Synthesis Of Castor Oil-based Bifunctional Lubricant Additive

Traditional petroleum-based lubricant additives are non-renewable and have adverse effects on the environment,so it is urgent to develop new lubricant additives from renewable resources.As a non-edible energy plant,castor oil has the advantages of renewability,lubricity and low toxicity,so it has great potential to replace traditional petroleum-based energy.Castor oil-methyl methacrylate copolymer(PCOM)、castor oil-styrene copolymer(PCOS)and castor oil-maleic anhydride-styrene terpolymer(PCMS)were synthesized from castor oil(CO)、methylmethacrylate(MMA)、styrene(ST)and maleic anhydride(MA)by using azodiisobutyronitrile(AIBN)as initiator and toluene as solvent under anhydrous and anaerobic conditions.The structure of copolymer was characterized by FT-IR and~1H NMR,and the thermal stability of the copolymer was investigated by TGA,the relative molecular mass and its distribution of the copolymer were determined by gel permeation chromatography(GPC).Performance of the synthesized pour point depressant and viscosity index improver were also evaluated.The wax crystal morphology of oil was observed by optical microscope.The optimum polymerization conditions were obtained by single factor experiment.For the copolymerization of castor oil and methyl methacrylate,the results showed that the copolymer had a yield of 59.20%,average relative molecular weight of 2.722×10~5and exhibited narrow relative molecular weight distribution(PDI=1.51)under the conditions of m(CO):m(MMA)=1:1,AIBN ratio of 0.25%(based on the total mass of monomers,the same below),at 80℃for 8h.For the copolymerization of castor oil and styrene,the results showed that the copolymer had a yield of 41.26%,average relative molecular weight of 3.115×10~4and the relative molecular weight distribution was 2.88 under the conditions of m(CO):m(ST)=1:1,AIBN ratio of 0.4%at90℃for 6h.For the copolymerization of castor oil and styrene、maleic anhydride,the results showed that the copolymer had a yield of 68.39%,average relative molecular weight of0.348×10~5and the relative molecular weight distribution was 4.77,under the conditions of m(CO):m(MA):m(ST)=1:0.20:1.2,AIBN ratio of 0.5%at 90℃for 4h.The pour point of lubricating oil could be decreased 4℃-17℃with adding the copolymers(PCOM15,PCOS8,PCMS7)synthesized under the optimal conditions.Compared with the commercial pour point depressant,the effect of the synthetic pour point depressant was better.In addition,the viscosity index of lubricating oil could be increased from 95 to 105-146.Therefore,castor oil-based copolymers could be used as a bifunctional lubricant additive with decreasing the pour point and improving the viscosity index.