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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Effect of cold-drawing on the secondary dielectric relaxation of bisphenol-A polycarbonate
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Effect of cold-drawing on the secondary dielectric relaxation of bisphenol-A polycarbonate

机译：冷拔对双酚A聚碳酸酯二次介电弛豫的影响

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摘要

To gain new insight into the molecular motions responsible for the excellent mechanical properties of bisphenol-A polycarbonate (BPA-PC), dielectric relaxation experiments have been performed on the secondary relaxation of BPA-PC uniaxially stretched below the glass transition temperature T,. It has been found that the dielectric gamma-relaxation of the cold-drawn samples is reduced significantly, mainly around the loss peak range, being the effect more apparent at higher temperatures. Moreover, this loss reduction is directly related with the level of molecular orientation as characterized by birefringence measurements. The results obtained are rationalized under the consideration of the gamma-relaxation of BPA-PC as produced by two distinct molecular motions which would be differently affected by the uniaxial stretching, the fastest one being more hindered by the chain orientation. The analysis of the dielectric loss reduction on the uniaxially stretched samples shows that the fast relaxation component of the gamma-relaxation of BPA-PC can be well characterized by a distribution of a Debye activated process with average activation energy of 29.5 kJ/mol and standard deviation of about 5.8 kJ/mol. These would be characteristic of a single molecular motion involving the carbonate group. (c) 2005 Elsevier B.V. All rights reserved.
机译：为了对负责双酚A聚碳酸酯（BPA-PC）优异机械性能的分子运动获得新的认识，已对单向拉伸至低于玻璃化转变温度T1的BPA-PC的二次弛豫进行了介电弛豫实验。已经发现，冷拉样品的介电γ弛豫显着降低，主要在损耗峰范围附近，在较高温度下效果更明显。而且，这种损失的减少与双折射测量所表征的分子取向水平直接相关。考虑到由两种不同的分子运动产生的BPA-PC的γ-松弛，这种结果是合理的，这两种分子运动会受到单轴拉伸的影响不同，最快的一种受到链取向的影响更大。对单轴拉伸样品的介电损耗降低的分析表明，BPA-PCγ弛豫的快速弛豫分量可以很好地表征为Debye活化过程的分布，平均活化能为29.5 kJ / mol，偏差约为5.8 kJ / mol。这些将是涉及碳酸酯基团的单个分子运动的特征。 （c）2005 Elsevier B.V.保留所有权利。

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