| Natural rubber(NR)has high elasticity and excellent mechanical properties,and is widely used as a strategic raw material in various fields such as tires,seals,and shock absorbers.However,NR molecular chains contain a large number of unsaturated double bonds,which is prone to aging and loss of application value of rubber products.At present,the industry usually uses the method of adding small molecule antioxidants during the rubber mixing stage to delay rubber aging,but this method has the disadvantages of uneven dispersion and easy migration of antioxidants.Based on the above problems,this study overcame the shortcomings of uneven dispersion of antioxidants and easy migration of small molecule antioxidants in the mechanical blending method by adding antioxidants in the lotion compounding process and improving the molecular weight of antioxidants,and achieved the goal of efficient and long-term protection of aging resistant natural rubber.Firstly,the latex compounding method was used to add phenol antioxidant(CPL)and amine antioxidant(4020)dispersions to natural rubber latex(NRL)to prepare aging resistant natural rubber,and the effect of the latex compounding method on aging resistance of natural rubber was explored.The results showed that compared with the anti-aging agent added by the mechanical blending method,the latex compounding method could effectively avoid aging during the initial processing of rubber,and was conducive to promoting the dispersion of anti-aging agent,increasing the contact area with the rubber matrix,and increasing the effective content of anti-aging agent.Therefore,the anti-aging natural rubber prepared by latex compounding method had better mechanical properties and heat and oxygen aging resistance.At the same time,to reduce the migration rate of small molecular antioxidants,this experiment successfully prepared PPDA-g-NR aging-resistant rubber using p-amino diphenylamine(PPDA)as raw material,using high-temperature conditions during the drying process of rubber particles,by grafting the small molecular antioxidant PPDA onto the NR matrix.The effect of the amount of PPDA on the physical and mechanical properties and thermal and oxygen aging properties of the PPDA-g-NR,as well as the effect of the amount of PPDA on its migration resistance were investigated.Experiments have shown that PPDA-g-NR composites not only have excellent mechanical properties and thermal oxygen aging properties,but also have a certain long-term thermal oxygen aging effect due to the reduced migration rate of PPDA.However,when the amount of PPDA antioxidant increases to 3 phr,the migration resistance of PPDA in rubber becomes poor.Analysis shows that the content of isomerization groups in natural rubber is relatively small and can only react with part of PPDA.Therefore,this method still has certain disadvantages when used in large doses of PPDA.Finally,to endow NR composites with more excellent long-term protective properties,this experiment successfully synthesized a macromolecular antioxidant CGE-g-PPDA using cardanol glycidyl ether(CGE)and PPDA as raw materials,and applied it to NR composites.Experimental results have shown that compared with traditional antioxidant 4020,the migration rate of CGE-g-PPDA is smaller,making natural rubber have longer thermal oxygen stability.Moreover,CGE-g-PPDA has the effect of promoting vulcanization and improving the crosslinking density of rubber,which endows NR composites with higher strength and excellent wear resistance and compression fatigue resistance;In addition,CGE is derived from inexpensive renewable substances,and the reaction process with PPDA is simple and easy to operate.Therefore,CGE-g-PPDA is an easy-to-synthesize and low-cost macromolecular antioxidant with broad application prospects. |
