Blow moulding process is a common method of plastic packaging container moulding. Blow moulding is a method of processing semi-molten tube blanks (or billets) obtained by extrusion or injection moulding into the die, then closed the die, and extended and expanded by injecting compressed air into the tube blank, so that it is close to the cavity wall, and then cooled and demoulded to obtain a certain shape of hollow products.

According to the different forming methods, blow moulding process can be divided into many kinds.

1、Drawing blow mouldingDrawing blow moulding is a moulding method in which the bottomed billet heated below the melting point at the appropriate temperature is placed in the mould and the drawing rod is used for axial stretching and then blow moulding immediately. At the same time of moulding, macromolecules are aligned and fixed in the wall of the product, thus greatly improving the performance of plastic containers.

The characteristics of this forming method are: low reject rate, high production efficiency and easy control of weight. The products have high impact toughness, high rigidity, improved transparency and gloss, good barrier and air tightness, but they require high temperature control and large investment in equipment. Most PP bottles and PET bottles are formed by injection-pull-blow method, such as Coke bottles.

2.、Multilayer Blowing Molding

Multilayer blow moulding is a method to prepare multi-layer container by using multi-layer composite parison and blow moulding process. Through the reasonable matching of different plastic layers, the effective complementarity of plastic properties of each layer can be realized, and some inherent shortcomings of single-layer plastic container can be overcome.

The characteristics of this forming method are as follows: it can improve the physical and mechanical properties of plastic containers and the properties of containers, such as shading, insulation, flammability and printability.