电子束辐照交联PVC/EVA共混物的研究

以丙烯酸酯类多官能团不饱和单体为交联敏化剂，采用电子束对聚氯乙烯(PVC)与乙烯—酸酸乙烯共聚物(EVA)的共混物进行辐照交联。研究了VA质量分数、交联敏化剂种类及用量、辐照剂量、EVA用量对共混物凝胶质量分数、力学性能以及热延伸性能的影响。结果表明：EVA共聚物能促进PVC的辐照交联，增加共混体系的凝胶质量分数，改善其力学及热延伸性能；EVA共聚物中VA质量分数增大，共混体系的凝胶质量分数增大，力学及热延伸性能改善更明显。     

Effect of electron‐beam irradiation on ethylene–methyl acrylate copolymer

Ethylene–methyl acrylate copolymer (Elvaloy 1330) was irradiated by an electron beam at different levels of radiation both in the presence and absence of a trimethylolpropane trimethacrylate sensitizer at various dosages of incorporation. The mechanical, thermal, and electrical properties of these samples were compared. The mechanical properties were observed to reach an optimum maximum around 6 Mrad of irradiation and 1 phr of sensitizer incorporation. Furthermore, an increase in either the radiation dose or the sensitizer level helped very little to further modify the properties. The thermal properties as determined by the thermogravimetric analysis and differential scanning calorimetry studies were quite supportive of the observation made during the study of the mechanical properties. The thermal stability of the irradiated samples underwent an increase with increasing electron‐beam dosage. In a manner similar to those of the mechanical properties, the increase in thermal stability was found to reach a maximum at a particular level of treatment and sensitizer incorporation, beyond which there was marginal or no effect at all. The α transition temperature underwent a substantial increase with increasing crosslink density, as evidenced by the increase in gel content with increasing proportion of electron‐beam radiation dose. The other glass‐transition temperature, however, appeared to remain unaffected. The electrical properties, as described by the dielectric constant, volume resistivity, and breakdown voltage, appeared to be affected very little by the electron‐beam radiation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Mechanical,Thermal and Electrical Properties of Ethylene Vinyl Acetate Irradiated by an Electron-Beam

The effects of electron beam irradiation of (ethylene vinyl acetate) EVA containing 18% vinyl acetate was studied. The EVA sample was then irradiated by using 3 MeV electron beam machine at doses ranging from 120 to 360 kGy in air at room temperature and analyzed for mechanical, thermal and electrical properties. It was revealed by DSC analysis that the crystallinity of the electron-beam radiated EVA decreased slightly as verified by a marginal reduction in the densities and heats of melting. Thermal degradation of EVA occurred through two steps as shown by the thermogravimetric curve with maximum rates of 350 and 450°C, respectively. The results obtained from both gel content and hot set tests showed that under the irradiation conditions employed, the EVA sample cross-linked by the electron beam irradiation, and the degree of cross-linking in the amorphous regions was dependent on the irradiation dose. A significant improvement in the tensile strength of the neat EVA samples was obtained upon electron-beam radiation up to 210 kGy with a concomitant decline in elongation of break. Various electrical properties of EVA such as surface and volume resistance, breakdown voltage and dielectric constant were studied as a function of radiation dose. It was revealed that the surface resistance and volume resistivity of the EVA reaches a maximum at a 190 kGy dose of radiation. No considerable change of breakdown voltage and dielectric constant was observed with increasing irradiation dose. These studies suggest that radiation-cured EVA is more thermally and mechanically stable than pure EVA. Similarly, the results from the electrical properties revealed that surface and volume resistance are higher than pure EVA.     

Effect of electron beam irradiation on the dielectric properties of fluorocarbon rubber

Terpolymeric fluorocarbon rubber (68 wt.-% fluorine, 1.4 wt.-% hydrogen) was subjected to electron beam irradiation using 1,1,1-trimethylolpropane triacrylate (TMPTA), tripropylene glycol diacrylate (TPGDA), and pentaerythritol tetracrylate as radiation sensitizers. Compared to the original sample both the dielectric constant and the dielectric loss factor decrease for samples treated to a certain dose level, beyond which there is an increase. Similar improvement in dielectric properties is observed at relatively higher levels of TMPTA, owing to the increased degree of crosslinking. Among the various polyfunctional monomers used as radiation sensitizers, both the dielectric constant and the dielectric loss factor are higher for systems based on TPGDA due to the reduced crosslink density.     

辐照改性制备长支链型高熔体强度聚丙烯流变性能(Ⅱ)拉伸流变

通过辐照法制备了长支链型高熔体强度聚丙烯(LCB-HMSPP),采用Rheotens熔体拉伸流变仪研究了辐照改性PP的熔体强度和拉伸流变行为,讨论了敏化剂含量、辐照剂量、高分子量物质和温度对PP拉伸流变行为的影响。研究结果表明：PP的熔体强度、拉伸应力、拉伸黏度等拉伸流变物理量随敏化剂增加而显著增强,并随辐照剂量呈先上升后下降的趋势,辐照剂量为5kGy时,熔体强度和拉伸黏度到达最大。添加极少量高分子量物质(UHMWPE)也能有效提高PP的熔体强度。LCB-HMSPP的熔体强度活化能显著降低,熔体强度温度敏感性下降,可在较宽的温度范围内表现出较高的熔体强度。     

Studies on the properties and structure of electron‐beam crosslinked low‐density polyethylene/poly[ethylene‐co‐(vinyl acetate)] blends

Blends of low‐density polyethylene (LDPE) and poly[ethylene‐co‐(vinyl acetate)] (PEVA), crosslinked by electron‐beam (EB) radiation, formed separate crystalline lattices with a homogeneous amorphous phase. The crystallinity of the EB‐exposed samples slightly decreased, as verified by a slight reduction in the densities and melting heats and temperatures of the samples. The results obtained from both gel content and hot set tests showed that the degree of crosslinking in the amorphous regions was dependent on the dose and blend composition. The molecular weights between the crosslinks, measured from creep data, showed that an increasing PEVA content resulted in tighter network structures, thus supporting the idea that the crosslinking density at a given irradiation dose depends on the amorphous portions of the polymers. Addition of trimethylolpropane trimethacrylate as a radiation sensitizer enhanced the gel content of the neat polyethylene significantly, while the addition of an antioxidant showed the reverse effect. A significant improvement in the tensile strength of the neat PEVA samples was obtained upon EB radiation up to 210 kGy. The irradiated LDPE/PEVA blends showed improved tensile strength and elongation at break when compared to LDPE. Copyright © 2004 Society of Chemical Industry     

Effect of electron beam irradiation and vinyl acetate content on the physicochemical properties of LDPE/EVA blends

The radiation‐induced crosslinking, compatibility, and surface modification of low density polyethylene/ethylene vinyl acetate blends (LDPE/EVA) were investigated. The structural and physical properties were characterized in terms of gel content, hot set, mechanical properties, contact angle, and surface free energy. The highest crosslink density was obtained at 20 wt % of EVA. Gel content of LDPE/EVA blends was increased with increasing irradiation dose, vinyl acetate (VA), and EVA contents. The hot set results are consistent with the gel content data. Mechanical testing showed that the tensile strength of samples increased with increasing irradiation dose up to 180 kGy, whereas the elongation at break was decreased with increasing irradiation dose. Contact angle measurements showed that the surface hydrophillicity of LDPE blend was increased with increasing irradiation dose and contents of both VA and EVA. The surface free energy was greatly dependent on irradiation dose and content of both VA and EVA. The total surface free energies of different LDPE formulations were in the range 17.25–32.51 mN/m, in which the polar (^pσ) and disperse (^dσ_s) values were within the range 16.52–26.6 and 0.9–5.91 mN/m, respectively. In conclusion, electron beam irradiation and blending LDPE with EVA improved the wettability or adhesion properties of LDPE/EVA blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanical, electrical, and thermal properties of irradiated low-density polyethylene by electron beam

The effect of electron-beam (EB) irradiation on the mechanical, electrical, and thermal properties of low-density polyethylene (LDPE) was studied The LDPE was irradiated by using 3?MeV EB machine at doses ranging from 25 to 250?kGy in air at room temperature and analyzed for mechanical, thermal, and electrical properties. It was revealed by differential scanning calorimetry analysis that the crystallinity of the EB-radiated LDPE decreased slightly as verified by a marginal reduction in the densities, enthalpy, and melting points. Thermogravimetric analysis test showed that the thermal degradation of LDPE improved by increasing irradiation. The results obtained from both gel content and hot set tests, indicating whether the applicable LDPE has been properly cross-linked or not, showed that under the EB irradiation conditions employed, the cross-linking of the LDPE samples occur mainly in the amorphous region, and the cross-linking density at each irradiation dose depends almost on the amorphous portions of the LDPE. A significant improvement in the tensile strength of the neat LDPE samples was obtained upon EB up to 250?kGy with a concomitant decline in elongation at break. The results on the electrical properties revealed that the surface resistance, volume resistivity, and dielectric strength of the LDPE increase with irradiation dose and reaches a maximum at a 250?kGy irradiation dose. No considerable change of breakdown voltage, dielectric constant, and dielectric loss factor were observed with increasing irradiation dose. The enhancement in the heat deformation, hardness, and thermal aging properties of LDPE upon EB irradiation, suggests that irradiated LDPE is more thermally and mechanically stable than virgin LDPE.     

Mechanical and physicochemical properties of electron beam irradiated rubber/clay nanocomposites

Effect of electron beam irradiation on the mechanical and physicochemical properties of both styrene butadiene rubber (SBR)/clay and ethylene propylene diene monomer (EPDM)/clay nanocomposites containing clay contents from 3 to 10 phr prepared by melt blending method has been investigated. The prepared composites were subjected to electron beam irradiation doses of up to 150 kGy to induce radiation curing, whereas the mechanical properties in terms of tensile strength (TS), tear strength (Ts), and elongation at break (E_b) were studied as a function of irradiation dose and clay content. TS and Ts increased with increasing irradiation dose up to 100 kGy, they were decreased with further increase in dose. An increase in TS and Ts for SBR and EPDM nanocomposites containing various organomodified montmorillonite (OMMT) contents (3–5 phr) was noticed, whereas a decrement behavior was observed at higher OMMT content. The elongation at break decreased continuously with both irradiation dose and OMMT content. The crosslink density for either EPDM or SBR samples increases with increasing irradiation dose up to 150 kGy and by increasing clay content up to 5 phr, whereas it decreases at higher clay content (7–10 phr). At 5 phr OMMT and 100 kGy irradiation, SBR nanocomposites showed higher TS and Ts than EPDM nanocomposites, while the crosslink density of SBR is lower. POLYM. COMPOS., 34:1600–1610, 2013. © 2013 Society of Plastics Engineers     

Effect of irradiation on mechanical and structural properties of ethylene vinyl acetate copolymers hollow fibers

Effect of irradiation on mechanical and structural properties of ethylene vinyl acetate copolymers (EVA) hollow fibers was studied by the tests such as determination of gel content, density, tensile, FTIR, SEM, and DMA. These effects were discussed based on dose and irradiation environment. The results of gel content depicted that irradiated EVA in ambient conditions had tendency to chain scission while the crosslinking overcame in irradiated samples under nitrogen. Density insignificantly enhanced with irradiation dose. In tensile test, irradiation induced increase in tensile strength and decrease in elongation at break (especially in samples irradiated in nitrogen). Also, changing in layer orientation could be observed by SEM images. In addition, irradiation caused altering peak intensity in FTIR spectrum. DMA results demonstrated that irradiation broaden the elastic zone. Totally, irradiation enhances features especially in irradiated EVA18 in nitrogen. Since, according to stabilization of induced deformation and improvement of mechanical properties (that created by radiation), the irradiated samples can be used in different applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of electron beam irradiation on mechanical and dielectric properties of polypropylene films

In the present investigation the effect of electron beam irradiation on the mechanical properties of thin films of Polypropylene (PP) were measured. The dielectric properties of PP films were carried out in the frequency range from 20 Hz to 1 MHz at various DC bias potential. All measurements were carried out at room temperature. It is found that the electron beam irradiation caused an increase in Young's Modulus of PP film dose of up to 70 kGy were applied, but tensile strength and % elongation at break were found to be decrease with the increasing dose rate. The significant changes were observed in the case of dielectric constant and dielectric loss for electron irradiated PP films. The DSC results indicate that irradiation on PP films changes the thermal behavior. Minor differences in FTIR spectra were observed after irradiation treatment. It is observed that, the effect of radiation damage results in improvement in mechanical strength of the films. The increased dielectric constant and dependence of the bias voltage in case of irradiated and unirradiated PP films has been reported. It is suggested that, the PP films modified with the electron beam irradiation can be used as a good dielectric material for different electronic devices. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermal,mechanical, and corrosion resistance properties of vinyl ester/clay nanocomposites for the matrix of carbon fiber‐reinforced composites exposed to electron beam

Vinyl ester/clay nanocomposites with 1, 3, and 5% nanoclay contents were prepared. X‐ray diffractography patterns and Scanning Electron micrographs showed that nanocomposites with the exfoliated structure were formed. Thermogravimetric analysis, water absorption test, and Tafel polarization method, respectively, revealed the improvements in thermal resistance, water barrier properties, and corrosion resistance properties of the samples with an increase in the amount of the incorporated nanoclay. Tensile tests showed that nanoclay also enhanced the mechanical properties of the polymer, so that the tensile strength of the samples with 5% nanoclay was more than 3 times higher than tensile strength of pure vinyl ester samples. Overall, the best properties were observed for the samples containing 5% nanoclay. Pure vinyl ester and nanocomposite with 5% nanoclay content were exposed to the electron beam radiation and their mechanical properties improved up to 500 kGy irradiation dose. Finally, pure vinyl ester and vinyl ester/nanoclay (5%) matrixes were reinforced with carbon fiber and the effect of electron beam irradiation on their mechanical properties was examined. The tensile strength and the modulus of the samples initially increased after exposure to the radiation doses up to 500 kGy and then a decrease was observed as the irradiation dose rose to 1000 kGy. Moreover, nanoclay moderated the effect of the irradiation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42393.     

Influence of sepiolite and electron beam irradiation on the structural and physicochemical properties of polyethylene/starch nanocomposites

This study presents the influence of functionalized sepiolite and electron beam irradiation on the structural and physicochemical properties of high density polyethylene (HDPE)/starch blends. HDPE/Starch blends containing varying amounts of sepiolite [from 2 to 6 parts per hundred (phr) resins] were prepared in an internal mixer and subjected to electron beam irradiation. The structural analysis of nanocomposites revealed an interaction among the incorporated components. The morphological analysis depicted the void‐free dispersion of additives in the nanocomposites as well as an improvement in the compatibility between the matrix and additives. The sepiolite served as a heat barrier and improved the thermal stability of blend upto a maximum of 45°C. The ultimate tensile strength and Young's modulus (E) of blend was slightly improved with the incorporation of sepiolite and radiation. On the contrary, the E of nanocomposites was significantly improved with radiation dose. The sample containing 6 phr sepiolite and irradiated at 100 kGy showed 61% increase in E when compared with its unirradiated counterpart. Likewise, the thermal distortion temperature and Vicat softening temperature of the blend was slightly changed with the incorporation of sepiolite and radiation dose; however, increased with radiation dose in the nanocomposites. The improvements in the properties of nanocomposites with radiation dose were assigned to the formation of radiation‐induced crosslinked network as revealed by gel content analysis. The results presented here revealed substantial improvements in the properties of nanocomposites with irradiation, which pave way for their potential applications in various sectors including packaging materials for radiation sterilizable products. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Electron beam cross-linking of EVA/TPU blends

Abstract

Ethylene vinyl acetate (EVA) copolymer and thermoplastic polyurethane (TPU) with different blending ratios were melt mixed in an internal mixer. The blends were then exposed to electron beam (EB) irradiation with different doses of 50, 100, 150, 200 and 250 kGy. FTIR spectroscopy and dynamic mechanical thermal analysis (DMTA) were used to investigate the effect of cross-linking and blending ratio on chemical structure as well as solid state viscoelastic properties of the blends. FTIR spectroscopy showed interchain cross-linking during melt blending and also radiation cross-linking during solid state irradiation. Observation of one damping peak for blends at almost all blending ratios was an indication of miscibility of these blends. The results indicated formation of interchain cross-linking stabilised with exposure to EB irradiation. Mechanical properties of the blends were investigated via stress–strain curves. Modulus showed a monotonic increasing trend with the radiation dose, but tensile strength and elongation at break were initially increased and then decreased with increasing radiation dose. This was attributed to two competing parallel factors of strain induced crystallisation and degree of cross-linking.     

Effect of electron beam radiation on structural changes of trimethylol propane trimethacrylate,ethylene vinyl acetate,and their blends

The effect of electron beam irradiation at different radiation doses (2, 5, 10, 15, and 20 Mrad) on trimethylol propane trimethacrylol propane trimethacrylate (TMPTMA), ethylene vinyl acetate (EVA, 12% vinyl acetate content), and their blends (0.5, 1, 1.5, 2, 2.5, 3, and 5 parts/100 parts EVA) was investigated. An IR study showed some residual unsaturations retained in irradiated pure TMPTMA, while in blends all unsaturations were used up at a very early stage of irradiation. The concentration of the carbonyl group due to air oxidation increased in pure EVA and blends, but it reached a maximum at the 1.5-part TMPTMA level and 5-Mrad dose. some ether linkages were formed during irradiation in pure EVA and the blends, although in pure EVA the concentration of ether linkages reached a maximum at the 2-Mrad dose and then decreased and in the blends it increased with an increase in radiation dose. Gel content showed an increasing trend with an increase in radiation dose, but it increased marginally with TMPTMA level. A blend of EVA with 1 part TMPTMA produced more gel than pure EVA at the same irradiation dose. © 1996 John Wiley & Sons, Inc.     

Radiation preparation of ultrafine carboxylated styrene–butadiene rubber powders and application for nylon 6 as an impact modifier

Ultrafine carboxylated styrene–butadiene rubber(CSBR) powders were prepared by using gamma irradiation and following spray‐drying method. The influences of dose rate, absorbed dose, and sensitizer content on the crosslinking density of CSBR latices were studied in detail. Then the ultrafine CSBR powders were used to toughen nylon 6. The toughness and thermal properties of nylon 6/CSBR blends were measured by using notched lzod impact test and differential scanning calorimetry and thermogravimetry, respectively. Results showed that the crosslinking density of CSBR increased with increasing of dose and sensitizer content, and it is independent on dose rate. The notched Izod impact strength of nylon 6 under room temperature increased after incorporation of irradiation crosslinked CSBR powders with appropriate crosslinking density. The morphology of higher impact nylon 6/CSBR blends indicated that the finer dispersion existed with dispersed particles of 150‐nm diameter. Fracture morphology of nylon 6/CSBR blend suggested that the shear yielding in matrix is the primary toughening mechanism for nylon 6/CSBR blends. The crystallinity of nylon 6/CSBR blends decreased slightly compared with pure nylon 6, whereas the addition of CSBR powders had little influence on the thermal stability of nylon 6. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3040–3046, 2002     

Influence of γ irradiation on the properties of polyacrylonitrile films

In this study, we examined the effects of γ irradiation on the mechanical, thermal, structural, and electrical properties of polyacrylonitrile (PAN). Irradiation doses of 20, 40, 60, 80, and 100 kGy were used, with nonirradiated PAN films serving as control samples. Microhardness measurements, mechanical tests, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry analysis, color determination, X‐ray diffraction, and electrical properties were investigated to evaluate the effects of the irradiation treatments on the PAN films. A fair consistency was observed between the microhardness results. Irradiation caused a significant deterioration in the mechanical properties of the samples. The tensile strength and percentage elongation at break decreased with increasing irradiation dose. Similarly, Young's modulus and toughness also decreased with increasing irradiation dose. The melting and crystallization temperatures decreased, whereas the degree of yellowness increased with increasing irradiation dose. The percentage crystallinity of the PAN film increased with increasing irradiation dose. The FTIR spectra showed that there was a tendency toward a greater effect of γ irradiation on the structure of PAN at higher irradiation doses. The values of the electrical parameters, such as capacitance in parallel, dielectric constant, dielectric loss, resistance in series, resistance in parallel, reactance, and quality factor, increased, whereas the values of capacitance in series, impedance, conductance, susceptance, admittance, and phase angle decreased because of the γ irradiation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

高密度聚乙烯电子束辐射交联的研究

用高能电子束辐射技术研究了添加敏化剂季戊四醇三丙烯酸酯(PETA)和抗氧剂300的高密度聚乙烯(HDPE)体系的辐射交联效应.通过测定试样辐射后交联度、拉伸强度、直角撕裂强度等性能,考察了辐射剂量、w(PETA)和 w(300)对 HDPE辐射交联的影响;并用差示扫描量热法和热重分析研究了HDPE辐射后的结晶性和热稳定...     

Engineering properties of electron beam‐crosslinked ethylene methyl acrylate copolymer

Effect of electron beam on mechanical, thermal, and morphological properties of ethylene methyl acrylate copolymer, grade Elvaloy 1335 has been investigated. The copolymer was subjected to varying doses of electron beam radiation with different proportion of the sensitizer trimethylolpropane trimethacrylate (TMPTMA). It was observed that with increase in electron beam dose, the physicomechanical properties of the crosslinked copolymer improve, reaches an optimum level and subsequently deteriorates. The thermal properties as envisaged from thermogravimetric analysis and differential scanning calorimetric studies revealed stability of the crosslinked irradiated samples over that of the unirradiated ones. The thermal stability was also found to attain the maximum at the same level of radiation and sensitizer. The morphological studies showed consistency with the mechanical properties. Based on the overall study, it may be concluded that ethylene methyl acrylate copolymer with 1 phr TMPTMA at 60 kGy radiation dose is the optimum condition within the range studied in this investigation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of gamma radiation on low density polyethylene

Low density monofilaments of polyethylene with varying draw ratios were subjected to high energy radiation using Co⁶⁰ gamma radiation source. It was found that the tensile strength is sharply improved with the increasing dose up to 20 Mrd beyond which a sharp decrease in tenacity and initial modulus was observed. The swelling behaviour also decreased with the increased in dose of irradiation. However, density showed an increasing trend. The shrinkage behaviour of all the filaments was found to increase with increasing dose and draw ratios. The results have been explained in terms of continuous increase in crosslink density with the increasing dose of irradiation along with loss of crystallinity, which appears to be more severe in the latter stages of exposure. The samples exhibited memory effect after redrawing at 100°C and cooling under tension followed by further heating at 110°C under relaxed condition. The shrinkage was still much higher but independent of draw ratio.