ABSTRACT
The paper, which is the second in a series of papers on the ageing resistance of sealants (see [1] for part I), describes methods of exposing sealants to natural outdoor weathering, accelerated outdoor weathering, and accelerated artificial weathering. Natural outdoor weathering with simultaneous mechanical cycling indicates that joint movement is the predominant factor in sealant failure. Natural outdoor weathering without simultaneous mechanical cycling is capable of reproducing many of the surface degradation effects observed in actual service joints. Accelerated artificial weathering is widely used by the sealant industry. Xenon arc and UVA-340 fluorescent light tubes have been found to provide the best correlation of results with outdoor exposure. In order to discern the effects of cure completion from those caused by degradation of the sealant due to weathering, it appears essential to achieve an almost complete state of cure prior to any weathering test. In order to reproduce the actual in-service conditions as closely as possible, it appears desirable to subject the sealant to forced mechanical cycling during or after accelerated artificial weathering.
