Polystyrene Foaming at High Pressure Drop Rates

Abstract

We studied the foaming of polystyrene with CO2 as the physical blowing agent at large pressure drop rates (PDRs) and at different foaming temperatures, with a novel batch foaming apparatus, capable of reaching PDRs as high as 500 MPa/s (in the underlying literature, the maximum so far achieved is 100 MPa/s). Results show that, at each foaming temperature, the number of nucleated bubbles per unit initial volume (N) linearly increases with PDR in a bilogarithmic scale, with slopes increasing with the temperature. The effect of talc as the nucleating agent was also investigated. Furthermore, a phenomenological model was developed and utilized to predict N at PDRs not experimentally accessible. The approach was validated and a good agreement with the experimental data was obtained.