Rheological behavior of polycarbonate/ultrafine octaphenyl silsesquioxane (OPS) composites

Polycarbonate (PC)/ultrafine polyhedral oligomeric octaphenyl silsesquioxane (OPS) composites were prepared by melt mixing method. The morphology and rheological behavior of PC/ultrafine OPS composites were investigated by scanning electron microscopy (SEM) melt indexer, high pressure capillary rheometer, and strain-controlled rheometer. The SEM results show that ultrafine OPS is dispersed in PC as the size of submicron and has a good dispersion in PC matrix, and a certain extent compatibility between PC and ultrafine OPS is found. OPS aggregation is found through the cross section at high ultrafine OPS content. The results of melt flow index (MFI) and capillary rheometer indicate that ultrafine OPS can effectively decrease the apparent viscosity and improve the flow property and processability of PC matrix as a lubricant. The oscillatory rheological analysis indicates that the storage modulus increases with increasing OPS content, and the appeared platform of storage modulus exhibits the solid-like behavior and the formation of three-dimensional network in the composites. The complex viscosity of PC/OPS composite shows a quasi-Newtonian regime at low OPS content and a typical shear-thinning behavior at high OPS content. The Cole-Cole, Han, and van Gurp plots show that ultrafine OPS particle is compatible with PC at low content (≤3 wt %), and interaction between particle and particle is the major factor when OPS at high content (≥6 wt %).