As the previous article mentioned, there are two new methods appeared now, multi layer blow molding and stretch blow molding. These two means are developed on the basis of injection blow molding and extrusion blow molding, with only little difference in the process. And this article will focus on multi layer blow molding.

Multi layer blow molding, as the name suggests, the wall of its products is not single layer but multiple layers. The raw material and the layer number of the multi-layer containers can be selected according to the needs. There are many options, including two layers’ structure with two kinds of plastics, three layers’ structure with two kinds of plastics and four layers’ structure with three or four kinds of plastic. Attention! The more layers, the higher the technical requirements.

The multi layer blow molding process needs more than two extruding machines. Firstly, the same or dissimilar plastic materials will be melted and mixed in different extruding machine, and then they will be composited and extrusion in the same head, and finally the plastic materials will be manufactured to multi-layer hollow containers through blow molding.

Besides, the multi-layer plastic products have smooth surface with no waste edge and there is no cut mark on their bottom. They also have the advantages of pressure resistance, impact resistance and heat resistance. Moreover, they have high chemical resistance, anti-oxidation, light-proof aging, anti-penetration of harmful substances and anti-odor migration. Therefore, the invention of multi-layer blow plastic products has addressed the growing requirements of air tightness in some packaging industries such as cosmetics, pharmaceuticals and food.