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。     

PP/LLDPE交联共混物的力学性能研究

采用两步交联加工法制备出具有优良力学性能的PP／LLDPE共混物。实验表明：当m(PP)／m(LLDPE)／m(SBS)／m(交联剂)为80／20／10／3时，交联共混物的冲击强度、拉伸强度和断裂伸长率分别达到466．3J／m、27．1MPa和715．1％，比未交联的共混物分别提高262％、8．28％和115％；交联作用的存在使共混物的脆韧转变点明显提前；随交联剂用量的增加，共混物的力学性能不断提高，但增大趋势逐渐变小。     

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。     

PVC/EVA共混物的研究

本文研究了混炼温度和时间对PVC/EVA共混物抗冲性能的影响,发现加入聚乙烯,共混体系的抗冲击强度能进一步提高.用TEM观察了PVC/EVA的形态结构,采用Brabender塑化仪和毛细管流变仪研究了共混物的塑化和熔体流变行为.通过计算机对实验结果进行二元线性回归,建立了共混物的熔体粘度与剪切应力和温度相关联的数学模型.     

辐照交联PVC／EVA共混物的形态结构与性能

以电子束为辐照源，以三羟甲基丙烷三丙烯酸酯（TMPTA）单体为交联敏化剂，对聚氯乙烯与乙烯－醋酸乙烯共聚物（EVA）的共混物进行辐照交联。采用红外吸收光谱、扫描电镜方法分析了添加改性EVA的共混物形态结构。通过凝胶含量、力学性能的测定，得到结论：EVA共聚物与PVC共混可以促进PVC辐照交联，改性EVA促进效果更明显；辐照剂量增大、体系凝胶含量增加，力学性能及热延伸性能提高，但辐射剂量高于5Mrad之后，体系降解程度明显增加。     

LLDPE-g-PGMA对PBT/LLDPE共混物的增容作用

用线性低密度聚乙烯接枝甲基丙烯酸缩水甘油酯（LLDPE－g-PGMA，简称LG）作为反应型增容剂，来改善聚对苯二甲酸本二酯（PBT）与LLDPE共混物的相容性，考察了LG的加入对PBT端羧基含量的影响，以及LG的加入量对不同配比共混体系力学性能的影响，并用扫描显微镜（SEM）对共混物形态结构进行了表征。研究结果表明，LG的加入降低了共混物中PBT的端羧基含量，改善了共混物中两相的相容性，使共混物的冲击强度提高58％以上。     

两步交联加工法制备的PS/PE共混物及其力学性能

采用两步交联加工法 ,制备了具有优良综合力学性能的PS/PE共混物。选择 85PS/15PE(质量比 )作为对象 ,研究了PE种类及不同加料方式、过氧化二异丙苯 (DCP)含量、加工温度、喂料速度、螺杆转速和SBS含量对该共混体系力学性能的影响。结果表明 :当PS/PE/SBS(质量比 )为 85 /15 /10 ,DCP用量为PE质量的 0 .3 % ,成核剂二苄基山梨醇 (DBS)的用量为PE质量的 0 .1% ,交联温度和加工温度均设置为 2 2 0℃ ,喂料转速为 2 5r/min ,主机转速为 10 0r/min时 ,共混物的冲击强度、拉抻强度、断裂伸长率分别达到 2 3 0 .7J/m、3 5 .7MPa和 62 .4% ,比PS/LLDPE二元共混物分别提高了172 0 %、5 3 .8%和 10 77%     

加工助剂对电子束辐照交联乙烯-甲基丙烯酸甲酯共聚物/三元乙丙橡胶共混物性能的影响

通过电子束辐照交联制备乙烯-甲基丙烯酸甲酯共聚物与三元乙丙橡胶的共混物,考察了辐照剂量和抗氧剂、助交联剂、炭黑及氧化锌等加工助剂对共混物拉伸性能、硬度、凝胶含量及耐热老化性能的影响。结果表明,电子束辐照提高了共混物的拉伸性能和硬度,主要是因其诱发了交联反应,使得共混物内部产生了交联结构。抗氧剂在起到抗氧化作用的同时也能够捕获辐照产生的自由基,使得达到所需交联度的辐照剂量增大,其用量以0.4~0.6份(质量,下同)为宜;助交联剂三羟甲基丙烷三甲基丙烯酸酯在低辐照剂量区表现出显著的敏化交联作用,但在高剂量区这种作用不明显,特别是添加量较大时其助交联的效果变差,其用量以3~5份为宜;炭黑添加量低于2份时不能够起到增强作用,但添加量过多共混物的硬度明显增大,以4~6份为宜;添加氧化锌能够起到很好的增强作用,但超过5份后共混物的拉伸强度会下降,因此以4~6份为宜。     

硅橡胶／EVA共混物性能的研究

本文研究了橡塑比、交联剂用量对硅橡胶/EVA共混物性能的影响,制得了具有优良物理机械性能、电性能、耐高温老化性能和热收缩性的新型材料,经适当配合可赋于材料优良的阻燃性能,可望获得实际工业应用。     

LLDPE/LLDPE-g-AA共混物的接触角及红外光谱表征

利用溶融共混的方法制备了线性低密度聚乙烯/线性低密度聚乙烯接枝丙烯酸（LLDPE/LLDPE-g-AA)共混物。用傅里叶红外光谱（FT-IR）和测定接触角的方法对不同LLDPE-g-AA含量的LLDPE/LLDPE-g-AA共混物膜的表面进行了表征。结果表明,随着共混物中LLDPE-g-AA含量的增加,水和甘油等极性液体与共混物表面的接触角下降。依据共混物的FT-IR计算了其羧基峰强度。发现极性液体与LLDPE/LLDPE-g-AA共混物膜表面的接触角越小,羧基峰强度越大。     

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     

LLDPE／EVA／CB复合导电体系电阻稳定性研究

以线性低密度聚乙烯（ＬＬＤＰＥ）和乙烯－醋酸乙烯共聚物（ＥＶＡ）为基体，油炉法炭黑（ＣＢ）为导电性赋与剂，探讨了热塑性半结晶性高聚物／炭黑复合体系的ＰＴＣ（正温度系数）效应及其电阻稳定性。结果表明，过氧化物交联剂（ＤＣＰ）可提高体系的ＰＴＣ性能稳定性和ＰＴＣ的转变温度，当用量为１％质量分数时，影响最为明显。炭黑接枝能提高体系的ＰＣＴ特性，比辐射更有效，使ＰＴＣ强度至少可提高１０倍。在所研究的极性高聚物Ａ、非极性高聚物Ｂ和极性物Ｃ三种接枝物中，以Ａ／ＰＥ／ＣＢ和Ｃ／ＰＥ／ＣＢ体系的ＰＴＣ特性明显，Ｂ／ＰＥ／ＣＢ体系峰值电阻率对应的温度低于Ａ／ＰＥ／ＣＢ约６～１５℃。在工作电压下通断电循环试验表明，ＬＬＤＰＥ／ＥＶＡ／Ａ－ｇ－ＣＢ体系在６０００ｈ的通电过程中，工作温度基本稳定在６５±５℃，通、断电循环试验的电阻率变化Ｒｆ／Ｒｉ大于２，功率变化Ｐｆ／Ｐｉ在１左右，而ＬＬＤＰＥ／ＥＶＡ／ＣＢ体系的发热温度下降很快，仅在７２０ｈ内就由８５℃下降到５０℃，直到３０℃才趋稳定，其电阻率增加３０倍以上，发热功率由１８Ｗ／ｍ下降到６Ｗ／ｍ。     

Structural characterization of LDPE/EVA blends containing nanoclay‐flame retardant combinations

The combination of different types of organo‐modified montmorillonite (MMT) with aluminum hydroxide (aluminum trihydrate—ATH), as a flame retardant system for polyethylene‐ethylene vinyl acetate (LDPE/EVA), blends were studied. Five different types of organically modified montmorillonite clays, each with different modifier, were used. The structural characterization was carried out by X‐ray diffraction (XRD) and scanning electron microscopy in transmission mode (STEM). The mechanical and rheological properties were also evaluated. The XRD analysis showed a clear displacement of the d₀₀₁ signal, which indicates a good degree of intercalation, especially for the MMT‐I28 and MMT‐20, from Nanocor and Southern Clay Products, respectively. The presence of ATH and the compatibilizer did not have any effect on the exfoliation of the studied samples. The thermal stability and flame retardant properties were evaluated by thermogravimetric analysis (TGA), limiting oxygen index (LOI—ASTM D2863), and flammability tests (Underwriters Laboratory—UL‐94). The effect of different compatibilizers on the clay dispersion and exfoliation was studied. The results indicated that the addition of montmorillonite makes it possible to substitute part of the ATH filler content while maintaining the flame retardant requirements. The thermal stability of MMT/ATH‐filled LDPE/EVA blends presented a slight increase over the reference ATH‐filled LDPE/EVA blend. Compositions with higher clay content (10 wt %) showed better physicochemical properties. The increased stability of the higher clay content compositions results from the greater inorganic residual formation; this material has been reported to impart better performance in flammability tests. The mechanical properties and flame retardancy remained similar to those of the reference compound. The reduced ATH content resulted in lower viscosities and densities, facilitating the processing of the polymer/ATH/clay compounds. Extrusion of these compounds produced a lower pressure in the extrusion head and required reduced electrical power consumption. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

The effect of mercapto‐modified EVA on rheological and dynamic mechanical properties of NBR/EVA blends

The effect of mercapto‐modified ethylene vinyl acetate copolymer (EVALSH) on the rheological and dynamic mechanical properties of acrylonitrile butadiene rubber (NBR) and ethylene vinyl acetate copolymer (EVA) blends was evaluated at different blend compositions. The addition of 5 phr of EVALSH in the blends resulted in an increase of the melt viscosity and a substantial decrease of the extrudate swell ratio. These results can be attributed to the interactions occurring between the double bond of the NBR phase and the mercapto groups along the EVALSH backbone. The power–law index also presents a slight increase in the presence of EVALSH, indicating a decrease in the pseudoplastic nature of the compatibilized blends. The reactive compatibilization of NBR/EVA blends with EVALSH was also confirmed by the decrease of damping values and an increase of glass transition temperature, in dynamic mechanical analysis. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2335–2344, 2002     

Radiation effects on HDPE/EVA blends

In this article, we discuss the radiation effects of high‐density polyethylene (HDPE)/ethylene–vinyl acetate (EVA) copolymer blends. In comparison with the low‐density polyethylene/EVA blends, the EVA content in the HDPE/EVA blends had a lower enhancement effect on radiation crosslinking by γ‐ray irradiation in air. The phenomenon is discussed with the compatibility, morphology, and thermal properties of HDPE/EVA blends. The HDPE/EVA blends were partly compatible in the amorphous region, and radiation crosslinking of the HDPE/EVA blend was less significant, although increasing the amorphous region's content of the HDPE/EVA blends and the vinyl acetate content of EVA were beneficial to radiation crosslinking. The good compatibility was a prerequisite for the enhancement effect of EVA on the radiation crosslinking of the polyethylene/EVA copolymer. The radiation crosslinking and the degradation mechanism of HDPE/EVA blends were examined quantitatively by a novel method, the step analysis process of irradiated HDPE/EVA blends with a thermal gravimetric analysis technique. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 553–558, 2002     

Effect of cross‐linked LLDPE/PP blend (LLDPE‐PP) as compatibilizer on morphology,crystallization behavior and mechanical property of LLDPE/PP blends

Moderate cross‐linked blend (LLDPE‐PP) of linear low‐density polyethylene (LLDPE) and polypropylene (PP) with benzoyl peroxide (BPO) were prepared by the reactive melt mixing in HAAKE mixer. Effect of LLDPE‐PP as compatibilizer on the morphology, crystallization behavior and mechanical properties of LLDPE/PP (87/13) blends were studied using scanning electron microscopy (SEM), polarized optical microscopy (POM), wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC) and mechanical testing machines. The results showed that LLDPE‐PP not only improved the interfacial adhesion between the LLDPE and PP but also acted as selective nucleating agent for crystal modification of PP. In the blends, the sizes of LLDPE and PP spherulites became smaller, and their melting enthalpies reduced in the presence of LLDPE‐PP. Furthermore, the mechanical properties of LLDPE/PP blends were improved with the addition of LLDPE‐PP, and when the concentration of LLDPE‐PP was 2 phr, the ternary blend had the best mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Covulcanization of LLDPE/EMA blends using dicumyl peroxide

The effect of dicumyl peroxide (DCP) content on the gel fraction, mechanical, dynamic mechanical, and thermal properties of linear low‐density polyethylene (LLDPE)/ethylene‐co‐methyl acrylate (EMA) blends were studied. Gel content of the blends increases with increasing DCP content, and EMA is more prone to crosslinking than LLDPE. Wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC) were used to study the effect of DCP crosslinking on percent crystallinity and crystalline structure of the blends and individual components. At lower level of DCP loading, crosslinking process does not have significant effect on the crystalline structure of the LLDPE, which was confirmed from the percent crystallinity and lattice distance value. However, at higher DCP content, percent crystallinity decreases significantly. At lower EMA concentration (<50%), percent crystallinity and lattice distance remain unchanged up to 2 wt % of DCP. For EMA contents of more than 50 wt %, increasing DCP content reduces the crystallinity of the blends and increases the lattice distance. The highest level of mechanical and dynamic mechanical properties was observed for 60/40 LLDPE/EMA blends at 2 wt % DCP. Addition of LLDPE‐g‐MA (3 wt %) as a compatibilizer enhances the properties of the vulcanizates. Blends crosslinked with DCP up to 0.3 wt % can easily be reprocessed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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.     

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 polyurethane structure on mechanical properties of nylon-66/polyurethane blends

A polyamide (nylon-66, N66) was blended with a series of polyurethanes (PU) based on different polyols or chain extenders. The effects of PU structure and content on the mechanical properties of the blends were investigated. The morphology of the polyblends was examined by scanning electron microscopy. The Izod impact strength of the blends increased with increasing PU content and showed a maximum value at the composition of 15 wt % PU. The effects of moisture content on the mechanical properties of the blends were also investigated. It was found that the water-toughened N66 could be further toughened by the addition of PU. Polyester-type PU rather than polyether type PU was recommended for the toughening of N66 because the blends containing the former showed higher tensile strength and Izod impact strength except at very low moisture (0.3 wt %) content. Carboxyl groups was introduced into the molecular chains of PU by using dimethylol propionic acid as chain extender replacing part of 1,4-butanediol. The blends containing PU with carboxyl groups showed a lower Izod impact strength than those without carboxyl groups in the structure of PU.