鉴于现有流变仪不能直接表征挤压过程的应力-应变关系,本工作设计了恒定接触面积模式平板挤压流动装置,通过测量上平板压力及移动位移来表征熔体的流变特征,再通过理论建模和数值计算分别研究了幂律模型、PTT模型和XPP模型表征挤压过程的准确性.结果表明:聚碳酸酯熔体挤压应力随应变的增加而增大,当熔体温度降低、挤压速率升高时,挤压应力随应变表现出三段分布,而初始挤压间距不影响应力应变分布模式,仅仅影响挤压应力的大小;黏弹本构模型可以预测出挤压应力的变化趋势,其中XPP模型的预测值更接近实验结果.
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