Kinetics of ageing and re-embrittlement of mechanically rejuvenated polystyrene
Kinetics of ageing and re-embrittlement of mechanically rejuvenated polystyrene
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DOI：
10.1016/s0032-3861(02)00863-7
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发表时间：
2003-02-01
期刊：
影响因子：
4.6
通讯作者：
Meijer, HEH
中科院分区：
文献类型：
--
作者：
van Melick, HGH;Govaert, LE;Meijer, HEH
预变形的聚苯乙烯通过轧制的结果在消除应变软化和诱导在随后的拉伸试验中的延性变形行为。然而，屈服应力和应变软化作为时效的结果及时恢复，导致更新的脆性破坏行为。本文讨论了这一过程的动力学。虽然屈服应力和应变软化的恢复过程没有表现出分子量的依赖性，再生后的恢复脆性断裂的时间尺度。只有当分子网络能够传递足够的载荷时，应变的任何局部化才能稳定。对于相对低分子量的聚苯乙烯，在短的老化时间内已经超过了承载能力，而对于较高分子量的等级，这需要更长的时间。由于与热再生聚苯乙烯相比，机械再生聚苯乙烯的蠕变柔量和位移速率显示出显著增加，因此机械再生样品中的链段迁移率增加，尽管自由体积较低。这表明，一个新的解释老化应假设，这是讨论。(C)2002爱思唯尔科技有限公司。保留所有权利。
Pre-deforming polystyrene by rolling results in elimination of strain softening and induces ductile deformation behaviour in a subsequent tensile test. However, both yield stress and strain softening recover in time as a result of ageing, resulting in renewed brittle failure behaviour. The kinetics of this process is addressed in this paper. Although the process of recovery of yield stress and strain softening shows no molecular weight dependence, the time-scale of renewed brittle fracture after rejuvenation does. Any localisation of strain can only be stabilised if the molecular network can transfer sufficient load. For relatively low molecular-weight polystyrene, the load bearing capacity is already exceeded at short ageing times, whereas for higher molecular-weight grades this takes longer. Since the creep compliance and shift-rate of mechanically rejuvenated polystyrene shows a pronounced increase as compared to thermally rejuvenated polystyrene, the segmental mobility in the mechanically rejuvenated samples has increased, despite a lower free volume. This indicates that a new explanation for ageing should be postulated, which is discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.