Ultrasonic foam processing of RIM type polyurethane was studied to investigate feasibility of ultrasonic bubble nucleation in the resin supersaturated with nitrogen. Bubble nucleation was also studied theoretically to predict the rate of nucleation. Classical nucleation theory and cluster theory were applied for explanation of the nucleation phenomena. Polyol was saturated with nitrogen at various pressure and the pressure was released to create supersaturated resin.
Other components of the polyurethane system selected were added to the superaturated resin and ultrasonic disruption was applied to the mixture for copious nucleation. The ultrasonic excitation created good foam structure even at low saturation pressure around 1.5 atm. The effect of the ultrasonic activation on the bubble nucleation was considered and applied to the nucleation theories. The cluster nucleation theory along with consideration of the ultrasonic effect enabled better prediction of the rate of nucleation than the classical nucleation theory.
