Environmental Testing Adhesives and Sealants

Short-term tests do not always give an adequate indication of an adhesive s performance during end user applications. Laboratory tests may only be carried out over a thousand hours, and the joint may only be exposed to one type of environmental effect at a time. During its service life, however, the bond is exposed to multiple types of environments. Temperature and humidity may cause an adhesive bond to degrade much faster than when exposed to any single environment. Applied stress accelerates the effect of the environment on an adhesive joint. Data are not always readily available from manufacturers on this phenomenon. Environmental testing should be carried out on the proposed adhesive and adherend prior to its use in service. 

Due to the significant use of sealants within the construction industry environmental effects are of importance. Sealants used in the glazing industry will undoubtedly be subject to the effects of ultra-violet light. It is relatively easy to test these effects using an environmental chamber in this type of test the sample 

Chemical and solvent contact can also inhibit the performance of both adhesives and sealants. While a mild solution of detergent may not affect performance, using the same undiluted may cause failure within hours of contact. Testing for the effects of chemical and solvent contact is relatively straightforward, but should only be carried out under local health and safety regulations most manufacturers will hold this information. 

Heat ageing can reduce the life of a sealant or adhesive, which is generally due to the loss of plasticiser from the material. Elevated temperatures may also increase the amount of crosslinking (post-cure hardening) and oxidisation, both of which may reduce the moveability of die sealant and induce brittle fracture in adhesive joints. In order to understand the effects of heat ageing, thermal testing should he carried out. 

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