Spatio-temporal growth of broken spiral and concentric ringed spherulites in blends of poly(vinylidene fluoride) and ethylene-vinylacetate copolymers

Melting and crystallization behavior in mixtures of poly(vinylidene fluoride) (PVDF) and several ethylene-vinyl acetate copolymers (EVAc) with various ethylene contents have been investigated by means of differential scanning calorimetry, atomic force microscope, and optical microscopy. PVDF/EVAc-80 exhibits the melting point depression of PVDF crystals, suggestive of a miscible character of the pair. Crystallization behavior and morphology development in blends of PVDF/EVAc-80 have been investigated with an emphasis on the spherulitic growth demonstrating the spiral and concentric ringed (or target) patterns. Of particular interest is the break-up of the spiral or concentric ringed patterns at very shallow supercoolings, which may be attributed to instabilities driven by the exclusion of amorphous PVDF and EVAc chains into the emerging inter- and intra-spiral (or target) lamellar regions.     

基于EVA电力上市公司的业绩评价

以股东超额期望收益率为出发点,选取我国沪深两市2006~2009年电力行业上市公司的样本数据资料,采用多元线性回归分析法对EVA在我国电力上市公司经营业绩评价的有效性进行实证检验.对电力上市公司业绩评价提供了可靠的决策依据,同时为电力上市公司的可持续发展提供了有价值的参数.     

Synthesis of new EVA graft copolymer and its pour point depressant performance evaluation for Daqing crude oil

EVA was widely used as the pour point depressant for waxy oil.In order to improve its effect,some graft copolymerization methods should be used to modify EVA's property.EVA has long side chains and nitrogen polar groups to enforce its adaptability and effect of waxy oil.The pure amine,maleicanhydride and their reaction product were tested using infrared spectra and the NMR spectral.The results show that when the modified EVA is added into oil,the wax deposits not only on the main chain but also on the side ...     

EVA插层复合材料的取向结构对阻燃性能的影响

利用蒙脱土(MMT)特殊的片层结构,采用挤出工艺、熔融插层法制备了乙烯醋酸乙烯脂/蒙脱土(EVA/MMT)和乙烯醋酸乙烯脂/有机蒙脱土(EVA/OMMT)纳米复合材料,用锥形量热仪测试并分析了材料的燃烧性能。结果表明,添加OMMT的复合材料具有阻燃作用;复合材料中蒙脱土片层的(横、纵)取向影响材料的阻燃性;横向取向的EVA/OMMT复合材料有更低的热释放速率和质量损失速率,具有较好的阻燃性。通过扫描电镜(SEM)表征不同取向材料燃烧后炭渣的形貌,表明形成的炭层也为横、纵取向,解释了插层复合材料的横、纵取向对材料阻燃性的影响。     

TAIC对辐照交联无卤阻燃EVA热缩材料的影响

向乙烯-醋酸乙烯共聚物(Ethylene-vinyl acetate copolymer,EVA)无卤阻燃热缩材料中添加不同含量的三烯丙基异氰脲酸酯(Triallyl isocyanurate,TAIC),然后采用电子束辐照,制备出交联型无卤阻燃EVA热缩材料。考察TAIC的含量和吸收剂量对样品的凝胶含量、机械性能和电性能的影响,并通过傅里叶红外(Fourier transform infrared,FTIR)光谱对EVA热缩材料进行表征。结果表明:TAIC的加入对辐射交联有促进作用,在吸收剂量一定的情况下,如150 k Gy,EVA热缩材料的凝胶含量随着TAIC含量增加;在TAIC的添加量一定的情况下,如3份(质量),EVA热缩材料的凝胶含量随着吸收剂量增加;对机械性能而言,断裂伸长率随着TAIC和吸收剂量的增加均呈下降趋势;在断裂强度方面,添加TAIC的样品断裂强度上升趋势比较明显;对电性能的影响,TAIC的加入增加了EVA热缩材料的体积电阻,其随着吸收剂量的增加先上升后下低;FTIR分析表明TAIC在电子束辐照下反应完全。     

EVA/EPDM/IR/IR共混发泡材料的性能研究

研究了乙烯醋酸乙烯酯共聚物（ＥＶＡ）／ＥＰＤＭ／ＩＲ三元共混和ＥＶＡ／ＥＰＤＭ／ＩＲ／ＩＲ四元共混发泡材料的性能。在ＥＶＡ中混入ＥＰＤＭ可使发泡材料的拉伸强度、撕裂强度和粘合强度提高,而收缩率和压缩永久变形降低;在ＥＶＡ中混入ＩＲ除具备混入ＥＰＤＭ同样的优点外,还可提高发泡材料的柔性;ＩＲ的混入可改善发泡材料二次热压成型制品的表面清晰度。     

EVA的应用与加工

EVA是一类重要的乙烯基共聚物。介绍了它的分类、性能、应用、各种加工技术及进展。     

阻燃半硬质LDPE/EVA泡沫塑料的研究

研究了添加型卤素阻燃剂、Ｓｂ２Ｏ２、Ａｌ（ＯＨ）３复合体系对ＬＤＰＥ／ＥＶＡ共混发泡体系的阻燃性能,并对制品结构与性能影响较大的因素进行了研究分析和讨论。实验结果表明,采用上述阻剂的复合体系对ＬＤＰＥ／ＥＶＡ发泡体系有良好的阻燃效果。制备出了氧指数为３５．５％,垂直燃烧性能达到了ＵＬ９４Ｖ－０级的ＬＤＰＥ／ＥＶＡ泡沫塑料。     

胶鞋帮面布用的复合胶乳

合成了一种可用于胶鞋帮面布———耐热型棉／ＥＶＡ复合布生产的丙烯酸类共聚乳液,讨论了影响复合胶耐热性的一些主要因素。用这种鞋帮制做的胶鞋在热硫化时不变形,从而提高了胶鞋成品的合格率。     

橡塑共混乒乓板用海绵的研制

较为详尽地叙述了ＮＲ／ＥＶＡ共混海绵制品的研制情况,对其橡塑比、发泡体系及硫化工艺等方面的选择进行了讨论,并阐明了产品的制造过程及共效果。