Compatibilization of polyhedral oligomeric silsesquioxane for polypropylene–titanium dioxide composites and effect of the processing temperature

Polyhedral oligomeric silsesquioxanes (POSSs), with inorganic cores, offer excellent mechanical properties and have external organic substituents. On the basis of their hybrid organic?inorganic characteristics, which allow for a tunable reaction or miscibility with various materials, in this study, we introduced a bifunctional POSS as a novel rigid compatibilizer for polypropylene (PP)–titanium dioxide (TiO₂) composites and evaluated its compatibilizing effects at different processing temperatures. The results show that the attached hydroxyl and isobutyl groups allowed for the reaction with TiO₂ and miscibility with the PP matrix. However, at lower processing temperatures, POSS existed in the form of solid particles, and its interfacial absorption was too poor for sufficient coverage of the TiO₂ surface; this resulted in a weak compatibilization effect on the PP–TiO₂ composite. When the processing temperature was increased to 240 °C, the solid POSS turned into a liquid and thus had strong mobility; this was favorable for the diffusion of TiO₂ onto the surface and the construction of a strong interfacial phase. Because the rigid characteristic of POSS made a positive contribution to the performances of the composites, the PP–TiO₂ composites prepared at higher processing temperatures exhibited better mechanical properties, with the maximum increases occurring in the compositions containing 5 wt % POSS. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44766