Preparation And Application Of Positive Temperature Coefficient Laminated Electric Heating Materials With Low Curie Temperature

With the rapid development of electronic products and power equipment,people need functional materials with good electrical and thermal properties urgently.Polymer materials have been widely studied and applied for their advantages of good flexibility,light weight,easy processing and low cost.As a new type of thermal control material,polymer-based positive temperature coefficient(PTC)composite has the advantages of polymer material and unique electrothermal performance,so it has been applied in many fields.However,the Curie temperature of widely used polymer-based PTC composite is generally high(50-300℃),which is difficult to meet the room temperature control requirements.In the cold environment,the human body and instruments need to stay at room temperature,so it is necessary to develop a new intelligent material which can automatically heat at low temperature and control the temperature at room temperature without other temperature control modules.In this paper,we prepared and studied the application of low Curie temperature PTC materials and layered temperature self-control electrothermal materials,hoping to broaden the application of polymerbased PTC composite materials.In this paper,we started from the preparation of two kinds of low Curie temperature point PTC materials with different conductive filler systems,and studied their electrothermal performance,to get two best PTC materials which can be applied to different conductive systems in the field of self-controlled heating.In order to better apply the materials to the field of self-controlled heating,the two PTC materials are obtained by structural design,and the materials are verified by experiments mechanical properties,electrical properties,heating and temperature control ability of the material.Firstly,the PTC materials of two different conductive fillers were obtained by mixing the conductive fillers,carbon black or nickel powder into the system of ndecanoic acid(CA)/ethylene vinyl acetate copolymer(EVA),with the method of solution mixing.The orthogonal experiment was designed,by changing the content of fillers and the proportion of CA/EVA,testing the electrical,thermal and mechanical properties of the materials,to obtain the best raw material matching ratio.For the carbon black system,when the carbon black content is 15wt%,CA/EVA content is 3.5/1,dispersant content is 0.15wt%,the material has the best comprehensive performance,the low-temperature resistivity of the material is 977 Ω cm,PTC intensity is 6.1.For the nickel powder system,when the nickel powder content is 20wt%,CA/EVA content is 3/1,the material has the best comprehensive performance,the low-temperature resistivity of the material is 340 Ω cm,the PTC intensity is 6.26.Secondly,the relationship between the properties of the materials and the components is verified by experiments.The results show that the best PTC effect occurs near the percolation threshold,and the n-decanoic acid plays a role in destroying the conductive network after reaching Curie temperature in the process of producing PTC effect and the thermal repeatability of the materials can be improved by reducing the agglomeration of conductive particles.Finally,through the preparation and testing of layered electrothermal materials,it shows that the "S" shaped bottom structure is helpful to reduce the low temperature resistance of materials,and the temperature control ability of the two kinds of material is affected by the voltage and temperature environment,which shows that the higher voltage,better insulation,higher ambient temperature,resulting in the faster heating of materials and the higher controlling temperature.At the same time,the experiment also shows that the electrothermal material can also maintain temperature self-control ability in 30 thermal cycles.In this paper,the PTC material with low Curie temperature is prepared and applied in the heating field of low temperature environment.This material is both a heating element and a temperature control element,which saves the temperature control module.By this paper,we provided a temperature control heating method in the low temperature field.