Cold/hot mold injection molding technology can greatly improve the aesthetics of injection molded parts. This process contributes to the improvement of the appearance of semi-crystalline and amorphous resin articles, particularly for amorphous resins.
In the injection phase, when the surface temperature of the mold exceeds the glass transition temperature of the amorphous resin, even if the surface material contacts the surface of the mold, the condensation phenomenon which is common in conventional injection molding production does not occur, thereby ensuring that the polymer can be injected during the injection phase. Free flow. As the cavity fills and the pressure in the cavity increases, the resin is forced to flow out, which contributes to the perfect replication of the cavity surface and improves the surface gloss of the article.
For filled materials, the resin that is forced to flow out forms a thin layer of polymer on the outer surface of the product, which coats the filler (glass fiber, carbon fiber or minerals, etc.), thereby improving the gloss of the product and reducing the surface. Roughness. Studies have shown that this method can increase the gloss by 50% to 90%.
In summary, the cold/hot mold injection molding process is very advantageous for improving the surface roughness of the article, which can improve the surface roughness of the glass fiber reinforced material article by 70%. Even for non-filled articles, the surface roughness can be improved by more than 20%.
1. Reduce visible weld lines, jets and flow marks
Cold/hot mold injection molding technology helps to improve the depth and visibility of the weld line. Using a test tool, SABIC Innovative Plastics processed three different materials using cold/hot die injection molding and conventional injection molding, respectively. Parts made using conventional injection molding technology have a surface weld line depth of between 6 and 13 μm, and the parts produced by the cold/hot mold injection molding process do not have a weld line at all, so the depth cannot be measured. . This groundbreaking improvement means that painting for certain products can be eliminated.
2. Reduce internal stress
Internal stress is often one of the main causes of warpage of the product, and in some cases it may also shorten the life of the part. In general, parts injection molded by conventional methods have high internal stresses, and if a well-known stress cracking accelerator such as carbon tetrachloride (CCl4) is used as a solvent for testing, cracking of the components may result. The parts injection molded by cold/hot mold technology have low internal stress, so even if CCl4 solvent is used, it will not cause cracking of the parts. Obviously, parts injection molded using cold/hot mold technology can be annealed prior to use.