Chemical Resistance of Films Evaluated by Microhardness and Standard S/N Ratio

Abstract

In the past, the chemical resistance of materials for applications such as elastic waterproof coatings has been evaluated comprehensively on the basis of tensile strength, change in weight, change in dimension, etc. These changes can only be detected if the chemical soaks into the entire coating, so the evaluation requires a long immersion time. The authors conjectured that the immersion time could be considerably shortened by using a microhardness gauge to measure the elasticity of approximately the top 20μm of the coating. This test method was used in the parameter design of a new elastic waterproof coating material of the type that is obtained by reaction curing of a two-liquid mixture of a solventless base compound and a curing agent. As a result, a test that would previously have taken several months was shortened to one week (one-twelfth of the previous time), and a product with much better chemical resistance than previous products was developed. This method is of great value in that it is widely applicable to the development of elastic waterproof coating materials.