Stress Development and Cracking During Drying of Latex films

这个项目提出了一个实验和理论研究如何干燥机构裂纹。这需要遵循随着水被移除而在颗粒体中产生的应力，并且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。将膜拉开的应力来自于颗粒之间的货车德瓦尔斯吸引力，该吸引力被限制横向收缩的基底阻碍。材料响应是通过随机排列的变形颗粒的主体传播单位长度的裂纹所消耗的能量的结果。该项目将模拟应力和材料断裂韧性，以预测干燥过程中的薄膜开裂。在实验上，将进行参数空间的系统映射，并对模型进行测试。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凝物结构以及随后的干燥来控制。这为系统地控制薄膜开裂提供了可能性。这项工作将使涂料配方得到改善，减少挥发性有机成分，这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是一个广泛而重要的研究领域。

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.