| Rubber and its products are easy to degrade and shorten service life due to aging.Adding antioxidants to prevent aging is the most convenient and effective method,but traditional amine antioxidants are toxic and cause color contamination,and the efficiency of hindered phenolic antioxidants is limited,both of they have also tend to be volatile,migratory,lack of resistance to be extracted.Moreover,they only have one single function.All these disadvantages make conventional antioxidants not to meet the antioxidants development requirements,that is high efficiency,multi-function,no pollution,low toxicity,and low price.Therefore,based on the advantages of reactive antioxidants,thiourea and its derivatives and rare earth complexes,three types of multifunctional rubber antioxidants containing allyl structure,thiourea structure,hindered phenolic structure and rare earth complex structure were constructed in this dissertation,and the synergistic effects between several structural units were utilized,which were able to solve the problems of amine antioxidants and hindered phenolic antioxidants as mentioned above.At the same time,they were endowed with the functions of promoting vulcanization,improving filler dispersion,enhancing the interface interaction between rubber and filler,all of these could improve the physical and mechanical properties of rubber composites.Therefore,this research does not only have scientific research value,but also has potential application value.The obtained results were shown as followed.(1)A kind of reactive multifunctional rubber antioxidant,APPT,which combined the structure of aromatic secondary amine,thiourea and allyl,was designed and synthesized.The synergistic effect of these three structural units enabled APPT to significantly improve the thermo-oxidative aging resistance of SBR/SiO2 composites,and the color pollution was significantly lower than that of the antioxidant 4010NA,and it had good volatile resistance,migration resistance and solvent extraction resistance,showing a good long-term thermo-oxidative aging resistance effect.Moreover,it could also accelerate the vulcanization of SBR/SiO2 uncured rubber,improve the dispersion of SiO2 in SBR matrix,enhance the interface interaction strength of filler/rubber,leading to the the improvement of tensile strength,stress at100%and 300%strain and hardness of SBR/SiO2 composites.The elongation at break and the DIN abrasion volume loss of SBR/SiO2 composites were reduced.(2)In order to eliminate the color contamination of rubber products caused by aromatic secondary amines,a multifunctional reactive rubber antioxidant,Glu ASm,was designed and synthesized using renewable glutamic acid instead of aniline derivatives as raw material,which combined thiourea structure,allyl structure and rare earth complex structure.The synergistic effect of these three structural units endowed Glu ASm excellent volatile resistance,migration resistance and methanol extraction resistance,which showed excellent thermo-oxidative aging resistance to SBR/SiO2 composites without obvious color pollution,and the effect was better than that of antioxidant MB and 4010NA.The resisting thermo-oxidative aging mechanism was as follows:the thiourea structure effectively decomposed the hydroperoxide ROOH,the sulfur free radical terminated R·,ROO·and other reactive oxygen free radicals,the sulfur oxide further decomposed the ROOH,inhibited the SBR to automatically accelerate the catalytic aging reaction;Rare earth Sm ions combined with active oxygen-containing radicals ROO·,RO·and HO·to form stable rare earth compounds and terminated the SBR radical chain reaction.The synergistic effect of thiourea group and Sm ion could effectively inhibited and delayed the thermo-oxidative aging process of SBR/SiO2 composites.Glu ASm could significantly accelerate the vulcanization of SBR/SiO2/Glu ASm uncured rubber,reduce the vulcanization temperature,promote the better dispersion of filler SiO2 in SBR,and endue SBR/SiO2/Glu ASm composites with better physical and mechanical properties.When the amount of SiO2 was kept at 30 phr,the SBR/SiO2/Glu ASm composites with 3 phr of Glu ASm,which was vulcanized at 140?,had lower filler dispersion parameter L value,glass transition temperature Tg,rolling resistance and DIN abrasion volume loss than composites without Glu ASm vulcanized at 160?.The crosslinking density,tensile strength,tear strength,reinforcing factor?F value and the mass fraction of polymer confined layer?im were all higher than those of the SBR/SiO2 composites without Glu ASm vulcanized at 160?.(3)In order to completely eliminate the color contamination of rubber products caused by antioxidants,a new multifunctional antioxidant DTSm was designed and synthesized,which combined the hindered phenolic structure and rare earth complex structure.The synergistic effect of these two structural units enabled DTSm to give SBR/SiO2 composites excellent thermo-oxidative aging resistance without color pollution.It had advantages as high thermal stability,outstanding long-term thermo-oxidative aging protection performance,better migration resistance,volatile resistance,and methanol extraction resistance than the antioxidant BHT.The hindered phenol in DTSm provided proton to combine with the active macromolecular radicals R·and ROO·to form stable macromolecular compounds.The rare earth Sm ions in DTSm combined with the active oxygen-containing radicals ROO·,RO·and HO·to form stable rare earth compounds,thus terminating the free radical chain reaction of SBR macromolecule.The synergistic effect of hindered phenols and rare earth ions effectively inhibited and delayed the thermo-oxidative aging process of SBR/SiO2 composites.When the dosage of DTSm was less than 3 phr,there was no negative effect on the vulcanization property of SBR/SiO2 compound.It could promote the dispersion of SiO2 filler in SBR,improve the tensile strength and elongation at break of SBR/SiO2 composites,reduce the hardness and improve the dynamic compression heat generation property,but the tear strength and stress at constant strain were reduced. |
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