Optimizing thermal behavior in HIPS/silicon nanocomposites: The role of cooling rates

Abstract

This study investigates how different cooling rates affect the thermal and structural properties of high-impact polystyrene (HIPS) reinforced with silicon (Si) nanoparticles. Nanocomposites were synthesized through solution mixing and hot pressing, then cooled under three conditions: slow cooling (SC-HIPS + Si), cooling in iced water (WC-HIPS + Si), and cooling in liquid nitrogen (NC-HIPS + Si). Thermal behavior was characterized via thermogravimetric analysis (TGA), differential thermal analysis (DTA), and differential scanning calorimetry (DSC). Structural changes were examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). TGA results reveal that early-stage thermal decomposition (temperatures corresponding to 5% and 50% mass loss) is highly sensitive to cooling rates, whereas later-stage decomposition (temperature corresponding to 93% mass loss) remains relatively unaffected. Additionally, the temperature of maximum mass loss, the maximum rate of mass loss, and the glass transition temperature of the HIPS matrix show a strong dependence on cooling rate. These findings are interpreted in the context of free volume theory and the enhanced segmental motion of the HIPS chains, with XRD and SEM analyses further elucidating how cooling rate influences nanocomposite morphology.