Studies Of The Silane Coupling Agent In The SSBR/SiO₂System

Solution-polymerized styrene-butadiene rubber (SSBR) was the matrix in this paper. SSBR was reinforced by silica (SiO2), which modified by bis-[3-(triethoxy silicon) propyl]-four sulphide (Si69), bis-[3-(triethoxy silicon) propyl]-disulfide (Si75),3-symplectic acyl thio-1-propyl triethoxy silane (NXT) respectively. Mechanism of SSBR/SiO2system modified by Si69, Si75, NXT were investigated. The effects of the processing temperature, mixing time and hot air aging on the physical and mechanical properties, stress relaxation, cross-linked density, blooming and dynamic mechanical properties of the silane-modified SSBR/SiO2system were discussed.Firstly, mechanism of SSBR/SiO2system modified by Si69, Si75, NXT were investigated. Si69and NXT-modified SiO2in different standing processing temperature were analyzed by FTlR, the results showed that the relative ratio of C-O bond and Si-O bond was smaller when SiO2modified at140℃, which indicated that more Si69and NXT grafted onto SiO2at this temperature. The results of DSC showed that the endothermic peak of SiO2modified by Si69and NXT appeared around140℃, indicating that there were a chemical reaction between Si69, NXT and SiO2at140℃. The thermal behavior of the SSBR/silane coupling agent was tested by DSC, which results showed that the silane and the SSBR could be able to react under certain conditions, and the order of endothermic peak is TNXT> Tsi75> T Si69. The results of no rotor rheometer tests showed that the MH of SSBR/silane coupling agent increased slowly as the vulcanization temperature increased,ML,TclO and Tc90gradually decreases, MH si69> MH si75> MH NXT> MH unmodified.Besides, the effects of mix processing temperature and mixing time on SSBR/SiO2system modified by silane coupling agent were studied. With the rubber compound processing temperature increased, the tensile strength and tear strength of the Si69modified SSBR/SiO2vulcanizates increased firstly and then decreased. Tensile strength, tear strength and cross-linked density of SSBR/SiO2vulcanizates modified at140℃were biggest, which consist with the temperature Si69reacts with SiO2and SSBR. The gum contents of NXT modified SSBR/SiO2increased as the kneading time extended and stabilized after kneading18min. With the kneading time increases, the hardness of SSBR/SiO2decreased, modulus under300%elongation, tensile strength and elongation at break increased firstly and then decreased, the tear strength decreased gradually. Modulus under300%elongation, tensile strength and elongation at break of vulcanizates mixed18min are biggest. The results of RPA and DMA showed that G’、G" and AG’of the SSBR/SiO2vulcanizates mixed18min are smaller, while the tanδ peak were higher.Finally, the effects of Si69, Si75and NXT on the hot air aging performance of SSBR/SiO2system were studied. Compared with the SSBR/SiO2system no added silane coupling agent, physical and mechanical properties, stress relaxation coefficient (σR), cross-linking density of vulcanizates modified by Si69, Si75and NXT increased. σR increased as the aging time extended, and the stress relaxation behavior of the SSBR/SiO2system modified by NXT gradually were weaker than Si69, Si75as the aging time extended. The silane coupling agent can decreased the crosslink density rate of SSBR/SiO2system, and crosslink density growth rate decreased as the increase of the amount of the silane coupling agent. The study also found that the silane coupling agent can weakened blooming of SSBR/SiO2system under the hot air aging.