Structural, thermal, and tribological properties of poly(vinylidene fluoride)/nano-TiO2 composites prepared by dry-mixing and hot-press technique

This paper describes the morphological, thermal, and tribological characteristics of poly(vinylidene fluoride) (PVDF)-based composites dispersed with nanosized TiO2 (nano-TiO2) particles. PVDF/nano-TiO2 composites with different nano-TiO2 loading (similar to 40 wt%) were prepared via a dry-mixing and uniaxial hot-press molding technique. The incorporation of nano-TiO2 led to changes in the crystal structure of the PVDF, as characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. The uniform distribution and good interactions of the composites were confirmed by scanning electron microscopy and energy-dispersive spectrometry. The frictional performances increased with the amount of nano-TiO2 owing to the preferential formation of a nonpolar alpha-phase crystal and the reduced viscoelastic characteristics of the PVDF. The PVDF/nano-TiO2 composite with 30% loading exhibited the best frictional performance (a staticfriction coefficient of 0.23 and a kinetic-friction coefficient of 0.17), which is comparable to that of the composite prepared via a costly, environmentally unfriendly wet-mixing technique. Furthermore, the taber abrasion resistances were comparable to that of commercialized ultra-high-molecular-weight polyethylene (UHMWPE), indicating the effectiveness of PVDF/nano-TiO2 hybridization.