Plastic bottles are ubiquitous – most of us will have grown up with them being a regular feature of our lives, no matter our age. They’re obviously useful products, but of course they also come at a cost – plastic bottles can’t be made without either extracting natural resources, or recycling old bottles. This is why it’s so important to recycle – because every bottle that doesn’t get recycled represents a little bit more of earth’s natural resources that gets used up.
These bottles are actually made of many different types of plastics – here’s a quick guide to the most commonly used types of plastic for bottles!
What are plastic bottles made of?
Well, it won’t be much of a surprise to learn that plastic bottles are made out of plastic! But it might surprise you to learn that there are actually many different types of plastics that can be used to make plastic bottles.
Here’s a look at some of them!
LDPE/HDPE (Low and High-Density Polyethylene)
These two variant forms of polyethylene are extremely common in plastic bottle production. In fact, HDPE is actually the most commonly used plastic for making plastic bottles. HDPE is particularly good for making plastic bottles out of because it has a good resistance to solvents, is waterproof, and has a favorable strength-to-density ratio.
HDPE is an extremely commonly used plastic worldwide, being used to make many other things aside from plastic bottles, such as pipes used in construction, toys, bin, bags… the uses for HDPE are extremely wide!
LDPE is typically used for bottles that need to be at least a little bit flexible – such as squeezable bottles. A bottle made from LDPE will be less strong than an equivalent bottle made from HDPE, but it will be more ductile too.
Around 100 million tons of polyethylene in its various forms are made each year – making polyethylene the most commonly used plastic on the planet. Nearly 35% of the plastic made in the world is some form of polyethylene!
PET (Polyethylene Terephthalate)
Polyethylene terephthalate is an extremely commonly used plastic in many industries, but two industries in particular – plastic bottles, and man-made fiber products. If you’ve used a plastic drinks bottle that had a carbonated beverage, then the chances are extremely high that the bottle was made from polyethylene terephthalate (abbreviated as PET or PETE).
It is a member of the polyester family of plastics – which is one of the most widely used types of plastic in the world, being able to be used in a wide variety of applications. In fact polyethylene terephthalate is the most common thermoplastic polymer resin in the polyester family of plastics.
In fact, PET is commonly referred to simply as “polyester”.
It’s used in an extremely wide range of ways – not just in plastic bottles and other containers, but most notably in clothing and other fabric products. Around 60% of the worldwide use for PET is in synthetic fiber products!
30% of the polyethylene terephthalate that’s produced in the entire world goes to making plastic bottles – which, as it’s the most commonly used form of one of the most widely used families of plastics in the world, should show you how much is used in plastic bottle production – 3.1 million tons of PET is produced annually in North America alone!, which means that nearly a million tons of this plastic is used in North America each year to make plastic bottles.
Around 18% of the world’s production of synthetic polymers revolves around the manufacture of PET.
Polypropylene is yet another type of plastic that can be used in the production of plastic bottles. And, of course, like many other types of plastic, it also has an extremely wide range of uses outside the plastic bottle industry!
One of the useful properties of polypropylene is that it is very stable at high temperatures. This means that it can be steam sterilized, as it can withstand temperatures up to 220 degrees Fahrenheit without losing structure.
However, a key weakness of polypropylene is its poor resistance to impacts. It does provide a good barrier to moisture, though, and excellent chemical resistance.
Polycarbonate makes for extremely clear bottles that are easy to view the contents of. It’s a commonly used plastic in medicine and scientific laboratories for this reason. It’s perfect for this job in a few ways.
Not only is polycarbonate able to make an extremely clear bottle, but it can also cope well with rough handling, and can even be sterilized in an autoclave.
However, compared to other plastics used to make bottles, it can be quite expensive. This means that, compared to other plastics, it’s not as common to see polycarbonate used to make bottles, Typically, only expensive bottles will be made from PC – such as pricey reusable water bottles, or certain bottles in labs. A bottle that needs to be able to cope with rough handling, and needs to let the contents be clearly visible too is a great candidate for being made from polycarbonate.
What is a polymer?
The plastics that are used to make plastic bottles are a type of material called polymers. Polymers are a very wide ranging group of materials – different polymers can have very different properties and applications. Not all polymers are plastics either – there are a great many natural polymers. In fact, your hair and nails are made from a natural polymer called keratin. Proteins are another natural type of polymer – something that all living creatures create!
Polymers are essentially large molecules, sometimes extremely complex, that are formed from chains of smaller molecules (called monomers). The only difference between some polymers made from the same materials can be the exact arrangement of these links and chains.
These monomers link together in absolutely huge chains, sometimes millions of atoms long for each single molecule in the polymer. Of course, that’s still tiny by human proportions, but in terms of molecules, these chains can be absolutely massive – so big that they are classified as macromolecules by scientists.
There are many more plastics that bottles can be made from, but these are the most common types of plastic in use today to make them. As so many bottles are made each year, it’s important to remember to get the most out of them – so reuse and recycle!