Causes of the Gloss Transition Defect on High-Gloss Injection-Molded Surfaces

Abstract

The gloss transition defect of injection-molded surfaces should be mitigated because it creates a poor impression of product quality. Conventional approaches for the suppression of the gloss transition defect employ a trial-and-error approach and additional equipment. The causes of the generation of a low-gloss polymer surface and the surface change during the molding process have not been systematically analyzed. This article proposes the causes of the generation of a low-gloss polymer surface and the occurrence of gloss transition according to the molding condition. The changes in the polymer surface and gloss were analyzed using gloss and topography measurements. The shrinkage of the polymer surface generates a rough topography and low glossiness. Replication to the smooth mold surface compensates for the effect of surface shrinkage and increases the surface gloss. The surface stiffness and melt pressure influence the degree of mold surface replication. The flow front speed and mold temperature are the main factors influencing the surface gloss because they affect the development rate of the melt pressure and the recovery rate of the surface stiffness. Therefore, the mold design and process condition should be optimized to enhance the uniformity of the flow front speed and mold temperature.

Novel Analysis Methodology of Cavity Pressure Profiles in Injection-Molding Processes Using Interpretation of Machine Learning Model

“…The packing pressure and time of the packing stage were expected to be the most influential factors on the part weight because the packing stage compensates for shrinkage of the polymer material. However, the injection speed was expected to be less influential than the packing pressure and time because the filling stage predominantly affects the surface quality, not shrinkage in the packing and cooling stages [ 34 ]. These are common process parameters that are tuned to optimize the injection-molding process.…”

Effect of Femtosecond-Laser-Structured Injection Molding Tool on Mechanical Properties of the Manufactured Product

“…The difference between the cooling times used did not cause a visible difference in the filling. Gim et al also concluded the fact that the higher injection speed could add more melt into the microstructures before the maximum cavity pressure was reached [ 9 ]. This was due to an increased injection rate, leading to a decrease in melt viscosity that improves the melt flow in microstructures.…”

“…The replication quality of molded parts or even their mechanical properties can be improved by optimizing process parameters and controlling material flow. Therefore, an optimization approach has been used to improve the mechanical properties of the molded part made by polypropylene (PP) [ 4 , 8 , 9 , 10 , 11 , 12 ].…”

Application of Magnetic Concentrator for Improvement in Rapid Temperature Cycling Technology

“…This can be also used to minimize the reduction in tensile strength in parts, where weld lines are present [ 21 , 22 , 23 ]. Besides, the high cavity surface temperature is commonly used to improve surface quality (removal of weld lines’ presence, obtaining high-gloss surface, better replication of microstructure of the cavity surface) [ 6 , 11 , 23 , 24 , 25 , 26 , 27 , 28 ].…”