4 Essential Steps to PET Bottling Manufacturing
The employment of steps to PET bottling manufacturing has led to the creation of a wide range of plastic bottles in different shapes and sizes.
These are bottles that can serve as a storage for water, drinks, beverages, food, each of which can be attributed to the pet bottle manufacturing method.
Generally, bottles are in high demand since they have become a part of people’s everyday lives thanks to their lightweight and durability.
But what makes PET unique?
What is PET?
PET denotes Polyethylene terephthalate (PET) and it is also known as polyester resin.
The material, itself, can either be opaque or transparent depending on its composition.
In the bottling manufacturing process of PET plastics, terephthalic acid is mixed with Methanol to give Dimethyl Terephthalate and water.
The resultant mixture is then combined with Ethylene Glycol at 305 degrees Fahrenheit. The mixture creates a substance called Bis(2-hydroxyethyl) terephthalate and methanol.
There’s a final step that helps to form the polymer while another molecule is released.
What Are the Uses of PET?
The thermal, chemical, mechanical, and dimensional stability characteristics of a PET material allow for the production of strong and durable bottles which are also lightweight.
As a result, PET is used in the production of food and water bottles for food and beverage, personal care and pharmaceutical industries.
PET recycled plastics have also found use cases in food packaging thanks to their chemical inertness and they can be recycled for several other purposes.
Other uses of PET include:
- Transparent films
- Rigid cosmetic jars
- Microwavable containers
- Tape applications due to its high mechanical strength
- Packaging trays and blisters through the use of Non-oriented PET sheet that has been thermoformed
Steps to Plastic Bottling Manufacturing
When it comes to the production of bottles for potable water or food, manufacturers may vary their processes which could add on to the PET bottle manufacturing cost.
Nonetheless, the same general steps to PET bottling manufacturing are employed.
A look at plastic bottling manufacturing process flow chart shows that despite the tweaks that are made by a manufacturer, the same universal method is used.
These steps include:
- Raw Materials
- Building a Preform
- Stretching the Preform
- Cooling and Trimming
1. Raw Materials:
The plastic bottle manufacturing raw materials used in the process is a plastic resin sourced from petroleum hydrocarbons.
The latter is able to create long chains of plastic molecules by taking advantage of polymerization (a process that helps in the creation of polymers or three-dimensional networks by reacting monomer molecules in a chemical reaction).
The petroleum hydrocarbons are then mixed with several chemical compounds.
During a bottle’s production, the resins in PET are cut into small, rounded compressed pieces before they are sent to a bottling plant.
A manufacturer at the plant creates a combination of PET resin pellets with “regrind“.
Regrind is a recycled plastic which has been processed and reduced to flakes.
Regrind is maintained at a quantity of 10 percent of the entire mix. This prevents the plastic from losing a significant part of its physical properties upon repeated heating.
2. Building a Preform:
At a temperature of about 500 degrees Fahrenheit, the PET and regrind mixture is melted using an extruder, a screw reactor machine that:
The extruder features a screw within its build and this screw compresses the PET mixture and injects the almost molten composition into molds.
This mold then forms the bottle preform which is known as a parison.
A closer look at the preform shows a resemblance to a thick-walled test tube already featuring the bottle’s screw top.
On the other hand, the preform cools as it is transported into the blow molder.
If it needs to be brought back up to meet a certain temperature, then it is done.
3. Stretching the Preform:
There’s also a step that helps to stretch the preform in a two-part mold.
The inside of the mold that encloses the preform is shaped to look like a finished bottle. The mold also has a long needle pushing the preform that is suspended with its screw end facing down.
- For its mode of operation, the needle helps to expand the preform upwards towards the mold’s top that will later become the bottom of the bottle.
- At the same time, pressurized air is blown into the preform which helps it to adopt the shape of the mold.
This stretching must be carried out quickly in a bid to ensure that the bottle’s integrity and its consistent shape are not tampered with.
To that effect, some manufacturers have attempted to make the latter possible by welding another bottom piece to the bottle as it undergoes blow molding.
Others, on the contrary, resort to creating a bottom using the perform and the rest of the bottle.
4. Cooling and Trimming:
There’s the final step that requires the bottle to be cooled immediately. This is so the bottle doesn’t lose its shape as it is pulled down by gravity in its heated state.
A cooling method some manufacturers use is to circulate cold water or nitrogen in its liquid state through the mold.
Another option for cooling is to fill the bottle with air at room temperature.
Finally, a clean bottle will emerge even though there might be an issue such as flashing (excess material on the product and needs to be removed) occurring at the region where the halves of the mold met.
The excess material that is created is trimmed away and then passed to the regrind to be used.
The steps to PET bottling manufacturing are quite simple but still need to be executed with great care and accuracy.
When that is done, the bottle will come in a remarkable shape that is expected with little or no flaws.
These steps also show how significant each procedure is in ensuring that the final product is of good quality, durable, and can meet consumer’s demand for bottles.
Now if you’re a manufacturer who intends to create PET bottles, these are methods to fall back on.
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