Preparation Of Rare-earth Complex Multifunctional Rubber Additives And Their Effects On Properties Of SBR/SiO₂ Composites

With the rapid development of rubber industry and the continuous improvement of environmental protection consciousness of people,the higher requirements on rubber additives have been put forward.The preparation of multifunctional rubber additives with high-efficiency,functionalization,nontoxicity,environmental protection and low-cost has been a tendency of the development of rubber industry.Therefore,in this dissertation,two kinds of rare earth complexes multifunctional rubber additives with different ligand,which could synchronously accelerate the vulcanization of rubber,improve the thermo-oxidative aging resistance and promote the dispersion of filler and rubber-filler interface bonding of rubber composites,were designed and synthesized.And their effects on the structures and performances of the SBR/SiO₂ composites had been investigated systematically.This work has important theoretical and practical significance for the development of both rare earth industry and rubber industry.All the results of this study were listed as below:?1?Sm-GMMP and Re-LDC?Re=La,Pr,Nd,Sm,Gd,Dy,Ho,Er,Yb?,were as designed synthesized.and their structures were confirmed by ¹H-NMR,¹³C-NMR,UV-vis,FTIR,XPS and Element analysis.?2?Sm-GMMP was conducive to accelerate the vulcanization of SBR/SiO₂ comosites,increase the crosslinking density of SBR/SiO₂ composites,improve the dispersion of SiO₂ and enhance the rubber-filler interface interaction in the composites.The comprehensive performance of SBR/SiO₂ composites in-situ modified by Sm-GMMP was optimal when the dosage of Sm-GMMP was 4 phr.Compared with unmodified SBR/SiO₂ composites,the tensile strength and tear strength of SBR/SiO₂/Sm-GMMP-4 composites were increased by53.3%and 21.7%respectively,and the rolling resistance of the composites was reduced by34.7%.The wear resistance performance and the dynamic compression fatigue thermal performance of the composites were also obviously improved.The possible reinforcement mechanism of SBR/SiO₂ composites in-situ modified by Sm-GMMP was that,Sm-GMMP anchored on the surface of SiO₂ via hydrogen bonding and coordination bonding formed between the carbonyl and samarium ion of Sm-GMMP and the silanol on the surface of SiO₂during the vulcanization process,facilitating SiO₂ to disperse in SBR matrix uniformly.The conjoint benzene rings of Sm-GMMP physically entangled with rubber chains,bridging the SBR matrix and SiO₂ effectively and enhancing the rubber-filler interface bonding significantly,leading to the remarkable improvement in the mechanical properties of SBR/Si O₂ composites.?3?Sm-GMMP showed the preeminent thermal stability,and could significantly improve the thermal,thermo-oxidative stability and thermo-oxidative aging resistance of SBR/Si O₂ composites without color contamination.The effect of thermal oxidative resistance of Sm-GMMP was superior to that of widely used industrial amine antioxidant 4010NA.The possible antioxidative mechanisms of Sm-GMMP in SBR/SiO₂ composites was that the hindered phenol groups reacted with the activated free radicals?R·,ROO·?to terminate the free radical chain reaction of oxidative process,and the thioether groups effectively decomposed the hydroperoxide?ROOH?to inhibit the autocatalytic oxidation of rubber chains significantly.The samarium ions of Sm-GMMP bonded with the activated oxygen free radicals?ROO·,RO·,HO·?and terminated the free radical chain reaction further.The synergism of above three effects enhanced the thermo-oxidative aging resistance of SBR/SiO₂composites dramaticlly.?4?Re-LDC accelerated the vulcanization of SBR/SiO₂ compounds efficiently even without zinc oxide and stearic acid,and the prepared SBR/SiO₂/Re-LDC composites revealed outstanding physical mechanical properties.The vulcanizing properties and mechanical performances of SBR/SiO₂/Re-LDC composites presented the“tetred effect”with the increasing of rare earth atomic number,and Sm-LDC showed the optimal effect on the vulcanizing properties and mechanical performances of SBR/SiO₂ composites.The vulcanizing properties of SBR/SiO₂ composites with 6 phr Sm-LDC had an advantage over that those with conventional vulcanization system containing 5 phr activators zinc oxide,2phr stearic acid and 2 phr accelerator zinc diethyl dithiocarbamate ZDC.Besides sulphur crosslinking,Sm-LDC and SiO₂ could construct the more complex and heterogeneous three-dimensional crosslinking network structure and improved the crosslinking density of SBR/Sm-LDC/SiO₂ composites.?5?SBR/Sm-LDC/SiO₂ composites exhibited excellent mechanical properties with high strength and high elasticity,but SBR/ZDC/SiO₂ composites submiited to destruction under a low strain with poor tensile strength.Under the equivalent filler loading,the tensile strength and tear strength of Sm-LDC-30 composites were increased by 160.7%and 37.0%respectively,and the rolling resistance of the composites was reduced by 54.4%,as compared with ZDC-30 composites.The wear resistance performance and the dynamic compression fatigue thermal performance of Sm-LDC-30 composites were also obviously improved when compared with ZDC-30 composites.The possible reinforcement mechanism of SBR/SiO₂composites in-situ modified by Sm-LDC was that Sm-LDC participated in the vulcanization of rubber and the surface modification of SiO₂ simultaneously.On the one hand,Sm-LDC anchored on the surface of SiO₂ via hydrogen bonding and coordination bonding during the vulcanization process,facilitating Si O₂ to disperse in SBR matrix uniformly.On the other hand,the dithiocarboxyl groups of Sm-LDC chemically grafted onto rubber chains in the end of vulcanization,bridging the SBR matrix and SiO₂ effectively and enhancing the rubber-filler interface bonding significantly,leading to the remarkable improvement in the mechanical properties of SBR/SiO₂ composites.?6?Sm-LDC could significantly improved the thermo-oxidative stability and the thermo-oxidative aging resistance of SBR/Si O₂ composites.The effect of Sm-LDC was superior to that of widely used industrial antioxidant 4010NA and MB,but was a little inferior to that of antioxidant RD.Sm-LDC exhibited excellent thermal stability with no color contamination,and its thermal stability had further improved by the hydrogen bonding and coordination bonding between Sm-LDC and SiO₂ formed in the process of vulcanization.The possible antioxidative mechanisms of Sm-LDC in SBR/Si O₂ composites was that the samarium ions of Sm-LDC bonded with the activated oxygen free radicals?ROO·,RO·,HO·?to terminate the free radical chain reaction of oxidative process,and the dithiocarboxyl of Sm-LDC effectively decomposed the hydroperoxide?ROOH?to inhibit the autocatalytic oxidation of rubber chains significantly.The synergism of above two effects enhanced the thermo-oxidative aging resistance of SBR/SiO₂ composites observably.