Effect of surface modification of nanosilica on crystallization, thermal and mechanical properties of poly(vinylidene fluoride)

Composites were prepared by solution blending ploy(vinylidene fluoride) (PVDF) and nanosilica which modified by different organic modifiers. Infrared analysis showed that the crystalline structure of PVDF was changed by the addition of RNS-A (silica with amino terminated group), while similar crystalline structure as pure PVDF was observed for composites with DNS-0 and DNS-2, unmodified silica and alkyl terminated group silica, respectively. With differential scanning calorimeter (DSC) and dynamic mechanic thermal analysis (DMTA) techniques, crystalline structure, thermal, and mechanical properties of the composite films were examined. As the DSC results showed, addition of SiO2 would lead to the increased cooling crystallization temperature (Tc), implying that SiO2 nanoparticles could act as nucleating agents, however the degree of crystallinity of PVDF was not elevated significantly. In the complementary modulated DSC curves, multi-melting peaks associated with non-reversing portion were observed and were explained from the viewpoint of melting-recrystallization in the DSC heating scan. In addition, dynamic mechanical properties as well as the thermal stability of the composites are also influenced by SiO2. As manifested by the corresponding DMTA and thermogravimetric analysis (TGA) results, a strong interaction should exist between PVDF and SiO2 nanoparticles.