Glycidyl methacrylate functionalized acrylonitrile-butadiene-styrene (ABS-g-GMA) particles were prepared and used to toughen polylactide (PLA). The characteristic absorption at 1728 cm À1 of the Fourier transform infrared spectra indicated that glycidyl methacrylate (GMA) was grafted onto the polybutadiene phase of acrylonitrile-butadiene-styrene (ABS). Chemical reactions analysis indicated that compatibilization and crosslinking reactions took place simultaneously between the epoxy groups of ABS-g-GMA and the end carboxyl or hydroxyl groups of PLA and that the increase of GMA content improved the reaction degree. Scanning electron microscopy results showed that 1 wt % GMA was sufficient to satisfy the compatibilization and that ABS-g-GMA particles with 1 wt % GMA dispersed in PLA uniformly. A further increase of GMA content induced the agglomeration of ABS-g-GMA particles because of crosslinking reactions. Dynamic mechanical analysis testing showed that the miscibility between PLA and ABS improved with the introduction of GMA onto ABS particles because of compatibilization reactions. The storage modulus decreased for the PLA blends with increasing GMA content. The decrease in the storage modulus was due to the chemical reactions in the PLA/ ABS-g-GMA blends, which improved the viscosity and decreased the crystallization of PLA. A notched impact strength of 540 J/m was achieved for the PLA/ABS-g-GMA blend with 1 wt % GMA, which was 27 times than the impact strength of pure PLA, and a further increase in the GMA content in the ABS-g-GMA particles was not beneficial to the toughness improvement.
Glycidyl methacrylate-functionalized methyl methacrylate-butadiene (MB-g-GMA) copolymers were prepared via an emulsion polymerization process. These functionalized copolymers were blended with polylactide (PLA). Dynamic mechanical analysis and differential scanning calorimetry results showed that the addition of MB-g-GMA did not result in a marked change in the glass transition temperature of PLA. With an increase of MB-g-GMA content, the tensile strength of the blends decreased; however, the elongation at break and impact strength increased significantly. From scanning electron micrographs, there was large plastic deformation (shear yielding) in blends subjected to impact tests, which was an important energy-dissipation process and led to a toughened polymer. Rheological investigation demonstrated that there was a significant dependence of viscosity on composition. When the MB-g-GMA content increased, the viscosity began to increase.
Acrylic impact modifier (ACR), one kind of methyl methacrylate–butyl acrylate copolymer with a 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 shell content of ACR. The impact strength of PLA/ACR blends reached the highest value of 77.1 kJ m−2 when the core–shell ratio of ACR was 79.2/20.8. Transmission electron microscope (TEM) photographs revealed that ACR was dispersed uniformly in the PLA matrix. Scanning electron microscopy (SEM) suggested that the plastic deformation and cavitations were the major toughening mechanism for the PLA/ACR blends. The shell partition PMMA of ACR was partially miscible with PLA from dynamic mechanical analysis.
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