1. The structure of the masterbatch and the effect of molding shrinkage The degree of plastic product molding shrinkage is determined by the shrinkage rate: the shrinkage rate of the plastic melt in each flow direction is different. Usually, the shrinkage rate MD and CD of the melt flow direction and its perpendicular direction are used to determine the shrinkage state of plastic molding. The difference in the degree of shrinkage in the two directions is expressed by (MD-CD)/MD shrinkage difference:

The shrinkage rate of plastic is not only related to its type, structure, molding temperature, pressure, time and other factors, but also related to the additives in the plastic. Among them, the addition of color masterbatches, especially organic color masterbatches, will cause increased molding shrinkage, especially for large containers. According to practical experience, the color masterbatch with symmetrical molecular structure is generally added, and the molding shrinkage of the colored plastic products is large.

2. The effect of the shape of the masterbatch on the molding shrinkage. The crystallization of the masterbatch is anisotropic. When the crystallization state is like a needle or a rod, the length direction is easy to align with the flow direction of the resin during molding, resulting in greater shrinkage. ; Spherical knots do not have the problem of directional alignment, so the shrinkage is small. Inorganic masterbatches are generally spherical crystals, so the shrinkage is small.

3. Effect of color masterbatch on stress cracking of plastic products Stress cracking is a phenomenon that the product breaks due to the internal stress of the product. When the resin strength is smaller than the internal stress, the product is destroyed. Cracks mostly occur at stress concentration places such as thick walls, turning points, and gaps. In addition, the masterbatch particles are poorly dispersed in the resin, causing tiny cracks to form on the surface of the product. The internal stress in the product will promote the crack expansion, and finally cause the product to crack. the solution. Try to avoid the use of masterbatches that have a great impact on the shrinkage of plastic products; surface treatment of the masterbatches to improve the dispersion of the masterbatches in the resin, increase the affinity between the masterbatches and the resin, and prevent the occurrence of micro-cracks ;Adjust the molding process and improve the mold.