Shrinkage of custom plastic containers

  The forming process of custom plastic containers is thermoplastic. Due to the volume change and large internal stress during the production process, there will be residual stress in the molding process, and the molecular orientation is very strong. Therefore, compared with thermosetting plastic products, its shrinkage rate is larger. Its contraction range is larger and its directivity is very obvious. During the molding of plastic parts, the outer layer of molten material contacting with the surface of mold cavity will immediately cool down to form a low-density solid shell. We all know that the thermal conductivity of plastics is very poor, and the inner layer of custom plastic containers cools very slowly, forming a high-density solid layer with large shrinkage. If the wall is thick and the cooling is slow, the shrinkage rate will be greater if the high density layer is thick.

  The molding conditions have a great influence on the shrinkage of custom plastic containers. For example, if the mold temperature is high, and the melt cooling is slow and the density is high, the shrinkage rate will be relatively large. High crystallinity of crystalline material, the volume will become larger, so the shrinkage rate will become larger. Mold temperature distribution, internal and external cooling degree, density uniformity and other factors will directly affect the size and direction of shrinkage of each part of the product. The size and duration of holding pressure also have great influence on the shrinkage. When the pressure is high and the time is long, the shrinkage rate will be smaller, but the directivity will be greater. The shrinkage of custom plastic containers can be changed by adjusting the mold temperature, pressure, injection speed and cooling time.