Performance-based Adhesion Testing of Structural Sealants

Abstract

Existing accelerated laboratory procedures for the assessment of the adhesion of silicone sealants fail to consider the fact that the sealant/substrate interface in a building facade is continuously subjected to a combination of both mechanical and environmental stress. As a result of this, standardised test protocols lack the discrimination necessary to assess relative adhesive behaviour. A novel test procedure is offered which enables improved discrimination of the adhesive strength of the sealant/substrate system. The method is based on the simultaneous application of both mechanical and hydrothermal stress, in order to promote adhesive failure at loads below the cohesive strength of the bulk sealant. A simpler version of the novel procedure allows for the screening of sealant/substrate combinations that represent potential long-term durability risks. This is achieved by the combination of hydrothermal and mechanical stress at a level close to the structural silicone design stress (0.138 MPa) applied through imposing a 12.5% strain (equal to the normal design strain in silicone sealants) together with immersion of the joint in hot water.