Delamination is a injection products defect with the surface layers of a molded part peeled off which is also appear as fish-scaling. It may also be called lamination or layering. There are several reasons that cause the problem. It may be caused by material, processing, equipment and tooling.

From a material standpoint, TPU material tend to be hygroscopic and moisture can hydrolyze TPU resins and harm the surface properties. Ensure that the TPU material is fully dried prior to molding. When two materials can’t bond together, it results in separation that very quickly becomes delamination. As TPU resin and TPE resin are incompatible and the melt temperature are different, so TPU and TPE must be compound as one mixed granule before injection molding. Compatibilizer agent which can bond TPU and TPE together is necessary for TPU and TPE compound. An easier flowing grade of TPU material is more easier to bond with TPE material, easier flowing often help resolve the delamination problem. Ensure that the material is not contaminated when using regrind

From a processing standpoint, Normally If the injection speed is too slow or the temperature is too low or back pressure is too high, The material enters the cavity in layers which is easier to cause delamination. As to prevent delamination, it is necessary to increase the mold temperature, melt temperature and reduce the injection speed.

From a equipment and tooling standpoint, small gate is usually accompany with higher shear stress. that’s why delamination often occurs in the small feed gate area. It may be necessary to increase the gate size in order to reduce the shear stress on the material.

Delamination can occur in any area of the molded part and can be a small or large defect.