Study On The Multiple Interactions In Silica Reinforced SSBR System

In this thesis,the multi-interaction and network structure of silica 1165 MP reinforced SSBR systems were studied.Firstly,the effects of SSBR microstructure and mixing process on silica-SSBR interaction were discussed;And then,the formation and evolution of chemical crosslinking network between silica and SSBR were investigated in detail.Finally,the interaction between SSBR / BR and silica,as well as SSBR and silica / carbon black,was also discussed.The main findings are as follows:The basic mechanical properties of SSBR5025-2 and SSBR2564 S are similar in the 1165 MP reinforced three SSBR,and SSBR2564 S and SSBR72612 S have better wear resistance due to the high content of cis-structure;Because of its wide molecular weight distribution,SSBR2564 S has the best processing performance,the end-coupled SSBR72612 S has the strongest interfacial interaction with silica but has poor processability,the dispersion of filler in SSBR5025-2 system is poor,and the interaction between filler and rubber is the weakest;SSBR72612S system has the lowest rolling resistance,SSBR2564 S system has the best wet skid resistance,and SSBR5025-2 with block styrene structure has the worst overall dynamic performance.Increasing the temperature of the cooling medium and the rotor speed of the mixer can improve the discharging temperature and thus facilitate the silanization of silica,and the two-stage mixing effectively improves the dispersion of silica,all the factors can reduce the G' value,Payne effect is weakened,and so the interaction between silica and SSBR is enhanced;The addition of D in the internal mixing stage can promote the silanization reaction,and the interaction between silica and SSBR is improved,but the D can be consumed in advance,and so the crosslinking degree of the matrix is affected.It is possible to improve the dynamic performance of vulcanizates to a certain extent by increasing the temperature of the cooling medium,two-stage mixing,increasing the rotor speed and adding D in the internal mixing stage.The silanization of silica with and without acid-base additives were investigated via TG-FTIR(Thermogravimetry coupled with Fourier transform infrared)technology and reaction kinetic simulation.The results showed that two parallel reactions were included in the silanization process of silica: one is the hydrolysis of ethoxy group of TESPT followed by the condensation with the silanol of silica(the activity energy E=57kJ/mol);and the other is the direct condensation between the silanol of silica and the ethoxy group of TESPT(E=90.4kJ/mol).The hydrolysis of ethoxy group is much easier in comparison with the direct condensation with the silanol.The silanization was effectively promoted by means of adding stearic acid(HST)or diphenyl guanidine(D),and the reaction rate increased with the increase of HST or D in a reasonable range.HST promoted the condensation between ethoxy group and silanol(E=69.5kJ/mol),without affecting the hydrolysis of ethoxy group.However,D promoted both of the two reactions obviously(E=59.5kJ/mol and 70.8kJ/mol,respectively).When HST and D coexisted in the system,the condensation between ethoxy group and silanol was promoted more obviously by the acid-base complex(E=53.5kJ/mol).The two-step parallel reaction model was used to simulate the silanization processes and good fitting results were achieved.In situ FTIR spectroscopy analysis of two silane and SSBR mixtures confirmed that the addition reaction of mercapto silane Si747 and polysulfide silane TESPT with SSBR vinyl was carried out under constant temperature conditions at 140?,but the TESPT reaction was slow,After the rise to 160?,TESPT and vinyl addition rate significantly accelerated.The in situ FTIR spectra of two silanes and SSBR compounds were analyzed by MW2 D correlation analysis,and the change of ?-methylene peak intensity was successfully separated.The results show that the single sulfur free radicals produced by the decomposition of mercapto silane Si747 not only react with SSBR vinyl groups,but also capture ?-methylene hydrogen atoms and finally transfer to the vinyl groups;The reaction rate of mercapto silane with SSBR depends on the initiation of sulfur radicals,and the presence of trace amount of oxygen can initiate rapid addition of mercaptosilane to vinyl group.In the case of TESPT,the weak S-S bond breaks at a high temperature,and the pyrolyzed free radical first initiates the substitution reaction of ?-methylene hydrogen,and the resulting mercapto silane is subsequently added to the vinyl group;the polysulfide substituent is continuously decomposed to produce a mercapto silane at the same time to achieve cross-linking between molecular chains.After adding D,the reaction of TESPT with vinyl was accelerated,which was related to the decrease of decomposition temperature of TESPT;the addition of D increased the ionicity of Si747 mercapto groups and inhibited the addition of vinyl groups.Through the study of SSBR/BR system,it was found that the BR content increased,and the interaction of rubber-filler was weakened and the degree of silica network was increased.BR can increase the vulcanization speed of SSBR,and the wear resistance of the system can be improved obviously;the elongation at break,the tear strength and the rebound are increased;the 300% tensile stress and the enhancement factor M300/M100 decreased,while the tensile strength and hardness change little.With the increase of BR,the wet skid resistance of the two SSBR/BR systems was decreased,and the rolling resistance of the SSBR2564S/BR was reduced.However,for SSBR72612 S system,the BR had little effect on rolling resistance.In the silica/CB reinforced SSBR system,the ?G' values of the two SSBR compounds increase with the increase of the ratio of CB/silica,that is,the more obvious Payne effect,the interaction between the filler and the rubber becomes weaker,and the crosslinking density decreases.The tensile strength,hardness and the reinforcement factor M300/M100 of SSBR decreased with the increase of the amount of CB,and the wear resistance of the two SSBR vulcanizates deteriorates.The rolling resistance of the vulcanizate increases and the wet skid resistance decreases,so the CB has a negative effect on the rolling resistance and the wet skid resistance.