There are several common types of polyurethane adhesives. They can be classified primarily as reactive and nonreactive types and they are summarized in Table 1. This article will discuss mainly the thermoplastic polyurethanes that are used in solvent borne and hot melt adhesive systems. Novel, soft grades of thermoplastic polyurethane adhesives based on polybutadiene diols have been discussed in a previous SpecialChem4Adhesives article 1. This current article will focus more on the general chemistry and properties of this rather large family of polyurethane adhesives. The reactive polyurethane adhesive types have also been the subject of previous SpecialChem4Adhesives articles.
In the early 1960s B.F. Goodrich developed thermoplastic polyester polyurethanes that could be used to bond leather and vinyl. 5 Since that time polyurethane adhesives have been sold into an ever widening array of markets, where they are known for their adhesion, flexibility, low temperature performance, high cohesive strength, and end-use properties that can be tailored to the specific application.