Study On Preparation And Properties Of PLA/MAM Blends

Poly(lactic acid)(PLA)is a thermoplastic polyester,which has the advantages of biodegradability,biocompatibility and high strength.However,the brittleness of PLA greatly limites its application in some fields.In order to solve this problem,PLA needs to be toughened and modified.In this paper,a triblock copolymer poly(methyl methacrylate)-b-poly(butylacrylate)-b-poly(methyl ethacrylate)(MAM)elastomer was used as toughening agent to improve the toughness of PLA.PLA/MAM blends were prepared by melt blending using two kinds of PLA with different structure as matrix,MAM with different molecular weight as toughening agent.The structure and properties of the blends were characterized and analyzed by differential scanning calorimetry(DSC),dynamic thermomechanical analyzer(DMA),rotational rheometer(RHE),scanning electron microscopy(SEM),and infrared spectrometer(FTIR).The experimental research results were as follows.(1)PLA2003D and PLA4032D were selected to study the effect of matrix properties on toughening.The results showed that MAM M3 had a toughening effect on both PLA2003D and PLA4032D,the toughness of PLA4032D/MAM M3 blends was better.When the content of MAM M3 was20wt%,the impact strength of PLA4032D/MAM M3 blends was 20k J/m~2,which was 7 times larger than that of pure PLA4032D,and larger than that of PLA2003D/MAM M3 blends about 2.4k J/m~2.According to the SEM results,the particle size of the dispersed phase of MAM M3 in PLA4032D/MAM M3 blends and PLA2003D/MAM M3 blends was similar.The DSC test results illustrated that the crystallinity of PLA4032D was higher than that of PLA2003D,and after blending with MAM M3,PLA4032D still contained crystalline phase,while PLA2003D became amorphous.Therefore,the crystalline properties of the matrix might be an important factor affecting the toughening effect.(2)The block copolymer MAM with the same composition and different molecular weight was blended with PLA4032D to analysis the effect of elastomer molecular weight on the properties of the PLA blends.The results demonstrated that with the increase of the molecular weight of MAM,the toughness of PLA/MAM blends increased.The impact strength of the blends of PLA4032D and MAM M3 with larger molecular weight was10 times that of the blends of PLA4032D and MAM M1 with smaller molecular weight.The elongation at break of the PLA4032D/MAM M3blends was about 4 times that of the PLA4032D/MAM M1 blends.The results of DSC and DMA showed that PLA4032D had some compatibility with three kinds of MAM with different molecular weight.And PLA4032D had better compatibility with MAM M3.SEM images illustrated that MAM M3 with a higher molecular weight had a smaller dispersed phase particle size in PLA/MAM blends,MAM M1 with a lower molecular weight had a larger dispersed phase particle size in PLA/MAM blends.The larger the molecular weight of the elastomer,the better its dispersion in the matrix and the better the mechanical properties of the PLA blends,indicating that good dispersion was the main factor affecting the performance of PLA/MAM blends.(3)Two kinds MAM block copolymers with different structures were selected to be blended with PLA4032D to investigate the effect of elastomer polarity on the properties of PLA/MAM blends.The results demonstrated that the elastomer MAM M2N with dimethylacrylamide functional group had better compatibility with PLA4032D,which was more conducive to improving the toughness of PLA4032D.The impact strength of the PLA4032D/MAM M2N blends was larger,with a maximum value of13.1k J/m2,which is about twice that of the PLA4032D/MAM M2 blends.And the elongation at break of the PLA4032D/MAM M2N blends was twice that of the PLA4032D/MAM M2 blends.FTIR found that dimethylacrylamide could react with PLA4032D.SEM results showed that the elastomer with dimethylacrylamide functional group had more uniform dispersion and smaller particle size in the PLA blends.Therefore,the presence of the dimethylacrylamide functional group was beneficial to improve the compatibility of MAM and PLA4032D and improve the toughness of the matrix.