A Brief Introduction to the Injection Moulding Technique of Making PET Bottles

PET bottles are one of the most popular types of bottles used worldwide today. Their attributes such as easy production, high durability, easy packaging, easy transportation, and easy recycling, have contributed a lot in making these bottles so popular. They make use of polyethylene terephthalate, a thermoplastic polymer from the polyester family; the use of this polymer is also behind these bottles christened PET. The industries that make use of PET the most are beverages, mineral water, wine, chemicals, and pharmaceuticals, among others.

These bottles need to be produced in bulk owing to their high demand across various industries. Naturally some quick, effective and economical technique would be required for such production. That technique is the injection molding technique. As the name suggests, this technique make use of moulds of various shapes and sizes. The mould making companies in South Africa, India, China, and various other countries, witness the greatest demand for their products in the PET manufacturing industry.

Now coming to the technique itself; the injection moulding technique of PET bottle manufacturing makes use of PET pellets, which are basically plastic granules or small plastic tablets. These pellets are melted to form a plastic resin, which is then inserted into a mould cavity. The molten plastic is then left to cool inside the mould through natural process. As the resin cools down, it assumes the form of the PET preform, possessing the texture and contour as per the mould. Most of the moulds are made of tool steel, but the stainless steel moulds are deemed superior.


The injection molding method also has two sub divisions, namely: one-step method and two-step method. In the one-step method, PET preform, made inside the injection mould, is introduced in the blow-molding compartment of the same machine. The preform is converted into a PET bottle inside this compartment. This method saves energy and it is mostly used by small factories.

Then, there is the two-step method in which, the preform made inside the injection mould is introduced into a separate machine meant for stretch blow molding. Before putting the preform inside this other machine, it is reheated to make it elastic. After that, the preform is blow moulded inside the machine to provide it the shape of a bottle. Though this method is relatively costlier, it is considered good for bulk production and provides more flexibility. Therefore, the medium and large scale production facilities widely use this two-step method.


Irrespective of the method that you use under the injection moulding technique, one thing remains important: the quality of mould. If the mould is of good quality, then the final product, i.e., the PET bottle, will also be good and vice-versa.

Acme Disys is a leading supplier of high precision pet preform and cap molds. The company caters to various industries such as beverages, packaged water, edible oil, and pharmaceuticals. They have over a decade of experience into the Pet Preform Mold Industry.

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