Waste Rubber Powder Modified By Both Microwave And Sol-gel Method And Study On The Properties Of Natural Rubber Blended With Modified Waste Rubber Powder

At first the effect of different meshes waste rubber powder(WRP) on the properties of composite was studied. The result showed that with increase of meshes, the mechanical properties of composite increased gradually. Then WRP was modified by microwave treatment and WRP modified by microwave treatment was immersed in tetraethoxysilane. During hydrolysis and condensation reaction process, SiO2network was in situ generated on the surface of WRP by sol-gel method, which prepared modified waste rubber powder(MWRP). NR/MWRP composite was prepared by NR blended with MWRP. The properties of NR/MWRP composite were investigated.With the increase of microwave time, tensile strength and the elongation at break of NR/MWRP composite both increased first and then decreased. Differential scanning calorimeter analysis of WRP modified by microwave treatment showed that with the increase of microwave time, the glass transition temperature decreased first and then increased. Thermogravimetric analyzer analysis of WRP modified by microwave treatment showed that the long time microwave treatment led to degradation of rubber chains and increase of carbon black content. So the best microwave treatment time was20s. Thermogravimetric analyzer analysis of WRP modified by microwave treatment and sol-gel method showed that100phr WRP contained24.5phr in situ generated silica particles.Through reinforcement of in situ generated silica and improvement of the compatibility between NR and WRP, NR/MWRP composite owned better mechanical properties. With increase of bis-(3-(triethoxysilyl)-propyl)-tetrasulfide(Si69) content, SiO2particles aggregation was inhibited and the dispersion of SiO2particles improved. So the mechanical properties of NR/MWRP composite further improved. The result of scanning electron microscopy showed that the addition of Si69improved the interaction between NR and WRP. The result of strain sweep showed that with the increase of Si69content, the Payne effect decreased. The result of frequency sweep showed that with the increase of frequency, the storage modulus increased. The result of temperature sweep showed that with increase of temperature, the aggregation of SiO2particles increased and the aging phenomenon of NR/MWRP composite appeared. Through the result of Fourier transform infrared analysis, the composite aging was due to degradation of sulfur crosslinks and main rubber chains modification which resulted in appearance of carbon-carbon conjugated double bonds. To improve the aging resistance properties and study the mechanism of aging resistance, maleic anhydride(MA) and N, N-m-phenylene bismaleimide(BMI) was added to composite, respectively. The result showed that compared with MA, BMI improved the aging resistance properties greatly. On the one hand, BMI stopped the formation of the conjugated double bonds by Diels-Alder reaction. On the other hand, through Diels-Alder reaction, WRP chains were bonded together by BMI, which acted as chemical vulcanization, and benzene ring was introduced into system. By these two hands, the aging resistance properties of composite improved dramatically.The result of dynamic mechanical analyzer analysis showed that due to improvement of rubber-fillef, camposite owned low rolling resistance. Due to the formation of rubber shell, relaxation time of rubber chains became longer. Composite absorbed more energy and owned the best wetting resistance property.