Article written by Pete Shaw
Introduction
As part of the Water and Waste project, we are interested in the types of plastic that are used for packaging foods and drinks. There are two main reasons for this. First, we want to find out how much there is of the different types of plastics, which will give us an idea of the potential to collect and recycle waste packaging from people’s homes. Secondly, we want to find out which types of plastics go where – are there some that are already collected and recycled, and others that end up as scattered litter in the environment?
This type of information will help us to change things so we can make better use of the resources we have and improve our environment.
Uncollected waste blocks surface drainage in Nima, Accra
We hope you found this guide useful. This is part of ongoing work on the Water and Waste project, and we will update these pages as and when our approach evolves. There is a research paper on this approach and its accuracy that is currently under review; we’ll add a link to this paper in due course
How to identify packaging plastics
①
Sometimes it can be quite simple to identify the type of plastic used for packaging. You may have seen labels printed on bottles and wrappers that tell you what they are made from. If you collect a pile of packaging waste from somewhere and everything is labelled like this, it is easy to work out how much you have of the different types of plastics.
Often, there are no labels and you have to do something else if you want to find out which types of plastic packaging is made of. This can be done with laboratory equipment, but this can be expensive – and you might need an expert analyst to do the work.
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If you don’t have labels and don’t have a laboratory, there is another way. The plastics we use most are all slightly different and we can use these difference to help us identify them.
Here, we provide a guide on how to do this. All you will need are some simple tools:
- A sharp knife
- A plain glass beaker of water
- A pair of scissors
Rigid or flexible?
First, you’ll need to decide if a piece of plastic packaging is “rigid” or “flexible”.
Flexible packaging is typically a bag, sachet, wrapper or film – something that can easily be reshaped.
Rigid packaging is typically a bottle, tub, or tray – something that holds its own shape.
Follows the next steps to identify the type of plastic. The steps are slightly different for flexible and rigid packaging.
How to identify flexible packaging plastics
First, rub the packaging together between your fingers and thumb. Does it make a “soft, swishing” or a “crinkly” sound?
If it makes a soft, swishing sound, then this will most likely be Low Density Polyethylene (LDPE).
If it makes a crinkly sound, then it could be one of two other plastics.
Cut a strip of the packaging about 1cm wide and 10cm long. Hold the piece firmly between two hands and pull; does it stretch?
If it stretches, then this will most likely be High Density Polyethylene (HDPE). If it doesn’t stretch, it is most likely Polypropylene (PP).
How to identify rigid packaging plastics ①
You’ll need your sharp tools and glass beaker of water for this.
Carefully cut the packaging with your sharp knife. Is the cut edge smooth or sharp to the touch?
If it is sharp to the touch, then this will most likely be Polyethylene terephthalate (PET or PETE).
If the cut edge feels smooth, then you’ll have to do some more tests.
How to identify rigid packaging plastics ②
Cut the packaging with a sharp knife, held at an angle of 30-45° to the surface.
If the cut edge appears white, then this will most likely be Polypropylene (PP).
If the cut edge doesn’t look white, you’ll have to do another test.
How to identify rigid packaging plastics ③
Cut three pieces of the packaging, each about 1cm square.
Drop the pieces onto the water in your beaker and push them under the surface. Make sure there are no air bubbles on the pieces of plastic.
If the pieces of plastic float, then this will most likely be High Density Polyethylene (HDPE).
If the pieces don’t float, it is most likely Polyvinyl Chloride (PVC).
Gallery of photos during our research discussion in identifying and characterising plastics using low-cost methods
