Preparation and Density Control of PMMA Microcellular Foams via Supercritical Carbon Dioxide Foaming

Microcellular polymeric foam is a new class of materials which has been widely used in many industries. The foaming of polymethyl metacrylate (PMMA) using supercritical carbon dioxide (ScCO2) which is inexpensive and environmental friendly has been studied to better understand the foaming process. The pieces of PMMA are put into a saturation vessel of which temperature and pressure are kept constant. Supercritical carbon dioxide (ScCO2) at temperature between 65 degrees C and 105 degrees C and pressure between 8 MPa and 16 MPa is used as a foaming agent. After saturation of carbon dioxide, rapid decompression of ScCO2 saturated PMMA yields expanded microcellular foams. The densities of foamed PMMA materials are tested by true density analyzer, while the microstructures of a variety of density foamed PMMA materials are characterized by scaning electron microscopy (SEM). The cell size and cell density are calculated via image analysis. The effect of the process condition on the cell morphologies and mass density of the foam is investigated by considering the solubility of carbon dioxide in PMMA. The relationship between the mass density of foamed PMMA (rho) and foaming temperature (T) and pressure (P) are respectively certained quantificationally.