Water-ethanol separation by pervaporation through plasma graft polymerized membranes

Water-ethanol permselective membranes were prepared through plasma graft polymerization of acrylic acid, methacrylic acid, and acrylamide onto porous polypropylene film. In these membranes, the functions of permseparation and mechanical properties are shared respectively to the graft polymer layer and the substrate film. Higher permselectivity of water is achieved with the ionization of the acrylic acid and the methacrylic acid-grafted membranes. Permselectivity is dependent on the degree of grafting, and it is necessary to fill the pores of substrate film with graft polymers. Permseparation of water was investigated with respect to the feed ethanol concentration and also to the temperature dependence.     

Photografting of acrylic monomers on polystyrene support

Polystyrene xanthates, prepared through the reaction of chloromethylated polystyrene resins with potassium O-ethyl xanthate, have been used for the photografting of acrylic monomers. Monomers such as acrylamide, acrylic acid, methacrylic acid, and methyl methacrylate were grafted onto the xanthate polymers on irradiation with a 450 W medium-pressure mercury lamp (Hanovia). Among these monomers, the maximum graft efficiency was obtained for methyl methacrylate. The effect of cross-link density of the xanthate polymer on the percentage graft yield was also studied. Scanning electron microscopic studies have shown that appreciable grafting has taken place on the surface of the polymer in a uniform manner. © 1992 John Wiley & Sons, Inc.     

Radiation-Induced graft copolymerization of methacrylic acid onto polypropylene fibers. V. Mechanical properties

Mechanical properties of polypropylene-g-poly(methacrylic acid) fibers, prepared by graft copolymerization of methacrylic acid onto polypropylene fiber using simultaneous gamma ray irradiation technique, were evaluated. In general, an improvement in the mechanical behavior of the polypropylene fiber by grafting was observed. Denier and initial modulus of the fiber showed a linear increase with the percent graft, and elongation showed an opposite trend. The results have been explained in terms of reinforcing effect of poly(methacrylic acid) grafts and reduction in the segmental mobility of the polymeric chains. Tenacity also increases up to certain graft level, beyond which a sharp decrease occurs, probably due to the influence on the compactness of the macromolecular chains with the further grafting.     

Studies on preparation and ion-exchange properties of weakly acidic cation exchange fiber by preirradiation-induced graft copolymerization with electron beam

Weak acidic cational exchange fibers were obtained by means of preirradiation-induced graft copolymerization of methacrylic acid, acrylic acid, and diglycol acrylate onto polypropylene nonwoven fabric with electron beam. Effects that influence grafting and the exchange adsorptive property of the ion-exchange fibers obtained toward transition and rare-earth metal ions have been investigated. © 1994 John Wiley & Sons, Inc.     

Graft copolymerization of methacrylic acid onto isotactic polypropylene by radiochemical methods

Graft copolymerization of methacrylic acid onto isotactic polypropylene has been studied in water–methanol medium using γ-rays as the source of initiation. Graft copolymerization has been conducted by (1) mutual irradiation, (2) preirradiation, and (3) double irradiation methods. All of the reaction parameters that seem to influence grafting have been studied, and the optimum conditions leading to maximum percentage of grafting have been evaluated. A plausible mechanism for radiation-induced grafting of methacrylic acid onto polypropylene has been suggested, and the results have been explained on the basis of the proposed mechanism. A comparative study of graft copolymerization by different radiation methods has been made, and it was observed that the preirradiation method affords the best results. Evidence of grafting has been obtained from differential scanning calorimetric analysis and the dyeing behavior of the grafted material. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 143–152, 1998     

Radiation grafting of acrylic and methacrylic acids onto poly(tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride) TFB films

A study has been made for the preparation of membranes by the direct radiation grafting of acrylic and methacrylic acids onto poly(tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride) TFB films. The appropriate reaction conditions were selected under which the graft polymerization was carried out successfully. In this grafting system, ammonium ferrous sulfate (Mohr's salt), ferric chloride, and cuppric chloride were used as inhibitors to minimize the homopolymerization of acrylic acid and methacrylic acid. Also, the effect of monomer concentration on the rate of grafting was investigated. The dependence of the grafting rate on monomer concentration was found to be of the order of 1.1 and 1.0 for acrylic acid and methacrylic acid, respectively. This grafting system was proceeded by a front mechanism. Some selected properties of the grafted films such as swelling behavior, dimensional change, and mechanical and electrical properties were investigated. It was found that the grafted membranes possess good hydrophilic properties that may make them promising in some practical applications. © 1993 John Wiley & Sons, Inc.     

Synthesis and characterizing a novel polymeric flocculant based on amylopectin-graft-polyacrylamide-graft-polyacrylic acid [(AP-g-PAM)-g-PAA]

The article highlights the development of a new generation of polymeric flocculant by grafting binary monomer mixture of acrylamide and acrylic acid onto a natural polymer—amylopectin [(AP-g-PAM)-g-PAA]. Primary graft copolymerization of acrylamide onto AP and binary graft copolymerization of acrylic acid onto AP-g-PAM was accomplished in 84 and 91?% grafting efficiency (% GE) using potassium persulphate as initiator. The influence of initiator concentration onto % GE was investigated. The developed binary graft copolymer was characterized using various materials characterization techniques like viscometry, elemental analysis, FTIR spectroscopy, ¹³C NMR spectroscopy, molecular weight and radius of gyration by Zimm plot using SLS analysis. Flocculation studies reveal that the synthesized binary grafted product is an efficient flocculant, which is because of its higher molecular weight and radius of gyration.     

Radiation-induced graft copolymerization of mixtures of styrene and acrylamide onto cellulose acetate. IV. Studies on some physical properties and structural characterization by means of scanning electron microscopy

Binary mixtures of monomers, e.g., styrene and acrylamide in 1:1 methanol:water solution, were grafted onto cellulose acetate film by taking recourse to preirradiation grafting procedure. The surface modification of the films due to grafting was examined by means of scanning electron microscopy. The mechanical properties, e.g., tensile strength elongation at break, and elasticity as well as water vapor permeability of the grafted films, were investigated. In the case of ungrafted films or when acrylamide was grafted to a low extent, the film surfaces were smooth and hence were not modified to any significant extent. But when acrylamide was grafted appreciably, or when styrene was grafted singly or in binary mixture with acrylamide, the surfaces were found to be covered with fibrils. The pattern of the surface modification also changes with the increase of the extent of grafting. The observed properties of the grafted films were explained on the basis of the electron microscopic results.     

Radiation-Induced graft copolymerization of methacrylic acid onto polypropylene fibers. IV. Thermal behavior

Thermal behavior of polypropylene-g-poly(methacrylic acid) fibers prepared by graft copolymerization of methacrylic acid onto polypropylene fibers, using simultaneous-irradiation technique, was evaluated by thermogravimetric analysis, differential scanning calorimetry, and limiting oxygen index measurements. In general, the thermal properties of polypropylene fiber were markedly improved by the grafting of methacrylic acid. The inherent crystallinity of polypropylene, as deduced from DSC, did not show any change in the grafted fibers, suggesting that the grafting occurs in the amorphous region, without disrupting the crystalline part of the polymer. The LOI of grafted fibers showed an increase over the original fiber.     

Graft copolymerization of vinyl monomers onto chitin with cerium (IV) ion

Graft copolymerization of vinyl compounds onto chitin was studied, and an efficient and reproducible procedure has been established, cerium (IV) being used as the initiator. The reactions with acrylamide and acrylic acid onto powdery chitin were carried out under various conditions to elucidate the polymerization behavior in terms of grafting percentage. The amount of cerium (IV) affected the polymerization most strikingly, and grafting percentages showed maxima with suitable amounts of initiator for both the monomers. As a solvent water proved to be superior to aqueous nitric acid except the reaction with a small amount of initiator. Under appropriate conditions, around 240 and 200% grafting percentages were achieved for acrylamide and acrylic acid, respectively. The resulting graft copolymers showed much improved affinity for solvents and hygroscopicity compared to the original chitin.     

Graft copolymerization of hydrophilic monomers onto irradiated polypropylene fibers

A method of graft copolymerization of hydrophilic monomers, such as 1-vinyl-2-pyrrolidone, acrylonitrile, acrylic acid, and acrylamide, onto irradiated polypropylene fibers has been studied. γ ray as well as electron beam were employed for the irradiation processes. Graft-copolymerization kinetics and the properties of grafted fibers have been investigated. Moisture regain, dyes absorption, and melting point of the grafted fibers were found to increase with the increasing of the degree of grafting. Polypropylene for 1-vinyl-2-pyrrolidone grafted fibers showed excellent dye absorption for almost all kinds of dyes such as direct, basic, acid, reactive, disper, and naphthol dyes. However, for polypropylene acrylic acid grafted fibers, the colorfastness to washing was found to be unsatisfactory. The colorfastness to washing for polypropylene 1-vinyl-2-pyrrolidone grafted fibers was found to be fairly good for certain types of dyes such as vat and naphthol dyes.     

Grafting of polypropylene fibers. I. Radiation grafting of vinyl monomers,dyeing, and hydrophilic characteristics of the grafted polymer

Radiation-initiated grafting of methacrylic acid, acrylonitrile, and vinyl acetate on polypropylene fibers and the moisture content and dyeing characteristics of the grafted fibers have been reported. The extent of grafting with methacrylic acid is quite large when compared to acrylonitrile and vinyl acetate. The grafted fibers show an increase in moisture content with increase in the amount of graft. In general, the dyeability with disperse dyes increases due to grafting. In the case of cationic dyes, the polypropylene fibers grafted with methacrylic acid and acrylonitrile alone could be dyed.     

Performance evaluation of synthesized acrylic acid grafted polypropylene within CaCO3/polypropylene composites

A polymeric coupling agent acrylic acid grafted polypropylene (AAgPP) was synthesized and its efficiency in CaCO₃/PP composite was investigated. The grafting of acrylic acid monomer (AA) onto polypropylene was performed using an internal mixer. The effect of peroxyde, acrylic acid monomer content, temperature and RPM was studied. A grafting reaction between the polypropylene and the acrylic acid was evidenced through FTIR, UV, DSC and MFI testing. The highest grafting yield was obtained at 0.85 phr peroxide and 5 phr acrylic acid. The selected mixing temperature was 200°C, the rotor speed 150 rpm and the residence time 5 min. The obtained coupling agent (AAgPP) was used with 30 wt% CaCO₃ filled polypropylene. Strong interactions with the composite were observed. The effect of increasing the coupling agent content on Izod impact and tensile properties was investigated. A maximum in the above properties is attained at 15 wt% AAgPP. The most important effect is clearly shown in the Izod test. In fact, a threefold increase has been observed for either notched and untoched specimen. The 15 wt% AAgPP is considered to be a critical concentration for the composite considered. This corresonds to maximum interactions occurring between the matrix and the filler. SEM analysis clearly shows strong interactions between the filler and the matrix in the presence of acrylic acid grafted polypropylene. This is another proof of the efficiency of the synthesized AAgPP as a potential coupling agent for CaCO₃ filled PP.     

Fouling control in a submerged membrane‐bioreactor by the membrane surface modification

To improve the antifouling characteristics, polypropylene microporous membranes (PPHFMMs) were surface‐modified by the sequential photoinduced graft polymerization of acrylic acid and acrylamide. The grafting density and the grafting chain length, which played important roles in the antifouling characteristics, were controlled in the first and the second step, respectively. The ATR/FTIR results clearly indicated the successful modification on the membrane surface. The static water contact angle of the modified membrane reduced obviously with the increase of the grafting chain length. The contact angle of the acrylic acid modified membranes was lower than that of the acrylamide modified membrane with similar grafting chain length. The grafting chain length increased with the increase of UV irradiation time and monomer concentration. The grafting chain length of poly(acrylic acid) (PAAc) was lower than that of the polyacrylamide (PAAm) under the same polymerization conditions. Pure water flux for the modified membranes increased with the increase of grafting chain length, and had maximums. The antifouling characteristics of the modified membranes in a submerged membrane‐bioreactor (SMBR) were evaluated. The modified membranes showed better filtration performances in the SMBR than the unmodified membrane, and the acrylic acid grafted membrane presented better antifouling characteristics than acrylamide modified membranes. The results demonstrated that the surface carboxyl‐containing membranes were better than the surface amido‐containing membranes. The results of Pearson correlations demonstrated that the PAAc modified membranes with longer grafting chain length had higher flux recoveries, while the PAAm modified membranes with longer grafting chain length had lower flux recoveries. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Analysis of the solid phase copolymerization grafting process

Solid phase grafting, which is an emerging process for the production of graft copolymers, was analyzed and reviewed as an environmentally friendly and inexpensive graft copolymerization process. The effect of the process variables; amount of initiator, catalyst, interfacial agent, monomer, reaction temperature and reaction time were examined. Two graft copolymers, produced by solid phase grafting, were used to show differences in graft percentage by changing the process conditions. The two graft copolymers used were maleic anhydride graft onto polypropylene and acrylic acid graft onto polystyrene. A proposed mechanism was given for each example and characteristic bonds proposed in the PP-g-MA mechanism was positively identified by NMR spectroscopy. Graft levels of 4 wt% PS-g-AAc and 9.6 wt% PP-g-MA were obtained providing comparable or superior graft levels to other grafting processes. Successful scale-up of the solid phase technique proved that this process is efficient and marketable.     

Electrokinetic properties of acrylic acid- and methacrylic acid-grafted polypropylene during chemically initiated graft copolymerization

Electrokinetic properties such as zeta potential (ζ), surface charge density (σ) and surface conductivity (K_s) of polypropylene fibers and those grafted with acrylic acid and methacrylic acid have been studied using the streaming potential method. At pH 7, the zeta potential of ?58.5 mV for control fibers reduced with increase in the amount of acrylic acid (16.2%) and methacrylic acid (28.2%) grafts to ?38.15 mV and ?38.30 mV, respectively. The drop in the negative zeta potential value is attributed to rendering polypropylene hydrophilic. The acrylic acid graft was found to be more effective than the equivalent amount of methacrylic acid graft in this respect due to the different chemical characters of the two graft copolymers. The negative zeta potential was also reduced to a considerable extent when cationic dye solution was streamed through the grafted polypropylene fibers, which is attributed to the deposition of dye cations on the negatively charged surface of the grafted fibers. The results on surface charge density and surface conductivity also indicated the hydrophilic character of grafted polypropylene.     

Radiation-induced solid-state polymerization in binary systems. VIII. Polymerization and foaming of multicomponent systems including acrylamide and acrylic acid

Radiation-induced polymerization and foaming of multicomponent systems including acrylamide, acrylic acid, and foaming agents were studied. Eutectic mixtures such as acrylamide–itaconic acid were polymerized in solid state and then foamed by heating at 130 ～ 200°C. The solution systems such as acrylamide–itaconic acid–water and acrylamide–maleic anhydride–urea–water were polymerized in liquid and supercooled phases at higher rates and foamed to a higher degree of expansion. Foams of poly(acrylic acid) and poly(methacrylic acid) were obtained by polymerization and heating of acrylic acid (methacrylic acid)–urea–water systems. It was deduced that the nonmelting or flowing property of these acrylic polymers, especially the semithermosetting property of polyacrylamide, had an important effect on the foaming mechanism.     

Grafting of polypropylene fibers. III. Electrical conductivity of grafted fibers polypropylene grafted with various vinyl monomers

Electrical conductivity of polypropylene fibers grafted with methacrylic acid, vinyl acetate, and acrylonitrile for the samples conditioned at various relative humidities is reported. Electrical conductivity increases with the increase in graft in all three grafted polymers. The increase in conductivity of polypropylene fibers grafted with methacrylic acid is two orders of magnitude higher than control, while the increase in other cases in small. The results are explained on the basis of chemical structure of the grafted fibers. Increase in electrical conductivity with respect to methacrylic acid graft could be due to charge migration and electronic conductivity. In the case of the other two monomer-grafted PPs, increase could be predominantly due to electronic conduction.     

Graft Copolymers of Polypropylene Films. 1. Radiation-induced Grafting of Mixed Monomers

Radiation graft copolymerization of comonomer mixtures of acrylic acid (AAc) and styrene (S) onto polypropylene (PP) films by the mutual method has been investigated. The effect of different factors that may affect the grafting yield, such as inhibitor concentration (Mohr’s salt), solvent composition (MeOH and H₂O), radiation dose and dose rate, was studied. It was found that Mohr’s salt was very effective when the content of AAc in the comonomer mixtures was low. However, the addition of 1·25wt% of Mohr’s salt reduced homopolymer formation and enhanced the grafting process. Graft copolymerization in the presence of a solvent mixture composed of methanol and water was found to afford a higher grafting yield than in pure methanol, regardless of the composition of the comonomer mixture used. However, the highest degree of grafting was obtained at a solvent composition of 20% H₂O: 80% MeOH and a comonomer mixture of 20% AAc: 80% S. An attempt was made to determine each PAAc and PS fraction by different methods in the graft copolymer obtained. Elemental analysis indicated that the PAAc fraction with respect to PS in the graft copolymer decreased with increasing AAc ratio in the comonomer feed solution. The rough assessment of these fractions by IR spectroscopy showed similar trends. The reactivity ratios of AAc and S monomers determined in the present graft copolymerization system were found to be 0·45 and 1·3, respectively. © of SCI.     

Porous bead aliphatic-aromatic methacrylate copolymers V. Grafting of acrylic monomers onto MMA-DMN copolymers

Porous methyl methacrylate-di(methacryloyloxymethyl)-naphthalene (DMN) copolymers were subjected to superficial grafting processes with engagement of double bonds present in the polymer structure. Grafting monomers were acrylic and methacrylic acids, acrylonitrile, acrylamide, and glycidyl methacrylate. Grafted copolymers were investigated by elemental analysis, infra-red measurements, adsorptiondesorption isotherms of nitrogen and scanning electron microscopy. Irrespective of low grafting efficiency, the changes due to grafting with respect to the parent copolymers were easy to observe.