Compression molding is to directly add powdery or loose granular solid plastics into the mold, and gradually soften and melt them by heating and pressurizing, and then shape them according to the shape of the mold cavity, solidify them into plastic parts, and compress them into profiles. Most of the materials are thermosetting plastics.
In the forming process, follow plastic part design guidelines. The rmosetting plastics react with heat or chemical polymerization to form cross-linking structure. Once the reaction is complete, the polymer molecular bonds form a three-dimensional network structure. These cross-linked bonds will prevent the molecular chains from sliding. As a result, that the thermosetting plastics become an immiscible and insoluble solid. The nature of thermosetting plastics can be imagined as boiled eggs. The yolk changes from liquid to solid, but it can no longer change into liquid.
As compression moulding materials, the highest temperature of plastic melt is higher than the mold temperature, the curing time is shorter and the molding time is longer due to the exothermic effect of crosslinking reaction. If the molding temperature is too high, the curing time will be short, which will make it difficult to fill the mold, and make the surface of plastic parts dim, lusterless, even swelling, deformation and cracking; if the molding temperature is too low, the curing time will be slow, and the molding time will be long.
Therefore, in the compression molding of this kind of compression moulding materials, it needs to be maintained at a certain temperature and pressure for a certain period of time in order to fully crosslink and solidify and become an excellent plastic part.