Kinetics and dynamics of thermally-induced shape-memory behavior of crosslinked short-chain branched polyethylenes
Kinetics and dynamics of thermally-induced shape-memory behavior of crosslinked short-chain branched polyethylenes
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DOI：
10.1016/j.polymer.2009.09.062
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发表时间：
2009-11-03
期刊：
影响因子：
4.6
通讯作者：
Radusch, Hans-Joachim
中科院分区：
文献类型：
--
作者：
Kolesov, Igor S.;Kratz, Karl;Radusch, Hans-Joachim
系统地研究了交联聚合物的形状记忆（SM）行为与共价网络和结晶域的特性之间的关系，即，交联密度和结晶度。以均相乙烯-1-辛烯共聚物（EOC）为模型聚合物进行了研究。EOCs通过2，5-二甲基-2，5-二（叔丁基过氧基）己烷（DHBP）分解而交联。采用具有每1000个C原子30和60个己基侧链的支化度的两种EOC，每种EOC具有四种不同的交联密度。所研究的EOCs在结晶度、熔融温度（T-m）和交联密度方面存在显著差异。在100%的应变下进行程序化处理的交联EOC显示出高的应变固定比（Rf）和应变恢复比（R-r）。Rf和R-r值分别随着结晶度和交联密度的增加而增加，并且在随后的SM循环中仅略微下降。转换温度（T-sw）与T-m严格相关，并且在101-63 ℃的温度范围内随着支化度以及交联密度的增加而降低。当编程温度（T-pr）或SM恢复期间的负载变化时，T-sw几乎保持不变。SM回收的动力学特征在于回收率的温度依赖性由熔融行为控制。在恒定载荷下的热致恢复过程中所产生的特定工作的编程标本，增益与交联密度的增加，并提出了实际相关的动态特性。通过改变支化度和交联密度来定制T-sw的机会使得此类聚合物对于需要T-sw温度在60至100摄氏度范围内的应用而言是有吸引力的候选物。(C)2009爱思唯尔有限公司保留所有权利。
Systematic investigation of the relation between shape-memory (SM) behavior and characteristics of the covalent network and the crystalline domains of a crosslinked polymer, i.e., crosslink density and crystallinity, respectively. was performed using homogeneous ethylene-1-octenecopolymers (EOC) as model polymers. The EOCs have been crosslinked by 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (DHBP) decomposition. Two EOCs with a degree of branching of 30 and 60 hexyl side chains per 1000C atoms with each four different crosslink densities were employed. The investigated EOCs differ significantly in crystallinity, melting temperature (T-m) and crosslink density. The crosslinked EOC undergone the programming at a strain of 100% showed high strain fixity ratio (R-f) and strain recovery ratio (R-r). The R-f and R-r values increase with increasing crystallinity and crosslink density, respectively, and decline only slightly in a subsequent SM cycle. The switching temperature (T-sw) is strictly related to T-m and decreases with increasing degree of branching as well as crosslink density in the temperature range of 101-63 degrees C. T-sw remains nearly unchanged when the programming temperature (T-pr) or the load during SM recovery is varied. The kinetics of SM recovery as characterized by the temperature dependence of recovery rate is controlled by the melting behavior. The specific work generated by the programmed specimen during thermally-induced recovery under constant load, gains with increasing crosslink density, and is proposed as dynamical characteristic of practical relevance. The opportunity of tailoring T-sw by variation of the degree of branching and crosslink density makes such polymers attractive candidates for applications requiring T-sw temperatures in the range from 60 to 100 degrees C. (C) 2009 Elsevier Ltd. All rights reserved.