Polyurethanes are extensively and successfully used as adhesives and sealants, and they have an excellent record of durability. Isocyanates are used in most of these formulation. Polyurethane adhesives are often chosen over other adhesives when greater resistance to plasticizer migration is required or difficult to bond polymeric substrates are involved. Polyurethane adhesives also give the formulator more freedom in “engineering” the modulus and elongation required of the adhesive film to meet specific applications.
RESULTING PROPERTIES
There are many types of polyurethanes used in the building and construction industry. A very popular type is one that is formulated with hydroxyl terminated polybutadiene and conventional isocyanates. These formulations provide excellent compatibility with modified asphalt systems. Some specific applications include penetration joints and adhesives on EPDM or asphalt roofing, adhesives and sealants for crack filling or expansion joints, and waterproof membranes and coatings (see next section). Typical formulations for polybutadiene based polyurethane sealants are shown in the table above.
