Cracking of drying films

干燥膜破裂

• 批准号: EP/E05949X/1
• 负责人: William Clegg
• 金额: $ 42.96万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FE05949X%2F1
• 关键词: Cracking; drying; films

This aim of this proposal is to study an unsolved but incredibly common, conceptually pleasing and industrially relevant problem: Why colloidal films crack when they dry. There is clear experimental evidence that associates the capillary pressure with the tendency of a film to crack during drying and shows that the observed cracking patterns are those expected for a film in tension. This has led to ideas which predict cracks that grow into material where it was either still fluid or where the pores have begun to empty of fluid. Neither is observed. Instead the cracks grow in a liquid-filled particle array with some mechanical strength and on which the capillary pressure should impose a compressive stress.Using alumina suspensions we have recently shown that there was a shrinkage of the liquid-filled particle array and that this shrinkage was associated with the onset of cracking. Using existing fluid flow analyses and the position of the growing cracks we have predicted the pressure required for this shrinkage to be of the order of the capillary pressure, much larger than other colloidal forces.Because the shrinkage is so clearly associated with cracking in these alumina suspensions, we wish to understand the processes that lead to the shrinkage, and learn to control it. To achieve this understanding, we will study how the shrinkage events vary in different systems; the nature of the liquid-filled particle array; how the array changes as it shrinks, presumably under stress and, having established the underlying mechanisms occurring, to analyse the cracking quantitatively. There has recently been a considerable scientific activity in both drying, cracking and the nature of very short range forces in colloids, driven primarily from the coatings industries and the two investigators have been fortunate to be involved in the dissemination process. As discussed below the stress profile in the drying film is becoming clear and the experiments necessary to elucidate the physics of film cracking are now possible. It is the aim of this work to develop our new ideas in this area, taking advantage of the colloid expertise of AFR and the fracture expertise of WJC.

这个提议的目的是研究一个未解决但非常普遍的，概念上令人愉快的和工业相关的问题：为什么胶体膜在干燥时会破裂。有明确的实验证据表明，毛细管压力与干燥过程中薄膜开裂的趋势有关，并表明观察到的开裂模式是拉伸薄膜的预期模式。这导致了一些想法，预测裂缝会生长到材料中，在那里它仍然是流体或孔隙已经开始清空流体。两者都没有被观察到。相反，裂纹生长在一个充满液体的颗粒阵列，具有一定的机械强度和毛细管压力应施加压缩stress.Using氧化铝悬浮液，我们最近已经表明，有一个收缩的充满液体的颗粒阵列，这种收缩与裂纹的发生。利用现有的流体流动分析和裂纹生长的位置，我们预测了这种收缩所需的压力是毛细管压力的量级，比其他胶体力大得多。因为这种收缩与这些氧化铝悬浮液中的裂纹如此明显地相关，我们希望了解导致收缩的过程，并学会控制它。为了实现这种理解，我们将研究收缩事件如何在不同系统中变化;充满液体的颗粒阵列的性质;阵列在收缩时如何变化，大概是在应力下，并且已经建立了发生的基本机制，以定量分析开裂。最近，在干燥、开裂和胶体中非常短程力的性质方面有相当多的科学活动，主要来自涂料行业，两位研究人员有幸参与了传播过程。如下面所讨论的，干燥膜中的应力分布变得清晰，并且阐明膜破裂的物理学所必需的实验现在是可能的。这项工作的目的是发展我们在这一领域的新想法，利用AFR的胶体专业知识和WJC的断裂专业知识。

项目成果

Evolution of mud-crack patterns during repeated drying cycles

• DOI: 10.1039/b922206e
• 发表时间: 2010-01-01
• 期刊: SOFT MATTER
• 影响因子: 3.4
• 作者: Goehring, Lucas;Conroy, Rebecca;Routh, Alexander F.
• 通讯作者: Routh, Alexander F.

Wavy cracks in drying colloidal films

干燥胶体膜中出现波状裂纹

• DOI: 10.1039/c1sm05979c
• 发表时间: 2011
• 期刊: Soft Matter
• 影响因子: 3.4
• 作者: Goehring L