GMT-Sheet 성형품의 표면거칠기에 관한 연구

Abstract

Observing of GMT(Glass Mat Reinforced Thermoplastic)-Sheet in molding conditions, we have investigated unexpected phenomenons of moldings surface. In microscope investigation, we observe that there exist deficiencies on the surface of GMT-Sheet moldings, such as the spherulite, fiber projection, crack, exposure of fiber, micro-weldline, pinhole and winding. They are caused to arise unevenness and phenomenons influence polish on surface. Especially, the major cause of the unevenness, effected to surface roughness, is a shrinking of matrix in the process of holding pressure and cooling temperature. The higher holding pressure load in a molding process and the lower demolding temperature in an annealing experiment, the better GMT-Sheet moldings improved its appearance. In order to determine the fiber projection height from the shrinking of matrix, we have calculated it by modelling a short fiber of the moldings surface. In addition, considering holding pressure and demolding temperature, we find out the process of the unevenness in moldings surface and the variation of the fiber projection height. Coating layer of GMT-Sheet surface effectively improve surface roughness to the level of the polypropylene which is a single material.