Preparation And Properties Of Toughened And Reinforced Polylactic Acid By Melt Polymerization

In this paper,PLA-GMA polymer with excellent toughness was prepared by melt extrusion with poly(lactic acid)(PLA)as matrix,tert butyl peroxypropionate(TBPB)as free radical initiator and glycidyl methacrylate(GMA)as reactive monomer.Bagasse cellulose(BC)was prepared by alkali treatment and hydrogen peroxide bleaching from sugarcane bagasse of Guangxi characteristic agricultural waste,BC-GMA was obtained by grafting BC with GMA through ring opening reaction of epoxy group;Finally,BC/PLA-GMA/PLA composite was prepared by physical blending method.BC-GMA/PLA composite was prepared by chemical grafting method,The toughening and strengthening of PLA were combined with physical and chemical methods,so as to obtain industrial application in 3D printing field and packaging materials.The main conclusions are as follows:(1)The effects of reaction temperature,reaction time,GMA content and TBPB content on the grafting rate of PLA-GMA were investigated by single factor experiments method.The results showed that the optimum toughening conditions of PLA were as follows:the reaction temperature was 185℃,the addition of GMA was 20%,the addition of TBPB was 3%,and the grafting yeild of PLA-GMA was 10.33%.GPC results show that,the number-average molecular(M_n)is 125286 g/mol,weight-average molecular(M_w)is 196520 g/mol and polymer dispersity index(PDI)is 1.57,the tensile strength is 15.94MPa,the elastic modulus is 969.01 MPa,the elongation at break is 278.17%,which is about 44 times of that of pure PLA.(2)Bagasse cellulose(BC)obtained by alkali treatment,hydrogen peroxide bleaching and sieving pretreatment increased the cellulose content from 45.46%to 82.16%.The longer the grafting reaction time was,the smaller the particle size of BC was,the higher the grafting yield of BC-GMA was.The maximum thermal decomposition temperature was increased to 359.31℃.(3)PLA/PLA-GMA/BC composites with high cellulose loading were prepared by physical blending,the effects of PLA-GMA content,BC particle size and BCB content on the properties of the composites were investigated.The results showed that the compatibilization effect was the best when the content of PLA-GMA was 25%,BCB/PLA-GMA/PLA composites obtained good mechanical properties even if the content of BCB is 40%;The addition of PLA-GMA is not conducive to the formation of crystalline regions of PLA,however,the addition of BC can promote the crystallization of PLA.BC-GMA/PLA composites with high cellulose loading were prepared by grafting modification method.The effects of different types of BC-GMA(BCA-GMA,BCB-GMA and BCC-GMA)and BCC-GMA content on properties were investigated.The results showed that when the content of BCC-GMA was 30%,the elastic modulus,tensile strength and elongation at break were 2484.79 MPa,46.92 MPa and 3.56%,respectively.BC-GMA formed macromolecular production chain with PLA under the action of initiator,played a role of lubricant in the system and promoted the full crystallization of PLA,relative crystallinity of PLA in BC-GMA/PLA composite increased;the thermal stability of the two composites was improved a little.