官能化LLDPE及其合金材料(LLDPE/HIPS)的制备及结构性能研究

本文采用核磁共振碳谱、电喷雾质谱研究LLDPE-g-AA接枝产物的链结构。电喷雾质谱显示所有的丙烯酸单体都发生自聚形成低聚物，核磁共振碳谱进一步证明了丙烯酸在聚乙烯链上形成支链，并且由于反应挤出过程中的高温作用，丙烯酸支链脱水形成酸酐。丙烯酸支链在聚乙烯的结晶过程中影响链段的规整性排列，并有可能充当成核剂，使得聚乙烯晶体随着接枝率的升高变得小而不规整。接枝产物的流变行为表明丙烯酸支链起到内增塑剂作用，降低接枝产物的表观粘度，有利于产物的后加工处理。由于接枝率低的缘故，我们采用角鲨烷模拟乙丙共聚物与马来酸酐进行接枝反应。在170℃，单体浓度为2%W/V，引发剂浓度为0.2%W/V下，体系中存在马来酸酐自聚和接枝一对竞争反应。但由于存在链转移，马来酸酐大部分以单个分子形式接在角鲨烷上。对于LLDPE/HIPS共混体系，我们采用不同于以外加增容剂的办法，直接在共混过程中加入路易斯酸，利用聚乙烯本身带有或降解过程中生成的少量双键与苯发生Friedel-Crafts烷基化反应。为了找到最佳反应条件，我们研究了不同AlCl_3含量、反应时间、反应温度对增容效果的影响。增容共混物的力学性能，特别是冲击强度和微观形态照片表明加入AlCl_3后，在PE/HIPS两相界面处生成接枝共聚物PE-g-HIPS，降低界面张力，改善共混性。由于增容剂只在两相界面处生成，因此加入AlCl_3对共混物中聚乙烯组分的热学性能和结晶性并没有太大影响。~(13)C-NMR、MS were used to characterize the structure of LLDPE-g-AA prepared by reactive extrusion. MS spectrum showed that all AA extracted from gross product formed oligomers, and no single unreacted AA monomers were remained. AA branch chain grafted onto LLDPE was confirmed by ~(13)C-NMR spectrum. Because of the high temperature during reactive extrusion, AA branch chain grafted onto LLDPE dehydrated and converted to anhydride. AA branch chain hindered the movement of LLDPE chain and acted as nucleating agent during crystallization process, which made LLDPE morphology become more anomalous. AA branch chain behaved as inner-plasticizer on the LLDPE-g-AA's rheological property at the shear stress range from 3*10~4Pa to 1.4*10~5Pa and temperature range from 170℃ to 200℃, which made functionalized LLDPE easier for further processing. We selected squalane as a substrate to investigate the mechanism of peroxide-induced MAH grafting reaction due to low grafting degree. From the product, we concluded that at the condition of 170℃, initiator/MAH/squalane (0.2/2/100), MAH can form oligomers. But because of H-transfer, most MAH grafted onto squalane was single unit. Other than traditional method of adding pre-synthesized compatibilier, we adopted an original blending method, known as polyolefin/polystyrene in situ compatibilization using Friedel-Crafts alkylation. Because of few double bond which existing in plain LLDPE or formed during LLDPE chain scission reacted with benzene ring of HIPS, forming compatibilizer (LLDPE-g-HIPS) at the interface of LLDPE and HIPS. To get the optimum blending condition, we intensively investigated the effects of blending parameters, such as AlCl_3 concentration, blending temperature and blending time. Mechanical properties, especially impact strength were considerably improved after adding AlCl_3. TEM showed that a finer dispersion and more stable morphology due to the reduced interfacial tension and increased interfacial adhesion. Because LLDPE-g-HIPS located preferentially at the interface, there's no significant difference in the thermal and crystallization properties of PE component after adding AlCl_3