Study On The Applicaton Of Liquid Natural Rubber In NR/SiO₂Composite

Liquid natural rubber (Liquid Natural Rubber, LNR) is a kind of low molecular weight natural rubber which molecular weight is less than20000. It’s viscous oily liquid at room temperature. Because of its good fluidity, LNR can be used as processing agents to improve the processibility of rubber. The reactive group on the surface of SiO2and poor compatibility with NR lead to the aggregation of SiO2in NR/SiO2composites. Therefore, It’s important to improve the dispersion of SiO2.This paper aimed to improve the dispersion of fillers in rubber matrix by the use of liquid natural rubber.Natural rubber and epoxidized natural rubber were degraded by periodic acid to prepare liquid natural rubber (LNR) and epoxidized liquid natural rubber (ELNR).The results showed that the double bonds were destroyed instead of opening the epoxy group by periodic acid. The infrared spectrum proved the present of carbonyl groups after degradation. The initial degradation temperatur(Ti) of LNR was increased to361℃.There was a new degradation peak near250℃of ELNR, the degree of the degradation was about10%.The Ti in main degradation stage was396℃.Liquid natural rubber was added in NR/SiO2composites by mechanical-blending to explor the effect of LNR for NR/SiO2composites.The results showed that the Payne effect could be significantly reduced by the addition of LNR,the maximum elastic modulus decreased from50Kpa to28Kpa. The flow index increased from0.37to0.41in the present of LNR. It indicated that the fluidity and processibility were improved.Scanning electron microscopy showed that the dispersion of silica was improved by the addition of LNR. The tensile strength decreased to22.46Mpa with the increased of LNR.While the maximum elongation at break was746.06%with5phr LNR present. Thermal stability of NR/S1O2composites increase with the addition of LNR, the initial degradation temperature increased from347℃to354℃.Epoxidized liquid natural rubber was added in NR/S1O2composites by mechanical-blending to explor the effect of ELNR for NR/S1O2composites.The result show that Payne effect was weakened with ELNR joined. With the addition of5phr ELNR,the Payne effece was weakest and maximum elastic modulus decreased to35Kpa. The flow index increased to0.40in the present of2.5phr ELNR.lt meaned that the fluidity and processibility were improved.The Scanning Electron Microscopy showed the distribution of fillers was improved.Mechanical properties of NR/S102composite was improved with the addition of ELNR as well.The tensile strength and elongation at break could reach25.70Mpa and797.70%respectively, in the present of5phr ELNR. The thermal stability of composites was improved and Ti was increase to354℃when the ELNR was7.5phr.