The effect of cooling rate on the impact performance and dynamic mechanical properties of rotationally molded metallocene catalyzed linear low density polyethylene

This article examines changes to the morphology of rotationally molded metallocene catalyzed linear low density polyethylene brought about by varying the cooling rate during processing. These changes in morphology lead to variations in the impact performance, which is reflected in the dynamic mechanical characteristics of the materials. Various analytical techniques are used in an attempt to explain the differences in impact behavior. Slow cooling is shown to result in high crystallinity, and in the formation of large spherulites, which in turn is detrimental to the impact performance of the material, particularly at low temperatures. The high crystallinity corresponds with a shift in the β transition of the material to a higher temperature, and is shown to result in a higher brittle–ductile transition. A case study was also carried out on samples from a finished part provided by an industrial molder, one section of which failed in a brittle manner when impact tested while the other failed in a ductile manner. Microscopy results showed that the brittle material had large spherulites at the inside surface, while the ductile material showed incipient degradation at this surface, which has previously been shown to be of benefit to impact strength in rotationally molded parts. Dynamic mechanical studies again showed a β transition at a higher temperature in the brittle samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1963–1971, 2006     

mPE-g-MAH对HDPE/木粉复合材料的改性

采用废木粉填充高密度聚乙烯（HDPE）制备木塑复合材料。采用马来酸酐接枝茂金属聚乙烯（mPE—g-MAH）对复合材料进行增容和增韧，并阐述了它的增容和增韧机理。讨论了mPE—g—MAH用量对复合材料的力学性能如拉伸强度、冲击强度、弯曲强度、弯曲模量的影响。结果表明，mPE—g—MAH不仅可明显提高复合材料的强度和韧性，而且也使材料的弯曲模量有了一定的提高。当其质量分数为16％时，复合材料的拉伸强度、冲击强度分别由原来的16．2MPa和4．5kJ／m^2提高到30．5MPa和9．8kJ／m^2。     

过氧化物DCP母料的研制

研究了采用过氧化物DCP、将DCP制成母料、在DCP母料中加入分散剂、在加入分散剂的母料中再加入助交联剂MAH(顺丁烯二酸酐)这4种条件下LDPE的交联情况，讨论了DCP的加入量对LDPE交联度的影响，同时讨论了交联度随交联时间的变化。     

Polyamide‐reinforced ethylene–propylene–diene rubber compatibilized with chlorinated polyethylene

Vulcanizates of blends of ethylene–propylene–diene rubber and polyamide copolymers were prepared by reactive compatibilization. A reactive route was employed for compatibilizing these blends with the addition of chlorinated polyethylene (CPE). The influence of the compatibilizers, crosslinking agents, blend compositions, and addition modes of the compatibilizers on the mechanical properties of the blends was investigated. The morphologies of the blends were determined with scanning electron microscopy. The addition of CPE was found to reduce the particle size of the dispersed phase remarkably. The stability of the blends with compatibilizers was measured by high‐temperature thermal aging. The mechanical properties were examined by stress–strain measurements and dynamic mechanical thermal measurements; the addition of polyamide copolymers caused significant improvements in the tensile properties of these blends.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1727–1736, 2003     

相容剂对PE-HD／PET共混合金性能的影响

以乙烯-丙烯酸丁酯-甲基丙烯酸缩水甘油酯三元共聚物（PTW）作为高密度聚乙烯（PE-HD）／聚对苯二甲酸乙二醇酯（PET）共混合金的反应性相容剂，采用熔融挤出法制备了以PE-HD为基体的PE～Hi）／PET、共混合金。通过力学性能和流变性能测试，扫描电镜（SEM）和动态力学分析（DMA）等手段，研究丁PTW对共混合金性能的影响。结果表明：PTW提高了体系的综合性能，当PE-HD／PET配比为90／10，PTW含量在5份时，其缺口冲击强度提高了近400％，拉伸强度和断裂伸长率分别提高了25％和50％，同时改善了共混合金的加工性能。SEM分析表明PTW的加入增大了共混合金的界面相互作用，促进了分散相粒子的细化，从而提高丁体系相容性，DMA测试表明，PTW的加入使PET的玻璃化转变温度向PE—HD的玻璃化转变温度靠近：     

Gamma‐ray irradiation effect of polyethylene on dimaleimides as a class of new multifunctional monomers

Multifunctional monomers, m‐xylylenedimaleimide, p‐phenylenedimaleimide, m‐phenylenedimaleimide, and p‐phenylenedinadimide, all of which have maleimide groups, were synthesized to increase thermal and radiation stabilities. The synthesized multifunctional monomers showed good compatibility with low‐density polyethylene (LDPE). Mixtures of LDPE and these multifunctional monomers were irradiated with γ‐rays from a Co‐60 source at room temperature in a nitrogen atmosphere. The absorbed dose ranged from 0 to 160 KGy. Among these multifunctional monomers, m‐xylylenedimaleimide was the best in gel fraction enhancement. Crosslinked LDPE with m‐xylylenedimaleimide displayed a higher modulus than that of crosslinked LDPE with triallyl cyanurate. For the elongation property, LDPE with m‐xylylenedimaleimide as a multifunctional monomer showed better results than that with commercial multifunctional monomers such as triallyl cyanurate (TAC) and trimethylol propane triacrylate (TMPTA). © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2339–2345, 2003     

Compatibilization of Poly(ethylene terephthalate)/Polypropylene Blends with Maleic Anhydride Grafted Polyethylene-Octene Elastomer

Blends of poly(ethylene terephthalate) (PET) and polypropylene (PP) at composition 80/20 with and without a compatibilizing agent were studied. Both materials are widely used in the soft drink bottle industry. The compatibilizing agent was a maleic anhydride grafted polyethylene-octene elastomer (POE-g-MA). The olefinic segment of POE is compatible with PP, whereas the maleic anhydride is affined with PET carbonyl groups. The effectiveness of the compatibilizing agent was evaluated using different techniques, such as Fourier transform IR spectroscopy, mechanical analysis, scanning electron microscopy, dynamic mechanical analysis, and rheological analysis. The results show that the addition of POE-g-MA promotes a fine dispersed-phase morphology, and improves process ability and toughness of these blends. Shifts in the glass-transition temperature of the PET phase and the increase in the melt viscosity of the compatibilized blends indicated enhanced interactions between the discrete PET and PP phases induced by the functional compatibilizer.     

氯化聚乙烯的生产工艺及其应用前景

介绍了以聚乙烯为原料进行氯化合成氯化聚乙烯的三种工艺:溶液法、水相悬浮法和固相法,并进一步对其应用情况及市场前景作了介绍。     

气相法聚乙烯BCG-Ⅱ型催化剂的开发和应用

对气相法聚乙烯BCG-Ⅱ型催化剂的组成、粒径分布及催化剂的淤浆聚合性能进行了研究。研究结果表明，BCG—Ⅱ型催化剂的活性较高，聚合物堆密度适中，应用在Unipol乙烯气相聚合工艺装置上操作良好，所生产的树脂颗粒均匀。干爽且流动性好，产品质量合格、稳定。