Reactivity ratios during radiation‐induced grafting of comonomer mixtures onto polyester fabrics

Radiation‐induced grafting of binary mixtures of acrylonitrile (AN)/styrene (S) and acrylamide (AAm)/styrene (S) onto polyester fabric (PET) has been investigated. Synergism during radiation grafting was investigated by determining the graft yield fraction for each monomer in the final graft copolymer. Moreover, by knowing the mole fraction of each monomer in the grafting solution, the reactivity ratio of the individual monomers in the comonomer mixture during graft copolymerization could be determined: in the case of AN/S comonomer mixture, the calculated reactivity ratios for AN and S are 0.04 and 0.05, respectively; the calculated reactivity ratios of AAm and S in their comonomer mixture are 1.82 and 0.41, respectively. © 2001 Society of Chemical Industry     

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.     

Grafting onto polyester fibers. IV. Synergism during graft copolymerization of binary mixtures of vinyl monomers onto polyester fibers

Graft-copolymerization reactions of binary mixtures of vinyl monomers (acrylamide–acrylic acid and acrylonitrile–acrylic acid) with polyester fibers have been studied by chemical initiation technique using benzoyl peroxide as an initiator. The total graft add-on was determined gravimetrically, while the modified Kjeldahl's method for N-estimation was employed to determine acrylamide and acrylonitrile grafts in their mixtures with acrylic acid grafts. Synergism of very high order was noticed during the graft-copolymerization reactions. In the case of the acrylamide–acrylic acid system a very high order of synergism (129.15%) was noticed at equimolar proportions of the monomers in the grafting bath. Both acrylamide and acrylic acid showed synergistic influence over each other during graft-copolymerization reactions. In the case of the acrylonitrile–acrylic acid system, however, the presence of acrylonitrile reduced the graft yield of the acrylic acid component showing a negative synergism; but acrylic acid enhanced the acrylonitrile graft yield to a considerable extent. The results have been explained in terms of reactivity ratios of the monomers. The conductivity results of the monomer mixtures also supported the experimental results.     

Investigation of synergism during radiation graft copolymerization of binary mixtures of vinyl monomers onto different textile fabrics by a dyeing method

Radiation-induced graft copolymerization of binary mixtures of acrylic acid (AAc) and styrene (S) onto cotton, cotton/polyester’ and viscose rayon has been investigated. The different factors that may affect the total graft yield (the sum of polyacrylic acid (PAAc) fraction and polystyrene (PS) fraction, such as solvent composition, comonomer mixture, and irradiation dose were studied. It was found that there is always a certain solvent composition of (MeOH and H₂O) and comonomer mixture at which a maximum value of total graft yield (TGY) was obtained. Moreover, the TGY was greatly influenced by other factors such as radiation dosage. An attempt was made to investigate synergism during graft copolymerization, i.e. the effect of each monomer on the other and their participation in the resulting graft copolymer. In this respect, the PAAc and PS graft fractions in the resulting graft copolymers of the different textile fabrics under investigation were determined approximately by dyeing with basic dye (Sandocryl Blue) and disperse dye (Samaron Blue FBL). By this method, it was possible to determine each fraction in the graft copolymer. It was also observed that the graft copolymerization increased the dye affinity for such dyestuffs to a great extent. The accuracy and validity of the dyeing method applied was supported by the estimation of the carboxyl group content by analytical technique based on acid–base volumetric titration. ©1997 SCI     

Removal of cesium‐134 and cobalt‐60 with radiation‐grafted copolymers from their liquid wastes

The introduction of new characteristics to some synthetic polymers was achieved through the γ‐radiation‐induced graft copolymerization of an acrylamide/vinyl acetate comonomer onto polypropylene films for the preparation of synthetic membranes. The influence of the reaction conditions on the grafting yield, such as the solvent and its composition and the inhibitor and its concentration, was investigated. An alkaline treatment was carried out for the prepared graft copolymer to improve its ion‐exchange property. The grafted and treated membranes were characterized to determine the structural changes with X‐ray diffraction and Fourier transform infrared spectroscopy. The mechanical properties, swelling behavior, and electrical conductivity for the graft copolymer were studied. Improvements in the tensile strength, electrical conductivity, and hydrophilicity with grafting were observed. The KOH‐treated membranes possessed greater hydrophilic properties than the untreated ones. The possibility of practical uses for these membranes in the removal of cesium‐134 and cobalt‐60 from their liquid wastes was also investigated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 936–945, 2005     

Thermal behavior of cellulosic graft copolymers. II. Cotton grafted with binary mixtures of vinyl acetate and methyl acrylate

Thermal degradation of cotton, mercerized cotton, cotton grafted with vinyl acetate-methyl acrylate mixtures at different compositions, and mercerized cotton grafted with vinyl acetate–methyl acrylate mixture at a composition of 60 : 40 has been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) in nitrogen. The kinetic parameters E, n, and A have been obtained following several methods of thermogravimetric analyses. The mercerization shows a little effect upon thermic properties of cotton cellulose, making cotton thermally more stable. Graft copolymerization of vinyl acetate-methyl acrylate mixture makes cotton thermally less stable if the composition of the copolymer grafted is 100, 90, and 70 mol % VA, while in the case of cellulose graft copolymers with compositions of VA–MA of 80 : 20, 20 : 80, 5 : 95, and 0 : 100 the thermal stability is higher than that of original cotton. The thermal stability of the mercerized cotton grafted with vinyl acetate-methyl acrylate mixture with a composition of 60 : 40 depends on the percent grafting yield. The thermal stability of mercerized cotton grafted with the monomer mixture is higher than that of cotton grafted with that monomer mixture. The degradation of cellulose and cellulose graft copolymers is complex as is shown by DTA thermograms and kinetic parameters.     

Radiation-initiated graft copolymerization of individual monomer and comonomer onto polyethylene and polytetrafluoroethylene films

Preparation and some properties of the graft copolymers obtained by radiation-induced graft polymerization of methacrylic acid (MAA) and (acrylonitrile/MAA) comonomer onto polyethylene and polytetrafluoroethylene films, were investigated. The effect of reaction conditions, solvent, monomer, and inhibitor concentration, comonomer composition, and comonomer concentration, on the graft copolymerization process was studied. The grafting process was enhanced in the presence of comonomer (AN/MAA) as compared with individual grafting of MAA or acrylonitrile (AN). The optimum comonomer composition, at which the highest grafting yield was obtained, was found to be (80/20) wt % of (AN/MAA) comonomer. The graft copolymerization of (AN/MAA) comonomer was enhanced in presence of AN due to its higher polarity strength. The electrical and swelling properties of the graft copolymers were greatly affected by the contents of PAN and PMAA graft chains. Mechanical properties of the graft copolymers were significantly changed with the grafting yield.     

Preparation of poly(vinyl alcohol) grafted with acrylic acid/styrene binary monomers for selective permeation of heavy metals

A study was made to modify water‐soluble poly(vinyl alcohol) (PVA) by grafting acrylic acid and styrene (AAc/Sty) comonomers using gamma rays as an initiator. The factors that affect the preparation process and grafting yield were studied and more economical grafts under the most favorable reaction conditions were obtained. It was found that the high degree of grafting in such systems was obtained in the presence of an ethanol–water mixture in which water plays a significant role in enhancing the graft copolymerization. The critical amount of water to afford the maximum grafting yield was evaluated. The effect of the comonomer composition on the grafting yield was also investigated and it was observed that using a mixture of AAc/Sty monomers influences the extent of grafting of each monomer onto the PVA substrate and the phenomenon of synergism occurs during such a reaction. Also, the degree of grafting increases as the content of the solvent decreases in the reaction medium. However, the grafting yield increased as the total dose increased. The graft copolymer was characterized by IR and UV spectroscopic methods. The permeation of heavy metals such as Ni and Co through the grafted membranes was investigated and the efficiency of the separation process was also determined. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 806–815, 1999     

Radiation-induced Grafting of Acrylic Acid and Vinyl Acetate Monomers onto Heavy-duty Poly(ethylene–vinyl acetate) Films

The preparation of graft films was carried out by direct radiation-induced graft polymerization of acrylic acid and vinyl acetate comonomer onto heavy-duty poly(ethylene–vinyl acetate) films. The effect of various comonomer compositions on the degree of grafting was investigated. The characterization and some selected properties of the graft copolymers prepared were studied. Thermal stability, mechanical and electrical properties of the films showed great promise for some practical applications. © of SCI.     

Radiation-initiated graft copolymerization of binary monomer mixtures containing acrylonitrile with cotton cellulose

By the use of the cobalt 60 postirradiation grafting technique, purified cotton cellulose fibers were graft-copolymerized with binary mixtures of acrylonitrile and other monomers, including styrene, 1,3-butylene dimethacrylate, vinylpyrrolidone, vinylidene chloride, and methyl, butyl, lauryl, glycidyl, and allyl methacrylates. The irradiated cotton fibers were immersed in solutions of the monomers at 25°C to initiate graft copolymerization. Solvents were water, methanol, dimethyl sulfoxide, and methyl ethyl ketone, alone or in several combinations. The extent of graft copolymerization and the composition of the grafted copolymer depended on the composition of the binary mixtures of monomers and on the solvent or mixtures of solvents used. For example, addition of styrene, 1,3-butylene dimethacrylate, or vinylpyrrolidone to acrylonitrile increased the extent of graft copolymerization to a maximum value; addition of vinylidene chloride or allyl methacrylate to acrylonitrile did not greatly affect the extent of graft copolymerization; and addition of methyl or glycidyl methacrylate to acrylonitrile increased the extent of graft copolymerization without passing through a maximum value. The proportion of acrylonitrile in the grafted copolymer was generally less than that in the binary mixtures. As the reaction time was increased, the extent of graft copolymerization increased to a maximum value; however, the composition of the grafted copolymer did not change significantly. Generally, the addition of water to the solutions increased the extent of graft copolymerization. The mechanisms of these graft copolymerization reactions are discussed.     

Investigation of radiation grafting of vinyl acetate onto (tetrafluoroethylene–perfluorovinyl ether) copolymer films

A study has been made of radiation-induced grafting of vinyl acetate (VAc) on to (tetrafluoroethylene–perfluorovinyl ether) copolymer (PFA). Effects of grafting conditions such as inhibitor and monomer concentrations and irradiation dose on the grafting yield were investigated. In this grafting system, ammonium ferrous sulphate (Mohr′s salt) was added to the monomer-solvent mixture to minimize the homopolymerization of VAc and the most suitable concentration was found to be 2.0 wt%. It was found that the dependence of the initial grafting rate on monomer concentration is of the order 1.5. The degree of grafting tends to level off at high irradiation doses due to the recombination of formed free radicals without initiating graft polymerization. Some properties of the prepared graft copolymer such as swelling behaviour, electrical conductivity, thermal and mechanical properties were also investigated. The electrical conductivity was improved by hydrolysis of poly(vinyl acetate) in the grafted chains to their respective vinyl alcohols. The tensile properties were improved by grafting; however, the elongation percent decreased. The DTA data showed thermal stability of such graft copolymers for temperatures up to 300°C, but stability decreased at higher temperatures.     

Elucidation of the nanoparticle effect on the grafting of vinyl monomers onto cotton fabric

The grafting emulsion polymerization of vinyl monomers onto cotton was carried out in the presence of double‐modified montmorillonite clay. The obtained results show that grafting with glycidyl methacrylate/montmorillonite gave a higher rate of grafting than grafting with methyl methacrylate/montmorillonite in all clay percentages, and also, the grafting yield of glycidyl methacrylate monomer onto cotton in the presence of montmorillonite clay had a higher value than that in the absence of the clay for all factors studied. Cotton grafted with glycidyl methacrylate/montmorillonite with a graft yield of about 50% was prepared according to the emulsion polymerization technique and was treated with different concentrations of dibutylamine solutions ranging from 1 to 4%. The obtained samples were characterized according to nitrogen content, thermal stability, scanning electron microscopy, mechanical properties, water absorption, and color strength according to acid, basic, and reactive dyes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Prospects for Radiation Techniques in Dyeing and Finishing

This paper evaluates the role, actual and potential, of high-energy and low-energy radiation in textile technology. Emphasis is placed on the cobalt-60 source and the electron accelerator as high-energy sources, and the glow discharge as a source of low-energy radiation. The effect of high-energy radiation on the structure and properties of fibres is reviewed. Two types of effect may be produced: crosslinking and degradation. The latter predominates with some polymers, whereas with others crosslinking of the polymer chains is the major effect. It is concluded that the direct effects of high-energy radiation are of insufficient value to justify its application to textiles without some simultaneous or subsequent chemical treatment of the fibre. The free radicals produced by the radiation serve as reactive sites at which the graft copolymerisation of monomers may be initiated within the fibre structure. Three methods are available for the radiation grafting of unsaturated monomers on to fibrous substrates: the ‘simultaneous’ method, the ‘post-irradiation’ method, and the ‘peroxide’ method. Most effort in this area has been devoted to the modification of synthetic-polymer fibres to make them more readily dyeable. Several examples of this are described. To achieve good penetration of the graft copolymer into the fibre, it is necessary that the fibre should be sufficiently swollen to permit penetration by the monomer molecules. Experiments on the swelling of polyester fibres in relation to grafting are described. The use of radiation-initiated grafting in the finishing of textiles is discussed next. The outstanding example of this, one that has achieved commercial exploitation, is the Deering Milliken Visa process for conferring durable-press properties on cotton and cotton–polyester fabrics. Flame-resistant cotton can also be produced by radiation-grafting techniques. The modification of the surfaces of textile fibres, for example, to confer soil-release and antistatic properties, is another potential application of radiation grafting in textile finishing. The deposition of coatings on solid surfaces by low-energy gas-discharge techniques has been the subject of many investigations. Recent work at the Shirley Institute, in collaboration with the Electricity Council Research Centre, has shown that several percent of vinyl monomers can be deposited on polyester fabric by means of the glow discharge. With hydrophilic monomers, the fabrics have improved antisoil and soil-release properties. Terylene (ICI) fabrics treated in a glow discharge with acrylic acid can be dyed to solid colours with basic dyes. The paper concludes with a brief assessment of the economics of radiation processes in relation to their use in textile technology.     

Glycidyl methacrylate–grafted linear low‐density polyethylene fabrication and application for polyester/polyethylene bonding

The grafting of glycidyl methacrylate (GMA) onto linear low‐density polyethylene (LLDPE) was investigated. The grafting was performed by free‐radical grafting in the melt state in a twin‐screw extruder using an organic peroxide as initiator. The effect of initial GMA and peroxide concentration, styrene comonomer addition, as well as initial resin viscosity, on the final content in grafted moieties, unbound homopolymer, and unreacted monomer was assessed. The effect of process parameters such as flow rate, screw rotation speed, and barrel temperature was also investigated. Chemical composition was shown to be the main parameter for controlling grafting level and grafting efficiency. Grafting levels up to 1.8% and efficiency of 90% were reported even though in most conditions, the graft efficiency was severely decreased by the homopolymerization of GMA into polyGMA chains not bound to LLDPE. Finally, the effect of grafting level and the presence of unbound GMA‐based species on the efficiency GMA‐grafted LLDPE as adhesive between polyethylene and polyester were discussed. Good adhesion to poly(ethylene terephthalate) copolymer was found for low viscosity grafted polyethylene resins. A significant improvement in adhesive strength on polyester was observed when the molecular weight of the grafted LLDPE was increased. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3180–3191, 2004     

Grafting of methyl methacrylate onto cellulose nitrate initiated by benzoyl peroxide

It has been observed that grafting of vinyl monomers onto cellulose nitrate in solution takes place using benzoyl peroxode. The graft copolymer was isolated from the unreacted backbone and homopolymer by selective solvent extraction. The effect of variables, such as the initiator concentration, the monomer concentration and the reaction time on the percent grafting and the grafting efficiency, were discussed. A probable mechanism for grafting of vinyl monomers to cellulose nitrate in solution has been proposed.     

Preparation and thermal characterization of graft copolymer obtained by radiation grafting of individual and binary monomer systems

Graft copolymers were obtained by radiation-induced grafting of vinyl acetate (VAc) and N-vinylpyrrolidone (NVP) individually and in binary mixture on to polypropylene (PP) films. The effect of some grafting conditions on the grafting yield was determined. The addition of Cu₂Cl₂ as inhibitor to the reaction medium inhibited the homopolymerization of the comonomer. The grafting process was remarkably enhanced by using dioxan as a diluent compared with other solvents used. The addition of some inorganic salts has a great influence on the individual grafting of both monomers. The gel percent in the graft copolymer was determined; it increased as the grafting yield increased. The swelling behaviour and electrical conductivity for the grafted films slightly increased by grafting. The changes in thermal parameters such as glass transition (T_g), melting (T_m) and recrystallization (T_rc) temperatures and heats of melting (ΔH_m) and recrystallization (ΔH_rc) of the graft copolymers were also followed by differential scanning calorimetry (DSC). These thermal parameters of PP were varied by grafting with VAc and NVP and depend on the graft yield, which reflects the change in its crystalline domains and formation of crosslinks in the graft chains. The heat of recrystallization of the graft copolymer by cooling from the molten state decreases by grafting which is a good indication of crosslink formation, since crosslinking decreases the crystallizability of the polymer matrix.     

Development and physicochemical characterization of modified polymeric surfaces for bacterial adhesion

Radiation‐induced graft polymerization was used to modify the surfaces of polypropylene (PP) sheets for bacterial adhesion. For the experiments, two monomers were mixed: the quaternary ammonium salt (QAS) [2‐(methacryloyloxy)ethyl]trimethylammonium chloride and acrylic acid (AAc). The PP sheets were activated by electron‐beam radiation before the grafting reaction. Different AAc/QAS comonomer mixture ratios (50 : 10, 40 : 20, 30 : 30, 20 : 40, and 10 : 50) were used to determine the degree of grafting and to make the PP surfaces hydrophilic. The graft level increased with an increase in the percentage of AAc in the comonomer mixtures. Synergism was investigated during graft polymerization to quantify the poly(acrylic acid) and poly{[2‐(methacryloyloxy)ethyl]trimethylammonium chloride} graft fractions in the resulting graft copolymers. An approximation of the graft fractions was made with an analytical technique based on acid–base volumetric titration. The wettability of the modified surfaces was determined by the measurement of the water contact angles. The surfaces prepared with higher percentages of QAS in the comonomer mixtures had lower contact angles than those prepared with lower percentages of QAS. The presence of oxygen and nitrogen on the modified PP surfaces was investigated with X‐ray photoelectron spectroscopy. Structural changes in unmodified and modified PP were characterized with differential scanning calorimetry. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The influence of chemical surface modification on the performance of sisal‐polyester biocomposites

This article concerns the effectiveness of various types and degrees of surface modification of sisal fibers involving dewaxing, alkali treatment, bleaching cyanoethylation and viny1 grafting in enhancing the mechanical properties, such as tensile, flexural and impact strength, of sisal‐polyester biocomposites. The mechanical properties are optimum at a fiber loading of 30 wt%. Among all modifications, cyanoethylation and alkali treatment result in improved properties of the biocomposites. Cyanoethylated sisal‐polyester composite exhibited maximum tensile strength (84.29 MPa). The alkali treated sisal‐polyester composite exhibited best flexural (153.94 MPa) and impac strength (197.88 J/m), which are, respectively, 21.8% and 20.9% higher than the corresponding mechanical properties of the untreated sisal‐polyester composites. In the case of vinyl grafting, acrylonitrile (AN)‐grafted sisal‐polyester composites show better mechanical properties than methyl‐methacrylate (MMA)‐grafted sisal composites. Scanning electron microscopic studies were carried out to analyze the fiber‐matrix interaction in various surface‐modified sisal‐polyester composites.     

Ataktisches polypropylen als pfropfgrundlage für die monomeren vinylacetat und vinylchlorid. Herstellung undeigenschaften der pfropfprodukte

The possibility of the application of atactic polypropylene is investigated as graft base for the preparation of graft copolymers of vinyl acetate and vinyl chloride respectively graft copolymers from vinyl acetate onto polypropylene as graft base for the preparation of graft copolymers of vinyl chloride in relation to the composition of the original mixture. After compounding of the graft products with polyvinyl chloride or ABS/polyvinyl-chloride mixtures selected mechanical properties are presented in relation to the quantity and composition of the incorporated graft copolymers.     

Metal complexes of natural and synthetic fabrics grafted with vinyl monomers by gamma irradiation

Graft copolymers of natural and synthetic fabrics with acrylic acid (AAc) prepared by gamma irradiation were transformed into metal complexes of the divalent metal ions of cobalt, nickel, and copper. The factors that affect the grafting process without affecting the physical properties of fabrics and homogeneous grafting were studied. These factors involved inhibitor (FeCl₂) concentration, solvent composition, AAc concentration, and irradiation dose. The results showed that the appropriate irradiation dose in all cases was 20 kGy, whereas the inhibitor concentration was 0.1 wt% in the case of cotton and 0.2 wt% in the case of cotton/polyester blend and polyester fabrics. The suitable solvent composition was H₂O (90%)/MeOH(10%) in the case of cotton and H₂O (90%)/MeOH(10%) in the cotton/polyester blend and polyester fabrics. On the other hand, the suitable AAc concentration was 30% in the case of cotton and 50% in the cotton/polyester blend and polyester fabrics. The homogenous grafting and subsequent distribution of metal complexation was illustrated by a method based on the measurement of color parameters. Moreover, the effect of radiation grafting and metal complexation on the water absorption and mechanical properties of fabrics was investigated. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers