Paper Title
Effect of Water Absorption on Volume Resistivity for Heat Resistant Polymers

Abstract
A number of aliphatic biobased polymers have been developed thus far, however, their low glass transition temperature, Tg, and only a small percentage of their substitutes limited their use for various applications.We have developed so far biobased polyimides (PIs) from bioavailable aromatic diamines, which were photodimers of 4-aminocinnamic acid (4ACA) derived from genetically manipulated Escherichia coli [1-3]. The physical properties of PIs from bioavailable aromatic diamines which were photodimers of 4-aminocinnamic acid derived from genetically manipulated Escherichia coli has been studied. Particularly, the electric properties, resistivity, dielectric constant and dielectric breakdown behavior, of polyimide films under high electric fields has been investigated. In this study, the effect of water absorption on the electric resistivity for poly(4,4’-oxydiphenylene pyromellitimide) (Kapton) and biobased PI films with a thickness of 127 m was investigated. The change in weight increased with an elapse of time due to water absorption and saturated at approximately 8 h. The water absorption at the equilibrium was 2.2%. Similar to this, the electric resistivity decreased from 1017cm to 1015cm with the time and was constant at approximately 8 h. A plot of electric conductivity and the volume fraction of water revealed that a percolation of electric conduction occurs at c=0.024. At volume fractions at c>0.024, the electric conductivity obeyed a power low as ~(c)0.25, indicating the percolation conduction. According to the theory of reaction kinetics, the hopping distance of carriers was determined by the electric field dependence of electric current. The critical electric field decreased with the absorption time while the hopping distance of the carrier was almost independent of the absorption time. A possible mechanism of electric conductance in these films is discussed.