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     

Simultaneous radiation grafting of vinylbenzyl chloride onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) films

In this study, we demonstrated that vinylbenzyl chloride (VBC), a versatile monomer with reactive a chloromethyl group could be grafted onto a poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP) film without a degradation of the chloromethyl group during a simultaneous irradiation process. The effects of various irradiation conditions such as the total dose, dose rate, solvent, and VBC concentration on the degree of grafting of VBC onto a FEP film were also investigated. The prepared PVBC‐grafted films were characterized using FTIR, TGA, and SEM EDX. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Proton exchange membranes prepared by simultaneous radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) films. II. Properties of sulfonated membranes

Proton exchange membranes were prepared by radiation‐induced grafting of styrene onto commercial poly(tetrafluoroethylene‐co‐hexafluoropropylene) films using a simultaneous irradiation technique followed by a sulfonation reaction. The resulting membranes were characterized by measuring their physicochemical properties such as water uptake, ion exchange capacity, hydration number, and proton conductivity as a function of the degree of grafting. The thermal properties (melting and glass transition temperatures) and thermal stability of the membrane were also investigated using differential scanning calorimetry and thermal gravimetric analysis, respectively. Membranes having degrees of grafting of 16% and above showed proton conductivity of the magnitude of 10⁻² Ω⁻¹ cm⁻¹ at room temperature, as well as thermal stability at up to 290°C under an oxygen atmosphere. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2443–2453, 2000     

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     

Radiation‐induced grafting of styrene onto poly(tetrafluoroethylene) (PTFE) films. I. Effect of grafting conditions and properties of the grafted films

Radiation‐induced grafting of styrene onto poly(tetrafluoroethylene) (PTFE) films was studied by a simultaneous irradiation technique. Grafting was carried out using γ‐radiation from a ⁶⁰Co source at dose rates of 1.32–15.0 kGy h⁻¹ at room temperature. The effects of type of diluent, dose rate, irradiation dose, and the initial monomer concentration in the grafting solution on the degree of grafting were investigated. The degree of grafting was found to be strongly dependent upon the grafting conditions. The dependence of the initial rate of grafting on the dose rate and the initial monomer concentration in the grafting solution was found to be in the order of 0.6 and 1.7, respectively. The chemical structure and the crystallinity of the grafted PTFE films were studied by means of Fourier‐transform infrared, (FTIR), electron spectroscopy for chemical analysis (ESCA) and X‐ray diffractometry (XRD). © 2000 Society of Chemical Industry     

Solvothermal process for grafting dibutylmaleate onto poly(ethylene‐co‐1‐octene)

Solvothermal process was successfully developed to graft dibutylmaleate (DBM) onto poly(ethylene‐co‐1‐octene) (POE) with dicumyl peroxide (DCP) as free radical‐initiator. FTIR spectra demonstrate that DBM is successfully grafted onto the backbone of POE by this novel method. The influences of DBM content, DCP concentration, POE concentration, reaction temperature and reaction time on the grafting copolymerization have been investigated in detail through grafting degree (GD). It is worthy to indicate that high grafting degree (above 15%) can be achieved through the one‐pot way when the graft reaction is carried out in 40 mL toluene at 150°C for 5 h with 1.6 g DBM, 6–8 g POE and 0.35 g DCP. This developed solvothermal process is becoming an effective way to prepare POE‐g‐DBM graft copolymers, and can be extended to other systems. In addition, TGA results show that the thermal properties of POE are enhanced after the grafting reaction. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Iron(III) complexed with radiation‐grafted acrylic acid onto poly(tetrafluoroethylene‐co‐perfluorovinyl ether) films

To introduce functional moieties to a poly(tetrafluoroethylene‐co‐perfluorovinyl ether) film, graft copolymerization of vinyl monomers such as acrylic acid was attempted by a simultaneous technique in aqueous solution using γ‐irradiation. The graft copolymers were complexed with the Fe(III) in aqueous solution. The grafted copolymer–metal complexes were examined by infrared (IR), ultraviolet/visible, energy‐dispersive X‐ray spectroscopy, and electron spin resonance techniques. The effect of temperature on the trunk copolymer, untreated grafted, and treated grafted copolymer films was investigated by IR and thermogravimetric analysis. The overall results suggest octahedral structure for Fe(III) and revealed the high stability of the obtained ligand–metal complexes. Furthermore, scanning electron microscope investigation of the grafted and modified films, both unheated and heated (200°C), showed changes in the structure and surface morphology. Promising results were achieved enhancing the practical applications of modified grafted membranes in the recovery of metal ions from aqueous systems. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4065–4071, 2007     

Radiation‐induced grafting of acrylic acid and sodium styrene sulfonate onto high‐density polyethylene membranes. I. Effect of grafting conditions

Radiation‐induced grafting of sodium styrene sulfonate and acrylic acid onto high‐density polyethylene (HDPE) membranes was studied by the preirradiation technique. Grafting was carried out using an electronic beam from a 2‐MeV accelerator at room temperature. The effects of the type of solvent, inhibitor concentration, preirradiation atmosphere, monomer concentration, and storage time of preirradiated HDPE membranes on the grafting yield were investigated. Easy control over the grafting yield was achieved by proper selection of the reaction conditions. IR spectroscopy analysis of the grafted membrane confirmed the existence of sulfonate and carboxylic acid groups in the grafted membranes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3401–3405, 2006     

Kinetics of radiation‐induced grafting of 2‐hydroxyethyl methacrylate onto chloroprene rubber membrane and computer verification

Grafting of 2‐hydroxyethyl methacrylate(HEMA) onto chloroprene rubber(CR) membrane was carried out in ethanol by direct cobalt‐60 gamma ray irradiation. The kinetics of the grafting reaction was studied in respect of concentration of monomer, dose rate and temperature. The experimental results show that the functional relationship equation is dg₀/dt = k[M]^1.5 Ḋ. The apparent activation energy and collision frequency factor of the grafting polymerization are 46.2 kJ mol⁻¹ and 4.98 × 10⁷ mg cm⁻² kGy⁻¹ mol^−1.5 litre^1.5, respectively. The work established the relationship of the initial grafting rate (dg₀/dt) with various effect factors: ln (dg₀ dt) = 17.7 − 5560(1/T) + 1.5 ln [M] + ln Ḋ. This equation is also verified for the first time by a software named SMR, which function is using multiple linear regression to calculate the regression coefficient of a linear equation. © 1999 Society of Chemical Industry     

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.     

Modeling,prediction, and multifactorial optimization of radiation‐induced grafting of 4‐vinylpyridine onto poly(vinylidene fluoride) films using statistical simulator

The traditional method for obtaining best combination of reaction parameters for graft copolymerization of 4‐vinylpyridine onto poly(vinylidene fluoride) films was modified using Box‐Behnken factorial design available in the response surface method (RSM). A computer‐assisted statistical simulator was used to obtain the optimum absorbed dose, monomer concentration, grafting time and reaction temperature to achieve the highest degree of grafting (G%) based a quadratic model. The validity of the developed model was confirmed by experimental data, which only deviated by a 2% from the predicted value of G% confirming the effectiveness of RSM in optimization of the reaction parameters in the present grafting system. A comparison was also made between the obtained model and that of 1‐vinylimidazole/poly(ethylene‐co‐tetrafluoroethylene) grafting system. The chemical structure, morphology and thermal stability of the obtained graft copolymers was investigated by means of Fourier transform infrared, filed emission scanning electron microscope, and thermogravimetric analysis, respectively. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Kinetics study of radiation‐grafting of acrylic acid,acrylonitrile, and their mixture onto wool fabric

The effect of monomer concentration, exposure time, irradiation temperature, and weaving direction on the kinetics of grafting acrylic acid (AA), acrylonitrile (AN), and their mixture onto wool fabric has been studied at the dose rate of 1.38 Gy/s. The degree of grafting is found to depend on the methanol‐to‐water solvent ratio and fabric‐to‐liquor ratio. The grafting rate and rate constant are dependent on irradiation temperature, type of grafted monomer, and weaving direction. The grafting rates increase with the increase in irradiation temperature (276–308 K). The calculated activation energy is nearly the same (16.4–17.2 kJ mol^?1) and the preexponential rate constant is dependent on the type of grafted monomer. The grafting of AA, AN, and their mixture are confirmed from the dyeing affinity of grafted fabrics towards Sandocryl Blue (SB), a basic dye. The formation of wool grafts and structural changes resulting from grafting were verified by using FTIR spectrometry and X‐ray diffraction analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4328–4340, 2006     

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.     

Functionalization of poly(tetrafluoroethylene‐co‐ethylene) film by radiation‐induced graft copolymerization

To introduce functional moieties to Tefzel film, a copolymer of tetrafluoroethylene and ethylene, graft copolymerization of vinyl monomers such as acrylonitrile (AN) and methacrylonitrile (MAN) was attempted by a preirradiation method in aqueous medium. Optimum conditions for obtaining the maximum percentage of grafting have been evaluated for both monomers. Maximum grafting of AN (52.2%) and MAN (77.7%) is obtained at a total dose of 3.14 and 2.69 × 10⁴ Gy, respectively, using [AN] = 3.018 mol/L and [MAN] = 1.177 mol/L in 10 mL of water. The effect of aliphatic alcohols of varying chain length, such as methanol, ethanol, isopropanol, n‐butanol, and cyclohexanol, on percentage add‐on of AN and MAN has also been studied. It has been found that all the alcohols decreased the percentage of grafting. Characterization of Tefzel and grafted Tefzel films has been carried out by IR spectroscopy and thermogravimetric analysis. Grafted Tefzel film has been found to have improved thermal resistance. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1171–1178, 2000     

Comparative investigations of radiation‐grafted proton‐exchange membranes prepared using single‐step and conventional two‐step radiation‐induced grafting methods

Proton‐exchange membranes containing poly(styrene sulfonic acid) grafts hosted in poly(vinylidene fluoride) (PVDF) films were prepared using two radiation‐induced grafting methods: a single‐step grafting method (SSGM) involving grafting of sodium styrene sulfonate onto electron beam (EB)‐irradiated PVDF films and a conventional two‐step grafting method (CTSGM) in which styrene monomer is grafted onto EB‐irradiated PVDF films and subsequently sulfonated. Differential scanning calorimetry, universal mechanical testing and scanning transmission electron microscopy were used to evaluate the thermal, mechanical and structural changes developed in the membranes during the preparation procedures. Physicochemical properties such as water uptake, hydration number and ionic conductivity were studied as functions of ion‐exchange capacity and the results obtained were correlated with the structural changes accompanying each preparation method. Membranes obtained using the SSGM were found to have superior properties compared to their counterparts prepared using the CTSGM suggesting the former method is more effective than the latter for imparting desired functionality and stability properties to the membranes. Copyright © 2010 Society of Chemical Industry     

Complexation of rhodium on radiation-grafted acrylic acid onto poly(tetrafluoroethylene–perfluorovinyl ether) copolymer films

Radiation-induced graft polymerization of acrylic acid onto poly(tetrafluoroethylene–perfluorovinyl ether) copolymer films has been prepared using γ-irradiation by the mutual method. The grafted copolymer rapidly complexes with rhodium ions through the carboxylic groups. The complexation process was followed by measuring the variation of the pH of aqueous RhCl₃ solution of several concentrations as a function of time. Spectroscopic, electrical, optical, thermal, and diffraction measurements have been investigated. The results revealed the high stability of the ligand–metal complex formed. Thus, a practical application of the grafted copolymer in the field of rare metal waste treatment is implied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1449–1455, 1998     

Cation exchange membranes by radiation‐induced graft copolymerization of styrene onto PFA copolymer films. II. Characterization of sulfonated graft copolymer membranes

PFA‐g‐polystyrene sulfonic acid membranes were prepared by simultaneous radiation‐induced graft copolymerization of styrene onto poly(tetrafluoroethylene‐co‐perfluorovinyl ether) (PFA) film followed by sulfonation. The membrane physico‐chemical properties such as swelling behavior, ion exchange capacity, hydration number, and ionic conductivity were studied as a function of the degree of grafting. Thermal as well as chemical stability of the membranes was also investigated. The membrane properties were found to be mainly dependent upon the degree of grafting. The water uptake, ion exchange capacity, hydration number, and ionic conductivity of the membranes were increased, whereas the chemical stability decreased as the degree of grafting increased. The membranes showed reasonable physico‐chemical properties compared to Nafion 117 membranes. However, their chemical stability has to be further improved to make them acceptable for practical use in electrochemical applications. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1–11, 2000     

Cation exchange membranes by radiation‐induced graft copolymerization of styrene onto PFA copolymer films. IV. Morphological investigations using X‐ray photoelectron spectroscopy

Morphological investigations of poly(tetrafluoroethylene‐co‐perfluorovinyl ether) (PFA)‐g‐polystyrene sulfonic acid membranes prepared by radiation‐induced graft copolymerization of styrene onto PFA films followed by sulfonation were performed by X‐ray photoelectron spectroscopy. The analyzed materials included grafted film and sulfonated membrane samples having various degrees of grafting. Original PFA film was used as a reference material. The results of the X‐ray photoelectron spectral analysis show that PFA film undergoes changes in terms of chemical compositions and binding energies of its basic elemental components under the influence of membrane preparation procedure, i.e., grafting and sulfonation. The chemical compositions of the surfaces of the membranes were found to be dependent on the degree of grafting unlike the binding energies of their elemental components (C, F, O, and S), which were found to be independent of the degree of grafting. The atomic ratio of F/C was found to decrease drastically with the increase in the degree of grafting and the membranes were found to have almost pure hydrocarbon structure at the layers close to their surfaces where degradation is suggested to be concentrated. The results of these investigations suggest that the morphology of the membranes plays an important role in the chemical degradation of the membranes. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2455–2463, 2000     

Influence of the radiation grafting conditions on the cross‐sectional distribution of poly(vinylbenzyl chloride) grafted polymer onto poly(tetrafluoroethylene‐co‐hexafluoropropylene) films

Poly(vinylbenzyl chloride) (PVBC)‐grafted poly(tetrafluoroethylene‐co‐hexafluoropropylene) (FEP) films were prepared as precursors for ion‐exchange membranes with a radiation grafting technique. A scanning electron microscopy–energy dispersive X‐ray spectroscopy (SEM‐EDX) instrument was used to investigate the effects of the radiation grafting conditions on the distribution profiles of the grafts in the FEP‐g‐PVBC films because the properties of the ion‐exchange membranes were largely affected not only by the degree of grafting (DOG) but also by the distribution of the graft chain. These results indicate that the distribution profile of the grafts largely depended on the grafting parameters, such as the solvent, monomer concentration, film thickness, and irradiation dose. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Grafting of telechelic poly(lactic‐co‐glycolic acid) onto O2 plasma‐treated polypropylene flakes

An operating window, which is bounded by two temperatures and draw ratios, defines the stable and defect‐free stretching region of a polymer film. Physical properties including the coefficient of thermal expansion (CTE), birefringence, and Young's modulus of a recyclable polyimide (PIR) film were measured under stretching conditions. While values of birefringence and Young's modulus increased with increasing stretching stress in the machine direction, the CTE was found to decrease. A semiempirical model for the prediction of birefringence and Young's modulus under stretching conditions was developed, from which the CTE could be estimated from the Young's modulus data. Theoretically evaluated physical properties were found to be in qualitative agreement with the experimental data. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011