High Grafting Degree Research Articles

A PROTON EXCHANGE MEMBRANE PREPARED BY RADIATION GRAFTING OF p-STYRYLTRIMETHOXYSILANE INTO PTFE MEMBRANE

A proton exchange membrane ( PEM) was produced by simultaneous radiation grafting of p- styryltrimethoxysilane ( StSi ) into polytetrafluoroethylene ( PTFE ) membranes,followed by sulfonation,hydrolyzation and condensation.The effects of solvent,absorbed dose,absorbed dose rate and monomer concentration on the degree of grafting ( DOG) were studied.Toluene was chosen for its higher boiling point and giving a higher DOG with acceptable mechanical strength.DOG increased with increasing the absorbed dose and monomer concentration and changed little with the absorbed dose rate at 10 ～ 43 Gy·min -1.Monomer concentration of 3 mol·L -1 was better for reducing the copolymer.The degree of sulfonation (DOS) was as high as 92% ～ 97% at DOG 23% ,making the properties of the PEM rely much on the DOG.Scanning electron microscopy (SEM) gave imagines of radiation grafting happened through the surface to the centre of the membrane.The ion exchange capacity( IEC),water uptake,dimension expansion and proton conductivity grew up with the increase of DOG for more hydrophilic —SO3H,—Si—O—Si— crosslinking structure,and Si—OH groups were incorporated in the PEM.In addition,proton conductivity got better with temperature increase due to the good water uptake.Most of the grafted membranes exhibited lower methanol permeability than Nafion .The prepared PEM in this work showed a good combination of high IEC (1.53 mmol·g -1 ),dimension stability (dimension changed less than Nafion 117 at 90℃ ),acceptable water uptake ( 63% at 90℃ ) and proton conductivity ( 1.5 × 10 -2 S·cm -1 at 90℃ and DOG 72.5% ),and low methanol permeability (0.82 × 10 -6cm2·s -1 at DOG 50.1% ).

Structure, optical and thermal decomposition characters of LDPE graft copolymers synthesized by gamma irradiation

Methyl methacrylate (MMA) monomer was grafted onto Low density Polyethylene by the direct method of radiation grafting. The effect of cohesive energy density of different organic solvents on the degree of grafting was investigated. It was found that the extent of grafting depends largely on the kind of solvent, in which the highest degree of grafting was achieved in the presence of dioxane, whereas the lowest degree of grafting occurred in the presence of methanol. This behaviour was attributed to the solubility parameters of the solvent, monomer and polymer. The change in structure of the LDPE graft copolymer films was characterized by scanning electron microscopy, X-ray diffraction, UV/vis absorption and thermogravimetric analysis. The X-ray diffraction results showed a decrease in the crystallinity of LDPE graft copolymer matrix at high degree of grafting. Studies were made on the UV-absorption edge, indirect allowed transitions with their optical energy gaps are determined. At the same time the Urbach energy was evaluated. The activation energy of the thermal decomposition was calculated according to Horowitz and Metzger method.

Dissolution of fir powder and its graft copolymer in ionic liquid

Ionic liquid of 1-(2-hydroxylethyl)-3-ethyl imidazolium chloride ([HeEIM]Cl) was synthesized and its chemical structure was examined by FTIR and 1HNMR. Dissolution of the fir powder which was activated with 25% NaOH under different conditions in the ionic liquid was studied. Acrylamide (AM) was grafted onto the dissolved fir powder in [HeEIM]Cl and aqueous medium, respectively. Technologic conditions for graft copolymerization were optimized by orthogonal test. The results showed that the ionic liquid exhibited good solubility for the fir powder, the dissolution rate was as high as 18.3%. The graft copolymer prepared in [HeEIM]Cl had higher grafting degree and grafting efficiency than in aqueous medium. The most suitable conditions for graft copolymerization were: mass fraction of AM 25%, fluid ratio of [HeEIM]Cl to wood 30:1, and mass proportion of wood to AM 1:4. FTIR and SEM suggested that AM had been grafted onto the fir powder. XRD and TG indicated that the crystalline structure of the wood fiber had been destroyed thoroughly after being grafted, and the thermal stability of graft copolymer had been improved.

Structure, optical and thermal decomposition characters of LDPE graft copolymers synthesized by gamma irradiation

Methyl methacrylate (MMA) monomer was grafted onto low density polyethylene by the direct method of radiation grafting. The effect of cohesive energy density of different organic solvents on the degree of grafting was investigated. It was found that the extent of grafting depends largely on the kind of solvent, in which the highest degree of grafting was achieved in the presence of dioxane, whereas the lowest degree of grafting occurred in the presence of methanol. This behaviour was attributed to the solubility parameters of the solvent, monomer and polymer. The change in structure of the LDPE graft copolymer films was characterized by scanning electron microscopy, X-ray diffraction, UV/vis absorption and thermogravimetric analysis. The X-ray diffraction results showed a decrease in the crystallinity of LDPE graft copolymer matrix at high degree of grafting. Studies were made on the UV-absorption edge, and indirect allowed transitions with their optical energy gaps are determined. At the same time the Urbach energy was evaluated. The activation energy of the thermal decomposition was calculated according to Horowitz and Metzger method.

스타이렌 술폰산 고분자가 그래프트된 ETFE 막의 방사선 제조 방법 및 특성 분석

In this study, ETFE-g-PSSA membranes with various degrees of grafting (DOG) and thicknesses were prepared by a simultaneous irradiation method. SEM-EDX instrument was applied to measure the relative distribution of sulfur which is corresponding to that of a grafted polymer over the Cross-section of the ETFE-g-PSSA membranes prepared at various irradiation conditions. The results indicate that to obtain the evenly-grafted membranes, a styrene/dichloromethane ratio is needed to be under 60 (v/v%), and a higher DOG is required as the film thickness increases. The effects of DOG and thickness on the ion exchanging capacity (IEC) and water uptake (WU) were investigated by measuring the IEC and WU values of the membranes with various DOG and thicknesses.

Morphological, mechanical properties, and fracture behavior of bulk‐made ABS resins toughened by high‐cis polybutadiene rubber

AbstractAcrylonitrile‐butadiene‐styrene (ABS) resins with various rubber contents were prepared by applying nickel catalyzed high‐cis polybutadiene rubber (BR9004) as toughening agent via bulk polymerization. The influence of rubber content and its characteristics on the morphology, mechanical properties, and fracture mechanisms of ABS resins were investigated. The relevant performance parameters were also evaluated and compared with a commercial injection grade resin (ABS‐8434). The results show that each synthesized resin generally contains some irregular microsized particles with a certain amount of subinclusions besides the analogous “sea‐island” morphology to ABS‐8434. The subinclusions considerably enhance the volume fraction of rubber phase; this leads to an increasing maximum loss tangent (tan δ) value, a decreasing storage modulus and glass transition temperature (Tg) of rubber phase. Besides, the higher grafting degree can not only produce a higher Tg of grafted copolymer but also improve the compatibility of rubber phase with matrix. Based on the performance measurements andfractography, the final product with a rubber content of 9.3% reveals ductile fracture behavior and excellent comprehensive properties far superior to ABS‐8434 due to combined shear yielding and massive crazing. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers

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

AbstractSolvothermal 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

Silane grafting and moisture crosslinking of polyethylene: The effect of molecular structure

AbstractThe silane grafting and moisture crosslinking of different grades of polyethylene have been investigated. Three types of polyethylene (HDPE, LLDPE, and LDPE) with different molecular structures and similar melt flow indices were selected. The initiator was dicumyl peroxide (DCP), and the silane was vinyltrimethoxysilane. The grafting reaction was carried out in an internal mixer. The extent of grafting and the degree of crosslinking were determined, and hot‐set tests were carried out to evaluate the crosslink structure of the different polyethylenes. The LLDPE had the highest degree of grafting, while the LDPE had the least. The rate of crosslinking for LDPE was higher than that of HDPE and LLDPE. The gel content of LDPE was higher than that of HDPE and LLDPE. Hot‐set elongation and the number‐average molecular weight between crosslinks (Mc) were lower for LLDPE and LDPE than for HDPE. Increasing the silane/DCP percentage led to peroxide crosslinking, thereby decreasing the Mc and hot‐set elongation. The number‐average molecular weight (Mn), molecular weight distribution, and number of chain branches were the most important parameters affecting the silane grafting and moisture crosslinking. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers

Characterization of a Poly(propylene-g-styrene) Graft Copolymer by Temperature Rising Elution Fractionation

A polystyrene-grafted polypropylene sample was prepared by solid-state grafting polymerization in the presence of 2,2,6,6-tetramethyl-piperidinyloxy. Temperature rising elution fractionation of the grafted PP was performed and the fractions were characterized by 1H- and 13C-NMR, FT-IR, GPC, DSC, and WAXD. Results show that the grafted PP fraction eluted at 114°C accounts for 42% of the graft copolymer and has the highest grafting degree, high melting temperature and crystallinity, and high molecular weight. All the phenomena suggest that the grafted polymer contains a major component that has low branch density and long branch chain and a minor component with high branch density and short branches.

Preparation of crosslinked polystyrene-grafted PFA films by a simultaneous irradiation method

A series of polystyrene (PS)/divinylbenzene (DVB)-grafted poly(tetrafluoroethylene- co-perfluorovinyl vinyl ether) (PFA) films with various DVB contents were prepared by a simultaneous radiation grafting method. The degree of grafting was found to be strongly dependent on the grafting conditions, such as the monomer concentration, irradiation dose, dose rate, and crosslinker concentration. The results show that the highest degree of grafting was achieved at a 10% DVB content at the same irradiation conditions. The prepared PFA- g-PS/DVB films were characterized using FTIR, TGA, and a mechanical strength test.

Effect of Solvents on Gamma Radiation–Induced Graft Copolymerization of Vinyl Acetate onto Poly(3-hydroxybutyrate)

The effect of different solvents on the radiation-induced graft copolymerization of vinyl acetate onto poly(3-hydroxybutyrate) was studied. Structures of copolymers were determined with the techniques of thermogravimetric analysis and differential scanning calorimetry. From the thermal analysis results, it was found that the more favorable solvent to be used in the graft reaction is hexane. However, a much higher grafting degree can be achieved in bulk. The thermodynamic parameter obtained varied, showing that the enthalpy of melting and crystallization temperature of graft copolymers decreased with increasing grafting degree, which implies changes in the crystallization behavior and decrease in the material cristallinity. Further hydrolysis of the higher grafting degree graft copolymer was also studied.

Grafting of polypropylene and its potential use as metal ion adsorption resin

AbstractPolypropylene (PP) was modified by radical grafting of acrylic acid (AA) in the melt by using dicumyl peroxide (DCP) as initiator. To reach a high grafting degree (GD) without substantially modifying PP‐chain structure, a few runs were carried out by employing butyl 3‐(2‐furanyl)propenoate (BFA), which is a coagent able to preserve the molecular weight (MW) of PP macromolecules in the presence of radical grafting reagents. All the samples were extracted with selective solvents to remove unreacted chemicals and free poly(acrylic acid) (PAA), and the GD was accurately determined by using the FTIR methodology. The GD ranged from 1.51 to 4.67 mol %. High‐temperature size permeation chromatography analysis was used to evaluate MW behavior, confirming the control exerted by the presence of BFA on the degradation reactions. DSC, TGA, and SEM analyses were performed to analyze the chemical modification effects on the polymer products' thermal and morphological properties. Finally, selected samples, with a particle size distribution in the range 100–850 μm, were tested as metal ion adsorption resins. Al(III), Cr(III), Zn(II), Cd(II), Pb(II), and Hg(II) were studied, and the highest adsorption efficiency values (in percentage) were obtained for Al(III) (15–20%) and Hg(II) (25–30%). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effects of solvents on post-irradiation grafting of styrene onto fluoropolymer films

AbstractDue to the interest in the development of low cost membranes with similar capabilities to Nafion®, grafting of styrene on fluorinated polymers by simultaneous irradiation and pre-irradiation methods at high temperature (higher than 50 °C) followed by sulfonation has been a process studied broadly. However, there is very little information about grafting yield at room temperature after simultaneous irradiation. Previous works reported that the surface morphology of the styrene grafts has showed an uneven profile under the studied conditions. This work aims to evaluate the grafting of styrene onto these films after simultaneous irradiation (in post-irradiation condition), using different solvent in periods until 28 days at room temperature. Films of poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) were immersed in styrene/toluene 1:4 or styrene/methanol 1:4 and then submitted to gamma radiation at 40 and 80 kGy doses. The degree of grafting (DOG) was determined gravimetrically and physical and chemical changes were evaluated by infrared spectroscopic analysis (FTIR), differential scanning calorimeter analysis (DSC), thermogravimetric analysis (TGA), and also by scanning electron microscopy (SEM). For PTFE films, the highest DOG was achieved using toluene as solvent while for PVDF films, the highest DOG was achieved with methanol. Surface images of the grafted films by SEM technique have presented a strong effect of the solvents on the films morphology. Finally, PVDF-g-PS in styrene/methanol film revealed higher DOG, although the surface showed small cavities and discontinuities. On the contrary, the surface of PTFE-g-PS in styrene/toluene presented homogeneous surface.

Maleic anhydride/styrene melt grafting and crosslinking onto ethylene‐octene copolymer

AbstractMelt grafting of the multimonomer system of maleic anhydride (MAH)/styrene (St) onto ethylene‐octene copolymer (POE) was performed by a twin‐screw extruder. The effects of St and initiator contents as well as MAH/St on the grafting reaction were investigated. The structure and properties of the grafted POE were characterized by the Fourier transform infrared spectroscopy, melt flow index, dynamic rheological behaviors, and thermogravimetric analysis. It is shown that the addition of St can significantly enhance MAH grafting degree onto POE. MFI values of grafted POE are affected not only by MAH/St copolymer concentration, but also by initiator concentration. These data indicate that the interaction and reaction between MAH and St monomers plays an important role in the grafting reaction. St improves the grafting reactivity of MAH and reacts with MAH before the two monomers graft onto POE. And high grafting degree can be obtained while the gel content is still low. Compared with neat POE, grafted POE shows different dynamic rheological behaviors and high thermal stability. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers

Preparation of a blocked isocyanate compound and its grafting onto styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer

The epsilon-caprolactam was used to block the isocyanate group to enhance the storage stability of allyl (3-isocyanate-4-tolyl) carbamate. The spectra of FTIR and NMR showed that blocked allyl (3-isocyanate-4-tolyl) carbamate (BTAI) possesses two chemical functions, an 1-olefin double bond and a blocked isocyanate group. The FTIR spectrum showed BTAI could regenerate isocyanate group at elevated temperature. DSC and TG/DTA indicated the minimal dissociation temperature was about 135 degrees C and the maximal dissociation rate appeared at 226 degrees C. Then the styrene-b-(ethylene-co-1-butene)-b-styrene triblock copolymer (SEBS) was functionalized by BTAI via melt free radical grafting. The effect of temperature, monomer and initiator concentrations on the grafting degree and grafting efficiency was evaluated. The highest grafting degree was obtained at 200 degrees C. The grafting degree and grafting efficiency increased with the enhanced concentration of BTAI or initiator.

Properties of poly(ethylene 1‐octene)‐g‐maleic anhydride copolymers prepared via solvothermal process

AbstractThe poly(ethylene 1‐octene)‐g‐maleic anhydride copolymers (POE‐g‐MAH) with high grafting degree (GD) (>9%) have previously been obtained by a solvothermal method in our laboratory. It is found that the low GD (less than 2.5%) did not change the bulk properties of polyolefine elastomers (POE). Thereforefore, it is worth further understanding whether a high GD POE‐g‐MAH copolymer differs from the pure POE in its comprehensive properties and performance. In this article, POE‐g‐MAH with different GDs were synthesized and characterized by thermogravimetric analyze (TGA), differential scanning calorimetry (DSC), wide angle X‐ray diffraction spectroscopy (WAXD), and dynamic rheological testing. The results show that the thermal decomposition temperature, melting points, the crystallization temperatures, and the crystallinities were decreased by the increasing GD. By WAXD, three peaks respectively, attributed to the amorphous phase, the (110) and (200) interferences of the orthorhombic unit cell were detected, and they also decreased by the increasing GD. And the POE‐g‐MAH copolymers had higher storage modulus (G′), loss modulus (G″), and complex viscosity (η*) than those of pure POE. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Surface modification of lyocell fibres by graft copolymerization of thermo-sensitive poly- N-isopropylacrylamide

Thermo-sensitive poly- N-isopropylacrylamide (poly-NIPAAm) was grafted onto lyocell fibres using cerium ammonium nitrate (CAN) as initiator. The effects of initiation time, initiator concentration, monomer concentration and grafting time on the degree of grafting were investigated. A 15–60 min exposure time, 7.5 mM CAN solution concentration and a 0.5–1 mM NIPAAm monomer concentration were optimal for obtaining a maximum degree of grafting (60–70% at 24 h grafting time) of poly-NIPAAm on lyocell fibres. Higher degree of grafting was obtained increasing the grafting time, such as 120% at 72 h. The properties of the obtained poly-NIPAAm/lyocell copolymer were also investigated. Specifically, the effects of temperature and degree of grafting of poly-NIPAAm on the swelling behaviour of the copolymer were experimentally determined. Moreover, structural characterization, thermal behaviour and morphology of the poly-NIPAAm/lyocell copolymers were examined by Fourier Transform Infrared Spectroscopy (FTIR), Differencial Scanning Calorimetry (DSC) and Scanning electron microscopy (SEM) techniques, respectively.

Improvement of polymer electrolyte membrane by radiation-induced grafting of styrene onto FEP film with subsequent sulfonation

Poly(tetrafluoroethylene-co-hexafluoropropylene) (FEP) film was homogeneously and highly grafted by styrene monomer under simultaneous irradiation with an electron beam, whereas preirradiation with an electron beam was insufficient to accomplish a high degree of grafting without activation of the styrene monomer. Following its subsequent sulfonation, the styrene-grafted FEP film exhibited considerably higher values of both the IEC and IC and less methanol crossover than the Nafion membrane. The grafting of styrene onto the FEP polymer is thought to be initiated by the abstraction of F atoms from the CF3 groups in the polymeric structure. It was estimated that two sulfonic acid groups can be attached to the benzene ring of one styrene molecule. The profile of sulfur across the FEP film, which is related to the concentration profile of sulfonic acid groups inside the styrene-grafted FEP film, became more and more homogeneous over a period of several hours, due to the step by step diffusion of monomers into the film, eventually showing a high IC value of 0.25 S/cm in the case of the 125 μm thick FEP film, whereas Nafion 117 (125 μm thickness) exhibited an IC value of 0.12 S/cm.

Thermal, mechanical and electrical properties on the styrene-grafted and subsequently sulfonated FEP film induced by electron beam

This paper examined the mechanical and electrical properties of poly(tetrafluoroethylene- co-hexafluoropropylene: FEP) film modified by electron beam (EB). The simultaneous irradiation method with EB was adopted for the grafting of styrene and subsequent sulfonation onto FEP film. The thermal and mechanical characteristics of the irradiated FEP film, and also those of the grafted and sulfonated FEP films, were investigated by TGA, FT-IR spectrometer, and Instron. The simultaneous irradiation with EB facilitated the homogeneous grafting, as well as a high degree of grafting with a maximum value of around 60%, thereby allowing accurate control of the degree of grafting at doses ranging from 10 to 100 kGy. The grafting or sulfonation decreased the thermal stability of FEP, whereas it considerably increased its mechanical properties. The high radiation resistance of virgin FEP up to a dose of 100 kGy enabled the sulfonation of FEP film to considerably reinforce its polymeric structures except of 10 kGy, thereby increasing its tensile strength at 30 kGy by two-fold compared to that of the virgin FEP film. The ion conductivity (IC) and ion-exchange capacity (IEC) values of the FEP membrane (125 μm thick), which were dependant on the degree of grafting, were 0.25 S cm −1 and 2.4 mmol/g, respectively, at 59.2% of the degree of grafting and were superior to those of the commercialized Nafion membrane (IC, 0.12 S cm −1; IEC, 0.9–1.0 mmol/g).

Radiation-induced graft copolymerization of MMA monomer onto UHMWPE: Adhesion improvement

Graft copolymerization of methyl methacrylate monomer onto ultra high molecular weight polyethylene (UHMWPE) and acid-etched UHMWPE was conducted using preirradiation method in air in the presence of a Mohr salt and sulfuric acid to improve adhesion to the bone cement. The grafted samples were characterized by Fourier transform infrared (FTIR) spectroscopy, gravimetric method, goniometry, and interfacial bonding strength measurements. The FTIR results showed the presence of ether, carbonyl, and hydroxyl groups for grafted films. The gravimetric results showed that the chromic acid etching and graft copolymerization had a synergetic effect so, the irradiated, then chromic acid etched at room temperature and grafted sample (Rad etch25) had the highest grafting degree. The interfacial bonding strength between UHMWPE and poly methyl methacrylate bone cement was considerably improved by graft copolymerization and chromic acid etching. The surface morphology was studied by scanning electron microscopy. The substitution of polar groups into the backbone of UHMWPE by chromic acid etching and graft copolymerization changed its contact angles with water and methylene iodide and increased its surface energy, as evidenced by contact angle measurements. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008