MODIFICATION OF PP/HDPE BLENDS BY PP-PE SEQUENTIAL POLYMERIZATION PRODUCT

The morphology and mechanical properties of polypropylene/high-density polyethylene (PP/HDPE) blends in a wide range of compositions modified by a sequential Ziegler-Natta polymerization product (PP-PE) have been investigated. PP-PE contains multiple components such as PP, ethylene-propylene copolymer (EPC), and high molecular weight polyethylene (HMWPE). The effects of PP-PE on the mechanical properties and morphology of the PP/HDPE blends are the aggregative results of all its individual components. Addition of PP-PE to the blends not only improved the tensile strength of the blends, but the elongation at break increased linearly while the moduli were nearly unchanged. Morphological studies show that the adhesion between the two phases in all the blends of different compositions is enhanced and the dispersed domain sizes of the blends are reduced monotonously with the increment of the content of PP-PE. PP-PE has been demonstrated to be a more effective compatibilizer than EPC. Based on these results, it can be concluded that the tensile strength of the blends depends most on the adhesion between the two phases and the elongation at break depends most on the domain size of the dispersed component. (C) 1995 John Wiley & Sons, Inc.

EFFECT OF ETHYLENE-PROPYLENE COPOLYMER WITH RESIDUAL PE CRYSTALLINITY ON MECHANICAL-PROPERTIES AND MORPHOLOGY OF PP/HDPE BLENDS

Morphology and mechanical properties of polypropylene (PP)/high density polyethylene (HDPE) blends modified by ethylene-propylene copolymers (EPC) with residual PE crystallinity were investigated. The EPC showed different interfacial behavior in PP/HDPE blends of different compositions. A 25/75 blend of PP/HDPE (weight ratio) showed improved tensile strength and elongation at break at low EPC content (5 wt %). For the PP/HDPE = 50/50 blend, the presence of the EPC component tended to make the PP dispersed phase structure transform into a cocontinuous one, probably caused by improved viscosity matching of the two components. Both tensile strength and elongation at break were improved at EPC content of 5 wt %. For PP/HDPE 75/25 blends, the much smaller dispersed HDPE phase and significantly improved elongation at break resulted from compatibilization by EPC copolymers. (C) 1995 John Wiley & Sons, Inc.

SYNTHESIS AND CRYSTALLIZATION BEHAVIOR OF (PP-MA)-G-PEO

A new graft copolymer (PP-MA)-g-PEO was synthesized by means of the chemical reaction between maleated polypropylene (PP-MA) and mono hydroxyl poly(ethylene oxide) (PEO-OH). The effect of reaction conditions on the degree of grafting of PEO-OH was studied

EPDM对PP/LDPE共混物力学阻尼及结晶行为的影响

用动态粘弹谱仪和DSC研究了聚丙烯/三元乙丙橡胶(PP/EPDM)的动态力学性能,考察了EPDM对PP/LDPE(低密度聚乙烯)的力学行为的影响。结果表明,EPDM对PP有增塑作用,在PP/LDPE/EPDM共混物中,PP和LDPE的非晶部分与EPDM具有部分相容性;PP有两个结晶温度(T_c),较低的一个T_c随共混物中EPDM含量(5～25质量份)的增加逐渐向更低温度区迁移,说明EPDM具有加快冷却速率的作用。

酚酞型聚芳醚砜(Ⅶ):K_2C0_3存在下PP/DCDPS体系聚合反应机理的研究

利用~(13)C-NMR方法研究了弱碱K_2CO_3存在下酚酞成盐反应及其与活性双卤砜亲核缩聚反应过程中的结构特征。对一系列碱性条件下酚酞(PP)与4,4'-二氯二苯砜(DCDPS)的缩聚反应的研究表明任何影响内酯结构酚酞盐生成的因素都会严重阻碍聚合反应的进行。对模型化合物存在下K_2CO_3在极性非质子溶剂中的溶解/解离行为的研究结果表明酚酞类Card。双酚与固体K_2CO_3之间可能存在着一种特殊的络合作用。基于我们系列研究结果,本文中总结提出了弱碱K_2CO_3存在下酚酞的反应机理。

相差成像技术在PP/PE微结构研究中的应用

对半结晶的聚合物PE和PP而言,当结晶不满足Bragg取向时,靠散射反差几乎不可能区分非晶区和结晶区。所以,对大多数多相聚合物体系,相差是一种很重要的成像技术。在PP/PE共混体系中,如何区分PP和PE是聚合物透射电子显微学中的难点。本文采用相差成像技术成功地揭示出PP和PP/PE超薄膜中的片晶结构,而无需借助重金属修饰或化学染色技术。理论计算表明,只要样品足够薄,利用位相反差区分HDPE和PP的晶区是切实可行的。实验像证实了上述理论预测。

PP/EPO共混体系混容性与结晶结构

WAXD方法测定表明PP/EPO共混体系的结晶度随EPO组份含量的增加而降低,晶胞参数与组份比无关,并计算了第二类晶格畸变。根据PP/EPO的DSC和扭辫实验得出在所有组成下PP/EPO共混体系是不相容的。但在非晶区可能部分相容。

汽车保险杠用增韧PP材料的研究

本文以EPDM为增韧剂,用共混手段研制了用作汽车保险杆的PP/EPDM共混材料。采用对共混料进行可控降解的方法,使物料的熔体指数可在4～16范围内任意调节,以保证注塑的正常进行;用二异丙苯过氧化物作交联剂,使橡胶相内部形成部分交联结构,同时在橡胶相和塑料相之间形成一定程度的共交联结构,使材料的拉伸强度和断裂伸长率有明显提高;通过在材料中填充适量的滑石粉、碳酸钙等无机填料,材料的弯曲强度、热变形温度和硬度就不致有太大的下降;当共混料中橡胶含量控制在15～35%之间时,所得PP/EPDM共混料的常温和低温冲击强度能提高20～40倍,其他各项性能指标也都达到和超过国外同类材料的水平。

INVESTIGATIONS ON THE ENERGY-TRANSFER OF EXCITED PARTICLE COLLISION WITH DOUBLE LASER LINES FOR EXCITATION OF LA(I)

Generally speaking, productions of thermally-assisted and stepwise fluorescence are the consequence of energy transfer caused by particle collision. In some circumstances, energy transfer caused by particle collision is considerably intense. We have ever used the fluorescence produced by energy transfer of particle collision to measure the branching ratios in the atomic transitions and acquired good results. To our knowledge, the systematic in

A collision model for DNA separation by capillary electrophoresis in dilute polymer solution

A theoretical description. based on chemical kinetics and electrochemistry, is given of DNA separation in dilute polymer solution by capillary electrophoresis. A self-consistent model was developed leading to predictions of the DNA electrophoretic velocity as a function of the experimental conditions - polymer concentration, temperature, and electric field strength. The effect of selected experimental variables is discussed. The phenomena discussed are illustrated for the example of 100 bp DNA ladder separation in dilute HPMC solution by capillary electrophoresis. This model is the first single model that can fully explain the dependence of DNA electrophoretic velocity on electrophoretic conditions.