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。     

电子束辐照改性PVC／EVA共混物的研究

采用电子柬为辐照源，以三羟甲基丙烷三丙烯酸酯(TMPTA)单体为交联教化剂，对聚氯乙烯与乙烯-醋酸乙烯共聚物以及与改性乙烯-醋酸乙烯共聚物(mEVA)的共混物进行了辐照改性。研究了不同种类EVA对共混体系凝胶含量、力学以及热延伸性能的影响，测试结果表明VA含量越大，辐照改性后共混体系凝胶含量越高，力学及热延伸性能改善越明显，应用氯元素分析方法测定得到VA含量越高越有利于促进PVC接枝或交联反应。辐照剂量的研究表明，辐射剂量增大，共混体系凝胶含量增加，力学及热延伸性能提高，但通过对PVC／mEVA共混体系的研究，辐射剂量超过5Mrad，体系降解程度明显增加。实验中采用凝胶渗透色谱(GPc)、红外吸收光谱(IR)、扫描电镜(SEM)等方法，对性能表现优异的PVC／mEVA共混体系进行了形态与结构分析。     

热缩型硅橡胶复合绝缘子的研制

研究了乙烯醋酸乙烯共聚物（EVA）、硅橡胶（PDMVS）和氢氧化铝不同配比时所组成的共混物的力学性能和电学性能及辐射交联对EVA／KPDMVS共混物的凝胶含量和力学性能的影响规律，确定了适合的辐交联剂量及利用该共混物制备热缩型硅橡胶复合绝缘子的工艺条件。     

HDPE/EVA二元共混物敏化辐射交联与性能

以三烯丙基异氰脲酸酯(TAIC)为交联敏化剂,采用电子束对高密度聚乙烯(HDPE)与乙烯-乙酸乙烯酯共聚物(EVA)的共混物进行辐射交联。研究了TAIC的敏化作用机理以及辐照剂量对共混物的力学性能、电学性能以及结晶度与交联度之间的相互关系。结果表明:TAIC对共混体系的交联反应具有敏化作用,可显著减小辐射剂量,共混物产生交联反应后可获得较高的凝胶含量;在辐射剂量120 kGy时,1%的TAIC即可使复合材料的拉伸强度提高了20%,断裂伸长率达到475.4%。此外,电子束辐射并未改变复合材料的晶型,随着辐射剂量的增加,复合材料的结晶温度、熔点、介电常数下降,共混物的介电损耗在120 kGy剂量下达到最佳。     

电子束辐照和氢氧化铝对LLDPE/EVA共混物凝胶含量和力学性能的影响

研究了电子束辐照剂量和氢氧化铝(ATH)的含量对线性低密度聚乙烯(LLDPE)/乙烯-醋酸乙烯酯(EVA)共混物凝胶含量和力学性能的影响。辐照剂量是影响LLDPE/EVA/ATH阻燃体系凝胶含量的主要因素,而ATH对其凝胶含量的影响较小。随着ATH含量的增加,LLDPE/EVA共混物的拉伸强度逐步增加,断裂伸长率迅速下降。所有阻燃体系的拉伸强度均是随着辐照剂量的增加而逐步增大,但辐照剂量对这些阻燃体系的断裂伸长率的影响却比较复杂。     

增塑PVC/NBR共混胶的辐照改性

以三羟甲基丙烷三丙烯酸酯（TMPTA）单体为交联敏化剂，采用电子束对聚氯乙烯（PVC）与丁腈橡胶（NBR）的共混胶进行了辐照改性。研究结果表明，对增塑PVC/NBR共混胶进行辐照改性，可以大大提高共混胶的力学性能及耐热性能。     

EVA对HDPE光交联反应的影响

采用测定凝胶含量的方法,以二苯甲酮(BP)作为光引发剂、三羟甲基丙烷三丙烯酸酯(TMP-TA)为交联剂,研究了辐照时间、乙烯-醋酸乙酯共聚物(EVA)含量对EVA/HDPE复合材料光交联的影响,并且考察了光交联后EVA/HDPE复合材料的力学性能。研究结果表明,EVA的加入会显著改变体系的凝胶含量;而辐照时间对EVA/HDPE体系交联反应影响很大;体系的力学性能随着EVA含量的增加而变化。     

交联无卤阻燃LLDPE/EVA电缆料的研制

以LLDPE（线性低密度聚乙烯）、EVA（乙烯醋酸乙烯共聚物）为基体树脂，ATH（氢氧化铝）、MH（氢氧化镁）为主阻燃剂，有机硅为阻燃增效剂，EVA-g-MAH（马来酸酐接枝乙烯醋酸乙烯共聚物）为高分子相容剂，DCP（邻苯二甲酸二壬酯）为交联剂制备了交联无卤阻燃LLDPE／EVA电缆料。研究结果表明，在燃烧时有机硅能促进玻璃态无机炭化层隔氧膜的形成，有效地提高共混物的氧指数。以EVA-g-MAH作为共混体系的相容剂能够改善交联无卤阻燃LLDPE／EVA电缆料的加工性能、力学性能和阻燃性能。     

EVA／木质素薄膜的制备与性能研究

研究了经造粒、吹塑成膜的乙烯醋酸乙烯酯共聚物（EVA）／木质素共混物的结构、热性能以及力学性能。热重分析表明木质素与EVA共混物的热稳定性比单一组分的高；差示扫描量热分析表明木质素与EVA的相容性好；傅里叶红外光谱分析表明木质素与EVA之间存在分子间氢键相互作用；扫描电子显微分析表明木质素含量对共混物形貌有明显的影响；力学性能测试表明木质素含量在30％（质量分数，下同）以内，共混物薄膜仍具有较好的力学性能，随着木质素含量的增加，共混物力学性能降低。     

电子束辐照对EVA/NBR复合材料结构和性能的影响

利用电子束对乙烯-醋酸乙烯共聚物(EVA)与丁腈橡胶(NBR)的共混物进行辐照交联,得到不同共混比例的EVA/NBR复合材料。考察了该复合材料的力学性能、交联度、耐油性、结晶性能及形状记忆性能,并讨论了辐照剂量和共混比例对材料性能的影响。结果表明:电子束辐照提高了EVA/NBR复合材料的力学性能和耐油性,同时降低了材料的结晶性能,这主要是由于辐照诱发了交联反应使材料内部产生了交联结构。通过控制交联度以及结晶相与NBR的比例,能够得到综合性能良好的耐油热收缩材料。     

Crosslinking of polyvinyl chloride by electron beam irradiation in the presence of ethylene–vinyl acetate copolymer

Electron beam (EB) irradiation of polyvinyl chloride (PVC) was carried out in the presence of three different ethylene–vinyl acetate copolymers (EVA). The mechanical properties of the original and irradiated blends were tested. The gel content measurement, chlorine loss upon electron irradiation, and gel permeation chromatograph (GPC) were used to characterize the effect of EVA on the irradiation behavior of PVC/EVA blends. The content and the chemical structure of EVA in the blends had considerable effects on the mechanical properties and gel content of the blends. The incorporation of EVA into PVC blend can increase the gel content and reduce chlorine loss of the blends. The GPC analysis of the soluble part in the irradiated PVC samples showed that the addition of EVA into the PVC blend lowered the polydispersity of molecular weight of PVC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1571–1575, 2004     

Preparation and Electron Beam Irradiation of PVC/ENR/CNTs Nanocomposites

Poly (vinyl chloride), PVC/epoxidized natural rubber blend, ENR/carbon nanotubes, CNTs nanocomposites were prepared using melt intercalation and solution blending methods. In both preparation methods PVC: ENR: CNTs ratios were fixed at 50:50:2, while the 50/50 PVC/ENR blend without the addition of CNTs was used as control. The PVC/ENR/CNTs nanocomposites were exposed to electron beam (EB) irradiation at doses ranging from 0–200 kGy. The effects of two different preparation methods on the tensile properties, gel fraction and morphology of the PVC/ENR/CNTs nanocomposites were studied. Prior to EB irradiation, the addition of 2 phr of CNTs caused a drop in the tensile strength (Ts) of the 50/50 PVC/ENR blend, implying poor distribution of CNTs in the PVC/ENR blend matrix. However upon EB irradiation, the nanocomposites prepared by the melt blending method exhibited higher values of Ts as compared to the neat PVC/ENR blend due to occurrence of radiation-induced cross-linking in the PVC/ENR blend matrix. Transmission electron microscopy (TEM) images proved that a better dispersion of CNTs in PVC/ENR blend matrix can be achieved by melt intercalation compared to solution blending and the dispersion of CNTs was improved by irradiation. Scanning electron microscopy (SEM) results showed a distinct failure surface with formation of rough structure for the irradiated nanocomposites, which explains the higher values of tensile properties compared to the non-irradiated nanocomposites.     

Irradiation Modification of PVC/NBR Blend

Electron beam initiated cross-linking on the 50/50 poly(vinyl chloride), PVC/acrylonitrile butadiene rubber, NBR blend was studied in the absence and presence of 4 phr trimethylolpropane triacrylate (TMPTA). The 50/50 NBR/PVC blend was prepared by mixing in a Brabender Plasticoder at 170°C. The blend was then irradiated by using a 3.0 MeV electron beam machine at doses ranging from 0 to 200 kGy in air and room temperature. The changes in gel fraction, tensile strength, hardness, impact strength, scanning electron micrographs and dynamic mechanical properties of the samples were investigated. The gel fraction results indicate that under the irradiation conditions employed, the PVC/NBR blend cross-linked by electron beam irradiation. The addition of TMPTA was found to be effective in the acceleration of the radiation-induced cross-linking. Gradual increases in mechanical properties with irradiation dose were observed before exhibiting a decline due to embrittlement as a consequence of excessive cross-linking at higher irradiation doses. The gradual changeover from ductile to brittle fracture due to the irradiation-induced cross-linking was evident from the SEM examination The increase in the storage modulus and T_g as well as the reduction in the damping peak with the increase in irradiation dose reveal that the enhancement in mechanical properties of NBR/PVC blends upon irradiation is due to the irradiation-induced cross-linking, as well as the improved interaction between NBR and PVC.     

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.     

Vinyl acetate content and electron beam irradiation directed alteration of structure,morphology, and associated properties of EVA/EPDM blends

A series of ethylene vinyl acetate/ethylene–propylene diene elastomer (EVA/EPDM) blends with four types of EVAs with various vinyl acetate (VA) content, are prepared without and with crosslinker, trimethylol propane triacrylate (TMPTA). These are irradiated by electron beam (EB). As the VA content increases, the gel content, i.e., degree of crosslinking of EVA/EPDM blends, is increased. With increase in VA content, the modulus and tensile strength are decreased but elongation at break is increased due to increase in amorphousness. On EB irradiation, modulus and tensile strengths are increased but at the cost of elongation at break. Crystallinities of all blends are decreased with increase in VA and EB crosslinking. The thermal stability of EVA/EPDM blend is decreased with increase in VA content but increased after EB irradiation. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) show that with increase in VA content the miscibility of two polymers keeps on increasing, which even become more after EB irradiation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43468.     

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     

Evaluation of mechanical properties and physical interactions of a ternary blend of poly(ethylene‐co‐octene)/poly(ethylene‐co‐vinyl acetate)/poly(vinyl chloride) in the molten state

In this work, ethylene‐co‐vinyl acetate (EVA), poly(ethylene‐co‐octene) (POE), and poly(vinyl chloride) (PVC) blends were processed in a molten state process using a corotating twin‐screw extruder to assess both the balance of mechanical properties and physical interactions in the melt state. Tensile measurements, scanning electron microscopy, and oscillatory rheometry were performed. By means of flow curves, the parameters of the power law as well as the distribution of relaxation times were assessed with the aid of a nonlinear regularization method. The mechanical properties for the EVA‐POE blend approximated the values for POE, while inclusion of PVC shifted the modulus values to those of neat EVA. The rise in modulus was corroborated by the PVC phase dispersion as solid particles that act as a reinforcement for the ternary blend. The rheological properties in the molten state show that the POE does not present molecular entanglement effects and so tends both to diminish the EVA mechanical properties and increase the fluidity of the blend. However, the addition of PVC both restored the EVA typical pseudoplastic feature and promoted the increase in the viscosity and the mechanical properties of the ternary blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of electron beam irradiation on (waste tire dust)‐filled ethylene vinyl acetate in the presence of bisphenol a diglycidyl ether

The effect of bisphenol A diglycidyl ether (BADGE) and electron beam (EB) irradiation on the properties of waste tire dust (WTD) ‐filled ethylene vinyl acetate (EVA) has been studied. The EVA/WTD ratio was fixed to 80:20, whereas the BADGE concentration varied from 1 to 5 wt%. The samples were then irradiated using a 3.0‐MeV EB machine at 50 kGy to 200 kGy at increments of 50 kGy. All the samples were subjected to various mechanical, physical, and thermal tests. Prior to irradiation, the mechanical properties of the composites show a gradual decrease with increasing BADGE concentration. Such observation is attributed to the plasticizing effect of the BADGE, as indicated by the reduction in mixing torque and a 14% increase in the elongation at break with the addition of 5 wt% BADGE. Results of gel fraction indicated that BADGE did not accelerate the irradiation‐induced crosslinking of EVA/WTD composites. The scanning electron micrographs and tan δ curves of EVA/WTD composites showed evidence that the addition of BADGE and EB irradiation of the EVA/WTD improves the compatibility of the composite. The overall results revealed that the irradiated EVA/WTD composite without BADGE gives a better enhancement in mechanical properties compared with the composites incorporated with the BADGE. J. VINYL ADDIT. TECHNOL., 23:172–180, 2017. © 2015 Society of Plastics Engineers