Study On Preparation And Properties Of Graphite-based Electrothermal Paint

The electrothermal paint is developed on the basis of conductive coatings,which can directly convert electrical energy to heat energy as a special functional coating.With the progress of science and technology,the application fields of the electrothermal paint become more widely.However,the traditional electrothermal paint suffers some defects such as the low heating surface temperature,poor heat resistance,poor aging resistance performance and high cost of maintenance,which seriously restrict its rapid development and application in many application fields.Because graphite has many advantages such as high electric conductivity and thermal conductivity,low coefficient of thermal expansion,good mechanical performance,strong corrosion resistance,low cost and good adaptability,it become one of the most promising thermally conductive materials.In this thesis,based on related research,composite electrothermal coatings with excellent electric properties are prepared by using different types of graphite as a single or multiple conductive filler,the flexible material as the substrate differing from the traditional grinding technology.This thesis firstly uses spherical graphite processing by-products as raw materials and increases the economic value added of micro by-products in the spherical graphite production process,which can effectively reduce the cost of production.Then the high purity flake graphite is selected as conductive filler for comparison.After achieving the best formula,high purity flake graphite and copper powder are used as conductive filler to prepare composite electrothermal coating with excellent electric properties.The kind and content of conductive filler,binder type and content,coating thickness,the test voltage,preparation process parameters,curing conditions and a series of variables are changedto investigate about the influence on the conductive heating performance,adhesion,impact resistance,aging resistance and chemical corrosion resistance.The microstructure of the coating is analyzed and compared by the scanning electron microscope.The experimental results show that the optimum recipe is the proportion of conductive filler and binder keeping at 1:1.In addition,the graphite powder as conductive filler can greatly save the cost of production.For example,the temperature can increase from room temperature to 96 °C within 10 minutes,volume resistivity can reach 9 Ω·cm,and heating power can achieve up to 7 W,but compared with the high natural flake graphite,there is acertain gap between the electric performance.High purity flake graphite as conductive filler can quickly warm up to 96 °C in 3 minutes and the heating power can achieve up to 9 W.After adding 5% of the copper powder,the electric heating rate of the electrothermal coating achieves the fastest one,increasing to 95 °C only in 1.5 minutes.Moreover,the heating power reachs 14 W and the volume resistivity gets 2.5 Ω·cm.The results show that the electrothermal coating with the optimum formula of adding 5% copper powder has a strong adhesion,excellent aging resistance,good chemical corrosion resistance,stable microstructure and excellent comprehensive properties.The optimum preparation process parameters are the shear rotational speed of 10000rad/min,the dispersion time of 10 minutes,the curing and electric heating time of 30 minutes.The comprehensive performance of the electrothermal coating with the optimum parameters is very excellent.In this thesis,the use of high speed shearing machine for grinding and dispersing coatings is better than that of traditional spread technology,which not only can save time,but also make the paint dispersed evenly.