Radiation modification of bioplastic materials

Tago, Takanori; Nagasawa, Naotsugu; Kudo, Hisaaki*; Taguchi, Mitsumasa; Katsumura, Yosuke*

Poly (L-lactic acid)(PLA) is a hard and transparent bioplastic and now widespread with a potential to replace the conventional petroleum-derived plastics. The PLA crosslinked to improve the thermal property by irradiating with triallyl isocyanurate (TAIC). The impact resistance, however, is nearly un-improved. To improve the above-mentioned two properties of PLA, we investigated a new combination method of blending of PLA with polyamide11 (PA11) having high impact resistance, which is produced from castor oil, and then crosslinking with TAIC by radiation. The crosslinking structures were formed in irradiated PLA/PA11 blends with TAIC. The gel content of PLA/PA11 blends increased with increasing the mixing ratio of PA11 and absorbed dose. At the dose of 100 kGy and more, the network was formed about 80% in the PLA / PA11 blends. The thermal properties of the blends were evaluated from the deformation at the melting-temperature () by the thermo-mechanical analysis. The blends with high gel contents (80%) demonstrated very little deformation above the of PA11 around 185C. The improvement of the impact property was indicated by the Charpy impact testing. The blends (50/50wt%) irradiated with 100 kGy showed the higher impact resistance about 2.5 times of original PLA. Therefore, the applications of bioplastic will be expanded by the combination method of blending and radiation-induced crosslinking.