The high temperature (T > Tg) amorphous transition in atactic polystyrene
The high temperature (T > Tg) amorphous transition in atactic polystyrene
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DOI：
10.1002/polc.5070140120
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发表时间：
2007-03
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影响因子：
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通讯作者：
R. F. Boyer
中科院分区：
文献类型：
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作者：
R. F. Boyer
我们首先总结了现有的实验证据，表明在60至100°C的无规聚苯乙烯中存在二级转变或弛豫区。高于Tg。从137°C上升。分子量为3000至192 ℃。分子量为392000它出现在各种测量中，如热膨胀，热容，X射线研究，变形温度图，动态机械损失，应力松弛，熔体粘度和DTA。如果测试方法非常缓慢，则可能不会出现，可能是因为它与Tg合并。我们将这种现象归因于整个聚合物链作为一个单元的能力，因为可用的自由体积和在高温下增强的链流动性。这与这种转变在熔体粘度研究中出现并被交联完全抑制的事实一致。由于这表示从一种液态到另一种液态的变化，我们将这种转变指定为T1，1。
We first summarize available experimental evidence indicating the existence of a second-order transition or relaxation region in atactic polystyrene at 60 to 100°C. above Tg. It increases from 137°C. at a molecular weight of 3000 to 192°C. at a molecular weight of 392,000. It appears in such diverse measurements as thermal expansion, heat capacity, x-ray studies, deformation-temperature plots, dynamic mechanical loss, stress relaxation, melt viscosity, and DTA. It may not appear if the test method is a very slow one, presumably because it merges with Tg. We ascribe this phenomenon to an ability of the entire polymer chain to act as a unit because of the available free volume and enhanced chain mobility at elevated temperatures. This is consistent with the fact that this transition shows up in melt viscosity studies and is completely suppressed by crosslinking. Since this represents a change from one liquid state to another, we designate this transition as Tl,l.