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An Investigation on Preparation and Properties of PE/TiB2 PTC Thermal Composites

Author: WangJianFeng
Tutor: DuXiaoDong
School: Hefei University of Technology
Course: Materials Science
Keywords: PTC effect Conductive Composites Polyethylene Carbon black Titanium diboride Heat treatment
CLC: TB332
Type: Master's thesis
Year: 2010
Downloads: 89
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Abstract


Polymer-based PTC composites is the most popular smart polymer materials for research and development at home and abroad today. Such composites are widely used in the self-field of temperature control heating system, overcurrent protection devices, electromagnetic shielding materials and temperature-sensitive sensors. Based on the current domestic and international research on organic PTC conductive composite application status, try to take advantage of the quasi-metallic ceramic material with ultra-high conductive properties of titanium diboride prepared the PTC conductive composite material as the conductive filler. The paper, prepared by melt blending a polyethylene / titanium diboride conductive composites, and the use of X-ray diffraction (XRD), scanning electron microscopy, energy dispersive spectroscopy, gel content and flame retardant performance analytical instruments, electrical performance test instruments on phase of the composite material, the microstructure, electrical properties, etc. of the test and analysis, to study the composition of the composite system, the molding process conditions, heat treatment, the second conductive phase carbon black and other factors the room temperature resistivity of the composite material, the PTC strength and thermal cycle stability and performance. The study found that: the composition of the composite material to determine its performance. With increasing TiB2 content PE/TiB2 composite materials at room temperature resistivity decreases, the PTC intensity first increased and then decreased. When the the TiB2 content reached the percolation threshold (45 ~ 60wt%), the lowest room temperature resistivity of the composite material, the PTC highest intensity of 8.1. TiB2 particle size greater worse PE/TiB2 composite thermal cycling stability. Lubricants, crosslinking agents, flame retardants, and antioxidants added to improve the stability of the material PTC. Organizational performance analysis of the sample prepared under different conditions, the results showed that: each design factors affect the sample at room temperature resistivity order: cooling time gt; molding Temperature gt; molding pressure of gt; molding time. Cooling time and the molding temperature of the PTC intensity of the sample greater impact, the the PTC intensity variations are more than 3. Optimal molding conditions: molding pressure 10Mpa, the molding temperature of 160 ° C, the molding time 15min, molded after the cooling time of 30 min. · M of the sample obtained under this condition, the room temperature resistivity was 10-2Ω PTC intensity of 8.1. The study found that: Cart CB PE/TiB2-CB the mechanical properties of the composite material, and repetition stability than PE/TiB2 composite material has increased, the phase of the composite of the two conductive so that the respective percolation threshold significantly reduced. When the total content of the conductive filler is 30wt%, the increase of the CB content, the room temperature resistivity of the sample reduced; PTC strength first increased and then decreased, when the CB content of more than 6wt%, PTC intensity decreased significantly. Performance PE/TiB2-CB composite material after heat treatment The results show that the decrease in the room temperature resistivity of the sample after the heat treatment than before treatment, the room temperature resistivity of the sample heat treated at 120 ℃ minimum. The heat treatment temperature exceeds the HDPE m.p. PE/TiB2-CB a room temperature resistivity of the composite material increased to infer the thermal motion of the TiB2-CB and the thermal fluctuations induced by the tunnel effect is caused the class composites NTC phenomenon reasons.

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