Preparation Of Rare Earth Modified Calcium Manganate/Medical Stone Composite Conductive Fillers And WPUA Coatings

With increase in applications of conductive coatings in the fields of aerospace,aviation and electronic instruments,the high requirements have been put forward for the enhancement of the comprehensive performance,the improvement of environmental protection performance and the reduction of manufacturing cost.Especially,there are problems of poor conductivity,bad mechanical performance and high cost of the current conductive fillers,which are difficult to meet the application demand.As a kind of natural mineral resources,medical stone is not only rich in reserves and cheap in price,but also full of vesicular structure,which is propitious to the modification of rare earth penetration.Medical stone is transformed from insulating material to conductive material after modification.The conductive coatings with stable performance,anti-corrosion and oxidation resistance can be obtained,if the modified medical stone is applied in the field of conductive coatings.Waterborne polyurethane acrylate?WPUA?conductive coatings are studied based on the preparation of rare earth modified medical stone composite conductive powders in this paper.First of all,rare earth penetration technology is adopted to obtain rare earth modified medical stone powders,and XRD,SEM,XPS,CIP were characterized to study the variations of compose,structure,morphology and conductivity of medical stone and Sm modified medical stone.The results show that when the penetration temperature is 600 ^oC,penetration time of 5 h,solution concentration of 100 g L^-1,the conductivity of rare earth modified medical stone powders is the best,whose resistivity achieves 3.67?·m.Based on the preparation of Sm modified medical stone powders,calcium manganate/medical stone and nickel/medical stone composite powders are synthesized by hydrothermal-solvothermal method,and the composite powders were modified by rare earth penetration.Then after penetration,the medical stone composite conductive powders not only further decrease the resitivity to 2.01?·m,but also have mixed morphology of needle-like,block-shaped and flake structure,which is more favorable to the reduction the percolation threshold of conductive coatings.Then,based on the synthesis of waterborne polyurethane acrylate,waterborne conductive coatings were prepared with nickel powders,rare earth modified medical stone powders,rare earth modified calcium manganate/medical stone and rare earth modified nickel/medical stone composite powders as conductive fillers.The optimal formula of the waterborne conductive coatings were determined by testing the properties of coating resistance,hardness,and adhesion:waterborne polyurethane acrylate as matrix resin,rare earth modified calcium manganate/medical stone powders as conductive fillers,whose ratio of modified calcium manganate and medical stone is 1:1 and dosage is 50%;water as diluent,dosage of 25%;triethanolamine as curing agent,dosage of 10%;2,4,6-Trimethylbenzoyl-diphenylphosphine?TPO?as photoinitiator,dosage of 2%;peroxide benzoyl peroxide?BPO?as thermal initiator,dosage of 2%;curing distance of UV lamp of 15 cm.The properties of the resulting conductive coatings after curing are:hardness of 6H,adhesion of 1 grade,peeling strength of 5.68×10³ N m^-11 and tensile strength 9.36×10⁴Pa,moreover,the resitivity of the coatings achieved 3.2×10⁶?,which have a prospect of application in the antistatic field.