Study On The Effect Of Methionine Rare Earth Salts On The Vulcanization Properties Of Natural Rubber

Three rare-earth salts-lanthanum methionine,cerium methionine,and anthanum cerium methionine were synthesized from methionine,lanthanum chloride,and cerium chloride.Through characterization methods such as infrared spectroscopic analysis,thermal analysis,elemental analysis,their molecular formulas were determined to be La Cl₃(C₅H₁₀NO₂S)₃·2H₂O,Ce Cl₃(C₅H₁₀NO₂S)₃·2H₂O,La_0.35Ce_0.65Cl₃(C₅H₁₀NO₂S)₃·2H₂O,respectively.Three kinds of Methionine rare earth salt were added to the rubber at 0,0.25,0.5,0.75,1.0 phr as a vulcanization accelerator,and vulcanized at 180℃using a rotorless vulcanizer for 10 minutes.The comparison of the five sets of vulcanization curves and vulcanization data shows that the addition of Methionine rare earth salt can prolong the scorch time T₁₀ of the vulcanized rubber,shorten the positive vulcanization time T₉₀,and greatly increase the vulcanization rate in the hot vulcanization stage;Methionine rare earth salt can promote the crosslinking of vulcanized rubber and increase the crosslinking density;Methionine rare earth salt can reduce the activation energy in the vulcanization reaction stage and promote the vulcanization reaction.When lanthanum cerium methionine is used as a vulcanization accelerator to replace the traditional accelerator M,the mass ratio of each processing agent is zinc oxide:stearic acid:lanthanum cerium methionine:accelerator DM:sulfur=5:4:0.3:1.6:2.3.At this movement,the maximum modulus M_H slightly increases;the scorch time T₁₀ is reduced,and the positive process time T₉₀ is reduced.When 1 phr lanthanum cerium methionine is added to replace 10%by weight of other processing agents,the maximum modulus M_H increases from 0.455 N·m of the blank rubber to 0.478 N·m,and the scorch time T₁₀ increases from1.22min to 1.45min.The positive process time T₉₀ is reduced from 2.53min to 2.47min.The addition ratio of each processing agents is zinc oxide:stearic acid:accelerator M:accelerator DM:sulfur:lanthanum cerium methionine=4.5:3.6:0.27:1.44:2.07:1.Methionine can replace part of the active agent and vulcanizing agent,and can reduce its usage while maintaining the original performance.Methionine rare earth salt can not only act as an accelerator and antioxidant,but also act as an active agent.Then,a thermal analyzer was used to study the thermo-oxidative degradation process of the blank vulcanizate and the vulcanizates respectively added with three kinds of Methionine rare earth salt at different heating rates.The Kissinger method and the FWO method were used to calculate the curve,and it is found that the addition of Methionine rare earth salt can improve the thermal-oxidation resistance of vulcanized rubber.Among them,the effect of lanthanum cerium methionine is the best.The activation energy of thermo-oxidative degradation of blank rubber E=76.03 KJ/mol,and the activation energy of thermo-oxidative degradation of rubber added with lanthanum cerium methionine E=89.79 KJ/mol.Compared with the blank rubber,the rubber added with Methionine rare earth salt has a larger thermo-oxidative degradation activation energy and a higher thermo-oxidative degradation characteristic temperature,proving that Methionine rare earth salt has good thermal-oxidation protection performance.Among them,lanthanum cerium methionine has the most outstanding protective ability.