Preparation And Properties Of High Toughness And High Heat Resistance Polylactic Acid Composites

Poly(lactic acid)(PLA),a promising bio-based polymer,has received a lot of attention in recent years due to its renewability,biocompatibility,biodegradability and excellent processing properties.However,the inherent disadvantages of PLA,such as brittleness,low melt strength,and slow crystallization rate,still limit the wide application of PLA.Therefore,the study of modified PLA is particularly important.In this paper,a core-shell modifier with cross-linked acrylate and silicone copolymer as the core and poly(methyl methacrylate)(PMMA)as the shell(PASi-g-PMMA)was used to toughen brittle poly(lactic acid)(PLA).In addition,a copolymer of methyl methacrylate(MMA)and glycidyl methacrylate(GMA)(MG)was used to further improve the modification efficiency of PASi-g-PMMA.MG copolymer plays the dual role of compatibilizer and chain extender.The effects of MG content on the thermodynamic properties,rheological properties,optical transparency,mechanical properties and phase morphology of the PLA/PASi-g-PMMA blended system were investigated.On the other hand,polybutylene adipate-butylene terephthalate(PBAT)used as a toughening agent and MG copolymer used as a compatibilizer.The effect of MG content on the various properties of the PLA/PBAT blends was investigated in detail.The results are as follows:(1)The effects of MG and PASi-g-PMMA incorporation of PLA on the mechanical properties,crystallization,rheological properties,optical properties and microscopic morphology of the PLA blends were investigated.The MG copolymer plays the dual role of compatibilizer and chain extender,which not only improves the interfacial adhesion between PLA and PASi-g-PMMA particles,but also increases the molecular weight and chain entanglement of PLA.Compared to PASi-g-PMMA toughened PLA blends,PLA/PASi-g-PMMA/MG blends have much higher heat resistance,melt strength,transparency,toughness,and stiffness balance.When the PASi-g-PMMA content was 20wt%,20 wt%MG increased the glass transition temperature(Tg),composite viscosity(?*),transparency,impact and tensile strength of PLA/PASi-g-PMMA blends from 60.1?,1.9×10~3Pa·s,76.1%,748J/m and 37 MPa to 71.5?,0.5×10~4Pa·s,78.4%,860J/m and 45MPa.The SEM results demonstrate that shear yielding of PLA phase,cavitation of PASi-g PMMA particles or interfacial debonding between PLA and PASi-g-PMMA particle interfaces are the main toughening mechanisms.(2)The effects of MG and PBAT incorporation on the mechanical properties,rheological properties,thermal properties,dynamic mechanical properties and surface morphology of the PLA blends were investigated.DSC and DMA tests showed that the addition of MG improved the compatibility between PLA and PBAT phases and enhanced the heat resistance of the blends.The rheological properties showed that the addition of MG improved the melt strength of PLA blends.When the PBAT content was 50 wt%,5wt%MG increased the impact strength of the blends to 256.7 J/M.The SEM results demonstrate that shear yielding of PLA phase,cavitation of PBAT particles or interfacial debonding between PLA and PBAT particle interfaces are the main toughening mechanisms.