PET Bottle Manufacturing – Its Two Primary Methods

Though many types of bottles are in use these days, none of them matches the popularity of PET Bottles. PET bottles are used in daily life for a variety of purposes. The various examples of these bottles include: mineral water, cold beverage, or the simple water bottles available in the market. According to an estimate, more than 100 million PET bottles are used worldwide in one single day; isn’t it amazing? Let’s know how these bottles are manufactured in such huge quantities.

The chief raw material for manufacturing PET bottles is polyethylene terephthalate, which is a thermoplastic polymer belonging to the polyester family. The two primary methods of manufacturing these bottles are: Extrusion Stretch Blow Molding, and Injection Stretch Blow Molding. Let’s discuss both one by one.

Extrusion Stretch Blow Molding

In this technique, molten plastic is extruded into parison, a hollow tube. After that, parison is clamped inside a cooled metal mold to bring down its temperature. These molds can be obtained in various shapes, sizes, and properties from the mold manufacturers. Then, fresh air is blown into the clamped parison, which consequently inflates the parison and changes it into a bottle. This newly formed bottle is quite flimsy owing to the hot plastic; so to make it durable, it’s cooled down before removing it from the mold. This method is normally used for manufacturing shampoo, oil, and milk containers, and watering cans.

Injection Stretch Blow Molding

This method is used very often in the plastic industry for manufacturing PET bottles. It can be classified into two parts: single-stage process and two-stage process. Let’s first discuss the two-stage process. In the two-stage injection stretch blow molding procedure, plastic preforms are manufactured at the very onset using the injection molding technique. The preforms manufactured in this way consist of a neck and threads or finish; they are not finished products in themselves; instead, they are used for making the finished product. Several factories produce only these preforms, which are supplied to bottle manufacturers. These preforms could be heated again in a separate factory for producing PET bottles. The preforms are mostly reheated by means of infrared heaters. After heating them up to a certain temperature, fresh air is blown inside the preforms, which are covered with a metal mold. This technique provides greater flexibility in terms of giving the desired shape, size, and pattern to the bottles. But due to its capital intensive nature, this method is adopted primarily by big industries.

In the single-stage injection stretch blow molding method, the bottle is made out of preform inside a single machine; hence, the name single-stage injection. The benefits provided by this technique are cost saving; time saving; and more durable bottles, which makes them ideal for storing carbonated drinks. The demerit of this method is that it restricts the choice of design and patterns that could be given to the bottles. This technique is generally used by small industries as it does not require a large investment.

You might have noticed in the above two methods that they both make use of pet preform molds. Both these techniques are good at their place and manufacturers select them according their budget, requirement, and convenience. There are some good injection mold makers in the country who you may contact to obtain high quality molds.

Acme Disys Established in 2002, Acme Disys is a leader and an innovator in the Pet Preform Mold industry. Bottle Moulds Industries.