高聚物成型加工过程粘弹流动诱导取向结晶机理数值模拟与实验研究

The material structure usually transform from melts to crystalline state in commonly used polymer processing like extrusion, injection molding and blow molding. If the structure transformation can be reasonably controlled, the inner structure and performance of the final product can be improved. However, the corresponding mechanics is complicated for the reasons of the phase transformation phenomenon and the interaction of viscoelastic rheological and orientation crystallization behavior. The relevant research is still limited to single scale experimental and theoretical analysis that ignoring the effects of external processing field. The results are therefore difficult to afford to practical processing control. In the study, the theoretical model of viscoelastic flow induced orientation crystallization behavior of two phases including amorphous and semi-crystalline phase will be investigated. The key technology for two scale simulation of three-dimensional unsteady viscoelastic non-isothermal flow coupling flow induced orientation crystallization in polymer processing will be established. The variation characteristics of macroscopic mechanical and microstructure parameters under different processing conditions can be investigated by using the proposed simulation technology and experimental method. The evolution mechanism of processing history-morphology-performance can hence be revealed. The optimization of final product performance can be achieved by controlling the structure transformation from melts to crystalline state through the adjustment of processing conditions and die structure. The research aims at establishing key theory and technology for the control of polymer processing by combining theoretical and experimental research, and has both theoretical significance and prospects for engineering applications.

高聚物挤塑、注塑和吹塑等常用加工操作过程中，材料会发生由熔体向晶态结构的转变。合理控制该转变，可有效改善材料内部结构，提高制品性能。由于转变过程中存在液固两相的变化，且材料粘弹流变与取向结晶行为相互影响，其机理复杂。目前，国内外相关研究仍局限于单一尺度实验和理论分析，忽略加工外场作用影响，其结论难以指导实际成型工艺控制。为此，本项目拟系统研究无定形和半结晶两相共存体系粘弹流动诱导取向结晶理论建模方法，建立三维宏观粘弹非稳态流动与介观流动诱导取向结晶相耦合的双尺度数值模型和求解方案，结合工艺实验研究，探讨不同成型加工条件下材料宏观力学与微结构参数变化规律，揭示加工历史-形态-性能演变机理，通过合理调整成型工艺条件与模具结构，控制材料由熔体向晶态结构的转变，为成型制品结构性能优化提供指导。项目将理论研究与工艺实验相结合，旨在建立高聚物成型工艺控制关键理论和方法，具有理论研究意义和工程应用前景。

高聚物成型加工过程中，材料由粘弹流动至冷却结晶，宏观热力条件影响下微结构转变过程决定了成型制品性能。本项目基于高聚物流变学、凝聚态物理理论、计算流体力学和有限元数值方法，针对高聚物成型加工过程材料粘弹流变行为和流动诱导取向结晶过程开展了理论建模、数值模拟和实验研究。提出并构建了基于罚函数方法和DEVSS/SU方法的高聚物粘弹流动和胀大过程多物理场稳定化有限元数值计算方法，研究了以多模态粘弹本构模型表征的材料线性和非线性粘弹流变参数拟合方法；基于自主开发的高聚物三维粘弹流动与胀大数值计算分析平台，研究了聚合物熔体在复杂口模流道内的奇异流变行为，分析了口模结构参数对材料成形过程的影响，揭示了成型制品离模胀大机理；提出了基于悬浮体理论和唯象方法的粘弹流动诱导取向结晶动力学模型，建立了基于构象张量和取向张量的非线性粘弹流变模型，推导了宏观粘弹流动与介观取向结晶相耦合的流动诱导结晶有限元/有限差分数值模型；基于自主开发的高聚物粘弹流动诱导取向结晶数值计算分析平台，研究了宏观热力条件影响下材料流动诱导取向结晶过程，分析获得了结晶度、晶体尺寸与分布等微结构参数变化规律，探明了工艺条件变化对微结构转变的影响。项目研究成果克服了目前理论和常规实验方法研究复杂外场作用下高聚物流变与结晶行为的局限性，为探讨高聚物成型工艺过程多因素耦合作用下材料聚集态结构性能演变提供了理论基础和计算分析条件。