Absorption and glass transition temperature of adhesives exposed to water and toluene

If adhesives are to be used in practical applications, such as for aerospace or marine components, it is essential that their long-term behaviour when exposed to aggressive environments, natural or man-made, should be known. The objective of this paper is to determine the liquid absorption behaviour of epoxy adhesives under complete immersion in two solvents (water and toluene) at two different temperatures (room temperature and 60 °C) and the effect on their glass transition temperature (Tg). The specimens were periodically removed from their environment for weighing and Tg measurement, the latter by using a rapid method which was developed previously by the authors. The rate of weight gain of the specimen (sorption) and the equilibrium level were higher for the higher temperature immersion than for the low temperature. The equilibrium level reached for toluene was higher than that of water. The values of Tg were significantly influenced by the liquid uptake. Finally, heating to a temperature above the Tg of the adhesive, even in a very short time, was found to significantly influence the results of the liquid uptake.