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 (/spl rho/) was larger than those of polyethylene (PE) and polypropylene (PP). The relative permittivity (/spl epsiv//sub r/') indicated intermediate values between that of polyester and those of PE and PP. The dielectric loss tangent (tan/spl delta/) 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 /spl rho/ rapidly decreased, with increasing electric field. Then, electric breakdown occurred when E/spl ap/2.8 MV/cm. From the results of thermal analyses, it was found that the glass transition temperature (T/sub g/) of PLA was about 60/spl deg/C and the melting point (T/sub m/) was about 166/spl deg/C.