材料科学
应力松弛
放松(心理学)
复合材料
弹性体
变形(气象学)
压力(语言学)
热塑性弹性体
韧性
无定形固体
应变率
聚合物
共聚物
蠕动
化学
结晶学
心理学
社会心理学
语言学
哲学
作者
Simone Sbrescia,Tap Tom Engels,Evelyne Van Ruymbeke,Michelle E. Seitz
摘要
The mechanical properties of multiblock copolymer thermoplastic elastomers (TPEs) are governed by the interplay of different reversible dynamics [e.g., hard block (HB) association and chain entanglements]. Understanding how these physical processes influence the high-temperature deformation behavior is relevant as many TPEs lose toughness with increasing temperature. Increasing molecular weight (Mw) improves their temperature resistance that is attributed to an increase in network connectivity. Indeed, longer chains are characterized by more HBs per chain and by a longer lifetime of the entanglements in the amorphous phase. Both the associating HB and disentanglement dynamics are temperature and rate dependent. To further understand the interconnected role of Mw, temperature and rate dependencies on the mechanical properties, we perform Temperature Scanning Stress Relaxation (TSSR) tests. The method consists of measuring the stress relaxation of the materials as the temperature monotonically increases, allowing us to probe the stress response as the HBs progressively disassociate due to the increase in temperature. The results show that increasing Mw improves the high-temperature relaxation behavior, allowing the material to retain more stress than its low Mw counterpart as the temperature increases. This distinction does not show itself when performing standard small strain dynamic mechanical thermal analyses. Depending on the deformation experienced before the TSSR is performed, different relaxation behaviors are observed illustrating the importance of the current microstructure in determining the mechanical properties. The TSSR approach is well-suited to benchmark the high-temperature stress-bearing properties of network-based polymers whose morphology and, hence, properties are strongly deformation dependent.
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