How Plastic Bottles Are Made – Plastic Bottle Manufacturing Process
If you read this article, you can expect to become more informed about how bottles are manufactured, the design or process limitations, and what materials may be viable options for you.
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Do you need to start manufacturing your plastic bottles?
Maybe your beverage factory is looking to move the bottling operation in house and wants to know where to begin?
If you read this article, you can expect to become more informed about how bottles are manufactured, the design or process limitations, and what materials may be viable options for you.
01.
What Do You Need Plastic Bottles For?
This should be the starting point; without knowing the result you’re aiming for then, you cannot plan accordingly.
Within the world of plastic bottles, you will discover many sizes, shapes and colours.
Some will be more suited to a particular use than other choices, so it is essential to get this right from the start seek professional guidance if uncertain.
If you have a specific liquid that needs to be contained, stored and transported within a plastic bottle, then making the correct decision will ensure the contents are safe and arrive at the end-user as planned.
Retention of tastes, flavours, smells, and physical properties must also be considered here.
Spending time and resources on developing a new product only to deteriorate or change once packed in a bottle can lead to an unhappy customer and subsequently returns, complaints and lower than projected sales.
The same is true if there are frequent failures or weaknesses within the packing. It can easily be damaged; leaking units or carbonated beverages that do not retain their gaseous properties are undesirable.
Selecting the suitable material for your bottles is essential also; the manufacturing process used is equally so.
As you will discover, not all materials can be handled the same way or processed into bottles suited to your particular application.
One material molded into bottles using several methods will yield vastly different results. To understand more about plastics as a whole, [this ] ?resource might be helpful in additional reading.
02.
Which Materials Are Used For Making Plastic Bottles?
Plastics used for bottles can be divided into two main groups: below, within these groups, you’ll find seven main types of plastic for manufacturing bottles.
Thermosoftening plastics, also known as thermoplastics or thermoplastic polymers, are extensively used in bottle production.
These are recyclable and can be reshaped by heating again, making them a good choice for plastic bottles on a mass scale.
They will be turned into a re-grind during the recycling process and may then be blended with a polymer base to unlock a new lease of life and reduce waste.
Blow molding is an effective way to transform this polymer into a bottle.
Thermosetting polymers are the other grouping, also referred to as thermosets.
Once formed, these cannot be reheated and used again in another shape; therefore, they are non-recyclable or impossible.
Since the bonds created between molecules are rigid and crosslinked effectively, this type of plastic tends to be more robust.
Knowing this is useful when establishing how bottles are made and which material to go with.
03.
What Plastics Are Used For Bottles?
Your next step in establishing the best manufacturing processes will be to select the correct material. Below you’ll find the most commonly used plastics for bottles.
Each will have its particular properties or reasons for being selected; this is based mainly on the temperature of liquid benign contained at the point of bottling, whether it’s a food and drink classified beverage, pressure which bottled under and storage/transportation conditions.
This plastic choice is most popular within the beverage industry . It is used for the properties of strength, ability to contain gases well and not transmit bad tastes or odours into the liquid.
Because it is transparent or can be tinted a shade of clear plastic, this also makes it an appealing choice as companies can stand out with their colour schemes amongst a packed shelf or fridge.
Also lightweight and able to cope with its demands during transportation, this material choice remains a favourite within the beverage bottling industry and will continue to be for the foreseeable future.
Single-use plastic bottles for water and carbonated drinks are the main application are generally regarded as a safe and inexpensive choice.
Both Similar to normal PET in many respects, this Glycol modified variant is more flexible in manufacturing methods.
You could use it to create your bottles on equipment that you would typically use with other plastics such as PC or PVC, which can prove very useful if your bottle manufacturing factory works with a range of materials.
The properties found in regular PET are affected so that you would be less likely to use this plastic for beverages but self-care liquids like shower gels and shampoo, hand soaps and cleaning detergents.
For both PET and PETG, there is no option to include handles within the shape of your bottle.
When seeking a transparent and shiny finish on the bottles, this option is ideal, along with regular PET.
In recent years has lost popularity to other plastic choices for some applications in the food and drink beverage industry.
However still widely available and extensively used for personal care products or oils that could be adversely affected by oxygen exposure.
Generally, pretty good chemical resistance or gas permeability can hold up to impacts but not heat very well, so it is solid and challenging, but up until a point.
It can be extrusion blow molded to incorporate more intricate detailing such as handles or injection stretch blow set with no handles. It is versatile in manufacturing techniques and is a cost-effective solution for bottles.
The use of this plastic is desirable due in part to its clear and challenging properties.
It is not too dissimilar to PET in some comparisons, yet it can be sterilised and exposed to higher temperatures within a bottling factory without deforming or warping.
Since thicker can withstand more impact forces or pressure, it has been a popular choice for markets such as baby bottles or other products likely to be dropped.
Shipping costs can be higher due to the extra weight when using this choice.
You’ll also want to consider this material choice for your bottles should you need hot or warm liquids and bottle sterilisation when filling.
The PC can withstand higher temperatures than some other materials available but does not cope very well with impacts or drops. It is more brittle and fragile, especially in colder environments.
This fragility can be troublesome when the contents need to be kept in the fridge.
This finish is a shiny, glossy look and feel, similar to the PET equivalents.
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It is a plastic choice that has been a favourite for many applications in bottle manufacturing for several reasons, including the chemical resistance, strength, flexibility, and tolerance to impact on its surfaces.
Typically, it can be supplied in translucent finishes or with the addition of coloured polymers, pigments, or additives, which will affect how it looks and the performance properties.
The production of milk bottles is a perfect example of this plastic being used. The soft and robust packaging doesn’t cope well with hot liquids or being exposed to high temperatures where it will easily deform.
It can be a pretty soft and squeezable choice.
In some ways, these plastic shares properties with the previously mentioned HDPE; they are pretty similar from a chemical or molecular makeup.
However, a key difference is rigidity and the ability to be more squeezable without succumbing to material fatigue and losing its integrity over time.
This plastic is also less tolerant to chemicals that can break down or affect the material.
Compared to the more matt-looking translucent HDPE, glossier finishes are possible.
If you’d like to read more in-depth about materials suitable for making plastic bottles check here .
Also, another resource that could prove to be useful is this site .
04.
How Plastic Bottles Are Made - The Manufacturing Techniques
Preforms or Parisons
The starting point for your bottle, if manufacturing the whole process start to finish in-house within your bottling plant, then the likelihood of you creating your preforms is quite probable.
A preform can be defined as a small plastic cast if you like, having been calculated very accurately, to produce the bottle you’d like once hot pressurised air is blown into it.
They have the neck of the bottle, complete with thread, formed as part of the initial cast.
Having had the exact amount of plastic provided to give a specific wall thickness, colour and tensile strength when full size and shape.
A parison is a hollow plastic tube that gets heated and blown to shape within the same machine.
This less complex casting is handled whilst still warm and blow molded into the desired bottle before it cools, saving energy.
05.
You Can Split Blow Molding Into Four Main Steps For Bottle Production As Detailed Below.
Whilst vastly different in some aspects, the Blow Molding Process shares the same commonalities across the four main steps involved, which are:
06.
Extrusion Blow Molding To Make Bottles (EBM)
In this manufacturing method for plastic bottles, the material is heated until it becomes workable, then extruded into a hollow tube, known as a parison.
This parison then goes onto the next stage, where a cooled mold is used with hot pressurised air. Firstly, the mold clamps the parison into position.
A blast of air inflates the hollow tube to desired size and shape based on the mold, where it cools rapidly when making contact with the colder metal.
This gives you a bottle that will require trimming or additional machining of the ‘flash’, which is, in essence, the extra material left over; you can witness this yourself by a line on the base of the bottle known as the pinch offline.
Often this will be done whilst the bottle is still in the mold, or it can be an additional step further along the production line.
Characteristics unique to the EBM bottles include handles, labels molded in and offset necks—also the ability to retain multi-layering of different materials into the same output bottle.
Types of plastic commonly used for bottle production with EBM are HDPE, PVC, PC, PP, and PETG.
07.
Injection Blow Molding To Make Plastic Bottles (IBM)
This manufacturing method is prevalent for a range of plastics and can be sued to produce a good selection of sizes and shapes.
You’ll need to insert a preform of plastic where it becomes heated and blown to teh desired bottle with high accuracy and thin-walled structure.
Wall strength isn’t as high or impermeable as the ISBM produced bottles as teh polymer molecules are not stretched and oriented.
Due to this, it can be used for liquids but not carbonated ones.
Popular material choices include; HDPE, PET, PP, PVC, LDPE.
08.
Injection Stretch Blow Molding To Make Bottles (ISBM)
Techniques developed which builds on the standard injection blow molding by using a metal rod to stretch the blown plastic into its final shape.
Doing so increases the overall wall strength of the bottle as the molecules become more tightly joined to one another. Also, the bottle becomes more impermeable to gases, making it ideal for carbonated beverages.
This method is used for PET plastic bottles in a transparent shiny finish and is considered the industry standard globally.
09.
Injection Molding For Making Plastic Bottles
The extent of this manufacturing method for bottles is usually reserved for creating bottle lids or caps.
It is not used to create bottles, but somewhat hollow containers open on one side. They don’t have necks, threads or the contours of a bottle.
Another technique that can be used for manufacturing lids or caps is compression molding, not a bottle but an item used in conjunction with.
The use of thermoset plastics here is typical.
10.
Co-Extrusion For Making Plastic Bottles
This article has a relatively recent development in plastic processing compared to some more time-tested methods.
However, don’t let its relatively new status deter you from the potential when it comes to your specialist bottle needs.
Used to produce multi-layered bottles that capitalise on properties of specific polymers, then combine them for best effect.
These layers can increase strength, durability, permeability and resistance to chemicals or breakdown from the contents stored inside.
11.
Conclusion
Once you’re clear on the type of liquid you’d like to contain, you should establish which manufacturing techniques and materials are best suited for your processes.
This will be used as a reference when either looking to manufacture yourself or outsource this aspect of the bottling operation.
Should you want to explore what the options are for your plastic bottle manufacturing specifically to your current operation, feel free to contact us directly via the website or email [email protected]