Mechanical, thermal properties, and flame retardancy of PC/ultrafine octaphenyl-POSS composites

Composites of ultrafine polyhedral oligomeric octaphenyl silsesquioxane (OPS) and polycarbonate (PC) were prepared by melt blending. The mechanical and thermal properties of the composites were characterized by tensile and flexural tests, impact test, differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), and thermal gravimetric analysis (TGA). Rheological properties of these melts were tested by torque rheometer. The flame retardancy of the composites was tested by limiting oxygen index (LOI), the vertical burning (UL-94), and cone calorimeter test. The char residue was characterized by scanning electron microscope (SEM) and ATR-FTIR spectrum. Furthermore, the dispersion of OPS particles in the PC matrix was evidenced by SEM. The results indicate that the glass transition temperatures (T _g) and torque of the composites decrease with increasing OPS loading. The onset decomposition temperatures of composites are lower than that of PC. The LOI value and UL-94 rating of the PC/OPS composites increase with increasing loading of OPS. When OPS loading reaches 6 wt %, the LOI value is 33.8%, UL-94 (1.6 mm) V-0 rating is obtained, and peak heat release rate (PHRR) decreases from 570 to 292 kJ m ^-2.