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首页> 外文期刊>Applied Mathematical Modelling >Effect of viscoelastic relaxation modes on stability of extrusion film casting process modeled using multi-mode Phan-Thien-Tanner constitutive equation
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Effect of viscoelastic relaxation modes on stability of extrusion film casting process modeled using multi-mode Phan-Thien-Tanner constitutive equation

机译：粘弹性松弛模式对挤塑薄膜浇铸过程稳定性的影响（采用多模式Phan-Thien-Tanner本构方程建模）

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Extrusion film casting (EFC) is a commercially important process that is used to produce a significant quantity of polymer films, sheets and coatings for both industrial and household applications. Recently, we have demonstrated the influence of polymer chain architecture on the extent of necking under isothermal as well as non-isothermal film casting operation for commercially relevant polyolefin based materials [1-4]. In the present research, we focus on another instability that frequently occurs in high-speed EFC process called as draw resonance. Draw resonance manifests itself as an instability that causes periodic fluctuations in both the width as well as thickness of the extruded molten film above a critical draw ratio (DR). In this work, we have carried out a linear stability analysis of the isothermal EFC process using a multi-mode Phan-Thien-Tanner (PTT) constitutive equation to determine the onset of draw resonance. We show that as the number of relaxation modes is increased there is a dramatic change in the stability regions. In particular, there is a marked variation in the stability regions obtained by simulating the multi-mode model and those obtained by taking averaged relaxation time of the modes. Additionally, as the number of faster-relaxing modes in a multi-mode spectrum is progressively increased, the process becomes increasingly stable as the level of elasticity in the melt decreases. Finally, the addition of a long relaxation mode in a multi-mode spectrum is akin to adding a long chain branch to a linear polymer that leads to a reduction in film necking and in many cases to enhanced process stability.
机译：挤出薄膜浇铸（EFC）是一项重要的商业过程，用于生产大量的工业和家庭应用的聚合物薄膜，片材和涂料。最近，我们已经证明了聚合物链结构对商业相关的聚烯烃基材料在等温和非等温薄膜流延操作下颈缩程度的影响[1-4]。在当前的研究中，我们关注在高速EFC过程中经常发生的另一种不稳定性，称为拉共振。拉伸共振表现为不稳定性，其导致挤出的熔融膜的宽度和厚度均在临界拉伸比（DR）以上周期性波动。在这项工作中，我们使用多模式Phan-Thien-Tanner（PTT）本构方程对等温EFC过程进行了线性稳定性分析，以确定拉伸共振的开始。我们表明，随着弛豫模式数量的增加，稳定区域将发生巨大变化。特别是，通过模拟多模式模型获得的稳定性区域和通过对模式的平均弛豫时间获得的稳定性区域存在明显的差异。另外，随着多模光谱中快速弛豫模的数量逐渐增加，随着熔体弹性水平降低，该过程变得越来越稳定。最后，在多模光谱中添加长弛豫模类似于在线性聚合物中添加长链支链，这会导致薄膜颈缩的减少，并且在许多情况下会提高工艺稳定性。

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