| Silica?Si O2?,an inorganic filler,is second only to carbon black in rubber industry.Silica-filled tire rubber shows lower rolling resistance and higher wet skid resistance compared to traditional filler carbon black and the tire was called"green tire".However,with a large number of silanols on the surface,silica exhibits strong hydrophilicity,leading to poor compatibility with non-polar rubber difficult dispersion.This paper aimed to improve the compatibility of silica and natural rubber?NR?to increase the dispersion of silica in the NR matrix and improve the interfacial properties between silica and NR,preparing silica/NR composites with excellent properties.Based on this,the following work was carried out:?1?Surface modification of silica was performed in an ethanol solution,and oleylamine?OA?was grafted onto the surface of silica by a silane coupling agent KH560.FTIR spectroscopy,TGA,water contact angle,and TEM-Mapping were used to confirm the successful grafting of oleylamine on the surface of silica,and the modified silica?Si O2-g-OA?was successfully prepared.The hydrophobicity of Si O2-g-OA has been greatly improved compared to Si O2.The water contact angle exceeds 140°,and the grafting rate calculated by TGA curves was 10.05%.?2?Si O2-g-OA/NR composites with different loadings were prepared by traditional mechanical blending,and the effect of Si O2-g-OA on NR performance was studied.Curing characteristics,static mechanical properties,abrasion performance,rubber processing performance,dynamic mechanical properties and dispersion of silica in NR matrix of Si O2-g-OA/NR composites were characterized respectively by rubber processing analyzer?RPA?,tensile tester,Akron abrasion machine,dynamic thermomechanical analyzer?DMA?and scanning electron microscope?SEM?.The results showed that the curing performance,the mechanical properties,the processing properties and abrasion properties were all improved to varying degrees.The tensile strength of Si O2-g-OA/NR reached the maximum when the loading was 30 phr;in addition,the Si O2-g-OA/NR composite had lower rolling resistance and higher wet skid resistance when the filling amount reached 30 phr and above compared with Si O2/NR.?3?The surface of silica was modified respectively with different silane coupling agents?KH560-OA,KH560-ODA,KH570,Si69 and cetyltrimethoxysilane?in ethanol solution.Then,mechanically blended methods were used to prepare modified silica/NR composites with a filling amount of 30 phr,and the effect of silica prepared by different silane coupling agents on NR performance was studied.The results showed that Si O2-g-OA modified by KH560-OA had good compatibility with NR,the tensile strength and abrasion performance was the best.Compared with the modification effect of KH560-ODA,it was confirmed that the double bond in oleylamine did co-vulcanize with the NR matrix,and the tear strength and abrasion performance were improved because of it.?4?The imino groups in KH560-OA and KH560-ODA can be combined with stearic acid during the mixing process to further reduce the polarity of silica and promote the dispersion of silica in the NR matrix.Based on the above findings,the modification method of introducing unsaturated hydrocarbon groups into the surface of silica through the silane coupling agent KH560 can improve the compatibility of silica and the NR matrix and also enhance the interaction between the silica and the NR matrix.The composite prepared by this method has better comprehensive performance and can be used to prepare the green tires with excellent performance. |
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