| Solution polymerized styrene butadiene rubber(SSBR)is widely used in tire tread rubber,because of its great abrasion resistance,lower rolling loss and great wet-skid resisitance.In recent years,the development of tires towards energy saving and environmental protection put forward a higher request for the comprehensive performance of the tire rubber.As a new type of layered carbon nanofillers,Graphene has very high mechanical strength,unqiue conductivity and heat-conducting properties.Graphene as a filler to modify tread rubber could increase the mechanical strength and improve the conductivity and heat-conducting properties as well as the abrasion resistance simultaneously,making the rubber composites obtain an excellent comprehensive performance.However,graphene could not disperse evenly in the rubber matrix.Graphene oxide as a derivative of graphene not only had the excellent performance of graphene but decreased the aggregation to some extent.The oxygen functional group of graphene oxide could make it be modified easily.To improve its dispersity and increase its interaction with SSBR,graphene oxide was covalently and noncovalently modified,respectively.The influences of the modified graphene oxide on the mechanical property,aging resistance,thermal property and wet-skid resistance as well as rolling loss of SSBR composites,were systematically studied.Graphite oxide was mechanically exfoliated through ultrasonic to obtain graphene oxide.P-phenylenediamine modified graphene oxide(PPD-GO)was prepared by chemically grafting graphene oxide with small organic molecule p-phenylenediamine.The composite filler(SiO2-GO)was prepared using white carbon black and graphene oxide with a mass ratio of 1:1.The structures of modified graphene were studied by XRD,Raman and FTIR.The results showed that,compared with graphene oxide,the oxygen-containing groups on PPD-GO were obviously decreased,the interlayer spacing and surface defect density increased obviously for PPD-GO.It was found that the interlayer spacing and surface defect density had little change for Si02-GO compared with graphene oxide,indicating that white carbon black had no influence on the chemical and layered structure of graphene oxide.The mechanical properties of the composite rubber were studied by an universal testing machine.The results showed that,the mechanical strength of SSBR both increased first and then decreased with increasing the content of PPD-GO and SiO2-GO.The mechanical strength reached a peak value at 4 phr of PPD-GO and 2 phr of SiO2-GO,respectively.The mechanical strength for composite rubber with 4 phr of PPD-GO increased by 29.5%and reached 21.5 MPa from 16.6 MPa,compared with the blank.For composite rubber with 2 phr of SiO2-GO,compared with the blank,the mechanical strength increased by 26.5%and reached 21.0 MPa from 16.6 MPa.The elongation at break increased from 301%to 350%for composite rubber with 4 phr of PPD-GO and 377%for composite rubber with 2 phr of SiO2-GO.Both the reinforcing effects of PPD-GO and SiO2-GO on SSBR were significantly higher than that of the unmodified graphene oxide with same content.The results of TGA showed that,the temperature under the maximum weight loss rate was increased by 5 0C for SSBR with PPD-GO,and the maximum weight loss rate of SSBR was obviously decreased by adding PPD-GO and SiO2-GO,indicating the improved thermal stability of SSBR.The results of DTG-DSC showed that,the temperature of thermal oxidative degradation was increased and the thermal oxygen degradation rate was decreased for SSBR both by adding PPD-GO and SiO2-GO,indicating that the thermal oxidative stability of SSBR was improved.The results of DMA showed that,compared with the blank,for SSBR with 1 phr of PPD-GO,the tan δ was increased by 5.6%at 0 ℃ and changed slightly at 60 ℃,which indicated that the wet-skid resistance was increased and the rolling charateristics had no change.For SSBR with 2 phr of SiO2-GO,compared with the blank,the tan δ at 0℃ and 60℃ was decreased by 2.8%and 16.7%,respectively,indicating that the rolling charateristics was obviously increased and the wet-skid resistance was just decreased slightly. |
