Effect of silica‐coated TiO 2 nanorods on the foamability of polypropylene and photostability of foamed polypropylene

Researches about the heterogeneous nucleation ability of nanorods and the weather resistance of polypropylene (PP) foams were very limited. In this study, the well-defined rutile TiO2 nanorods with UV-absorbing function were coated with silica and then calcined. The obtained nanorods (denoted as "TS") could be uniformly dispersed in PP matrix by melt blending. The foaming behavior of linear PP and its composites was investigated by using supercritical carbon dioxide (scCO(2)) as a physical foaming agent. The results demonstrated that the addition of 5 wt% TS made PP/TS-5% foam have higher cell density, regular cell structure and uniform cell distribution owing to the large numbers of nucleation sites provided by well-dispersed TS nanorods. At the same time, the aging performance of PP foam samples was evaluated by the changes of macro or micro morphology, melting and crystallization behavior before and after UVB irradiation. It was intuitively found that the damage to the surface of PP foams caused by UV light, involving the erosion of surface, the collapse of cells and the degradation of PP chains could be significantly suppressed by the incorporation of TS nanorods. These findings indicated that TS nanorods could be used as multifunctional nanofillers to achieve the PP foams with improved foamability and photostability.