Adhesion Properties of Sealants in Resealed Joints

Resealing of joints in a typical building structure needs to take place a number of times within the life-time of the building. The resealing process is more difficult than sealing joints for the first time and among the most significant difficulties are the removal of old sealant, and the likely presence of residues left in the joint. This aspect of obtaining adhesion to sealant residues left on surfaces represents the main focus of this paper. Following a review of the fundamental concepts of adhesion, surface analytical techniques are used to predict favourably the adhesion performance of tensile adhesion joints prepared with sealants and contaminated substrate surfaces typical of those encountered in practice. It is shown that surface energy measurements can provide a good prediction of adhesion performance, whilst surface tension measurements of uncured resealing materials indicate potential wettability and therefore resealed joint performance. In general, traces of existing sealant will almost always lead to a reduction in joint extension and performance, in proportion to the nature, amount and surface energy of the residue present.