A vinylidene fluoride resin has excellent resistance to chemicals, resistance to oils, mechanical strength and durability, and can be easily processed by thermoforming. As a result, the vinylidene fluoride resin has been conventionally used in various parts in chemical industries such as valves, joints or pipes. In particular, in the anticorrosion field such as pump housings, gears or bearings, high size precision and mechanical strength of the molded articles as well as the anticorrision are indispensable. For those utilities, a method has been employed, comprising blending carbon fibers or graphite fibers with the vinylidene fluoride resin.
Such a method is effective to improve the mechanical strength of the molded article, but the sink mark and warpage occur in the molded article and the surface roughness and deterioration of gloss also occur. For instance, in the case of an injection molding, the orientation distribution occurs in the direction of resin flow and the anisotropy causes in the coefficient of mold shrinkage of the molded article, so that the warpage occurs on the surface of the molded article. As a result, the fitting in assembling the molded article and other parts cannot be conducted sufficiently. Further, the fibrous fillers are present in the vicinity of the surface of the molded article and as a result, sink mark, surface roughness and deterioration of gloss occur.
USPTO Backgrounds
USPTO Backgrounds