Polymer Science and Technology

Polyvinyl alcohol (PVOH) has been chemically modified by crosslink copolymerization of acrylic acid (AA) and acrylamide (AM) in aqueous solution of PVOH and finally crosslinking the copolymer with methylene bis acrylamide (MBA) and PVOH with glutaraldehyde to produce a full interpenetrating network (FIPN) membrane. Accordingly, three such fully crosslinked IPNs i.e. FIPN25, FIPN50 and FIPN75 have been synthesized with different mass ratio of PVOH:copolymer i.e. 1:0.25 (FIPN25), 1:0.50 (FIPN50) and 1:0.75 (FIPN75). These full IPN membranes were used for pervaporative dehydration of ethylene glycol (EG). All of these IPN membranes were characterized with various conventional methods like FTIR, mechanical properties, DTA and SEM. The performances of the membranes were evaluated in terms of sorption and pervaporative dehydration of EG. The IPN membranes were found to show preferential sorption and diffusion for water. Flux and water selectivity of these membranes were found to increase with increasing amount of copolymer in PVOH matrix. However, among the three membranes, FIPN75 were found to show the highest flux but lower selectivity for water while FIPN50 membrane showed optimum performance in terms of both flux and selectivity. Diffusion coefficient and plasticization interaction of water and EG through all the IPN membranes were determined using modified solution-diffusion model.

Poly vinyl alcohol (PVOH) membrane, was crosslinked with 2, 4 and 6 mass% of four different kinds of crosslinkers i.e. glutaraldehyde (GLU), oxalic acid (OA), dimethylol urea (DMU) and tetra ethyl ortho silicate (TEOS) to produce four different kinds of crosslinked PVOH membranes termed here as PVGLU, PVOA, PVDMU and PVTEOS membrane, respectively. These membranes were first used for pervaporative separation of azeotropic feed concentration of 87.7 mass% of isopropyl alcohol (IPA) in water. Among all of these membranes PVOH membrane crosslinked with 2 mass% (of PVOH) GLU i.e. PVGLU2 was found to show optimum flux and water selectivity (79.75 g/m 2 h and 45.23, respectively, at 40 °C) for separation of this IPA–water azeotropic mixture. This PVGLU2 membrane was further filled with 2, 4, and 6 mass% hydrophilic aluminosilicate filler to produce three different filled membranes i.e. F2PVGLU2, F4PVGLU2 and F6PVGLU2, respectively. These three filled membranes were used for separation of the same azeotro-pic IPA–water mixtures and F6PVGLU2 membrane was found to show optimum flux and selectivity (109.84 g/m 2 h and 72.71, respectively, at 40 °C). This F6PVGLU2 membrane crosslinked with 2 mass% glutaraldehyde and filled with 6 mass% aluminosilicate filler showing optimum flux and selectivity for azeotropic IPA–water mixture was used for dehydration of IPA using IPA–water mixtures containing 75.87–99.36 mass% IPA in water. All of the filled and unfilled membranes synthesized were also characterized by various conventional methods.

Pervaporation (PV) membranes have been made from some homopolymers like unplasticized polyvinyl chloride (UPVC), plasticized PVC (PPVC), polystyrene (PSTY) and blends of UPVC and PSTY in different compositions. The morphology of the blend membranes was characterized by scanning electron microscopy (SEM). Sorption and pervaporation of tetrahydrofuran (THF) with different concentrations (0.44–11.3 wt.%) in water were studied under various conditions like feed concentration, temperature etc. Permeation factor and activation energy as a function of feed concentration were also studied in this work. For 0.44 wt.% of THF in feed at 30 • C the used membranes were found to show the following trend of flux i.e. PPVC(13.18 g/m 2 h) > PSTY(10.38 g/m 2 h) > Blend-5(8.51 g/m 2 h) > UPVC(4.79 g/m 2 h) while separation factor showed the opposite trend i.e. UPVC(170.28) > Blend-5(127.80)> PSTY(89.81)> PPVC-5(81.65). UPVC with its close packed structure showed highest separation factor while presence of polar DOP loosen its matrix and thus, UPVC showed highest flux. PSTY contains some free void space because of its aromat-acity and showed lower selectivity than Blend-5 membrane. Among the various blend membranes, THF selectivity decreases while flux increases with increasing amount of PSTY and Blend-5 containing 5 wt.% styrene showed good balance of flux and selectivity.

Polyvinyl alcohol (PVOH) membrane, was modified both physically and chemically by incorporation of inorganic filler, sodium aluminosilicate and chemical crosslinking with maleic acid and glutaraldehyde. The change of morphology and crystallinity of PVOH by this physical and chemical modification was studied by FTIR, DSC, TGA, SEM and XRD. These membranes were evaluated in terms of its potential for dehydration of dioxane by preferential sorption and permeation using pervaporation (PV) technique. These membranes were cast in the laboratory by solution casting from the polymer and other additives. The performance of the unfilled (containing no filler) glutaraldehyde (GA) crosslinked PVOH-1 and maleic acid (MA) crosslinked PVOH-2 membranes were compared with filled (containing aluminosilicate filler) but GA crosslinked PVOH-3 and filled but MA crosslinked PVOH-4 membranes. The filled membranes were found to show higher flux and water selectivity. Among all the four used membranes, the MA crosslinked filled PVOH-4 membrane was found to show best results in terms of both water selectivity and flux.

Polyvinyl alcohol (PVOH) has been chemically modified by crosslink copolymerization of acrylic acid (AA) and hydroxyethylmethacrylate (HEMA) in aqueous solution of PVOH and finally crosslinking PVOH to produce a full interpenetrating network (IPN) membrane termed as PVAH. Accordingly, three such full crosslink IPNs membranes, i.e. PVAHI, PVAHII and PVAHIII containing varied weight ratio of PVOH and copolymer have been synthesized and used for pervaporative separation of methanol from its mixtures with toluene. For comparison, a conventional PVOH membrane crosslinked with glutaraldehyde has also been used for the same pervaporation study. The flux and selectivity of these IPN membranes were found to be much higher than the conventional glutaraldehyde crosslinked PVOH membrane. Among the three membranes, PVAHII with 50 wt% polyAH incorporation showed optimum performance in terms of flux and methanol selectivity.

Polyvinyl alcohol (PVOH) has been chemically modified by crosslink copolymerization of acrylic acid (AA) and hydroxyethylmethacrylate (HEMA) in aqueous solution of PVOH and finally crosslinking PVOH to produce a full interpenetrating network (IPN) membrane termed as PVAH. Accordingly, three such full crosslink IPNs, i.e. PVAHI, PVAHII and PVAHIII containing varied weight ratio of PVOH and copolymer along with crosslink PVOH (which has not been modified by copolymerization) have been synthesized and used for pervaporative separation of isopropanol (IPA)–water mixtures. Permeability and water selectivity of these membranes were found to increase with increasing amount of copolymer in PVOH matrix. However, among the three membranes, PVAHIII were found to show highest flux but lower selectivity while PVAHI membrane showed optimum performance in terms of both flux and selectiv-ity.

Styrene butadiene rubber (SBR) was efficiently cured (crosslinked) by using sulfur to accelerator ratio less than unity. This cured SBR was further compounded with carbon black filler (grade N330) with three different doses i.e., 5, 10, and 20 wt % of filler to form three different filled and crosslinked membranes, i.e., SBR5, SBR10, and SBR20. These filled rubber membranes and one unfilled but efficiently cured membrane, i.e. SBR0, were used for pervaporative removal of pyridine from its mixtures with water.

Natural rubber (NR) of grade RSS4 was efficiently cured (crosslinked) by using sulfur: accelerator weight ratio of 1 : 4. This was further compounded with high abrasion grade carbon black filler (grade N330) with three different doses, that is, 5, 10, and 20 wt % of rubber to form three different filled and crosslinked membranes designated as NR5, NR10, and NR20, respectively. These filled rubber membranes and one unfilled but efficiently cured membrane, that is, NR0, were used for pervapora-tive removal of low concentration of pyridine from water. The filled membranes were found to show higher pyridine selectivity but lower flux than the unfilled membrane. All of these membranes showed reasonably good range of flux and pyridine selectivity. Among all of the used membranes, NR5-filled membrane yielded high pyridine selectivity (122) with reasonable thickness normalized flux (2.2 kg m À2 h À1 ml) at 40 C for 0.5 wt % of pyridine in water.

Organoselective membrane was prepared from ethylene propylene diene monomer (EPDM) rubber. Crosslinked EPDM rubber was filled with 2, 4 and 6 wt% N330 carbon black filler to produce three different filled membranes designated as EPDMCV2, EPDMCV4 and EPDMCV6, respectively. These filled rubber membranes were used for pervaporative recovery of low concentration of pyridine from water. These filled membranes were characterized by crosslink density, SEM, XRD and mechanical properties. Sorption thermodynamics were discussed. Partial permeability, intrinsic membrane selectivity and diffusion coefficients of solvents were also determined. The filled membranes showed much higher pyridine selectivity than most of the membranes reported for similar system.

Polyvinyl alcohol(PVOH) has been chemically modified by crosslinking copolymerization of acrylic acid(AA) and hydroxyethylmethacrylate (HEMA) in aqueous solution of PVOH and finally crosslinking PVOH with glutaraldehyde to produce a full interpenetrating network(IPN) membrane. Accordingly, three such full crosslink IPNs i.e., PVAHI, PVAHII and PVAHIII have been synthesized with different weight ratio of PVOH:Poly (AA-co-HEMA) i.e., 1:0.25 (PVAHI), 1:0.50 (PVAHII) and 1:0.75 (PVAHIII). These IPN membranes have been used for pervaporative separation of MTBE-methanol mixtures. All the PVAH membranes were also characterized with various conventional methods like FTIR, mechanical properties, DSC and TGA. Permeability and methanol selectivity of these membranes were found to increase with increasing amount of copolymer in PVOH matrix. However, among the three membranes, PVAHIII were found to show the highest flux but lower selectivity for methanol while PVAHII membrane showed optimum performance in terms of both flux and selectivity.

Polyvinyl alcohol (PVOH) has been chemically modified by polymerizing hydroxyethylmethacrylate (HEMA) in aqueous solution of PVOH and finally crosslinking PVOH with glutaraldehyde to produce a semi-interpenetrating network (SIPN) membrane. Accordingly, three such SIPNs i.e., SIPNI, SIPNII, and SIPNIII were synthesized with different weight ratio of PVOH: HEMA i.e., 1:0.25 (SIPNI), 1:0.50 (SIPNII) and 1:0.75 (SIPNIII). These SIPN membranes were used for pervaporative dehydration of dioxane. PVOH without any chemical modification but crosslinked with the same amount of glutaraldehyde has also been used for this study for comparison. All the SIPN membranes were also characterized with various conventional methods like mechanical properties, DSC and TGA. Water permeability and water selectivity of the IPN membranes were found to be much higher than those of the crosslinked PVOH membrane which was not chemically modified. The permeability of the membranes were also found to increase with increase in the HEMA content in PVOH matrix.

Polyvinyl alcohol (PVOH) has been chemically modified by polymerizing hydroxyethylmethacrylate (HEMA) in aqueous solution of PVOH and finally crosslinking PVOH with glutaraldehyde to produce a semi-interpenetrating network (SIPN) membrane. Accordingly, three such SIPN membranes, namely SIPNI, SIPNII, and SIPNIII were synthesized with different weight ratio of PVOH: HEMA i.e., 1:0.25 (SIPNI), 1:0.50 (SIPNII), and 1:0.75 (SIPNIII). These SIPN membranes were used for pervaporative separation of methanol from its mixtures with toluene. The flux and methanol selectivity of these SIPN membranes were found to be much higher than conventional PVOH membrane crosslinked with glutaraldehyde. Among the three membranes, SIPNIII with 75 wt% HEMA incorporation shows optimum performance in terms of flux and methanol selectivity. The permeability of the membranes was also found to increase with increase in HEMA content in PVOH matrix. The novelty of the work lies in synthesis and characterization of a new kind of membrane and its potential for selective removal of methanol from its mixtures with toluene.

For the first time, guar gum-g-(acrylic acid-co-acrylamide-co-3-acrylamido propanoic acid) (GGAAAMAPA), a smart environment-friendly and sustainable interpenetrating polymer network hydrogel having unprecedented thermomechanical/physicochemical properties and excellent recyclability, has been synthesized by the grafting of guar gum (GG) and in situ adjunct allocation of 3-acrylamido propanoic acid (APA) during solution polymerization of acrylic acid (AA) and acrylamide (AM), using N,N'-methylenebisacrylamide (MBA) and potassium persulfate (PPS)–sodium bisulfite (SBS) as a crosslinker and a redox pair of initiators, respectively, through systematic multistage optimization of the constituents and the temperature of the reaction, for a comprehensive understanding of the individual/synergistic superadsorption mechanism during recycling of hazardous dyes, like 2,8-dimethyl-3,7-diamino-phenazine (i.e. safranine, SF), 3,7-bis(dimethylamino)-pheno-thiazin-5-ium chloride (i.e. methylene blue, MB) and sodium 4{[4(dimethylamino)phenyl]diazenyl}benzene-1-sulfonate (i.e. methyl orange, MO), along with the adsorptive exclusion of metal ions, i.e. M(II), like Pb(II), Cd(II) and Cu(II). The unambiguous in situ addition of APA, the grafting of GG into the AA-co-AM-co-APA (AAAMAPA) matrix and the superadsorption mechanism have been systematically determined by extensive analyses of FTIR, 1 H-/ 13 C-NMR, O 1s-/N 1s-/C 1s-/Pb 4f 7/2,5/2-/Cd 3d 5/2,3/2-and Cu 2p 3/2,1/2-XPS, TGA, DSC, XRD, FESEM, EDX, and storage/loss moduli and supported by computational measurements via density functional theory (DFT), along with the measurements of %gel content (%GC), pH at point of zero charge (pH PZC), %graft ratio (%GR) and network parameters of hydrogels. The prevalence of ionic (I) and variegated interactions , like monodentate (M), bidentate bridging (BB) and bidentate chelating (BC), between GGAAAMAPA and M(II), has also been rationalized by FTIR and fitting of kinetics data to the pseudosecond order model and by the measurement of activation energies of adsorption. The individual/interactive effects of cationic and/or anionic dyes have been rationally determined via extensive UV-Vis analyses at 1 : 1, 1 : 2 and 2 : 1 mole ratios of dyes and pH i = 2/9, interpreted through the appearance of the metachromic effect, dye-aggregates, π–π stacking interaction, diprotonated MO etc. The BET and Langmuir isotherms have fitted the best to MB and SF/Cd(II)/Cu(II)/Pb(II), respectively. Thermodynamically spontaneous chemisorption processes have shown the maximum adsorption capacities (ACs) of 27.06, 39.35, 40.55, 39.42, and 41.98 mg g −1 for MB, SF, Cd(II), Cu(II) and Pb(II), respectively, at 303 K, adsorbent dose = 0.025 g and initial concentration of dyes/M(II) = 30 ppm.

Pervaporation (PV) has been considered as one of the most active and promising areas in membrane technologies in separating close boiling or azeotropic liquid mixtures, heat sensitive biomaterials, water or organics from its mixtures that are indispensable constituents for various important chemical and bio-separations. In the PV process, the membrane plays the most pivotal role and is of paramount importance in governing the overall efficiency. This article evaluates and collaborates the current research towards the development of next generation nanomaterials (NMs) and embedded polymeric membranes with regard to its synthesis, fabrication and application strategies, challenges and future prospects.