Diffusion of adhesion promoting and crosslinking additives in an uncured silicone sealant

A method has been devised for measuring the diffusion coefficient D of additives that act as adhesion promoters and crosslinking agents in uncured silicone sealants. This has been used to measure D for tetra-t-butyltitanate (TBT) and isobutyltrimethoxysilane (BTMS) in a sealant at 25°C. The value of D for TBT was found to be constant but that for BTMS decreased with the duration of the experiment, possibly due to the interaction of the silane with the silica particles.