基于熔体流动三维模拟的木塑复合材料共挤出界面畸变调控机理

Co-extrusion is a supporting technology to develop high quality functional wood plastic composites (WPC). However, its widely use and in-depth development is limited due to the complicated influence factors, unknown mechanism and uncontrollable on co-extrusion interface distortion. Base on three-dimensional simulation of melt flow, the flow characteristics of inner and outer layer of coextruded wood plastic composites, three-dimensional simulation of WPC melt flow in co-extrusion path, and the reason and control mechanism of co-extrusion interface distortion were investigated. Flow and heat transfer condition in the twin screw extruder was simulated based different flow characteristic parameters of WPC by computational fluid mechanics. The influence regularity of viscoelasticity of WPC, process conditions, and mold structure on position, shape, and stability of co-extrusion interface distortion was obtained. Ultimately to realize the goal on influence and change regularity between position, shape, offset and structure, morphology, bonding strength of co-extrusion interface. This study could provide theoretical support basis to promote high performance of co-extrusion WPC in the field of green household applications.

共挤出成型是木塑复合材料（WPC）向高品质功能化方向发展的支撑技术，然而由于共挤出界面发生畸变的影响因素复杂、机理不详、难以控制，其广泛使用和深入发展受到制约。项目以WPC共挤出流道熔体流动的三维模拟为主要手段，研究共挤出界面畸变产生原因及调控机理，开展共挤出WPC芯、表层材料的流动特性、挤出过程中的内部流场信息、共挤出流道的三维模型构建及共挤出界面畸变调控方法的研究。重点对不同流动特性参数下的双螺杆挤出机木塑熔体流动和传热进行数值模拟，构建共挤出流道熔体流动的三维有限元模型；获得材料黏弹性、共挤出工艺条件、模具结构对共挤出界面位置、形状和稳定性畸变的影响规律；揭示共挤出界面位置、形状和稳定性畸变与共挤出界面熔合结构、形貌及结合强度的变化关系，建立共挤出界面畸变调控机理，为推进共挤出WPC在绿色家居领域的应用提供理论依据。

共挤出成型是木塑复合材料（WPC）向高品质功能化方向发展的支撑技术，为了深入研究共挤出（多层）木塑复合材料的界面结合性能及功能性。本项目首先探究了木粉含量对芯、表层木塑复合材料流变性能的影响，模拟了芯、表层木塑流变性能和挤出工艺对挤出模具压力场、剪切速率场、速度场和粘度场的影响规律，为共挤出木塑复合材料的加工制备提供了理论基础；建立了基于响应曲面法的木塑复合材料力学强度分析模型，并对木塑复合材料的挤出工艺进行优化，成功构建了不同杨木纤维含量的芯、表层木塑复合材料的微观力学模型，并解释了木塑复合材料拉伸性能的变化规律；进一步制备了低热膨胀系数差异的共挤出木塑复合材料，并探讨了不同粒径SiO2对其长度和厚度方向上热膨胀性能的影响规律；通过膨胀石墨表层阻燃，聚磷酸铵芯层阻燃制备多层木塑复合材料，提升木塑复合材料阻燃性能的同时，改善了力学性能降低的弊端，并揭示了阻燃机理。综上所述，本项目的研究成果为推进共挤出WPC在绿色家居和建筑装饰领域的应用提供了理论依据。