Urethane-based thermoset polymers are used as adhesives and sealants because of their desirable chemical and mechanical properties. Often, these materials can be delivered as uncured resins of low viscosity and allowed to cure in situ, resulting in an excellent molded-sealant application.
However, the uncured monomer is often highly reactive at ambient conditions, and, as such, manufacturing procedures must be properly regulated. For example, feedstock urethane resin must be kept frozen to suppress pre-cure and rapidly delivered to the mold to ensure optimal post-cure performance.
One manufacturer of medical devices uses a polyurethane sealant in a heat-exchange device often used during open-heart surgery. Because of the medical application, there is zero tolerance for failure of the sealant as this could result in biological contamination. The manufacturer was interested in the time-to-cure and the viscosity profile of the urethane as a function of time and/or temperature.