Abstract

The thickness distribution of thermoformed products is greatly affected by the viscoelastic behavior of the extruded polymer sheet. In this work, linear and nonlinear rheological experiments are carried out to characterize the viscoelastic properties of acrylonitrile-butadiene-styrene sheets under thermoforming conditions including a wide range of temperatures, strains, and strain rates. First, aspects of linear viscoelasticity such as the storage modulus and loss modulus are measured by small-amplitude oscillatory shear experiments. The discrete relaxation spectra and the Williams-Landel-Ferry parameters are obtained from the constructed linear master curves. Then, nonlinear time-dependent extensional viscosity is measured by uniaxial extensional experiments. The parameters of the damping function are evaluated using an optimization method. In addition, the effect of the orientation of the polymer is analyzed. The uniaxial extensional stress and viscosity in the extruder direction demonstrate higher resistance against tearing and extreme thickness reduction during processing. Finally, the linear and nonlinear input parameters for the numerical simulation are prepared. Numerical simulations are performed using the Wagner model with the obtained nonlinear viscoelasticity. The thickness distribution in thermoformed ABS sheets, obtained numerically, shows good agreement with the experimentally obtained values.

中文翻译：

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ABS聚合物非线性粘弹性的流变学测量和热成型过程的数值模拟

摘要

热成型产品的厚度分布在很大程度上受到挤出聚合物片材的粘弹性行为的影响。在这项工作中，进行了线性和非线性流变实验，以表征在包括宽范围的温度，应变和应变速率的热成型条件下丙烯腈-丁二烯-苯乙烯片的粘弹性。首先，通过小振幅振荡剪切实验测量线性粘弹性，例如储能模量和损耗模量。从构造的线性主曲线中获得离散弛豫谱和Williams-Landel-Ferry参数。然后，通过单轴拉伸实验测量非线性随时间变化的拉伸粘度。使用优化方法评估阻尼函数的参数。另外，分析了聚合物取向的影响。挤出机方向上的单轴拉伸应力和粘度显示出更高的抗撕裂性和加工过程中的极薄厚度。最后，准备了用于数值模拟的线性和非线性输入参数。使用具有所获得的非线性粘弹性的瓦格纳模型进行数值模拟。通过数字获得的热成型ABS片材的厚度分布与实验获得的值显示出良好的一致性。准备用于数值模拟的线性和非线性输入参数。使用具有所获得的非线性粘弹性的瓦格纳模型进行数值模拟。数值获得的热成型ABS片材的厚度分布与实验获得的值显示出良好的一致性。准备用于数值模拟的线性和非线性输入参数。使用具有所获得的非线性粘弹性的瓦格纳模型进行数值模拟。数值获得的热成型ABS片材的厚度分布与实验获得的值显示出良好的一致性。