线性低密度聚乙烯和聚苯乙烯共混物的原位增容及其形态、结构和性能

Morphology, Structure and Properties of In-situ Compatibilized LLDPE/PS Blends

用反应挤出方法制备了线性低密度聚乙烯 /聚苯乙烯 (LLDPE/PS)合金材料。为了增加两相间的相容性 ,采用了 Al Cl3作为催化剂引发烷基化反应。由于在反应挤出过程中原位形成了 LLDPE-g-PS接枝共聚物 ,该合金材料的抗冲击性能和韧性得到很大的提高。当 m(LLDPE)∶m(PS)为 80∶ 2 0时 ,与相同组成的用简单物理共混的 LLDPE/PS相比 ,其悬臂梁冲击强度由 88.5 J/m增加到 40 1 .6J/m,断裂伸长率由 3 70 %提高到 790 %。对经四氢呋喃抽提后的接枝共聚物用拉曼光谱进行了表征 ,发现聚乙烯分子链接枝到聚苯乙烯的苯环对位上。用扫描电镜观察了反应共混体系和简单物理共混物的形态 ,前者分散相的尺寸小于 1 μm,后者分散相的尺寸则较大 ,一般为 3～ 4μm。对反应共混体系中聚乙烯的结晶行为的研究结果表明 ,该体系中的 LLDPE产生了分步结晶现象 ,这可以解释为体系中接枝共聚物的存在对

Blends (LLDPE/PS) of linear low density polyethylene(LLDPE) with polystyrene(PS) were prepared by a reactive extrusion method. In order to increase the compatibility of two blending components, a kind of Lewis acid catalyst, AlCl 3, was adopted to initiate the Friedel Crafts alkylation reaction between blending components. Due to the fact that in situ generated LLDPE g PS copolymer could act as a compatibilizer in the relative blending system, the mechanical properties of LLDPE/PS system were greatly improved. For example, after compatibilization the Izod impact strength of a LLDPE/PS blend(80/20, by mass) was increased from 88 5 J/m to 401 6 J/m and its elongation at break increased from 370% to 790%. The Raman spectra of the LLDPE/PS blends extracted with tetrahydrofuran verified that LLDPE segments were grafted to the para position of benzene rings of PS, which suggested that Friedel Crafts alkylation did happen during reactive extrusion blending. SEM micrographs showed that the size of domains was decreased from 4~5 μm to less than 1 μm depending upon the mas fraction of AlCl 3 added. The crystallization behavior of LLDPE/PS blend was investigated by DSC. The fractionated crystallization phenomena were noticed, which could be mainly attributed to the confined crystallization rather than the reduction of the size of LLDPE domains.