Study on the Over-Voltage Resistance of Positive Temperature Coefficient (PTC) Polymeric Composites

• Main Authors: Ching-Shan Tsai, 蔡清山
• Other Authors: Chi_Yuan Huang
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/47118044138643539004

博士 === 大同大學 === 材料工程學系(所) === 97 === The over-voltage resistance of positive temperature coefficient (PTC) conductive composite that polyethylene (PE) was blended with the conductive carbon black (CB), and inorganic flame retardants, magnesium hydroxide (Mg(OH)2) and aluminum hydroxide (Al(OH)3), was prepared. Effects of the CB content (percolation effect), plasma treatment time, power of plasma, initiator (dicumyl peroxide, DCP), peroxide-initiated grafting maleic anhydride (LDPE-g-MA), and dosage of 60Co γ-ray radiation on the goals of enhansment of PTC intensity and the elimination of negative temperature coefficient (NTC) effect were studied. In addition, the cross-linking of composite was analysed particularly by analyses of scanning electron microscopy (SEM), gel content, differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). The characteristic of over-voltage resistance of composite was measured by test standard of YD/T 741-95. The structural stability of composite was analysed by aging and reproducibility. This study was researched, and conclusions were listed as follows. In the high-density polyethylene (HDPE)/CB/magnesium hydroxide (Mg(OH)2) composite, the results showed percolation theory was explained the abruptly decreased resistance in the CB content of 33.7 wt%. The room-temperature volume resistivity and PTC effect were improved with plasma treatment. The 1,1-diphenyl-2-picryhydrazyl (DPPH) method was adopted to estimate the free radicals content of PHDPE, which the maximum free radicals content was 1.14×10-6 mol g-1 by plasma treatment at 20 W for 1 min. The composite of PHDPE with DCP, and 60Co γ-ray radiation (20 Mards) eliminated the NTC effect of composites fully, and the PTC intensity of composite markedly increased 2 orders of magnitude. In this work, the irradiating dosage was decreased to 20 Mrads, and the response temperatures (120.9 °C to 107.8 °C) of composite were controlled by irradiating dosages. The composition of PH(201)DC33.7M28-20 successfully passed the over-voltage resistance test, and possessed good structural sability. To increase the processing characteristic of composite, aluminum hydroxide (Al(OH)3, particle size of 1.4 μm) was used to replace Mg(OH)2 (particle size of 10 μm) in the same composition. The results showed that the PTC intensity of composite markedly increased 3.26 orders of magnitude, and the NTC effect of composite eliminated fully in the composite of PHDPE with DCP, and 60Co γ-ray radiation (20 Mards). In this work, irradiating dosages was reduced to 20 Mrads effectively, and the response temperature (126.3 °C to 112.1 °C) of composite was controlled by irradiating dosages. The composition of PH(201)DC33.7A28-20 also successfully passed the over-voltage resistance test, and possessed good structural stability. In the low-density polyethylene (LDPE)/CB/Al(OH)3 composite was prepared. Effect of cross-linking of peroxide-initiated grafting maleic anhydride (LDPE-g-MA) in composite was studied. The PTC intensity of composite markedly increased 1.56 orders of magnitude, and the NTC effect of composite eliminated fully in the composite with LDPE-g-MA of 4.0 wt%. With increasing of LDPE-g-MA content from 2.0 wt% to 10.0 wt%, the gel content of composites increased up to 60.63 %, the degree of crystallinity of composites decreased up to 31.25 %, and the tanδ of composites decreased. The composition of LD0.5M4C33.7A28 also successfully passed the over-voltage resistance test, and possessed good structural stability. In the linear low-density polyethylene (LLDPE)/CB/Al(OH)3 composite. LLDPE was chemically cross-linking with various amounts of initiator (DCP). The PTC intensity of composite markedly increased 1.89 orders of magnitude, and the NTC effect of composite eliminated fully in the composite with DCP of 0.10 wt%. With increasing of DCP content from 0.03 wt% to 0.50 wt%, the gel content of composites increased up to 53.87 %, the degree of crystallinity of composites decreased up to 29.24 %, and the tanδ of composites decreased. The composition of LLD0.10C33.7A28 also successfully passed the over-voltage resistance test, and possessed good structural stability.