聚合物复合材料的组成、形态结构与其光降解行为和机理的关系

Inorganic particles influence the photo-degradation of polymer composites through the following ways: 1) more UV absorbance and catalyzed photo chemistry reactions by active functional groups and/or metal ions; 2) nucleation effect of inorganic particles that leads to the change of crystal phase, spherulite size and crystallinity, which change the diffusion of oxygen, other molecules and species, and thus modify the photo-chemical reaction rate; 3) more heterogeneity. All the factors have different effects and make the photo-degradation of polymer composites a very complex process. In the literatures, most research focused only on some of above aspects, and contradictory results can be found because they studied the effects of different factors. Therefore, the photo-degradation mechanism of polymer composites can only be clarified by comprehensively investigating the effects of all these factors. .This project aims to study the relationship between the chemical and physical structure of polypropylene composites and their photo-degradation behavior and mechanism. The chemical component and surface functional groups of inorganic particles will be characterized. The UV absorbance and crystallization morphology of polypropylene composites will be investigated.The photo-degradation will be carried out by accelerated artificial weathering and in-situ photo-oxidation. The changes in molecular chain, crystallization morphology as well as mechanical properties will be characterized. Based on the structure information and the photo-degradation behavior, the photo-degradation mechanism of polypropylene composites will be concluded. In order to relate the structure with aging performance, the chemometrics methods such as principal component analysis and cluster analysis will be adopted. The effects of various factors will be evaluated and the key factors will be highlighted. The weight of these factors and their interaction will also be evaluated. These results will push the aging research forward and are expected to be used in the stability evaluation and the lifetime prediction of polymer composites.

聚合物复合材料中，无机填料对基体的光降解会产生多方面的影响：促进对紫外光的吸收；填料的化学组成和表面官能团等影响基体的光化学反应；无机填料的成核作用改变基体的结晶形貌，影响氧气和分子等的扩散；无机填料的分散状况加剧了体系的不均一性。各方面的影响方式和程度不同，为老化研究带来很大挑战。本课题针对填充不同微米和纳米填料的聚丙烯复合材料，采用多种表征方法，研究填料的化学组成、表面官能团及含量、紫外光吸收特性；填料在聚合物基体中的分散状况；填料对聚合物结晶形貌的影响等；通过加速光氧化和红外原位光氧化实验，研究聚丙烯复合材料的光氧化降解行为，讨论光氧化降解机理。采用化学计量学方法，建立材料的光氧化行为与其组成、形态和结构的关联函数，分析影响聚丙烯复合材料光氧化降解的关键因素及其相互作用。研究结果对于深入认识高分子材料老化理论，准确评价材料稳定性和预测寿命都具有重要的理论和实际意义。

本课题以聚丙烯/碳酸钙、聚丙烯/二氧化硅复合材料为研究对象，研究了无机填料的不同粒径（微米/纳米）和不同表面处理（无/钛酸酯/硬脂酸/硅烷）对聚丙烯光氧化的影响。发现了填料/基体界面在聚丙烯降解中的关键作用，并通过聚丙烯/聚甲基丙烯酸甲酯、聚丙烯/聚苯乙烯共混物模型体系研究，证明了界面是两相发生相互影响的场所，且界面的化学特性（官能团）及界面面积是决定分散相影响程度的关键因素，据此提出了无机填料影响聚合物降解的数学模型。.建立了能快速评价材料老化状态和稳定性的红外原位光氧化法，搭建了系统装置，包括光谱检测、光控、温控和吹扫四个组成部分，并成功用于丁腈橡胶老化状态评价和低密度聚乙烯纳米复合材料稳定性评价。.发现了聚丙烯和其他高分子材料光氧化降解的相互传染现象，实验证明这种相互传染通过气相发生，并初步研究了醇、酸、醛、酮、酯等小分子对聚丙烯降解的影响。