Polyurethanes are extensively and successfully used as adhesives and sealants, and they have an excellent record of durability. However, they are susceptible to several common forms of environmental degradation. If used in the wrong application or improperly formulated, the performance of polyurethane adhesives and sealants can be disappointing.
The properties of polyurethanes are altered by the service environment in that both physical and chemical processes can occur. There are several environmental effects that are generally considered important to the stability of polyurethane adhesives and sealants.These degrading environments are recognized as:
* thermal,
* oxidative (thermal and photolytic),
* hydrolytic,
The factors affecting stability of polyurethane adhesives and sealants and the means by which these degradation processes can be repressed are the subjects of this article. Through an understanding of the degradation methods and the additives that are available to improve stabilization, the formulator and end-user of polyurethane systems can generally realize a highly successful product.