Nonlinear Elongational Rheology of Unentangled Polystyrene and Poly(p-tert-butylstyrene) Melts
Nonlinear Elongational Rheology of Unentangled Polystyrene and Poly(p-tert-butylstyrene) Melts
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DOI：
10.1021/acs.macromol.8b01954
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发表时间：
2018-11
期刊：
影响因子：
5.5
通讯作者：
Yumi Matsumiya;H. Watanabe;Y. Masubuchi;Qian Huang;O. Hassager
中科院分区：
文献类型：
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作者：
Yumi Matsumiya;H. Watanabe;Y. Masubuchi;Qian Huang;O. Hassager
研究了未纠缠的聚苯乙烯（PS27，分子量M = 27k）和聚对叔丁基苯乙烯（PtBS53, M = 53k）熔体在单轴延伸下的非线性流变行为，这两种熔体的库恩链段数几乎相同（PS27和PtBS53的nK分别为30和35）。两种材料的稳态拉伸黏度ηE均随着Weissenberg数Wi≥0.3的增加（Wi = τ1eq， τ1eq和e分别为线性粘弹性和Hencky应变速率下的最长松弛时间）先表现为应变速率硬化，后表现为应变速率软化。对于未纠缠的熔体，硬化和软化不受任何纠缠非线性的影响，因此硬化与链的有限可扩展非线性弹性（FENE）明确相关，而软化则与FENE效应的抑制有关，这是由于高度拉伸和定向链的段摩擦ζ减少而引起的。因此，ζ还原，推测…
Nonlinear rheological behavior under uniaxial elongation was examined for unentangled melts of polystyrene (PS27; molecular weight M = 27k) and poly(p-tert-butylstyrene) (PtBS53; M = 53k) having nearly the same number of Kuhn segments per chain (nK = 30 and 35 for PS27 and PtBS53, respectively). For both materials, the steady state elongational viscosity, ηE, exhibited strain-rate-hardening and then strain-rate-softening on an increase of the Weissenberg number Wi ≥ 0.3 (Wi = eτ1eq, with τ1eq and e being the longest relaxation time in the linear viscoelastic regime and the Hencky strain rate, respectively). For the unentangled melts, the hardening and softening were free from any entanglement nonlinearity, so that the hardening was unequivocally related to the finite extensible nonlinear elasticity (FENE) of the chain, and the softening, to the suppression of the FENE effect due to reduction of the segment friction ζ occurring for the highly stretched and oriented chain. Thus, the ζ reduction, speculati...