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Abstract

The Cole-Cole method has been applied for an analysis of the dielectric relaxation data of the natural resin shellac, obtained by Bhattacharya in the temperature range 20–110°C. Three relaxation processes were observed for temperatures 20–60°C. At 70°C, two relaxation processes were noticed, whereas only one was observed by Bhattacharya between 20 and 110°C. The relaxations at 80°C and above represented typical Cole-Cole type. The variation of the static dielectric constant with temperature revealed three distinct slopes, which indicated different phases of the resin during its thermal transition from solid to liquid state. Two “transformation points,” around 40 and 70°C were noted, i.e., the glass transition temperature and melting point of the resin, respectively. Significant changes in static dielectric constant, dielectric increment, relaxation time, and Cole-Cole distribution parameter were observed during a rise of temperature from 80 to 110°C. The results of the present study indicate that some rearrangement in the teriary disposition of the resin molecules takes place during the rise of temperature from 20 to 110°C.