Composite material for thermistor and its preparation method and application

Abstract

The invention provides a composite material for a thermistor. The composite material is prepared from the following components in parts by weight in a mixing and irradiation crosslinking manner: 70-85 parts of high density polyethylene, 20-30 parts of an ethylene-vinyl acetate copolymer, 20-35 parts of conductive packing, 4-6 parts of a coupling agent, 2-3 parts of a crosslinking agent, 1-2 parts of an antioxidant and 2-3 parts of a lubricant, wherein the content of high density polyethylene is preferably 75-80 parts; the content of the thylene-vinyl acetate copolymer EVA is preferably 20-25 parts; the content of the conductive packing is preferably 20-30 parts; the conductive packing is a mixture of titanium diboride, carbon fiber and multiwalled carbon nanotubes (MWNT); the weight ratio of titanium diboride to carbon fiber to MWNT is (4-5):(0.5-1):(0.5-1); the length of the carbon fiber is 30-300mu m, and preferably 100-200mu m; the diameter of the MWNT is 10-30nm; the length of the MWNT is 5-15mu m. The composite material is good in comprehensive properties such as the conductivity, the PTC strength and the stability at the room temperature, and can be well applied to PTC thermistors.

Description

technical field [0001] The invention relates to a composite material for a thermistor, in particular to a composite material for a thermistor for preparing a thermistor, a preparation method thereof and a thermistor comprising the same. Background technique [0002] Polymer composite materials with a positive temperature coefficient (PTC) are widely used in computers and their peripheral equipment, mobile phones, battery packs, telecommunication and network equipment, transformers, industrial control equipment, automobiles and other electronic products to play a role in overcurrent Or the role of over-temperature protection. PTC polymer composite material is a heat-sensitive material whose resistance value increases with the increase of temperature, that is, the resistance or resistivity of the material remains basically unchanged or only slightly changes within a certain temperature range, while When the temperature reaches a specific transition point temperature of the ma...

AI Technical Summary

Problems solved by technology

The PTC polymer composite material filled with carbon black has the characteristics of adjustable electrical conductivity in a wide range, easy molding, and low cost; however, the existing problems are high room temperature resistivity and poor stability of the PTC effect, resulting in PTC strength and output. The power attenuation is too fast, the leakage current is large after protection, etc.

However, in the PTC polymer composite material with metal particles as conductive fillers, since the metal particles are always rigid particles during the phase transition process of PTC temperature rise, no phase transition occurs, resulting in a more serious negative temperature resistance effect (NTC) during the continuous temperature rise process. ;The emergence of NTC phenomenon not only causes irreversible changes in the electrical properties of PTC materials, but also causes failure due to high temperature of the materials during the use of the materials, and even ignites and burns

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