pla electric prop2

1020 IEEE TRANSACTIONS ON INDUSTRY APPLICA TIONS, VOL. 40, NO. 4, JUL Y/AUGUST 2004 Electrical Properties of Biodegradable Polylactic Acid Film Takashi Nakagawa, Takuo Nakiri, Ryuichi Hosoya, and Yoshiro Tajitsu , Member , IEEE Abstract—We measured the basic electrical insulation charac- teristic of biodegradable polylactic acid (PLA), and the following results were obtained. The volume resistivity, dielectric constant, and dielectric loss tangent measured at room temperature were al- most the same as those of crosslinked polyethylene (XLPE) cur- rently used as insulating material for cables and electric wires. The mean imp uls e br eak down str eng th of PLA was abo ut 1.3 times tha t of XLPE. Also, space charge accumulation in PLA and XLPE was measured. The amount of space charge accumulation in PLA was one-half that in XLPE whe n dc vol tage wasappli ed for a short time. Index T erms—Biode grada ble polymer, elec tric al insulation characteristics, film, polylactic acid (PLA). I. INTRODUCTION E VERY YEAR, the amount of industrial waste increases, and as a result, environmental pollution is now becoming seri ous. Certain types of poly mers can be decompose d into thei r comp onent elements by the action of micr oorganis ms, even in a local environment [1], [2]. Such polymers are called biodegradable polymers [ 1], [ 2]. As materials that are expected to provide a solution to environmental pollution, biodegradable polymers hav e attracted much attention [1], [2]. Poly lact ic acid (PLA) is an aliphatic polyester with the most advanced biode grad abil ity rese arch [1], [2]. For this re as on, PLA is attracting much attention in industrial fields. PLA is manu- factured in three steps. First, starch is produced from corn, for example. Second, microorganisms are used to decompose starch into lactic acid. Third, PLA is produced from lactic acid throu gh chemical synthes is. The stru ctur al formula of PLA is shown in Fig. 1 [1], [2]. PLA is a chiral polymer in which molecules containing asymmetric carbon atoms have a helical orientation [ 1], [2]. Two optical isomers exist in PLA: PLLA and PDLA [1], [2]. The crystal structure of PLLA is based on Paper MSDAD-A-04-04, presented at the 2003 Joint Meeting of the Electro- statics Society of America and the IEEE Industry Applications Society Electro- stat ic Pro ces sesCommit tee , Little Roc k,AR,June24-27, andappr oved forpub- lication in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS by the Elec- trostatic Processes Committee of the IEEE Industry Applications Society. Man- uscript submitted for review June 27, 2003 and released for publication March 29, 2004. This work was supported in part by the Ministry of Education, Cul- ture, Sports, Science and Technology, Japan, under Grant-in-Aid for Scientific Research 15550100. T. Nakagawa is with Kansai Electric Power Company, Inc., Amagasaki 661- 0974, Japan (e-mail: [email protected]). T.Nakiri is with Kansai Te ch Compa ny , Inc.,Osaka 552-0013, Japan(e-mail: [email protected]). R. Hosoya was with the Department of Polymer Science and Engineering, Y amagata University, Y amagata 992-8510, Japan. He is now with The Ministry of Justice, Japan. Y. Tajitsu is with the Graduate School of Engineering, Kansai University, Osaka 564-8680, Japan (e-mail: [email protected]). Digital Object Identifier 10.1109/TIA.2004.830751 Fig. 1. Struc tural for mula of PLA. T wo optic al isomers ex ist in PLA: one is PLLA and the other is PDLA. an orthorhombic-base-centered unit cell that contains two 10/3 hel ica l chai ns arr ang ed along the axis, as shown in Fig. 1 [3]. The p oi nt group of t he PLLA cr ysta l i s [ 3]. We have investigated the optical properties of PLLA due to its chiral structure for the application of this material in optical devices [4]–[6]. In this study, in order to apply PLLA as an insulating 0093-9994/04$20.00 © 2004 IEEE

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