Characterization of expanded polystyrene and its composites by supercritical carbon dioxide foaming approach

Supercritical carbon dioxide (scCO2) has been used as a physical blowing agent to produce polymer expanded materials. Firstly, a statistic study was performed to determine the neat polystyrene (PS) expansion parameters, using the ANOVA and response desirability approach. The results suggested that the optimal parameters are 120 °C (temperature), 2500 psi/17.23 MPa (pressure), and 2 h (residence time). Secondly, defibrillated curaua fibers (CF) were used as reinforcement in the PS matrix, in three different proportions (1.0, 2.5, and 5.0% (w/w)), to produced expanded composites. The results showed that CF acted as a nucleating agent, facilitating scCO2 to sip into the composite due to the reinforcement/matrix interface. The expanded composites were characterized by SEM, apparent density, cell population density, void volume fraction, and mechanical properties by the compression test, water uptake, dye absorption and, water contact angle (WCA). CF incorporation in the composite increased the compressive strength value and modified the expanded composite final morphology, decreasing the cell size and increasing void content and density. The PS/CF 5.0% sample showed higher water and organic dye absorption and the addition of CF on the expanded composite slightly decrease WCA.