Key factors for regulation of cell morphology in supercritical CO2 direct rapid depressurization foaming silicone rubber process

Silicone rubber foam was prepared by direct rapid depressurization foaming process using supercritical CO₂ as foaming agent. It was found that under high temperature and pressure, the dissolution of CO₂ and the vulcanization reaction occurred simultaneously. The vulcanization degree range with good cell morphology was between 19.8% and 48.2%. When the saturation pressure exceeded 16 MPa, the cell morphology did not depend on foaming pressure. When the temperature was increased from 110 °C to 140 °C, the degree of vulcanization increased from 1.8% to 60.5%, and the cell size ranged from 13.9 µm to 646.4 µm, with an order of magnitude variation in cell density. This study identified the key control factors for supercritical CO₂ relief foaming of silicone rubber and provided a fast and efficient preparation method, as well as theoretical guidance, for obtaining lightweight microporous silicone rubber foams.