zirconium enamel, titanium enamel and glass. The rate of thermal oxidation of the oil-on-steel surface (at 100 C, based on peroxide values) was more than five times faster than that of oil-on-glass and more than 21 times faster than the neat oil when compared under similar thermal oxidative conditions. The rate of photooxidation at 60 C of oil-on-steel films was found to be about one and half times faster than their rate of thermal oxidation at the same temperature. Results from absorbance reflectance infrared microscopy with line scans taken across the depth of thermally oxidised oil-on-steel films suggest that the thermal oxidative toughening mechanism of the oil occurs by two different reaction pathways with the film outermost layers, i.e. furthest away from the steel surface, oxidising through a traditional free radical oxidation process involving the formation of various oxygenated products formed from the decomposition of allylic hydroperoxides, whereas, in the deeper layers closer to the steel surface, crosslinking reactions predominate.

The formaldehyde (H2CO) observed in cometary atmospheres presents a so‐called “extended source,” meaning that its distribution in the coma cannot be explained by sublimation from the nucleus alone; a production inside the coma has to be included. Polyoxymethylene (formaldehyde polymers: (‐CH2‐O‐)n, also called POM) is sometimes evoked as a parent molecule for this extended source. This solid polymer on cometary grains could release gaseous formaldehyde through thermal and photolytic degradation. We have developed an experimental program in order to study the chemical reactions of degradation of POM by UV photolysis and heating. It provides identification of the degradation products and the determination of the photo degradation quantum yields or the thermal degradation kinetics. In this paper we present the improvements of our experimental setup and new measurements on the kinetics of gaseous formaldehyde production by thermal degradation of two types of commercial POM on a greater ...

This paper presents some preliminary results concerning the degradation of refractory nitrogenated polymers, which could be responsible for the CN extended source in comets. We are studying hexamethylenetetramine (HMT) and HCN polymers. Both compounds have been irradiated or heated to simulate the degradation processes they undergo in the cometary atmosphere. We show that, even if both compounds are quite stable under photolysis, the heating leads to a much more efficient degradation with the formation of HCN, NH 3 , and other heavier compounds. Moreover, the thermal degradation of HCN polymers appears to be more efficient than that of HMT. Thus, the HCN polymers seem to be better candidates for the CN extended source. We are now developing a new reactor to quantify the production of gaseous molecules and to detect in situ CN radicals.

The effects of reprocessing cycles on the structure and properties of isotactic polypropylene (PP)/Cloisite 15A (OMMT) (5 wt. %) nanocomposites was studied in presence of maleic anhydride-grafted-polypropylene (PP-g-MA) (20 wt. %) used as the compatibiliser to improve the clay dispersion in the polymer matrix. The various nanocomposite samples were prepared by direct melt intercalation in an internal mixer, and further they were subjected to 4 reprocessing cycles. For comparative purposes, the neat PP was also processed under the same conditions. The nanocomposite structure and the clay dispersion have been characterized by wide angle X-ray scattering (WAXS), transmission electron microscopy (TEM) and rheological measurements. Other characterization techniques such as Fourier transform infrared spectroscopy (FT-IR), tensile measurements, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) have also been used to evaluate the property changes induced by reprocessing. The study showed through XRD patterns that the repetitive reprocessing cycles modified the initial morphology of PP/OMMT nanocomposites by improving the formation of intercalated structure, especially after the fourth cycle. Further, the addition of PP-g-MA promoted the development of intercalated/ exfoliated silicate layers in the PP matrix after the second cycle. These results are in agreement with TEM observations indicating an improved silicate dispersion in the polymer matrix with reprocessing cycles displaying a morphology with both intercalated/exfoliated structures. The initial storage modulus (G 0 ) of the nanocomposites, which was highly improved in presence of PP-g-MA seems to be less affected by reprocessing cycles at very low frequencies exhibiting a quasi-plateau compared to pristine PP/OMMT and PP. In contrast, the complex viscosity was found to decrease for the whole samples indicating that the main effect of reprocessing was a decrease in the molecular weight. Moreover, the thermal and mechanical properties of the nanocomposites were significantly reduced after the first cycle; nevertheless they remained almost unchanged during recycling. No change in the chemical structure was observed in the FT-IR spectra for both the nanocomposites and neat PP samples after 4 cycles.

The average amount of micro and nanoplastics in the human body can be measured in grams, such concentrations cause some concern, especially in connection with the possible biological activity of nanosized particles of synthetic polymers.

The danger of nanoplastics can be provoked by many specific features, one of which is some proximity to the terpene structure of essential plant oils, which in turn partly provoke an immune response. The mechanism of such action can be due to some similarity of plastic radicals and terpenes with amino acid radicals, which can remotely mimic protein pyrogens.

It is also likely that nanoplastics can absorb fragments of pyrogenic molecules and mimic a biological foreign object. Together with the special properties of nanosized materials, such agents can pose some danger.

Microplastics can accumulate in the lungs, intermediate particles can penetrate more or less deeply into organs, tissues and cells and act at different levels, possibly creating a whole cascade of undesirable effects.

Due to the widespread use and monopoly position of plastics throughout the world, there may be some vacuum of criticism of these materials. As it was earlier in history with lead pipes, Teflon and fluorinated acids, tetraethyl lead and much more.

Today, high titers of micro and nanoplastics in the body are a difficult problem to solve, since there are no available and effective methods for removing plastic from the body. There are only two methods that allow you to get rid of excess plastic, this is prevention, not using plastic components and water purification, using clean food products, and cleaning the blood from plastic particles using special filters in outpatient settings.

The problem of polymers is not new in the annals of planet Earth. During the Carboniferous period, 358 million years ago, microorganisms decomposing fern stems faced a new challenge. The tall trees that appeared contained cellulose reinforced with lignin, and were extremely biostable, since the lignin framework was not subject to decomposition by the enzymatic systems of bacteria and fungi available at that time. Thus, millions of tons of biogenic carbon accumulated at the bottom of ravines and swamps, this process stopped when the enzymatic systems of fungi and bacteria evolved and it became possible to dealkylated phenols, oxidize pyrocatechines - oxidize aromatic nuclei, absorb condensed structures. Modern plastics repeated this incident with a new level of bio inertness, since plastics such as polyethylene, polypropylene and polyvinyl chloride are much more bioinert than lignin. Accordingly, it takes more time for the enzymatic system of microorganisms and fungi to adapt, for the complete processing of plastics as a bioavailable resource.

The effects of reprocessing cycles on the structure and properties of isotactic polypropylene (PP)/Cloisite 15A (OMMT) (5 wt. %) nanocomposites was studied in presence of maleic anhydride-grafted-polypropylene (PP-g-MA) (20 wt. %) used as the compatibiliser to improve the clay dispersion in the polymer matrix. The various nanocomposite samples were prepared by direct melt intercalation in an internal mixer, and further they were subjected to 4 reprocessing cycles. For comparative purposes, the neat PP was also processed under the same conditions. The nanocomposite structure and the clay dispersion have been characterized by wide angle X-ray scattering (WAXS), transmission electron microscopy (TEM) and rheological measurements. Other characterization techniques such as Fourier transform infrared spectroscopy (FT-IR), tensile measurements, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) have also been used to evaluate the property changes induced by reprocessing. The study showed through XRD patterns that the repetitive reprocessing cycles modified the initial morphology of PP/OMMT nanocomposites by improving the formation of intercalated structure, especially after the fourth cycle. Further, the addition of PP-g-MA promoted the development of intercalated/ exfoliated silicate layers in the PP matrix after the second cycle. These results are in agreement with TEM observations indicating an improved silicate dispersion in the polymer matrix with reprocessing cycles displaying a morphology with both intercalated/exfoliated structures. The initial storage modulus (G 0 ) of the nanocomposites, which was highly improved in presence of PP-g-MA seems to be less affected by reprocessing cycles at very low frequencies exhibiting a quasi-plateau compared to pristine PP/OMMT and PP. In contrast, the complex viscosity was found to decrease for the whole samples indicating that the main effect of reprocessing was a decrease in the molecular weight. Moreover, the thermal and mechanical properties of the nanocomposites were significantly reduced after the first cycle; nevertheless they remained almost unchanged during recycling. No change in the chemical structure was observed in the FT-IR spectra for both the nanocomposites and neat PP samples after 4 cycles.

J'adresse tout d'abord ma sincère gratitude à mon directeur de thèse Abdelaziz LALLAM, pour son encadrement, sa patience, sa compréhension ses encouragements, et la confiance qu'il m'a accordée. Ses remarques et ses conseils avisés m'ont été d'une aide précieuse pour me guider et mener à bien ce projet de recherche. Merci pour tes encouragements et ton soutien je te suis infiniment reconnaissante. Je tiens à remercier mon co-directeur de thèse Dimitri Ivanov pour sa contribution et son soutien. Mes reconnaissances s'adressent également au Pr. Lahcène BENCHEIKH, pour son aide, sa générosité et sa bonne-humeur. Je remercie les membres de jury, Pr. Boussad ABBES, Pr. Christine CAMPAGNE, Pr. Stéphane FONTAINE et Dr. Hayriye GIDIK, d'avoir accepté d'évaluer mes travaux de recherche et assister à ma soutenance de thèse. Je remercie également tout le personnel du Laboratoire de Physique et Mécanique Textiles (LPMT) et plus particulièrement à Christian PIDANCIER pour sa disponibilité et son aide dans la mise en place des dispositifs expérimentaux. Mes remerciements à Philippe BLONDEL pour le temps qu'il m'a consacré pour me former sur les différentes machines. Merci à Estelle KNOPF de m'avoir facilité le volet administratif. Merci à tous mes collègues et ex-collègues du LPMT Donya, Clément, Charles, Emna, Claire, Sedik, Elise, Floriane, Imen et Wafa pour leur agréable compagnie durant ces années de thèse. Je ne manquerais pas de remercier mes amis Oussama, Maedeh, Zack, Abdul Rahmane, Imane et Naïma qui étaient toujours là quand j'en avais besoin et d'avoir trouvé les bons mots pour me motiver. Enfin et surtout, merci à mon père de m'avoir toujours soutenue dans toutes mes décisions, de m'avoir encouragée à poursuivre mes études par une thèse doctorale et vivre cette expérience enrichissante. J'aurais bien aimé que tu sois là parmi nous, cher papa, pour partager avec nous la joie de cet accomplissement. Merci à ma mère de m'avoir transmis sa force et sa volonté pour prendre de l'élan et viser plus haut.

Many of the moving components in accelerator and target environments require lubrication. Lubricants in such environments are exposed to high fluxes of secondary radiation, which originates from beam interactions with the target and from beam losses. The secondary radiation is a mix of components, which can include significant fractions of neutrons. Lubricants are radiation-sensitive polymeric materials. The radiation-induced modifications of their structure reduce their service lifetime and impose additional facility maintenance, which is complicated by the environmental radioactivity. The study of the lubricants radiation resistance is therefore necessary for the construction of new generation accelerators and target systems. Nevertheless, data collected in mixed radiation fields are scarce. Nine commercial greases were irradiated at a TRIGA Mark II Research Reactor to serve for the construction of new accelerator projects like the European Spallation Source (ESS) at Lund (Sweden) and Selective Production of Exotic Species (SPES) at Legnaro, (Italy). Mixed neutron and gamma doses ranging from 0.1 MGy to 9.0 MGy were delivered to the greases. For an experimental quantification of their degradation, consistency was measured. Two of the greases remained stable, while the others became fluid. Post-irradiation examinations evidence the cleavage of the polymeric structure as the dominant radiation effect. Dose and fluence limits for the use of each product are presented. Apart from the scientific significance, the results represent an original and useful reference in selecting radiation resistant greases for accelerator and target applications.

The heterogeneous features of the oxidation of polypropylene in the amorphous region are consistent with infectious spreading from a small number of sites, such as catalyst residues. A stochastic model was developed for demonstrating the spatial and temporal development of oxidation from these sites. In this model, the probability of passing the infection from one site to an adjacent site could be used in place of conventional rate constants. The probability of spreading was assumed to be temperature dependent, and modelled with Arrhenius behaviour. Each site was given a predefined lifetime such that the maximum probability of spreading coincided with the maximum rate of oxidation at a particular site. This has enabled visualisation of the spatial development of oxidation within the amorphous region. The epidemiological fractions corresponding to the remaining (unoxidised) polymer, the dead (oxidised) polymer and the infectious (oxidising) polymer, were calculated and used to test the limitations of the simple epidemiological model.

A straightforward chemical polymerization process was used to create the polyaniline/LiClO 4 /CuO nanoparticle (PLC) nanocomposite, which was then exposed to varying doses of electron beam (EB) radiation and studied. The FESEM, XRD, FTIR, DSC, TG/DTA, and electrochemical measurements with higher EB doses showed clear changes. The FTIR spectra of the PLC nanocomposite showed variations in the C-N and carbonyl groups at 1341 cm-1 and 1621 cm-1 , respectively. After a 120 kGy EB dose, the shape changed from a smooth, uneven surface to a well-connected, nanofiber-like structure, creating pathways for electricity to flow through the polymer matrix. The EB irradiation improved the thermal stability by decreasing the melting temperature, and the XRD and DSC studies reveal that the decrease in crystallinity is attributed to the dominant chain scission mechanism. The enhanced absorption and red shift in the wavelength (from 374 nm to 400 nm) observed in the UV-Visible spectroscopy were caused by electrons transitioning from a lower to a higher energy state, with a progressive drop in the band gaps (E g) from 2.15 to 1.77 eV following irradiation. The dielectric parameters increased with the temperature and electron beam doses because of the dissociation of the ion aggregates and the emergence of defects and/or disorders in the polymer band gaps. This was triggered by chain scission, discontinuity, and bond breaking in the molecular chains at elevated levels of radiation energy, leading to an augmented charge carrier density and, subsequently, enhanced conductivity. The cyclic voltammetry study revealed an enhanced electrochemical stability at a high scan rate of about 600 mV/s for the PLC nanocomposite with the increase in the EB doses. The I-V characteristics measured at room temperature exhibited nonohmic behavior with an expanded current range, and the electrical conductivity was estimated, using the I-V curve, to be around 1.05 × 10-4 S/cm post 20 kGy EB irradiation.

Przedstawiono wyniki ilościowych badań metalograficznych rozmieszczenia włókien w ęglowych w kompozytach na osnowie stopu AlSi13Cu2. Na zbrojenie kompozytów za stosowano włókna pokryte warstwą niklu (0,25 μm) HTA 5M81 firmy TENAX o średnicy 7,5 μm i długości 5 mm. Badaniom poddano odlewy kompozytowe o udzi ale objętościowym fazy zbrojącej 5, 10 i 15%. Kompozyty wytwarzano metodą mieszania mechanicznego, a nast ępnie odlewano na maszynie ci śnieniowej zimnokomorowej, poziomej DMKh160. Oceny rozmieszczenia fazy umacniającej w osnowie siluminu dokonano w oparciu o wskaźnik niejednorodości struktury ( ν). Wskaźnik ten kształtował się na poziomie 0,12÷0,22, co dla materiałów heterofazowych stanowi niską wartość i oznacza stosunkowo równomierne rozmieszczenie w objętości osnowy. Ujawniono takŜe tendencję, Ŝe jednorodność strukturalna wzrasta proporcjonalnie do udziału objętościowego włókien. Stwierdzono, Ŝe preparacja powierzchni włókien warstwą Ni polepsza ich zwil Ŝanie i ułatwia proces...

AAM) is copyrighted and published by Elsevier. It is posted here by agreement between Elsevier and the University of Turin. Changes resulting from the publishing process -such as editing, corrections, structural formatting, and other quality control mechanismsmay not be reflected in this version of the text. The definitive version of the text was subsequently published in Polymer Degradation and Stability 95 (2010) 756-762 You may download, copy and otherwise use the AAM for non-commercial purposes provided that your license is limited by the following restrictions: (1) You may use this AAM for non-commercial purposes only under the terms of the CC-BY-NC-ND license.

AAM) is copyrighted and published by Elsevier. It is posted here by agreement between Elsevier and the University of Turin. Changes resulting from the publishing process -such as editing, corrections, structural formatting, and other quality control mechanismsmay not be reflected in this version of the text. The definitive version of the text was subsequently published in Polymer Degradation and Stability 95 (2010) 756-762 You may download, copy and otherwise use the AAM for non-commercial purposes provided that your license is limited by the following restrictions: (1) You may use this AAM for non-commercial purposes only under the terms of the CC-BY-NC-ND license.

PhotoDSC has been applied to follow the global kinetics of chain scissions resulting from the UV light irradiation or from the thermal degradation of a high molecular weight PEO (4x10 6 g.mol -1 ). Infrared spectroscopy, XRD measurements and rheology experiments were performed to evidence the occurrence of chain scissions... Melting energy was used as a tool to quantify the extent of the degradation. It was found that the chain scissions reaction follows a first order kinetic law for both photo and thermal degradation. The activation energies were found identical in both cases (41 kJ.mol -1 ) whereas the degradation rate was higher in the case of UV irradiation than in the case of thermoageing

Cadmium adi pate and cadmium oxalate suitable for usc as stabilizer for vinyl polymers were prepared by metathesis in aqueous alcohol solutions. The thermal stabi lity of the carboxylates was measured grav imetri cally at 443. 453 and 463 K. Both cadmium adipate and cadmium oxalate showed less than 20% in wei ght indi catin g that th ey arc re lativel y stable within thi s temperature range. Kinetic studies of the thermal decomposition of the dicarbox ylates showed that the initi al rate constant for the decomposi tion of cadmium adi pate is hi gher th an th at of cadmium oxalate and they are of the order of magnitude of 10-2 min-1 • The enth alpy, entropy and fre e energy of acti vation fo r the decompos iti on of the metal dicarboxylates were also determined.

The thermoxidative (oven ageing) and photooxidative degradation of polypropylene films (2OOpm thick) containing a range of antioxidants and light stabilisers, together with anatase and rutile titanium dioxide pigments are studied by Fourier Transform infra-red (FTIR) spectroscopy. Rates of thermal and photooxidative degradation are determined by measuring the formation of non-volatile carbonyl and hydroperoxide oxidation products which absorb in the infra-red region of the spectrum with maxima at 1710 and 3410 cm-', respectively. During photooxidation the rutile pigment is synergistic in stabilisation with phenolic antioxidants and hindered piperidine stabilisers (HAS) but antagonistic with benzotriazole and benzophenone absorbers. In the case of anatase marked autocatalytic oxidation is observed giving strong antagonistic effects. With mixed antioxidant/stabiliser combinations, synergistic stabilisation is not significantly influenced by rutile but markedly antagonised by the presence of the anatase pigment. The most effective light stabiliser in retarding the catalytic oxidative effect of anatase is the polymeric HAS, Chimassorb 944. During thermal oxidation the polymeric HAS exhibit strong thermal antioxidant activity compared with the non-polymeric HAS. Both antioxidants and the benzophenone absorber are strongly antagonistic with rutile while the HAS and benzotriazole stabilisers display weak synergism. The anatase strongly accelerated and catalysed the thermal stabilisation effects with all the stabilisers and antioxidants. For the stabiliser combinations, the HAS are more effective at inhibiting oxidative degradation than the absorbers in the presence of both pigment types. The thermal catalytic effects of anatase are strongly suppressed by antioxidant/stabiliser combinations.

Blends containing 3 wt % low molecular weight polybutadiene (PB) in a polystyrene (PS) matrix were prepared via a precipitation technique that yielded spherical, submicron pools of PB. Tensile specimens made from these blends were then irradiated with high energy electrons in air at dose levels from 0 to 70 Mrads. The blends, which previously showed high levels of toughness approaching that of high impact PS, lost all enhanced toughness when irradiated above 10 Mrads. Analysis of pure PS specimens irradiated over the dose range from 0 to 45 Mrads showed no appreciable dependence of mechanical behavior on dose level. Molecular weight studies of the polybutadiene demonstrated only a very modest increase in molecular weight in the dose range studied here; therefore, reduced mobility of the PB in the blends was not the reason for the dramatic drop in toughness with radiation dose. It was concluded that radiation‐induced scission of the PS near the surface of the blends resulted in a sig...

Although chitosan (CS) is used in many industries because of its low cost, biodegradability, nontoxic, antibacterial, and antioxidant qualities, it lacks sufficient mechanical and barrier properties. Biodegradable polymers based on CS, polyvinyl alcohol (PVA), and starch (S) were prepared at various ratios (1/3/6 and 1/5/4) via a blending polymerization process in the presence of water as the solvent and glacial acetic acid as the catalyst. The obtained biodegradable polymers were characterized via FTIR, TGA, SEM, and mechanical tests. The biodegradable polymers were mixed with rice straw and carbon black to study the effects of rice straw and carbon black on the physicomechanical properties of the biodegradable polymer films, including viscosity, tensile strength, elongation, and contact angle. The incorporation of rice straw and carbon black into a polymer blend significantly enhanced the physical and mechanical properties while also boosting their biodegradability by 36% and 15%, respectively, due to their biological activity. Notably, the CS/PVA/S blend with a ratio of 1/5/4, combined with rice straw, emerged as the standout performer. It exhibited superior mechanical strength and the shortest degradation time, outperforming the CS/PVA/S blended with a ratio of 1/3/6 mixed with carbon black. According to these findings, the biodegradable polymers became more soluble as the temperature increased from 30 to 45 • C.

This paper presents the results of the studies on changes of selected quality parameters of hydrobiodegradable aliphatic-aromatic copolyester (AAC). Radiation treatment was performed at the Institute of Nuclear Chemistry and Technology in Warsaw, using cobalt gamma-ray sources "Issledovatel" (dose rate 0.389 Gy/h) and "GC 5000" (8.5 Gy/h). The material was subjected to the impact of radiation doses of 5, 10, 20 and 40 kGy. Selected parameters of the packaging material, important from the standpoint of a potential application, have been studied: gaseous products of radiolysis, strength parameters in accordance with PN EN ISO 527-3, global migration PN-EN-1186-1:2002, FT-IR analysis using PCA method, contact angle measurement using the drop shape method. The results have demonstrated that there is no significant influence of ionizing radiation on AAC film parameters. Correlation between doses applied and values of measurements has not been found.

The thermal and flammability properties of polypropylene/multi-walled carbon nanotube, (PP/MWNT) nanocomposites were measured with the MWNT content varied from 0.5 to 4% by mass. Dispersion of MWNTs in these nanocomposites was characterized by SEM and optical microscopy. Flammability properties were measured with a cone calorimeter in air and a gasification device in a nitrogen atmosphere. A significant reduction in the peak heat release rate was observed; the greatest reduction was obtained with a MWNT content of 1% by mass. Since the addition of carbon black powder to PP did not reduce the heat release rate as much as with the PP/MWNT nanocomposites, the size and shape of carbon particles appear to be important for effectively reducing the flammability of PP. The radiative ignition delay time of a nanocomposite having less than 2% by mass of MWNT was shorter than that of PP due to an increase in the radiation in-depth absorption coefficient by the addition of carbon nanotubes. The effects of residual iron particles and of defects in the MWNTs on the heat release rate of the nanocomposite were not significant. The flame retardant performance was achieved through the formation of a relatively uniform network-structured floccule layer covering the entire sample surface without any cracks or gaps. This layer re-emitted much of the incident radiation back into the gas phase from its hot surface and thus reduced the transmitted flux to the receding PP layers below it, slowing the PP pyrolysis rate. To gain insight into this phenomena, thermal conductivities of the nanocomposites were measured as a function of temperature while the thermal conductivity of the nanocomposite increases with an increase in MWNT content, the effect being particularly large above 160 8C, this increase is not as dramatic as the increase in electrical conductivity, however.

In this paper we studied the way in which the surface morphology and the bulk properties are modified when some porous polymer membranes, obtained from poly (hydroxy-urethane)(PHU) and poly (vinyl alcohol)(PVA) were treated with gamma radiation. When ...

A series of experiments was carried out to develop an additive package for HDPE blown films. The evaluation of the results yielded interesting correlations relating the colour of the polymer to its chain structure and to the properties of the films. Additional experiments proved that all reactions are related to each other. The discolouration of the polymer could be described by simple first order reaction kinetics and a linear correlation was found between stability and a quantity calculated from the kinetic model. The reaction of the vinyl functionality of the polymer seems to be related to the changes in its rheological properties. In spite of the good general correlations found, some details remained unexplained and need further investigation.

SEBS block copolymers were treated under mild conditions in an ozone atmosphere, producing very slightly chemically-modified surfaces. The thermal stability was analysed by chemiluminescence and related to morphological changes observed by AFM. The intrinsic thermal stability was diminished by ozone exposure, but the oxidation induction times were delayed which indicates an enhancement of thermal stability under oxidative conditions. Also, chemiluminescence analysis showed the presence of a typical orderedisorder transition at temperatures around 120 C. Two different sets of samples which showed different morphological patterns were imaged by AFM. The effects of micro-domain separation and inter-domain structure on thermal properties are discussed and explained by a coarsening of the internal interface induced by ozone. A detailed 2D Fourier transformed analysis of AFM images allowed us to identify a regular wrinkled nano-pattern induced by uniaxial strain combined with ozone treatment, offering new opportunities in applications ranging from organic electronics to bio-patterning.

The aim of this study was to prepare and evaluate both HA/bioactive glass and resorbable polymer PGLA/bioglass composites. The gel-derived bioglasses were added to HA and PGLA matrix in order to modify mechanical properties and improve bioactivity of obtained composite materials. We have developed two different composites made of hydroxyapatite (HA) and gel derived bioglasses designated S2 (80%mol. SiO 2 , 16%mol.CaO, 4%mol.P 2 O 5 ) or A2 (40%mol. SiO 2 , 54% mol.CaO, 6%mol.P 2 O 5 ). Concentration of added bioglasses were: 10% and 50 wt.%. Scanning electron microscopy and X-ray diffraction were used to characterize microstructure and phase composition of obtained materials. The elastic properties of HA/bioglass composites (Young modulus E) were analyzed with the use of pulse ultrasonic technique. The bioactivity of composites was assessed by determining the changes of surfaces morphology of composites after soaking in simulated body fluid (SBF) for 7 and 14 days (test in vitro in SBF). We have determined that 10%wt. addition of A2 ( E=12,24GPa) and 50wt. % addition of S2 (E=15,54GPa) to the HA matrix results in higher Young's modulus of composites in comparison to pure hydroxyapatite ( E=9,03GPa). The rate of Ca-P-rich layer formation in SBF was higher for HA/bioglass composites containing A2 compared to the composites containing S2 bioglass. Moreover, PGLA/bioglass composites were manufactured in the form of foils by solvent casting of the mixtures: dissolved PGLA and bioactive glass A2 and S2 particles. Composites containing 12%, 21% and 33%vol. of bioactive glass were manufactured. Mechanical properties (R m , E) of composites were evaluated as well as in vitro SBF test was conducted at 5 and 10 days periods times of incubation in SBF. The results of tensile tests show that the addition of bioactive glass increases both tensile strength and Young's modulus of the composites. Rapid formation of apatite-layer on composite surface after incubation in SBF indicates high bioactivity of these materials.

Synthetic plastics are pivotal in our current lifestyle and therefore, its accumulation is a major concern for environment and human health. Petroleum-derived (petro-)polymers such as polyethylene (PE), polyethylene terephthalate (PET), polyurethane (PU), polystyrene (PS), polypropylene (PP), and polyvinyl chloride (PVC) are extremely recalcitrant to natural biodegradation pathways. Some microorganisms with the ability to degrade petro-polymers under in vitro conditions have been isolated and characterized. In some cases, the enzymes expressed by these microbes have been cloned and sequenced. The rate of polymer biodegradation depends on several factors including chemical structures, molecular weights, and degrees of crystallinity. Polymers are large molecules having both regular crystals (crystalline region) and irregular groups (amorphous region), where the latter provides polymers with flexibility. Highly crystalline polymers like polyethylene (95%), are rigid with a low capacity...

The formation mechanism of secondary microplastics (issued from larger plastics) in the oceans is still an open question. However, it is commonly accepted that the chemical degradation undergone by polymers leads to their embrittlement and finally fragmentation. In the marine environment, polymers are subjected to different types of chemical and physical degradations. This study focuses on the coupling between two types of chemical degradation: hydrolysis and oxidation in the case of polyamide 6. To do so, polymer films (250 µm thick) were aged for durations up to 2 years and then characterized at the molecular scale using FTIR and at the macromolecular scale using mainly DSC and GPC. Results clearly show the existence of a chemical coupling between oxidation and hydrolysis in polyamide 6 that induces a large increase in the chain scission rate. The degradation rate is indeed 80 times faster in water with oxygen than in water without oxygen. Then, a two-stage ageing condition (first thermal oxidation in dry air and then hydrolysis in water without oxygen) was used to further study the nature of the coupling. These results have shown for the first time that a strong interaction occurs between thermal oxidation and hydrolysis of polyamide materials at the macromolecular scale. Highlights ► Chain scission is much faster in water in presence of oxygen compared to water without oxygen. ► An increase in humidity level of air leads to an increase in degradation rate in polyamide. ► A strong chemical coupling exists between oxidation and hydrolysis in polyamide 6.

Grevillea robusta, a Kenyan wood species of low durability was heat treated under inert atmosphere in laboratory conditions at temperatures between 220 and 250 C. Modulus of rupture (MOR) and modulus of elasticity (MOE) were determined for different heat treatment conditions. MOR and MOE reduced with increase in heat treatment weight loss. MOE reduced insignificantly for weight loss less than 16% while reduction of MOR was more significant. For a fixed heat treatment temperature by varying the treatment duration, sugar content was analysed by HPLC after acidic hydrolysis and Klason lignin was determined. The amount of sugars other than glucose decreased with treatment time and was near zero after 7 h, while lignin quantity increased gradually. Wood acidity determined by titration decreased after heat treatment indicating degradation of uronic acids present in hemicelluloses. Chemical modifications of wood components were determined by CP/MAS 13 C NMR analysis. Spectra indicated significant degradation of hemicelluloses. Increase of treatment duration resulted in the appearance of new signals, particularly obvious on spectra of samples treated for 15 h, attributed to carbonaceous materials involved in char formation.

Significant improvement in biodegradation performance has been demonstrated arising from the reduction of cytotoxicity provided by the sequestering of 4-nitrophenol (4NP) within Hytrel polymer beads added to a two-phase partitioning bioreactor (TPPB) operating in sequencing batch reactor (SBR) mode. This reduced toxicity is particularly apparent as the feed substrate concentration is increased; in fact it was shown that at a feed of 1000 mg/L 4NP, the inhibitory effect of the substrate completely prevents degradation from occurring in a singlephase system, whereas at only a 5% polymer loading, rapid and compete biodegradation is achieved. Different polymer/ aqueous phase ratios were used to detoxify varying feed concentrations, and degradation rates were enhanced through the use of increased polymer loadings. As demonstrated in oxygen uptake experiments, the addition of polymers also reduces the maximum demand for oxygen, relative to single-phase operation, and smoothes the demand for oxygen throughout the degradation process. Polymer regeneration has also been further characterized by quantifying the number of methanol washes required to achieve satisfactory 4NP residuals, and the addition of a small amount of cosolvent has been shown to dramatically increase the rate of bioregeneration to produce beads ready for reuse.

Complex cure kinetics involved in the elaboration of organic/inorganic hybrid silicate nanocomposites based on diglycidyl ether of bisphenol A (DGEBA), 1,3-phenylenediamine (m-PDA), and modified montmorillonite (MMTm) clay have been studied. An advanced isoconversional method has been applied to nonisothermal data in order to evaluate cure kinetic parameters. A new method based on nonlinear optimization was proposed to compute nonisothermal kinetic parameters avoiding complex optimization techniques. The objective is to obtain kinetic parameters rather than modeling values in order to give more insight into the elucidation of complex cure mechanisms. Key kinetic parameters of cure have been computed according to this method. It appears that the reaction mechanism changes if MMTm is added to the curing system. The results reveal an increase of the efficiency of collisions in presence of MMTm at the beginning of the cure and an increase of the frequency of diffusion jumps at the later stage of the reaction.

RESUMEN Se sintetizaron poliuretanos (PU) de polioles obtenidos del aceite de higuerilla y almidon de yuca, y metil difenil diisocianato (MDI) y/o isoforona diisocianato (IPDI). Estos polioles fueron producidos mediante dos rutas: la primera, fue la obtencion de una mezcla fisica entre al aceite y polioles derivados por transesterificacion del aceite con pentaeritritol, y el almidon denominada suspension. La segunda, fue la modificacion quimica del almidon por glucosilacion utilizando etilenglicol y glicerol; y posterior transesterificacion con el aceite de higuerilla y polioles derivados. El indice de hidroxilo, gravedad especifica y viscosidad de los polioles fueron determinados. Se determinaron las propiedades mecanicas, la resistencia al ataque quimico y propiedades termicas de los materiales producidos; la morfologia fue estudiada por microscopia electronica de barrido (SEM). Los resultados muestran que los PU obtenidos a traves de la modificacion quimica tienen mejores propied...