Modification Of Butadiene/Styrene Polymers Via Click Chemistry And Performances Research Of Their Nanocomposite

With the growing energy shortage and environmental concerms,environmental protection,energy conservation,high performance and low cost become the future direction of rubber development."Green tire tread material" with good wet-skid resistance,low rolling resistance,low heat build-up and abrasion resistance has become what people pursue.Based on the principle of adjusting the dispersion of filler and strengthening the interfacial interaction between filler and rubber,several model branched/comb solution-polymerized styrene-butadiene rubber(SSBR)were synthesized via thiol-ene click chemistry,and the performance of their silica/carbon black-filled nanocomposites was researched to achieve high performance of rubber.The main research contents and results of this thesis are as follows:1.Preparation of branched/comb polybutadiene(PB)and solution-polymerized styrene-butadiene rubber(SSBR)and study on performances of their composites filled by carbon black(CB).The branched/comb PB and SSBR were prepared through the thiol-ene click chemistry with the addition of ethyl mercaptan,hexyl mercaptan,dodecyl mercaptan and octadecyl mercaptan.The structure control of branched/comb PB and SSBR were realized through chang:ing the type of mercaptan,reaction time,reaction temperature and feed ratio of polymer/mercaptan.Thermal properties results study of the model polymer shows that:(1)as the chain length increasing from C2 to C6,C12,and C18,the glass transition temperature of the model polymer shows the trend of increasing,decreasing and then increasing again,and the model polymer with C18 side chains eventually crystallizes,which melt temperature is 7?29?;(2)as the grafting density increasing from 0 to 350,which is calculated by branched chain/polymer mole ratio,the glass transition temperature of branched/comb PB with C2,C6 and C12 side chains increases by 13?,decreases by 5oC,and decreases by 14?,respectively.The study of CB reinforced graft-butadiene rubber shows that:(1)the mooney viscosity of CB/comb SSBR compounds decreases by 55%?72%;(2)the Payne effect of CB/comb SSBR is significantly reduced,and the side chain length has little effect on that.Due to the introduction of branched chain,the cohesive energy of branched/comb polymer decreases,the crosslinking density of vulcanized rubber decreases,and its elongation at break increases,which is more and more significant with the increase of grafting density.2.Preparation of functionalized branched/comb SSBR and study on performances of their composites filled by silica.The branched/comb SSBR were prepared through the thiol-ene click chemistry with the addition of 3-mercapto-1-propanol,6-mercapto-1-hexanol,3-mercaptopropionnic acid,11-mercaptoundecanoicacid and 3-mercaptopropyltriethoxysilane.The silica/functionalized SSBR nanocomposites were prepared without adding silane coupl:ing agents through traditional processing technology.The silica/functionalized SSBR composites increase the bound rubber contents by 125%-290%and decrease Payne effect greatly,which lead to improve in tensile strength with wet skid resistance and decrease rolling resistance.The tensile strength,values of tan 6 at 0? and 60? reach 26 MPa,1.23 and 0.086 respectively,when the functionalized SSBR contains 70 carboxyl group.The inclusion of 70 siloxane groups increases the value of tan 6 at 0?by 184%,and decreases the value of tan6 at 60? by 13%.The functionalized SSBR can realize the in-situ modification of silica.The nanocomposites with functionalized SSBR exhibit better effect than the nanocomposites with silane coupling agents in the improvement of filler dispersion.The dispersion of silica gradually increase in the order of hydroxyl,carboxyl and siloxane groups functionalized SSBR,which is attributed to the improvement of interfacial interaction.The excessive interfacial interaction goes against the production of high-performance rubber.The length of side chain has less impact on the dispersion of silica and rubber properties.3.Preparation of grafted silica via ball-milling and study on performances of composites filled by SSBR.The modified silica was prepared by the grafting of branched/comb SSBR with carboxyl and siloxane groups onto the silica through ball-milling in cyclohexane.The grafted silica/SSBR nanocomposites are prepared through traditional processing technology.The grafted.silica/SSBR nanocomposites with improved bound rubber contents and reduced Payne effect show increased mechanical properties along with wet skid resistance and decreased rolling resistance.The excessive branched/comb SSBR reduce dynamic mechanics performances and improve rolling resistance.The branched/comb SSBR with carboxyl and siloxane groups have less impact on the dispersion of silica and rubber properties.