Some results from the second phase of a two year experimental study are reported and discussed. A range of well cured commercial sealants products was exposed to natural weather and to various laboratory simulations of the factors in weather which cause degradation or changes in properties, for up to 12 months. These include heat (70°C), with and without UV(B) radiation, and artificial weathering including UV(B) radiation and moisture condensation (QUV apparatus).
The cure properties of polyurethane, silicone and poly sulphide sealants over a two year period are described. For these materials, the majority of which were well cured in the second year of the study, the effects of heat and of UV(B) radiation are discussed. Polyurethane sealants showed significant correlations between changes in modulus and in extensibility, after exposure to UV and to artificial weather. The effect of heat was more significant for polysulphides and for some silicone sealants.
As in the earlier phase of this work it was possible to demonstrate significant correlations between modulus changes in the full range of sealants after exposure to weather for twelve months and to artificial weathering for eight weeks. In addition, heat aging caused changes in extensibility that correlated highly with the effects of natural weather.