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Study on PTC Effect in Polymer-Based Composites

Author: ShiDongHai
Tutor: DangZhiMin
School: Beijing University of Chemical Technology
Course: Materials Science
Keywords: Polymer matrix Filler Composites PTC effect Conductive network structure Seepage effect
CLC: TM215
Type: Master's thesis
Year: 2008
Downloads: 278
Quote: 1
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Abstract


The polymer-based conductive composite materials not only a combination of the conductive inorganic filler and a polymer material excellent in flexibility, and also has a single component does not have a new property, and because of its low cost, easy processing, can be designed and good characteristics of ceramic-based materials are irreplaceable, which quickly became hot PTC material developed. Present work high density polyethylene (HDPE) and polypropylene (PP), two non-fully crystalline polymer substrate, nano-carbon black (CB) and carbon fiber (CF), the inorganic particles do filler to study the conductivity of the composite material variation with temperature, the PTC performance. Include: (1) using a titanate coupling agent, a silane coupling agent and dilute nitric acid, etc., respectively, on the surface-modified nano-CB particles to PP as the base body, different modification methods resulting CB particles in the polymer dispersion behavior, as well as the modified method of conductive and dielectric behavior near the percolation threshold of the composite. Coupling agent can play a bridging role between the CB and the base body, and effectively improve the binding between the two, particularly a titanate coupling agent, due to the formation of the flexible monolayer structure, compared with the silane coupling agent is more effective to dielectric material and PTC performance, and increase the stability of the material. (2) to CB were filled single polymer HDPE and PP, and studied the influence of the thermal performance of the matrix component and the crystallization degree of the behavior of the conductivity of the composite material. Found that the the different matrix so that the material has a different percolation threshold in CB / HDPE composites than Paper No. CB / PP having a stronger PTC effect may be derived from HDPE having a higher degree of crystallinity. (3) incompatible polymer systems HDPE / PP, special conductive behavior of binary polymer matrix composites filled with CB. The results show that the percolation threshold is much lower than that of CB and a single polymer composite, and the lowest of the percolation threshold and the strongest PTC effect appears in the two-phase polymer volume ratio is very close to 1/1. Very low percolation threshold is attributable to the CB in one phase of the selective distribution in the matrix and when the threshold effect of the two-phase polymer volume caused by the same dual permeability significantly PTC effect may be precisely because such dual permeability threshold and structure characteristic of the binary polymer matrix phase is a continuous volume expansion caused. This has a special low percolation threshold two-component polymer matrix composites PTC material and high dielectric materials in the field has a potential value of engineering applications. (4) has an aspect ratio of CF filled CB / polymer composites, the second phase inorganic filler material conductive network and conductive properties. Appropriate CF is introduced because of its role as a bridge between the CB particles so that the same filler content, the conductivity of the composite material is improved, the PTC properties of the composite material of the filling of CF than the original composite material to be improved to some extent.

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CLC: > Industrial Technology > Electrotechnical > Electrical materials > Insulating materials,dielectric,and its products > Solid dielectric
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