TENSILE PROPERTIES OF CRYSTALLINE POLYMERS - RANDOM COPOLYMERS OF ETHYLENE
TENSILE PROPERTIES OF CRYSTALLINE POLYMERS - RANDOM COPOLYMERS OF ETHYLENE
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DOI：
10.1021/ma00109a012
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发表时间：
1995-02-27
期刊：
影响因子：
5.5
通讯作者：
MANDELKERN, L
中科院分区：
文献类型：
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作者：
KENNEDY, MA;PEACOCK, AJ;MANDELKERN, L
研究了一组乙烯-1-烯烃无规共聚物的力-伸长率曲线。共聚单体包括1-丁烯、1-己烯、1-辛烯和4-甲基-1-戊烯。共聚物均具有最可几的分子量和窄的组成分布。一组氢化聚（丁二烯），无规乙基支化共聚物，具有非常窄的分子量和组成分布也进行了研究作为参考。只研究了韧性变形。这项工作产生了几个重要的概括。一个重要的发现是，分子量，共聚物的组成，和化学性质的共聚单元被认为是独立的变量，在分析拉伸行为。即使是中等分子量的标称应力-应变曲线也由应变硬化主导。该特性类似于极高分子量线性聚乙烯的特性。然而，与其他共聚物相比，乙烯-丁烯的影响没有那么大。乙烯-丁烯共聚物的最终性能也不同于其它共聚物。对这些差异的解释可以通过假设在熔体结构中，因此在残留的类液体区域中，非结晶部分受到侧基相互作用的影响来给出。与此相反，屈服应力和初始模量不取决于共单元的化学性质，而仅取决于结晶度水平。在重叠区域中，线性聚乙烯和共聚物的屈服应力和初始模量之间存在显著差异。力-伸长率曲线的不同部分由不同的结构和分子特征控制，表明问题的复杂性。广泛的实验数据，提出的，彻底表征的样品，可以作为一个基础的无规共聚物的韧性变形的分子理解。
Force-elongation curves of a set of random ethylene-1-alkene copolymers have been studied. The comonomers included 1-butene, 1-hexene, 1-octene, and 4-methyl-1-pentene. The copolymers all had the most probable molecular weight and narrow composition distributions. A set of hydrogenated poly(butadienes), random ethyl-branched copolymers, that have very narrow molecular weight and composition distributions were also studied as reference. Only ductile type deformations were studied. Several important generalizations resulted from this work. An important finding was that the molecular weight, copolymer composition, and chemical nature of the co-units have to be considered as independent variables in analyzing the tensile behavior. The nominal stress-strain curves of even modest molecular weights are dominated by strain-hardening. This characteristic is similar to that of very high molecular weight linear polyethylenes. However,the effect is not as large for the ethylene-butenes as compared with the other copolymers. The ultimate properties of the ethylene-butene copolymers also differ from the others. An explanation for these differences can be given by postulating that in the melt structure, and thus in the residual liquid-like region, noncrystalline portions are affected by interaction of the side groups. In contrast, the yield stress and initial modulus do not depend on the chemical nature of the co-unit but only on the crystallinity level. In the regions of overlap there is a substantial difference between the yield stress and initial modulus of Linear polyethylene and the copolymers. Different portions of the force-elongation curves are governed by different structural and molecular features indicating the complexity of the problem. The wide range of experimental data that are presented, for thoroughly characterized samples, can serve as a basis for the molecular understanding of the ductile deformation of random copolymers.