Polymers conditioned with compressed CO2 and H2O underwent rapid foaming when exposed to microwaves using a conventional oven. The rapidly oscillating water molecule dipoles generated enough heat to allow nucleation and growth of closed cells. Microcellular foams with cells less than 10 μm were produced from polymers such as poly(methyl methacrylate) and polycarbonate. The technique provides a fast foaming process whereby the cell morphology can be easily controlled by adjusting the microwaves intensity and flux, and exposure time.
