| Summary: | 碩士 === 國立臺北科技大學 === 化學工程系碩士班 === 92 === Electrical stability and high conductivity are the basic requirements for the polymer composites with positive temperature coefficient (PTC) used in passive components. The electrical stability of materials can be determined from its resistance. Three methods, applying voltage intermittently, applying voltage continuously and voltage resistance test, were used to justify the electrical stability of materials. In this experiment, semi-crystalline polymers, HDPE and PVDF, were used as bulk materials; carbon black was added as conductive particle; and two kinds of nanomaterials, EVA covered with nanofibril and organically modified nanoclay, were used as additives. The polymer composites were prepared by melt-blending and were cross-linked by 60Co irradiation.
For the composites that EVA covered with nanofibril was added, the voltage endurance was decreased, the positive temperature coefficient was decreased, furthermore, the NTC (negative temperature coefficient) effect appearing at high temperature became more obvious.
For the composites that organically modified nanoclay was added, the positive temperature coefficient was increased, the NTC effect occurring at high temperature was less obvious. The result of voltage endurance test showed that HDPE/CB/nanoclay composite had excellent electrical stability. The resistivity ratio was effectively controlled at 1.00. Moreover, the resistivity ratio was lower than 1.0 after being irradiated with 60Co. Besides, the addition of nanoclay effectively inhibited the burning of PVDF/CB composite when voltage was applied.
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