Studies Of Polyacrylicester Copolymers With Core-Shell Structure In Polylactide (PLA) Toughening

PLA is one kind of very important biodegradable material. However, its application in daily life is limited because of its low notched impact strength. In order to improve the notched impact strength of PLA and broaden its use, methyl methacrylate-butyl acrylate copolymers with different structure was synthesized by seed emusion polymerization and blended with PLA.1. Methyl methacrylate-butyl acrylate (ACR), one kind of copolymer with core-shell structure, was prepared by seed emulsion polymerization. The weight ratio of core/shell ranges from 85.5/14.5 to 71.9/28.1. Then PLA/ACR blends were prepared with a constant ratio of 80/20. The effect of core-shell ratio of ACR on toughening PLA was investigated. Torque analysis revealed that the torque values of PLA/ACR blends increased with increasing PMMA content. The impact strength of PLA/ACR blends reached the highest value of 77.1 kJ/m2 when the core-shell ratio of ACR was 79.2/20.8. TEM photographs revealed that PMMA component was favorable for ACR dispersing uniformly in PLA matrix. SEM suggested that plastic deformation and cavitations were the major toughening mechanism for PLA/ACR blends. The crystallization degree of PLA/ACR blends was higher than that of pure PLA from DSC analysis. It was found that PMMA was partially miscible with PLA from DMA analysis.2. Glycidyl methacrylate functionalized methyl methacrylate-butyl acrylate (GACR) core-shell structure copolymers were synthesized to toughen polylactide (PLA). With an increase in GACR content, the PLA/GACR blends showed decreased tensile strength and modulus; however, the elongation at break and the impact strength were significantly increased compared with that of PLA. The brittle fracture of neat PLA was gradually transformed into ductile fracture by the addiction of GACR. From dynamic mechanical analysis, the rigidity of the PLA/GACR blends was decreased with the increase of GACR content. The addition of GACR decreased the degree of crystallinity of PLA. The GACR was found to aggregate to form clusters with size increasing with increasing GACR content by transmission electron microscope analysis. The clusters dispersed in PLA matrix uniformly. It was found that PLA demonstrated large area, plastic deformation (shear yielding) and cavities in the blend upon being subjected the tensile and impact tests, which was an important energy-dissipation process and leaded to a toughened and transparent blend.