Heat treatment method for improving strength of PTC (Positive Temperature Coefficient) thermistor core materials

Abstract

The invention relates to a heat treatment method for improving the strength of PTC (Positive Temperature Coefficient) thermistor core materials. The thermistor core materials comprise the following components in percentage by weight: 45-50 parts of high-density polyolefin and 50-55 parts of carbon black, wherein the polyolefin is the high-density polyolefin with high crystallinity of greater than or equal to 70 percent and the density of greater than or equal to 0.94g / cm<3>; and the carbon black is the stove method carbon black with good electrical conductivity, the grain size of 20-100nm and the DBP oil absorption value of greater than or equal to 70ml / 100g. The heat treatment method for composite materials comprises the step of annealing under the condition above a melting point of polymer at a temperature of 10-30 DEG C for 4-6 hours. Under the condition that the performances of the raw materials are unchanged, through optimization of an annealing temperature and the annealing manner, the PTC strength of the composite materials is greatly improved, and a foundation is laid for development of PTC thermistor components with high withstand voltage level.

Description

technical field [0001] The invention relates to a heat treatment method for improving the strength of a core material of a PTC thermistor, and relates to a heat treatment method for improving the strength of a core material for a PTC overcurrent and overtemperature protection element composed of crystalline high polymer and carbon black filler as main raw materials. Background technique [0002] Under normal conditions, the protection element connected in series with the load in the circuit is in a state of low temperature and low resistance. When an overcurrent or overheating condition occurs, the resistance of the protection element rises sharply to achieve the purpose of cutting off the power supply. On the one hand, this protection element requires that the resistance at room temperature is low enough to reduce the impact on the circuit to be protected. On the other hand, at high temperature, the resistance is required to be high enough to withstand higher voltage level...

AI Technical Summary

Problems solved by technology

Limited by the performance of raw materials such as crystalline polymers and carbon-based conductive fillers, in order to achieve low resistivity, a large amount of conductive fillers is added, which makes carbon black conductive particles easy to agglomerate, resulting in carbon black conductive particles at high temperatures. The formed conductive chain cannot be broken, and the high temperature resistance cannot meet the requirements

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