Previous studies have shown that the nonlinear rheological behavior of 3-arm star polymer melts in fast extensional flow is identical to that of linear polymers with the same span molecular weight, because the star polymers are highly aligned and have a similar conformation as the corresponding linear polymers. However, with more arms, it would be more difficult for the stars to be aligned like linear chains, and the nonlinear extensional rheology of star polymers with more arms under large deformations has not been investigated yet. Here we show that the star polystyrene (8–10 arms) melts behave differently from the linear polystyrenes. A transient stress overshoot is observed in the fast extensional flow, probably due to the difference in entanglement density near and far away from the branch point.

中文翻译：

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星形聚合物熔体拉伸流动中意外的应力过冲


先前的研究表明，三臂星形聚合物熔体在快速拉伸流动中的非线性流变行为与相同跨度分子量的线性聚合物相同，因为星形聚合物高度排列且与相应的线性聚合物具有相似的构象。聚合物。然而，随着臂的增多，星形聚合物像线性链一样排列起来会更加困难，并且具有更多臂的星形聚合物在大变形下的非线性拉伸流变性尚未得到研究。在这里，我们展示了星形聚苯乙烯（8-10 个臂）熔体的行为与线性聚苯乙烯不同。在快速拉伸流中观察到瞬态应力过冲，这可能是由于分支点附近和远离分支点的缠结密度不同所致。