| Electric radiant heating film is recognized as the most ideal heating way, because of its high electrothermal conversion efficiency, clean energy, health care, easy control and high comfort performance. The conductive ink is a key factor influencing the performances of the electrothermal film. It is a kind of functional conductive coating which can convert electrical energy directly into heat energy, and is widely used in the fields of aerospace, construction, industrial, civil etc. However, there are many problems such as unstable electrothermal performances, bad bonding properties, crazing and short service life etc. Carbon conductive ink has drawn much affection due to its high electrothermal conversion efficiency, low cost, and hardness to oxidation. In order to solve the existing problems in the application of conductive ink and make it more applicable for electric heating, the study of carbon conductive ink which has uniform heating, high electrothermal performance and good adhesion is of great significance.Here a proper dispersion process is determined through choosing the dispersant of carbon black and graphite and studying dispersion methods. Conductive ink has been prepared by using waterborne polyurethane as adhesive and graphite and carbon black as fillers, and then conductive fabric obtained by coating conductive ink on nylon cloth. Next the conductive properties, microstructure and adhesion of this conductive fabric were texted. The conductive fabric could be made into electric heating element, based on which finally we study the electric performance of conductive fabric heating element and heat transfer process in its practical application. Through the above steps, we can get the following conclusions:(1) Studying the dispersibility of carbon black and graphite in aqueous system, we could find the results: compared with ultrasonic method, ball milling method on carbon black can achieve better dispersion effect and dispersion stability, and the prepared carbon black water system has much smaller particle diameters. The dispersion effect of nonionic dispersant TrionX-100 is better than that of dodecyl benzene sulfonic acid sodium, polyoxyethylene laurel ether, Arab tree powder and anionic polyacrylamide. An average particle size of 243.6 nm in carbon black aqueous dispersions could be prepared by ball milling, and the carbon black particle size distributes narrowly. Based on this results, dispersibility of graphite has been studied, it's found the graphite particle size in aqueous dispersions reduced with the increase of milling time(other things being equal), while the dispersion effect of graphite aqueous dispersions is getting better.(2)Using graphite and carbon black as conductive filler respectively to prepare the electric conductive inks and then impregnate to get conductive fabric, we have studied the influences fillers and ball milling time have on the properties of ink. The results show: comparing 4h to 10 h in terms of ball milling time, conductive ink with graphite as conductive filler under the former situation has lower resistivity volume and better conductivity. Besides, the rate of the resistivity decreases with the increase of graphite content. As the quality proportion of graphite and polyurethane is 10:5, the conductive performance of conductive ink is good. At the same time, the surface coating of conductive fabric which prepared by conductive ink is smooth, uniform and has good adhesion. The conductive ink prepared with carbon black as conductive filler, will have thixotropic phenomenon when the carbon black content increases to a certain extent(carbon black: polyurethane = 10:3), which lead to uneven surface coating of conductive fabric. And when the quality proportion of carbon black and polyurethane reaches 10:5, the conductive ink has best conductive performance, the surface coating of conductive fabric is uniform and even.(3) Using graphite/carbon black as mixed conductive filler, we also study the influences the ration of graphite and carbon black has on properties of ink. The results show: the conductive ink prepared with mixed graphite and carbon black as filler, has good electric conductivity when compared with conductive ink use single filler, and also has a good volt-ampere characteristic. When the quality proportion of graphite, carbon black and polyurethane is 6:4:5, the resistivity of conductive fabric could reach its minimum volume of 1.27?·cm and also the surface of this conductive fabric is smooth and flat, and the adhesion of coating is at level 2.(4) After a conductive fabric electric heating element was made based on conductive fabric, we have studied its electrothermal performance and heat transfer during work process. Research shows that: the conductive fabric electric heating element has a property of quick heat and its heating up time is 5 min. There is a linear correlation between stability temperature increment and power density, and the reciprocal of the ratio of temperature rise and power density is integrated heat transfer coefficient, which is about 0.0022. Conductive fabric presents excellent temperature self-control performance, radiation heat exchange account for around 64% of the total heat transfer in the working process. This working process belongs to the radiation heat transfer. |
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