Effect of polycaprolactone-co-polylactide copolyesters' arms in enhancing optical transparent PLA toughness

摘要

Considering enhanced toughness of polylactic acid (PLA) including retaining its optical transparency, star-shaped copolyester was investigated. The star-shaped polycaprolactone-co-polylactide (stPCL-co-PLA) with a different number of arms was synthesized using star-shaped initiators. The thermal properties and crystallinity of stPCL-co-PLA were independent to the number of arms of the polymer. However, number of arms of stPCL-co-PLA affected to crystallinity of PLA in the blend of PLA/stPCL-co-PLA. The glass transition temperature of the blend was decreased with the addition of stPCL-co-PLA plasticizers. The stPCL-co-PLA with 2-arms and 4-arms provided increasing of crystallinity of PLA in the blends but 3-arms resulted in decreasing of crystallinity due to their steric hindrance. Moreover, the toughness of PLA was enhanced with mixed stPCL-co-PLA up to 3 phr; for example, 4-arms of stPCL-co-PLA provided increasing of toughness as 61% compared to neat PLA. The results revealed that an improvement in toughness might be obtained from shear-yielding deformation which was provided from rubbertoughened amorphous plastics accompanied with extensive orientation of the semicrystalline portion. Moreover, it was found that at 3 phr of stPCL-co-PLA, the compound retained its optical transparency comparable to neat PLA.