Controlled degradation of natural rubber by microparticles containing titanium dioxide

Abstract

Natural rubber is an important raw material of Thailand. Natural rubber waste becomes the most important problem since it cannot be naturally degraded after used เท environment. Producing natural rubber that is degradable or its degradation can be controlled is an attractive method to reduce problem due to natural rubber waste. In this research we studied oxidative degradation of natural rubber by incorporating microparticles containing titanium dioxide. Microparticles were prepared by gelatin-gum arable coacervation. The emulsion was homogenized at 14,000 rpm. After being recovered, microparticles were dried by freeze-drying method. Size of the microparticles were 30 μm in diameter as analyzed by scanning electron microscopy (SEM). Degradation of natural rubber under accelerated ultraviolet light and sunlight was studied by following viscosity-average molecular weight of natural rubber. Molecular weight of natural rubber decreased when the time of UV and sunlight exposure increased. When the time was increased, molecular weight of natural rubber, having titanium dioxide microparticles decreased more rapidly than the one having titanium dioxide powder. In the presence of water molecular weight of natural rubber decreased more than the normal condition. Degraded natural rubber was analyzed by Fourier transform infrared spectroscopy (FT-IR). IR spectra showed peak in 1700 - 1760 cm-1 region as an indication of carbonyl group. Degradation of vulcanized natural rubber under sunlight was monitored by mechanical property determination. Tensile strength of natural rubber containing titanium dioxide powder and microparticles decreased when the time of sunlight exposure increased and in the presence of water. The surface of degraded natural rubber was characterized by attenuated total reflection infrared spectroscopy (ATR-IR). IR spectra exhibited peaks in the region of 1700 - 1760 cm-1 indicating the existence of carbonyl group at the surface after natural rubber was degraded.