Effect of water on the behaviour of adhesives modified with thermally expandable particles

In this work, the water diffusion in Thermally Expandable Particles (TEPs) modified adhesives was measured and the residual strength of water saturated and desorbed TEPs-modified adhesives was assessed. Bulk specimens were used to measure the diffusion coefficient of water in a TEPs-modified adhesive and tensile dogbone specimens were used to measure the stress-strain curves as a function of water uptake. In addition, the glass transition temperature (Tg) of aged and unaged TEPs-modified adhesives was measured, and the fracture surfaces of failed tensile specimens were examined using a scanning electron microscopy (SEM). It was observed that the moisture uptake increases as a function of TEPs content. The tensile properties (i.e. strength and elastic modulus) of the TEPs-modified adhesive tend to decrease with increasing water content, which recover after desorption at the same temperature as the initial environmental conditioning.