Research On The Electrical Properties Of Low Pressure Molding Compound

Low pressure molding compound (LPMC) is a new kind of compressed material, which is developed from unsaturated polyester sheet molding compound (SMC). It can be used to produce high-strength, high-corrosion-resistance and high-insulation parts. Compared with the traditional SMC, LPMC has better economic benefit, due to its lower molding pressure and molding temperature. The main problem in SMC industry is that electrical properties of part of products can not reach the standards. For obtaining better performance products, and expand the applied field of products. This article studies on the electrical properties of LPMC.By adding different amount and quality ratio of different diameter of the single aluminum hydroxide filler, the results show that volume resistivity, dielectric constant and dielectric loss of products are the best, when the filler reach 160 copies (mass ratio to resin).Volume resistivity of products could be improved by adding the filler of smaller particle size to the filler of large particle size, when the dosage of the filler maintain 160 copies. As the amount of smaller particle size filler increases, the volume resistivity of products decline. This article studies on relation between dielectric properties of products and content of fiber. The results show that when the content of fiber reaches 30%, dielectric constant and dielectric loss of LPMC can obtain the best. This article has studied on effect between dielectric properties and interface which was produced among the fiber and rein.This article has studied relation among the thickness, temperature and environmental humidity on electrical strength of the products, and compared with electrical strength of SMC, LPMC and Epoxy laminate, which they have the same thickness. The results show that the electrical strength of the products decrease, as the thickness and the temperature of the products and the time which the products stay in damp environment increase.The electrical strength of LPMC and SMC molded products are be superior to the Epoxy laminate when they have the same thickness. This article has studied leakage tracking resistance of LPMC, and analyzed the mechanism of leakage resistance, by changing the amount of aluminum hydroxide filler. By adding different amount of Aluminum hydroxide powder which was modified by titanate coupling agent, and testing oil absorption value, we can obtain the optimum dosage of coupling agent. The results show that oil absorption value of the powder can reach minimum when the dosage of coupling agent was 2%.After the modification of aluminum hydroxide powder, the biggest amount of filled powder will increase and the volume resistivity can improve approximately 30%. When the same amount of Aluminum hydroxide powder was added, dielectric constant and dielectric loss of the modified products is less than that of unmodified.