The primer deals mainly with castable polyurethanes. They are a member of the polyurethane family of plastics that all contain the urethane group.
The polyurethane family consists of six main units each with a large number of subcomponents. The six groups include the following:
1. Castable 2. Foams 3. Fibers 4. Thermoplastics 5. Millable 6. Films
The castable, thermoplastic, and millable polyurethanes have similar chemistries. The main differences are as follows:
◾ Castables are made with an approximate 2-to-1 polyoldiisocyanate ratio followed by further chain extension.