Synthesis And Properties Of Carbon-based Self-regulating Electrothermal Composites

Electrothermal composites as a kind of functional materials can be convenience to process.These materials can translate electricenergy into hot energy effectively.Up to date,the study of the flexible electrothermal materials especially with self-regulating temperature is becoming hot spot in smart flexible devices.However,the electrothermal composites still have many problems to be solved before its large scale applications,such as poor self-regulating temperature,slow response speed,inferior weather resistance,binder ageing and so on.In this paper,a series of carbon-based self-regulating electrothermal composites have been developed and well investigated.The optimized carbon-based electrothermal composites were selected form different kinds of conductive and non-conductive fillers and binders.The main content are summarized as follows:?1?Different types of carbon materials as one-component conductive fillers were studied.The pyrolysis carbon N991,acetylene black and multi-walled carbon nanotubes were used as one-component conductive filler respectively.The poly?vinylidene fluoride??PVDF?that has strong environmental tolerance was used as binder.Both of them were grinded and mixed in gradient ratios.And the PET film was used as the substrate.The percolation threshold and first electrothermal performance of one-component carbon with PVDF were studied systemically.Experimental results showed that the percolation threshold is as high as 80% of the total mass with the pyrolysis carbon N991.And the percolation threshold decreases to 40% of the total mass with the acetylene black and the multi-walled carbon nanotubes.When the acetylene black was used as conductive fillers,the resistance decreased rapidly with the increase of the content.All the carbon materials have the high heating rate with a low resistivity under 24 V,Moreover,the sample with a large resistance and low heating rate will show the superior electrothermal performance.?2?Hybrid carbon materials as conductive fillers were studied.Various carbon materials were mixed together as the multicomponent conductive filler.The PVDF was still used as binder.A tiny content of silicon oxide was added as non-conductive fillers.The influences of the type and proportion of carbon and binder on conductivity,electrothermal performance and aging performance of electrothermal films were studied The results showed that when the binder content is 60% of the total mass and the mass ratio of acetylene black and multi-walled carbon nanotubes is 2:5,the sample exhibited the optimal electrothermal performance.?3?The electrothermal performance of electrothermal composites with high crystalline polyoxyethylene?PEO?as binder were studied.On the basis of the above experiments,the types and contents of non-conductive fillers?SiO₂,MgO,ZnO and CaCO3?were studied furtherly.The results showed that the electrothermal composites presented good electrothermal performance and acceptable aging resistance performance when the binder content is 50% of the total mass and the mass ratio of pyrolysis carbon N991 and multi-walled carbon nanotubes is 4:5.When the silicon oxide was used as the non-conductive fillers,the electrothermal composites showed the best electrothermal stability.But the zinc oxide as the non-conductive filler displayed the best ageing cycle performance.And when the content of silicon oxide is 2% and 5%,the sample exhibited the remarkable comprehensive performance.?4?A novel thermal discoloration flexible film was designed and fabricated by electrothermal composites as the heating element and reversible thermochromism paint as the temperature-sensing elements.Under the safe voltage of 24 V,the color changing process was observed and the curves of temperature-time and current-time were record.The results showed that after the thermal discoloration electrothermal flexible film were electrified,the color changed gradually with the increasing temperature.After five minutes,the temperature rose to about 43?,the temperature sensing pattern changed obviously.When the power was switched off,the color of temperature sensing pattern was quickly restored within 20 s.?5?The manufacturing process of carbon-based self-regulating electrothermal flexible film was designed.Based on the above experimental results,the carbon materials,binders and additive were optimally.The production process,electrode configuration on the electrothermal films and layout of the production workshop were designed.At last,several main equipments in the actual production process were introduced.