Research On The Manufacture Of Low Density Bulk Molding Compound

Bulk molding compound (BMC) is a thermoseting material made of unsaturated polyester resin, orgaanic additives, the initiator, powdery filling, thickener and chopped glass fibres strands that are mixed. The BMC molding pressure and the formation temperature are low, may reduce to the equipment and mold's cost of investment, suits the processing configuration complex large-scale component. Because it has the fine electrical specification, the mechanical property, the thermal stability, bears chemistry corrosiveness, may satisfy each product to the performance request, the application scope is quite widespread. The material application request is enhanced along with the energy anxious day by day, People have to higher request to the BMC lightweight, the product stability proposed, therefore low density BMC becomes a big hot spot which nowadays studies.This article has prepared one kind of low density bulk molding compound, which uses the calcium carbonate and the hollow glass microballoons mixed packing. After surface treatment, hollow glass microballoons' surface increased one kind of organic ingredient, this can accommodate with the resin, increased with the resin compatibility and reduced the blotting value. The experiment indicated that along with hollow glass microballoon content increasing, BMC density drop, mechanical properties also along with it drop, and the padding gradation has the remarkable influence to the BMC viscosity and the mechanical properties. Through the reasonable gradation, in the proper attention to both intensity and under the density condition, this article determined that selects the glass micro bead and the calcium carbonate 1:5 mass ratio, the particle size ratio is 400:800.This article in the synthesis introduced BMC with in the low outline chemical additive LPA development process's foundation, has studied nonpolar LPA separately polystyrene PS, nonpolar and polar transition form LPA polymethyl acrylic acid methyl ester PMMA and polar LPA polyvinyl acetate PVAc, and it has analyzed three kind of LPA to the BMC product performance influence and the contraction control effect. In the article has the LPA tree ester solidification type cross section appearance using SEM to Canada to carry on the attribute, mechanically has analyzed LPA to the BMC contraction control reason.. The result indicated that three kind of LPA has the good contraction control effect to BMC, simultaneously causes the BMC mechanical properties varying degree the drop. The overall evaluation mechanical properties and contraction control's balanced, suggests to produce the PS system actual in the shrinkage is in 0.1-0.2% formula amount of use should be 30-35phr; The PMMA system is in 0.05-0.1% formula amount of use should be smaller than 35phr in the shrinkage; The PVAc system is in 0.05%-0 formula amount of use should be smaller than 45phr in the shrinkage, it has realized the compound design optimizationThe flow property of BMC during molding was discussed by means of Brabender torque rheometer and the determination of the mass fraction of short glass fiber in BMC by sampling in concentric circle in this paper. The effects of temperature, the mass fraction and length of the glass fiber, the particle size of filler and content of thickening agent on the flow viscosity of BMC and the distribution of short glass fiber in BMC were studied.