| abstract |
A one-part spray foam formed by Michael addition chemistry is provided. The foamable composition includes at least one electron donor, at least one electron acceptor, an encapsulated catalyst, and one or more blowing agents. The catalyst is a weak or strong base. The encapsulation of the catalyst controls the polymerization of the Michael addition compounds such that the catalyst can be added and/or activated at a desired time to begin the foaming reaction. The catalyst may be encapsulated in a high molecular weight inert polymer or wax. In some embodiments, the chemical blowing agent(s) are also encapsulated. To produce a foam according to the invention, a single stream of the foamable composition is fed into an application gun where the slurry is heated and mixed. The heat and/or mixing in the gun releases the catalyst, which initiates the reaction between the Michael donor and Michael acceptor to form the foam. |