Stress Development and Cracking During Drying of Latex films

该项目提出了一种干燥体如何破裂的实验和理论研究。这需要跟随颗粒体内产生的应力，因为水被移除，颗粒变形以填充所有空间。从稳定的胶体分散体开始，颗粒以主要由温度决定的方式堆积和变形。拉开薄膜的应力来自于粒子之间的范德华引力，这些粒子受到限制横向收缩的衬底的阻碍。材料响应是单位长度的裂纹通过随机排列的变形粒子体传播所消耗的能量的结果。该项目将对应力和材料断裂韧性进行建模，以预测干燥过程中的薄膜破裂。在实验上，对参数空间进行了系统的映射，并对模型进行了检验。颗粒的堆积被直观地认为是应力产生和断裂韧性发展的关键。这可以通过操纵聚集分散体中的絮体结构来控制，并随后进行干燥。这为系统控制薄膜开裂提供了可能。这项工作将使涂料配方得到改进，减少挥发性有机成分，挥发性有机成分是空气污染的主要来源。在学术上，这是一个主要的胶体问题，应力产生和材料性能发展之间的耦合使之成为一个具有挑战性但又重要的研究领域。

This project proposes an experimental and theoretical examination of how drying bodies crack. This entails following the stresses developing in a body of particles as water is removed and the particles deform to fill all space. Starting with a stable colloidal dispersion, the particles pack and deform in a manner determined mainly by temperature. The stress, pulling the film apart, follows from the van der Waals attraction between particles being hindered by the substrate restricting lateral contraction. The material response is a result of the energy consumed by propagating a crack a unit length through a body of randomly aligned deforming particles. This project will model stresses and material fracture toughness to allow prediction of film cracking during drying. Experimentally, a systematic mapping of parameter space will be carried out and the model tested. The packing of particles is intuitively thought to be crucial in both stress generation and fracture toughness development. This can be controlled by manipulation of floc structures in aggregating dispersions, with subsequent drying. This presents the possibility of systematically controlling cracking of thin films.This work will enable coatings formulations to improve, with a reduction in volatile organic components, a major source of air pollution. Academically this is a major colloidal problem, with the coupling between stress generation and material property development making a challanging yet important area for study.