Study On Positive Temperature Coefficient Effect And Application Of Double Polymer-based Composites With Low Curie Temperature

Polymer-based Positive Temperature Coefficient(PTC)material as a new type of thermal control material get rapidly developed in recent years.It has become the fastest developing intelligent thermal control material with the advantages of good self-adaptation,safety and easy processing.However,the Curie temperature point of the polymer-based PTC materials developed at present is generally high,which is difficult to meet the thermal control requirements of most components.Moreover,other problems such as poor stability and mechanical properties,which also affect the application of the materials.In this paper,from the point of reducing the room temperature resistivity and percolation threshold,improving the PTC strength and stability of materials,the research on the development and application of PTC materials with lower Curie temperature point was carried out.The conductive filler and organic acid crystals were added into the polymer matrix by solution mixing,then the PTC materials were formed after recrystallization.The influence of the type and proportion of components on the PTC effect of the materials was discussed by the characterization test methods.Added CB,Ni and the mixture of both as conductive fillers,compared the effects of different types and amounts of conductive fillers on the conductivity and the PTC effect.By adding EVA,water-based acrylic resin and conductive fillers to form the "isolation-double percolation" structure,determined the optimal ratio for the formation of structure,the room temperature resistivity and percolation threshold of the material can be further reduced.Myristic acid and stearic acid were added as phase change materials,reduce the Curie temperature of the materials,and finally obtained the Curie temperature of the materials were between 40 and 50?,the PTC strength of which between 5 and 7.Observed the structures of the crystals inside the materials,measured the influence of the amount and proportion of organic acid on the glass transition temperature,crystallinity and mechanical property of PTC materials,determined their relationship with the Curie temperature point and PTC strength of the materials.At the best raw material matching ratio,when the conductive filler content is 15 wt%,the Curie temperature is about 47?,the room temperature resistivity of the material is 18.2 ?·cm,PTC intensity can reach 5.9,which has good thermal stability.By analyzing the factors affecting the material properties,established the mechanism model of PTC effect,and tested the electric heating performance and temperature control ability of the materials.The results show that,the temperature control ability of materials is not greatly affected by environmental factors,which can achieve rapid heating and precise temperature control under different environments and voltages.Due to the effect of heat dissipation balance,the overall performance of the materials is that the heating rate and equilibrium temperature increased with the increase of ambient temperature and voltage,but could not exceed the temperature control point of the materials.After 30 thermal cycle tests,the properties of the materials had no obvious change,which has good stability.In this paper,through the study of polymer-based PTC material properties and the establishment of theoretical models,obtained the polymer-based PTC materials which the Curie temperature point can be used for heat treatment and preservation of human body,electronic components and equipment,have the characteristics of light weight,flexibility,and high energy efficiency.Which also provides a new idea for the preparation of lower Curie point PTC materials.