WATER DURABILITY OF ADHESIVE BONDS BETWEEN GLASS AND POLYSULFIDE SEALANTS

Joints consisting of glass bonded with polysulfide sealants have been aged at 95% relative humidity and 60-degrees-C for up to 14 months. Al l were weakened and some with higher levels of plasticizer fell apart during exposure. The amount of interfacial failure increased with expo sure, and was related to a discolouration which develops in the sealan t and can be seen through the glass. The rate of joint weakening is gr eater than can be accounted for by the rate at which water diffuses in to the sealant. Thermodynamic predictions based on measurements of con tact angles show that the bonds are probably unstable in the presence of water.