Nonlinear viscoelasticity of PP/PS/SEBS blends
Nonlinear viscoelasticity of PP/PS/SEBS blends
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DOI：
10.1007/s00397-004-0411-6
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发表时间：
2005
期刊：
影响因子：
2.3
通讯作者：
P. H. P. Macaubas-P.-H.-P.-Macaubas-93101826;N. Demarquette;J. Dealy
中科院分区：
文献类型：
--
作者：
P. H. P. Macaubas-P.-H.-P.-Macaubas-93101826;N. Demarquette;J. Dealy
研究了线性三嵌段共聚物（苯乙烯-乙烯-/丁烯-苯乙烯，SEBS）对聚丙烯/聚苯乙烯（PP/PS）共混物的非线性粘弹行为的影响。使用受控应变旋转流变仪和滑板流变仪以0.1至10 s-1的速率启动稳态剪切，以获得涉及一个或多个剪切速率的应变历史。测量了剪切应力和第一法向剪切应力差随时间的变化，并对剪切前后样品的形貌进行了测定。对于每个应变历史，除了涉及0.1 s-1的单一剪切速率外，共混物显示出典型的非线性粘弹性行为：剪切应力过冲/下冲，取决于历史，然后是每个步骤的稳态。第一法向应力差单调增加到稳态值。随着SEBS的加入，应力值增加。剪切应力的过冲和下冲以及它们发生的时间强烈地依赖于应变历史，对于在与前者相同的方向上进行的后续剪切速率步骤减小，并且对于在相反方向上进行的后续剪切速率步骤，应力下冲发生的时间增加，而不管剪切速率的大小。对于所研究的所有共混物都观察到这种行为。单步剪切速率实验中的超调时间与剪切速率成反比，稳态N1值与剪切速率成线性关系，而稳态剪切应力与剪切速率不成线性关系。分散相的平均直径下降的所有应变的历史时，共混物不相容。当共混物被增容，分散相的平均直径仅在较强的流动期间改变。将实验数据与使用Doi和Ohta（1991）、Lacroix等人（1998）和Bousmina等人（2001）的想法制定的模型的预测进行比较。该模型正确地预测了单步剪切速率的非增容共混物的行为，但不是增容共混物，也没有预测剪切后的形态。
The nonlinear viscoelastic behavior of polypropylene/polystyrene (PP/PS) blends compatibilized or not with the linear triblock copolymer (styrene-ethylene-/butylene-styrene, SEBS) was investigated. Start-up of steady-shear at rates from 0.1 to 10 s−1was carried out using a controlled strain rotational rheometer and a sliding plate rheometer for strain histories involving one or several shear rates. The shear stress and first normal shear stress difference were measured as functions of time, and the morphologies of the samples before and after shearing were determined. For each strain history except that involving a single shear rate of 0.1 s−1the blends showed typical non-linear viscoelastic behavior: a shear stress overshoot/undershoot, depending on the history, followed by a steady state for each step. The first normal stress difference increased monotonically to a steady-state value. The values of the stresses increased with the addition of SEBS. The shear stress overshoot and undershoot and the times at which they occurred depended strongly on the strain history, decreasing for a subsequent shear rate step performed in the same direction as the former, and the time at which stress undershoot occurred increased for a subsequent shear rate step performed in the opposite direction, irrespective of the magnitude of the shear rate. This behavior was observed for all the blends studied. The time of overshoot in a single-step shear rate experiment is inversely proportional to the shear rate, and the steady-state value ofN1scaled linearly with shear rate, whereas the steady-state shear stress did not. The average diameter of the dispersed phase decreased for all strain histories when the blend was not compatibilized. When the blend was compatibilized, the average diameter of the dispersed phase changed only during the stronger flows. Experimental data were compared with the predictions of a model formulated using ideas of Doi and Ohta (1991), Lacroix et al. (1998) and Bousmina et al. (2001). The model correctly predicted the behavior of the uncompatibilized blends for single-step shear rates but not that of the compatibilized blends, nor did it predict morphologies after shearing.