Baydur 645 is a rigid polyurethane structural foam system used in the reaction injection molding (RIM) process. The system is supplied as two reactive liquid components. Component A is a polymeric diphenylmethane diisocyanate (PMDI), and Component B is a formulated polyol system containing no CFC- or HCFC-blowing additives.

The Baydur 645 system is used to produce foam cores for composite applications, such as water skis, agricultural and construction equipment, and various components for the transportation and marine markets. As with any product, use of the Baydur 645 system in a given application must be tested (including field testing, etc.) in advance by the user to determine suitability.