Spherulite boundary strengthening concept for toughening polypropylene
Spherulite boundary strengthening concept for toughening polypropylene
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DOI：
10.1002/(sici)1099-0488(19980915)36:12
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发表时间：
1998-09
期刊：
影响因子：
--
通讯作者：
A. Lustiger;C. Marzinsky;R. Mueller
中科院分区：
文献类型：
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作者：
A. Lustiger;C. Marzinsky;R. Mueller
在聚合物的球晶结晶过程中，有一种从球晶体内排出低分子量和其他较难结晶的实体的趋势。这种排斥过程导致这些物种被隔离到球晶撞击的区域。由于这种偏析，片状晶界和球晶晶界有变弱的趋势，经常导致过早的机械破坏。从拟人的角度讲，这项工作的目的是开发一种熔体可混溶的共混体系，其中丙烯共聚物欺骗聚丙烯均聚物，使其将共聚物作为杂质拒绝到球晶边界。然而，一旦共聚物到达这些边界，共聚物随后通过丙烯共聚物链段的共结晶将相邻的球晶连接起来。研究发现，加入无规乙烯-丙烯共聚物或全同立构-无规嵌段共聚物均能产生预期的效果。量热法证实了共结晶，并在显微镜下直接观察到共聚物在球晶晶界的偏析和随后的增强。使用这种方法，在几乎不损失刚度的情况下，韧性得到了提高。
During spherulitic crystallization of polymers, there is a tendency for low molecular weight and other less crystallizable entities to be rejected from the body of the spherulites. This rejection process causes a segregation of these species to those areas where spherulites impinge. As a result of this segregation, lamellar and spherulite boundaries have a tendency to become weak, often resulting in premature mechanical failure. The objective of this work, anthropomorphically speaking, is to develop a melt miscible blend system in which a propylene copolymer fools a polypropylene homopolymer into rejecting the copolymer to the spherulite boundaries as an impurity. However, once the copolymer arrives at these boundaries, the copolymer subsequently connects adjacent spherulites through cocrystallization of the propylene copolymer segments. It was found that addition of either a random ethylene-propylene copolymer or an isotactic-atactic block copolymer was able to yield the desired effect. Cocrystallization was confirmed by calorimetry, and segregation of copolymer and subsequent reinforcement at the spherulite boundaries was directly observed microscopically. Using this approach, toughness was increased with little loss in stiffness.