Study On Lipase-catalyzed Synthesis Of Polyester As Plasticizer

Nitrile rubber(NBR)is an important synthetic rubber widely used in national economy and people's livelihood.Since the specificity of molecular composition makes it difficult to process and utilize,the study of new plasticizers to optimize the processing and molding technology has become a key issue to be solved urgently.The purpose of this research is to synthesize non-toxic polyester plasticizers in a green and efficient way.Multi-element polyesters were bio-catalyzed to replace the traditional dioctyl phthalate(DOP)with side effects of toxic.In this thesis,three or more dibasic acids and glycols are used as substrates,lipase is used as a catalyst,and six linear polyesters are synthesized through a two-step method of the autocatalytic prepolymerization of dibasic acids and the enzyme-catalyzed polycondensation:poly(amber acid-sebacic acid-pentanediol-hexanediol-octanediol ester)(PASPHO),poly(amber acid-propylene glycolbutanediol ester)(PAPB),poly(hexanedioic acid-propylene glycolbutanediol ester)(PHPB),poly(sebacate-propylene glycol-butanediol ester)(PSPB),poly(itaconic acid-amber acid-sebacic acid-propylene glycol-butanediol ester)(PIASPB)and poly(itaconic acid-adipatepropylene glycol ester)(PIAP).The polyester synthesis process was optimized,and the number average molecular weight and molecular structure of polyesters were analyzed and characterized.The results show that the number average molecular weight of these six polyesters is between 1000 and 2500,the dispersion coefficient is between 1.1 and 1.5,and conversion of the substrate acid is over 98%.The six synthetic polyester plasticizers are used in the processing and molding of NBR.The effect of different plasticizers on the processability and mechanical properties of rubber is explored,and the plasticizing effect is investigated by observing the morphology of rubber test pieces.The results show that:PASPHO polyester has the best plasticizing effect in NBR.The molecular chain of PASPHO is more flexible,hard to crystallize,and the regularity of the molecular chain decreases.When the amount of added PASPHO is 15%,the Mooney viscosity of rubber is less than DOP by 8.4%,and the crosslinking density is increased by 9.3%.The resulting rubber product is hard to deform,and the mechanical properties of the rubber compound and the cold resistance are similar to DOP.All six polyester plasticizers show good solvents resistances(water,ethanol,petroleum ether).The enzyme degradation test and cytotoxicity test found cytotoxicity test found that the degradation effects of the six polyester plasticizers are better than DOP,with good bio-compatibility.