How are plastic bottles made?

As a plastics bottle manufacturer, many new customers that approach us are interested in how plastic bottles are actually made. At B&I Polycontainers, we really enjoy taking these customers through our factory and showing them the entire process.

However, many people who do not visit us directly don’t have the time or demographical opportunity to visit us and check out how our factory actually turns plastic into plastic bottles for everyday use. That’s why this blog will explain exactly how our bottles are made in a very basic and easy to understand way.

If you would like a more detailed explanation and to see the bottle making process in action for yourself, please feel free to contact us. We will be happy to give you a full tour of the process.

For now, let’s begin by taking a look at the plastic bottle making process.

 

STEP ONE – Raw Materials

Every plastic bottle you see begins life as a plastic pellet – or rather, hundreds of thousands of plastic pellets. These pellets are the resit derived from petroleum hydrocarbons. The supplier of these pellets creates long chains of plastic molecules through a process called polymerization, and then mixes the material with several chemical compounds. They cut the resin into small pellets and send it on to us. 

Sometimes, we mix the resin pellets with “regrind” – recycled plastic that has been reduced to flakes. Plastic loses some of its physical properties when repeatedly heated, so we often limit the amount of regrind we use, typically capping this ingredient at 10% of the total mix. Unless producing clear bottles, dyes are introduced to the mix as well.

 

STEP TWO – Heating and Compressing

This is where the production diverges a little based on whether we’re making PET bottles or other products.

PET bottles must first be made into a preform before we move onto the next step. Currently, this is taken care of by a third party who we then buy the preforms from. We then use the preform for the next step,
For other forms of plastic, we heat the pellets and regrind mix at temperatures of about 260 degrees Celsius. A screw inside the extruder compresses the mix and injects the nearly molten material into moulds. 

 

STEP THREE – Moulding, Cooling and Trimming

Finally, this molten mix is pushed down into the mould, which is compressed with extreme pressure and cooled. This forces the molten mix to become the basic form of a plastic container, but this blow molding process must happen quickly in order to maintain the bottle’s integrity and consistent shape.

The bottle must be cooled almost instantly or it will lose its shape when gravity causes it to creep downward in its malleable, heated state. Some manufacturers cool the bottle by circulating cold water or liquid nitrogen through the mould, while others elect to fill it with a shot of air at room temperature. The mold typically yields a clean bottle, but some flashing may occur at the bottle seams, where the two mould halves meet. If so, operators trim away the excess material and add it to the regrind.

In terms of PET bottles, the preforms are preheated and then blown to shape using compressed air.

 

STEP FOUR – Quality Control and Packaging

The above process is continued for each plastic bottle created, but that isn’t the end of the plastic bottle manufacturing process.

Quality control measures are conducted throughout the manufacturing process, and a final check is performed before the bottles are packed to specification, stamped and marked for storing.

 

See it first hand

While it is great to find out how plastic bottles are made, nothing can compare to seeing it first hand in the factory of its origin. From PET bottles to PVC, B&I Polycontainers makes thousands of bottles every day, and each of them undergoes the same rigorous process above.
If you’d like to see how a plastic bottle is produced first hand, contact B&I Polycontainers today and we’ll gladly give you a full tour of our factory. Alternatively, check out our products here, to find your ideal bottle today.