How are plastic bottles made step by step?


Production of plastic bottles
Production of plastic bottles
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Plastic bottles have been widely used as packaging materials of beverages, detergents, and other basic commodities since the 1970s. Thanks to compounds like recycled plastic, plastic containers have multiple benefits, such as robustness, energy efficiency, and manufacturability. Bottles made of plastic are inexpensive to produce, secure for use, as well as recyclable.

Advantages:

  • Lightweight: Produced at a lower price and uses fewer resources to deliver.
  • If badly damaged, don’t really break and pose risks.
  • These are therefore ideal for drinking since they are safe and portable.
  • It can be recycled, allowing us to use it again and again.

Production of plastic bottles

There are two steps for the production of plastic bottles

1. “hot perform” method.

2. “cold perform” method.

1. The “hot perform” method

In this approach, most of the processing is performed through one integrated machinery, from grains to final bottles. According to the injection mould of the prototype to the withdrawal of the prototype from the injection cavity and the stretch blowing of the prototype to a bottle, all in one machine, with the temperature being fixed throughout the injection moulding and blow moulding processes. Because the material is only heated once, it is fed into the cavity to generate the prototype. This process saves a great deal of energy. Small and medium-sized manufacturing firms frequently employ the One-Step approach.

2. The “cold perform” method

In this procedure, the injection and blow moulding are done by two different machines. The prototype is injected into shape on the first machine, then reheated and blown on the second machine because it isn’t sent immediately to the blow moulding machine. This method is time-consuming since the heat loss is perceived as an energy loss. However, these machines are fully automated. Most medium to large-scale manufacturing enterprises employs this technology. This machine exceeds the one-step machine by 200 percent.

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Plastic bottles are usually made using the Two-Step Method.

  • The material is drained and dehumidified.
  • Plastic with a liquid limit of 0.05 percent absorbs moisture. The plastic is dried to remove the moisture of the created resin to less than or equal to 0.005% to improve the preform’s transparency and physical performance. The following ways of drying are utilized.
  • Oven Dry – The drying is done at 110°C for a total of 8 hours, and after that, the plastic begins to fail. The trays with the material in them are around 50mm thick when placed in the oven. The oven is not linked to the injection machine, and the dried bottle must be transported by hand.
  • Hopper dryer is the most extensively used drying the plastic since it is very cost-effective and works in conjunction with an autoloader, making the process constant and automated.
  • A dehumidifier is identical to a hopper dryer in that it works in tandem with an autoloader, and it is the most effective way to dry. At a temperature of around -32°C, the material dries in, improving a plastic bottle’s toughness and ultimate appearance.
  • The ideal drying temperature is at 150-170°C. The optimal time to dry the Plastic is for it to take about 4 hours. The drying period should not exceed 78 minutes, as this will degrade the Plastic.
  • The procedure is straightforward: heated plastic in molten form is injected into the machine’s injection chamber (2) by rotating the screw barrel (1) till the chamber is filled.
  • When the chamber is full, the screw is pressed forward (3), filling the injection cavity with molten plastic and injecting this into the mould through the nozzle.
  • The temperature inside the injection moulding machine varies; the temperature at the back end of the machine should be around 275°C, the temperature in the middle of the machine is about 282°C, and the temperature at the nozzle should be around 280°C. For the bottle created to have optimal specifications, the temperature at the runner should be around 270°C. (Depending on the design of the mould, these temperatures may vary slightly.)
  • The molten plastic in the mould, known as the preform, should then be cooled. The cooling water temperature used to cool the perform should be between 15 and 20°C, and the pressure must also be controlled. Hence a water chiller is needed. The pressure should be maintained at roughly 500,000 Pa (5Bar). From the mould, the plastic prototype is expelled (4). The preform is now warmed to the proper temperature for the blowing operation.
  • 105°C is the optimal temperature for PET orientation.
  • An air purifier cleans the compressed air blown into the Preform first (). The air must be cleaned because it contains moisture and oil, which will directly impact the bottle’s quality. The blowing machine is attached to the preform (). Air is blasted into the preheated preform using a blower onto the mould after it has been purified.
  • The stretched-blown bottles have a thickness of 0.250.38mm. This thickness is sufficient because the orientation will improve the quality of the products.
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Therefore, the process mentioned above is how plastic bottles are manufactured. You can buy the best bottles from the stretch blow molding machine manufacturers by visiting the official site.


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Niraj Kumar