Study on the electrical properties of a biodegradable plastic

A polylactic acid (PLA) that is a biodegradable plastic, was subjected to measurements of conduction current and dielectric properties as well as thermal analysis. For the electrical properties of PLA, its volume resistivity (ρ) was larger than those of polyethylene (PE) and polypropylene (PP). The relative permittivity (ε_r´) indicated intermediate values between that of polyester and those of PE and PP. The dielectric loss tangent (tanδ) was larger than those of PE and PP, but smaller than that of Polyester. For the electric field dependence of the conduction current of PLA in the high electric field, the current density (J) rapidly increased and ρ rapidly decreased, with increasing electric field. Then, electric breakdown occurred when E≈2.8 MV/cm. From the results of thermal analyses, it was found that the glass transition temperature (T_g) of PLA was about 60°C and the melting point (T_m) was about 166°C.