透光性厚壁制品成型热固化效应下微气孔诱导裂纹形成机制研究

Research on polymer solidified skin and core structure of the "long time, large gradient distribution characteristics during the high light transmittance thick wall products injection molding, and the formation mechanism and the thermodynamic behavior of defects such as depressed, shrinkage and crack, etc.is stduied as well. Study on the solid-liquid two phase transient distribution of temperature and stress coupling calculation method. Study on the relationship between polymer molecular orientation and structure evolution and flow stress with the temperature and stress coupling effects. And the theoretical model has been build up, which could reflect the polymer deformation characteristics in macro and micro fields. Study on the melt front interface molecular morphology of solid - liquid/gas two-phase. Nevertheless, the possible forms, evolution and drift mechanism of inner microscopic bubble is studied. And the aggregate state of them is studied by molecular dynamics simulation technology. Polymer molecular orientation "instantaneous freezing" technology and the visualization technology of the aggregate state microscopic bubble were studied. And the in-suit measurement method was developed. Project has novelty of the research content and research methods, the application of the theory is scientific and clear background. Its implementation will help reveal high light transmittance thick wall products molding many microscopic mechanism of the scientific nature, its application and provided theoretical basis to promote the social technology progress has important scientific significance. Project has novelty of the research content and research method, the application of the theory is scientific and clear background. Research of this project helps to reveal scientificalness of many microscopic mechanism for high-transparency and thick wall products. Moreover,the application of this technology and the theoretical basis it provides have both important scientific significance and application values for promoting social technology progress.

研究透光性厚壁制品成型充模热固化分布特性，制品在一定加工条件下引起凹痕、缩孔、龟裂等不良缺陷形成的机理及热力学行为，实现"固－液"两相瞬时分布的温度－应力耦合计算；研究聚合物充模过程中，在制品内部温度和应力的偶合作用下分子取向与结构演变，构建能真实反映聚合物宏、微观形变特性的理论模型；研究料流前锋"液/固－气"两相界面流场，制品内部残余微气孔分布形态、嬗变与漂移机制，实现对制品内部微气孔聚集形态演化的分子模拟；研究聚合物取向与微气孔聚集形态的原位表征技术及其对制品相关光学属性的影响机制，以及透光性厚壁制品成型模具结构以及精确成型的可靠工艺技术和数值计算方法。项目具有研究内容与研究手段上的新颖性及理论上的科学性与明确的应用背景，其结果有助于揭示高透光性厚壁制品成型微观形态与裂纹形成的机理，其技术的应用及所提供理论方法为推动该领域的技术进步具有重要的科学意义。

厚壁高透光性塑料制品广泛应用于电子、军工、航空航天等领域，具有高强度、高透光性、耐候性等服役要求，在成型过程中往往由于其不均匀冷却和收缩导致诸如：表面凹馅、内部缩孔、龟裂等不良缺陷的产生。因此将成型过程中的物理场微观形态与制品最终成型宏观性态联系起来，探索缺陷形成内在的非均匀固化热力学与动力学机制以及聚合物制品分子取向和结构演化形态是其关键和核心。本研究所提供理论方法和技术应用对于推动该领域的技术进步具有重要的科学意义。完成的主要研究工作为：.（1）厚壁成型聚合物表皮层、料流前锋充填行为分子机制。构建了具有纳米微坑结构的聚合物/金属型腔界面模型，采用分子动力学模拟实验的方法，深入研究了模具温度对聚合物熔体在型腔表面流动的充填分子机制以及塑件表皮凝固层形成、固化与形变的的分子构象演化行为。.（2）注塑成型聚合物前沿及内部低分子微气泡形成与迁移机制。研究了温度─应力耦合作用下，厚壁注塑成型聚合物熔体前沿微气泡形成与包覆、材料内部低分子气泡扩散机制。通过构建微气泡在PMMA熔体内的扩散映射分子物理模型，研究得到了能够表征低分子气泡扩散行为的物性参数以及在注射保压阶段熔体内部微气泡的形成与扩散的规律。.（3）注塑成型聚合物大分子取向构象演化与定量化理论。研究了厚壁注塑成型聚合物材料在流动─固化耦合作用下的内部大分子链取向演化的分子机制，建立了特定物理场作用下聚合物取向形态-应力关系理论模型。分子链团均方位移表明流动取向过程实质上是分子链团的空间构象协调变形结果。.（4） 生产实验与优化技术应用。以高透光性塑件制品为例，采用响应曲面法（RSM）、多目标工艺优化技术以及成型模具实验相结合的方法，实现了高透光类塑件的精密成型与工艺优化。设计和制造了生产医用注射器针筒的整套模具，使研究得到了实际应用。