Interrupted shear flow of unentangled polystyrene melts
Interrupted shear flow of unentangled polystyrene melts
复制标题
未缠结聚苯乙烯熔体的断续剪切流
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
C. M. Roland
中科院分区：
文献类型：
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作者：
P. Santangelo;C. M. Roland
低分子量聚苯乙烯熔体受到周期性停止的剪切流。尽管不存在缠结，但在流动启动时观察到粘度和正应力的弱最大值。与粘度最大值相关的应变与剪切速率无关，并且与缠结聚合物的超调应变一致。当流动在短暂中断后恢复时，应力过冲消失或强度较弱。在流动之间有足够长的休息时间，原始行为被再现。恢复最大值的时间尺度与稳态流应力松弛的时间尺度大致相同。这与缠结聚合物的行为不同。
Low molecular weight polystyrene melts were subjected to shearing flow which was periodically halted. Weak maxima in both the viscosity and normal stress were observed upon startup of the flow, notwithstanding the absence of entanglements. The strain associated with the viscosity maxima was independent of shear rate, and consistent with the overshoot strains for entangled polymers. The stress overshoots disappeared or were of weaker intensity when the flow was resumed after a brief interruption. For sufficiently long rest periods between flow, the original behavior was reproduced. The time scale for recovery of the maxima was about the same as that for relaxation of the stress from steady state flow. This differs from the behavior of entangled polymers.