PVC is a heat-sensitive plastic. Overheating or excessi […]
PVC is a heat-sensitive plastic. Overheating or excessive shearing will cause decomposition and spread rapidly, because one of the decomposition products (such as acid or HCI) will produce a catalytic effect, causing the process to further decompose, and the acid will attack the metal and Plastic medical mould make it change. If it becomes dent, it will peel off the protective layer of the metal and cause rust, which is more harmful to the human body.
PVC is a heat-sensitive material, and its injection molding processability is poor. The reason is that too high melting temperature or too long heating time can easily decompose PVC. Therefore, controlling the melting temperature is the key to injection molding PVC products. The heat source for melting PVC raw materials comes from two aspects: the shear heat generated by the screw movement to the plastic and the resistance wire heating on the outer wall of the barrel, and the shear heat of the screw movement is the main source. The outer heating of the barrel is mainly the heat source when the machine starts. Due to the poor thermal conductivity of PVC, during the heating process, although the outer plastic has been heated, the intermediate material is still in a condensed state, and even the outer part has been overheated and decomposed, and there may be unmelted parts inside. All kinds of reasons must be fully paid attention to in product design, mold design, injection molding process, etc.