Comparative study of the radiation‐induced grafting of styrene onto poly(tetrafluoroethylene‐co‐perfluoropropylvinyl ether) and polypropylene substrates. I: Kinetics and structural investigation

A comparative study has been made of the radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐perfluoropropyl vinyl ether) (PFA) and polypropylene (PP) substrates, using the simultaneous irradiation method. Effects of grafting conditions such as monomer concentrations, type of solvent, dose rate and irradiation dose on the grafting yield were investigated. Under the same grafting conditions it was found that a higher degree of grafting of styrene was obtained using a mixture of dichloromethane/methanol solvents for PFA and methanol for PP and the degree of grafting was higher in PP than in PFA at all doses. However, the micro‐Raman spectroscopy analysis of the graft revealed that, for the same degree of grafting, the penetration depth of the grafted polystyrene into the substrate was higher in PFA than in PP substrates. In both polymers the crystallinity was hardly affected by the grafting process and the degree of crystallinity decreased slightly with grafting dose. The dependence of the initial rate of grafting on the dose rate and the monomer concentration was found to be 0.6 and 1.4 order for PFA and 0.15 and 2.2 for PP, respectively. The degree of grafting increased with increasing radiation dose in both polymers. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield for PFA and PP was accompanied by a proportional increase in the penetration depth of the graft into the substrates. Copyright © 2003 Society of Chemical Industry     

Effect of solvents on radiation‐induced grafting of styrene onto fluorinated polymer films

The effect of solvents on radiation‐induced grafting of styrene onto commercial fluorinated polymer films such as poly(tetrafluoroethylene) (PTFE), poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP) and poly(tetrafluoroethylene‐co‐perfluorovinyl ether) (PFA) was investigated by a simultaneous irradiation technique. Three solvents, ie methanol, benzene and dichloromethane, were used to dilute styrene under various irradiation doses, dose rates and monomer concentrations. The effect of addition of mineral and organic acids on the degree of grafting in the presence of the three solvents was also studied. The degree of grafting was found to be strongly dependent upon the type of solvent and composition of the monomer/solvent mixture. Dilution of styrene with dichloromethane in various grafting conditions was found to enhance dramatically the degree of grafting compared with other solvents, and the maximum degree of grafting was achieved at a monomer/solvent mixture having a composition of 60:40 (v/v). The formation of polystyrene grafts in the three fluorinated films was verified using FTIR spectrometry. © 2001 Society of Chemical Industry     

The graft copolymerization of styrene and lignin. II. Kraft softwood lignin

The radiation-induced graft copolymerization of styrene and various kraft softwood lignins was studied. Expression of the results as the usual “per cent graft” was impossible, because grafting caused the lignin to become extractable in solvents for the styrene homopolymer. However, evaluation of the effects of various solvents on the degree of reaction was made through an indirect, and possibly more characteristic, measure. Grafting was least pronounced under conditions of low lignin accessibility (e.g., when less than 10% methanol was present), but increased with the addition of better lignin solvents or with higher methanol concentrations. The precipitating nature of the latter conditions was also found to contribute to an accelerated rate of grafting. Surprisingly, the graft copolymer was found to degrade at higher doses. Proof of grafting is offered in a fractionation scheme. Measurement of the molecular weight of the polystyrene separated from the lignin backbone allows the estimation of approximately one polystyrene graft per lignin molecule in benzene-extractable copolymers. Two glass transition temperatures could be detected in several fractionated copolymers.     

Structure and properties of cellulose graft copolymers. I. Radiation-induced rayon–styrene graft copolymer

Rayon–styrene graft copolymers were prepared by the direct radiation method, with the use of the preswelling technique, by irradiation with γ-rays from ⁶⁰Co. The grafting was carried out in bulk styrene and in styrene–solvent mixtures, such as styrene–methanol and styrene–acetone, to study their effect on the graft copolymerization reaction and the structure of the resulting graft copolymer. The effects of carbon tetrachloride, a chain-transfer agent, was also investigated. Three different types of rayon yarn were used; Fortisan, a modifier-type high wet-modulus rayon, and a high-tenacity tire yarn, in order to study the effect of rayon microstructure on the grafting reaction. The molecular structure of the rayon–styrene graft copolymers was studied by hydrolyzing away the cellulose backbone and measuring the molecular weights of the grafted polystyrene branches. For grafting in bulk styrene, the molecular weights of the grafted polystyrene ranged from 400,000 to 1,000,000, while those of the polystyrene homopolymer formed in the outside solution were of the order of 30,000–50,000. The molecular weights of the grafted polystyrene branches tended to increase with per cent grafting in the graft copolymer. For grafting in styrene–methanol and styrene–acetone mixtures, the molecular weights of the polystyrene branches decreased with increasing solvent content. The addition of carbon tetrachloride to bulk styrene resulted in a sharp decrease in the molecular weights of the grafted branches. The grafting frequency or number of polystyrene branches per cellulose chain was calculated from the per cent grafting and the molecular weights of the polystyrene branches. The morphology of the rayon–styrene graft copolymers and some of their physical properties are discussed.     

Synthesis of graft copolymers based on polyphenylene xylylene and fullerene grafted polystyrene

Graft copolymers containing poly(phenylene xylyene) (PPX) backbone and polystyrene fullerene (PSFu) grafting chains (PPX‐g‐PSFu) were prepared by using a purposed synthetic route comprising a combination of reaction mechanisms namely the modified Wessling route, an iniferter polymerization, and an atom transfer radical addition (ATRA). The monomer was first prepared by reacting dichloroxylene with tetrahydrothiophene. After that the monomer was polymerized in a sodium hydroxide solution to provide a polymer precursor. Subsequently, the polymer precursor was modified by reacting it with a dithiocarbamate (DTC) compound. The macroiniferter was obtained and then copolymerized with styrene and chloromethylstyrene via an iniferter polymerization. Finally, the graft copolymer was reacted with fullerene through an ATRA technique to attach the C60 groups onto the graft copolymer molecule. The products obtained from each of the steps were characterized by using various techniques including Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, gel permeation chromatography, differential scanning calorimetry, UV–visible spectroscopy, and thermal gravimetric analysis. The aforementioned results suggest that the graft copolymers were prepared. The grafting yield and grafting efficiency were found to increase with the monomers concentration and the amount of DTC used. Some homopolymer contaminants also occurred but those could be minimized and subsequently removed by extraction with selective solvents. These graft copolymer products might be used for the development of a bulk heterojunction polymer solar cell. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Adhesion studies of tyre cords with rubber. I. Synthesis and characterization of natural rubber graft copolymers

Glycidyl methacrylate and N-vinyl pyrrolidone have been grafted onto natural rubber at 32°C using the simultaneous cobalt-60 irradiation technique. The natural rubber samples were swollen in the monomers for 24 h and thereafter subjected to gamma irradiation. The homopolymers formed in the graft copolymerization reactions and unreacted monomer were removed by solvent extraction using acetone and methanol for glycidyl methacrylate and N-vinyl pyrrolidone monomer, respectively. The influence of total dose and monomer concentration on the graft parameters was investigated. The dependence of the rate of grafting on the monomer concentration was found to be 0.93 and 0.80 for glycidyl methacrylate and N-vinyl pyrrolidone, respectively. DSC and TGA studies of the polymers were undertaken. Grafted copolymers based on glycidyl methacrylate were relatively less thermally stable compared with ungrafted natural rubber.     

Radiation-induced grafting of N,N′-dimethylaminoethylmethacrylate onto chitosan films

Chitosan films were grafted with N,N ′-dimethylaminoethylmethacrylate using the ⁶⁰Co gamma irradiation method. The effect of solvent composition, monomer concentration, dose rate, and total dose on grafting was studied. The solvent composition has a marked effect on the degree of grafting. Maximum yield was obtained in the water-methanol (1 : 1) system. The percent grafting increased with monomer concentration and was found to be higher at a lower dose rate for a constant total dose of 0.216 Mrad. The tensile strength, crystallinity, and degree of swelling of grafted films decreased on increasing graft level. However, the graft copolymers showed improved thermal stability. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 869–877, 1997     

Gamma radiation‐induced graft copolymerization of styrene onto poly(ethyleneterephthalate) films

Gamma radiation‐induced graft copolymerization of styrene onto poly(ethylene terephthalate) (PET) films was studied using simultaneous irradiation technique. The effects of grafting conditions on the degree of grafting were investigated. The grafting conditions include monomer concentration, irradiation dose, dose rate, and the type of solvent. Moreover, the effect of the addition of crosslinking agents [i.e., divinylbenzene (DVB) and triallyl cyanurate (TAC)] having various concentrations were also investigated. The degree of grafting was found to be greatly dependent on the grafting conditions. Of the three diluents employed, methylene chloride was found to drastically enhance the degree of grafting. The order of dependence of the initial rate of grafting on the monomer concentration was found to be 2.2. The grafted PET films were identified by FTIR spectroscopy and characterized by X‐ray diffraction (XRD). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1003–1012, 2000     

Study of radiation-induced graft copolymerization of vinyl acetate onto ethylene-co-propylene rubber

The radiation-induced graft copolymerization of vinyl acetate (VAc) onto ethylene-copropylene rubber (EPR) has been studied in methanol with radiation of cobalt-60. The effects of irradiation dose, dose rate, concentration of monomer, Cu⁺⁺ concentration, and temperature on the degree of grafting were investigated. The dependence of the initial grafting rate on dose rate, monome, and Cu⁺⁺ concentration were found to be 1.0, 1.95, and 0.5 order, respectively. The apparent activation energy was calculated to be 49 kJ/mol. Mechanical properties of the grafted polymer were investigated as a function of the grafting percentage. The tensile strength increases and elongation of break decreases with the increase of the degree of grafting in the region of low grafting percentage (≅ 10%). © 1996 John Wiley & Sons, Inc.     

Modification of polypropylene fiber by radiation-induced graft copolymerization of acrylonitrile monomer

Modification of polypropylene fiber was carried out by graft copolymerization of acrylonitrile monomer using the preirradiation method. The influence of synthesis conditions (preirradiation dose, monomer concentration, temperature, draw ratio, and storage) on the degree of grafting was investigated. For all preirradiation doses, the degree of grafting was found to increase with the reaction time. The higher the preirradiation dose, the higher the degree of grafting was. The dilution of monomer with DMF showed peak maxima for the degree of grafting at 80% monomer concentration. Both the initial rate of grafting and the final degree of grafting were found to increase with an increase in the reaction temperature. An activation energy of 31.2 kJ/mol was found for the grafting reaction. The degree of grafting in the drawn fiber showed different behavior as compared to the undrawn fiber. The storage of the irradiated fiber at −4°C prior to the grafting showed a decrease in the degree of grafting initially for a period of 8 days, beyond which the degree of grafting remained constant. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1343–1348, 1998     

Homogeneous graft copolymerization of chitosan with methyl methacrylate by γ‐irradiation via a phthaloylchitosan intermediate

The graft copolymerization of methyl methacrylate (MMA) onto chitosan was tried via a new protection‐graft‐deprotection procedure. Because the intermediate phthaloylchitosan was soluble in organic solvents, the graft copolymerization was carried out in a homogeneous system. Grafting was initiated by γ‐irradiation. The graft percentage extent was dependent on the irradiation dose and the concentration of MMA monomer, and copolymers with grafting above 100 % were readily prepared. The graft copolymers exhibited a high affinity not only for aqueous acid but also for some organic solvents. Differential scanning calorimetry measurements revealed the presence of a glass transition phenomenon, which could be ascribed to the poly(methyl methacrylate) side‐chains. Copyright © 2004 Society of Chemical Industry     

Polymers from renewable resources: Kinetics studies of the radiochemical graft copolymerization of styrene onto cellulose extracted from pine needles and the effect of some additives on the grafting parameters in an aqueous medium

In an attempt to develop an alternative to petro‐based polymers, we graft‐copolymerized cellulose isolated from the needles of Pinus roxburghii with styrene in a limited aqueous medium in air by simultaneous irradiation using gamma rays as the initiator. The optimum conditions for obtaining maximum grafting were determined as a function of monomer concentration, total dose of irradiation, and amount of water. Maximum percentage of grafting (P_g; 79.9) was obtained at a total dose of 1.152 × 10⁴ Gy with 1.325 × 10^?4 mol of styrene. The effect of methanol, LiNO₃, Cu(NO₃)₂, Mohr's salt, H₂SO₄, HNO₃, and AcOH on P_g was studied. All the additives were found to decrease graft yield, contrary to some reported studies. Total percentage conversion and rates of polymerization, grafting, and homopolymerization were evaluated. Evidence of grafting was provided by the characterization of cellulose and its graft copolymers by Fourier transform infrared spectroscopy, thermogravimetry, and observation of the swelling behavior in some solvents. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1490–1500, 2002     

超声-微波共辐射法合成纤维素-MMA接枝共聚物

引言纤维素作为一种天然的可再生高分子材料,存在于丰富的绿色植物中,是自然界取之不尽用之不竭的清洁资源。因此,在煤、石油、天然气的储量日益减少的今天,纤维素可作为一种可持续发展的绿色资源来研究和开发。而且天然植物纤维资源丰富、价格低廉,并且具有较好的生物可降解性,在     

Proton exchange membranes prepared by simultaneous radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) films. I. Effect of grafting conditions

The simultaneous radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP) films was studied at room temperature. The effects of grafting conditions (type of solvent, irradiation dose, dose rate, and monomer concentration) were investigated. The degree of grafting was found to be dependent on the investigated grafting conditions. The dependence of the initial rate of grafting on the dose rate and the monomer concentration was found to be of 0.5 and 1.3 orders, respectively. The results suggest that grafting proceeds by the so‐called front mechanism in which the grafting front starts at the surface of the film and moves internally toward the middle of the film by successive diffusion of styrene through the grafted layers. Some selected properties of the grafted films were evaluated in correlation with the degree of grafting. We found that the grafted FEP films possess good mechanical stability, which encourages their use for the preparation of proton exchange membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 220–227, 2000     

Radiation‐induced graft copolymerization of α‐methyl styrene and butyl acrylate mixture into polyetheretherketone films

Radiation‐induced graft copolymerization of α‐methyl styrene (AMS), butyl acrylate (BA) monomers, and their mixture was investigated on poly(etheretherketone) films. The graft polymerization was carried out using ethyl methyl ketone as the medium for the copolymerization and the maximum degree of grafting of 27% was achieved. It was observed that the grafting is significantly influenced by the reaction conditions, such as reaction time, preirrradiation dose, monomer concentration, monomer ratio, and the reaction temperature. The degree of grafting increases as the monomer concentration increases up to 30%, beyond which a decrease in the grafting was observed. The degree of grafting showed a maximum at 40% BA content in the monomer mixture. The temperature dependence of the grafting process shows decreasing grafting with the increase in the reaction temperature. The presence of AMS and BA grafts in the film was confirmed by FTIR spectra. The relative change in the PBA/PAMS fraction with respect to the reaction temperature has been found in this study. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Molecular weight distribution of the graft copolymer comprising mixtures of styrene and acrylamiae on cellulose acetate film by means of gel permeation chromatography

Styrene portion of the radiation-induced graft copolymer comprising styrene and acrylamide was separated by acid hydrolysis and the effects of various grafting parameters (e.g., reaction time, reaction temperature, solvents, monomer composition, etc.) on molecular weight distribution were evaluated by means of gel permeation chromatography. When a single monomer or mixture of two monomers are grafted, the molecular weights is found to increase, but polymer dispersity decreases with the increase of reaction time or reaction temperature except at a higher reaction time due to the continuous enlargment of the growing chain through increased swelling and molecular motion of the trapped radicals. At higher reaction time the degradation of the graft chains lead to lower molecular weight and higher polymer dispersity. Effects of solvents (e.g., methanol, ethanol, and t-butanol) on the molecular weight and molecular weight distribution were discussed on the basis of swelling property and chain transfer constants of the solvents. Styrene-type graft radical being long lived compared to acrylamide type, gave long-chain styrene graft with the increase of styrene content in the reaction mixture. A comparison of the effect of one-and two-component systems on a molecular weight distribution is also 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.     

微波辐射下淀粉-丙烯酰胺接枝共聚物的合成

以硝酸铈铵作为引发剂、丙烯酰胺为单体,用微波辐射法合成了淀粉接枝丙烯酰胺共聚物。探讨了反应时间、引发剂浓度、单体和淀粉质量比和反应温度等因素对接枝反应的影响。正交实验确定的最优工艺条件为:反应时间20 m in,引发剂浓度4 mmol/L,丙烯酰胺和淀粉质量比2.5∶1,反应温度55℃,最高接枝率和接枝效率分别达到211.6%和74.3%。     

Radiation-induced graft polymerization of acrylonitrile onto isotactic polypropylene and poly(tetrafluoroethylene–ethylene) copolymer films

Direct radiation-induced grafting of acrylonitrile (AN) onto both isotactic polypropylene (IPP) and (tetrafluoroethylene–ethylene) copolymer (ET) films has been studied. The effect of grafting conditions such as inhibitor and monomer concentrations and irradiation dose on the grafting yield was investigated. Homopolymerization of acrylonitrile was reduced to a minimum using ferric chloride (FeCl₃), and the suitable optimum concentration of the inhibitor was found to be 0.1 wt%. The higher the monomer concentration, the higher the degree of grafting obtained. It was observed that the degree of grafting onto IPP was higher than onto ET, at given grafting conditions. The effect of aging on IPP was also examined. IR spectroscopy showed that IPP was susceptible to photooxidation by aging. The swelling behaviour and electrical conductivity of the graft and hydrolysed graft films were investigated. The electrical conductivity was improved by hydrolysis of polyacrylonitrile in the graft chains.     

Electron‐beam‐radiation‐induced grafting of acrylonitrile onto polypropylene fibers: Influence of the synthesis conditions

Electron‐beam‐radiation‐induced grafting of acrylonitrile onto polypropylene fibers was investigated with a pre‐irradiation method. Grafting conditions such as the solvents, additives, monomer concentration, radiation dose, and temperature were varied, and the effects on the degree of grafting were studied. The nature of the reaction medium and additives had a considerable influence on the degree of grafting. The dilution of acrylonitrile with N,N‐dimethylformamide significantly enhanced the degree of grafting in comparison with other solvents. The addition of sulfuric acid to the reaction mixture led to an increase in the degree of grafting and an acceleration of the rate of grafting. The order of dependence of the rate of grafting on the pre‐irradiation dose and monomer concentration was found to be 1.31 and 1.21, respectively, in the presence of sulfuric acid. The activation energy for grafting was calculated to be 21.9 kJ/mol. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010