Polyolefins is the collective term for the kinds of plastics that include polyethylene, namely low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE) and polypropylene (PP).
The word polyolefin means ‘oil-like’– It comes from the oily or waxy texture of plastics types that include polyethylene. POLYCO facilitates the recycling of all the different types of polyolefins used in packaging, including :
- Low-density polyethylene (LDPE) – Examples: shrink film, carrier bags, and heavy-duty refuse bags.
- Linear low-density polyethylene (LLDPE) – Examples: stretch film, industrial packaging film, thin-walled containers, and heavy-duty, medium and small bags.
- High-density polyethylene (HDPE) – Examples: crates and boxes, bottles (for food products, detergents, cosmetics), food containers, industrial wrapping, carrier bags, and drums for food, beverages and chemicals.
- Polypropylene (PP) – Examples: food packaging (e.g. yoghurt and margarine tubs)
How are polyolefins made?
Polyolefins are produced from substances that are rich in carbon: coal, oil or natural gas. In South Africa, this means mainly coal. Polyethylene (the substance common to all polyolefins), is made up of many molecules of ethylenes linked together to become one molecule, called a polymer.
Thus ‘poly’ (many) + ethylenes = the polymer called polyethylene (or also commonly called polythene).
Most polyolefin packaging materials are made through film extrusion or moulding :
- During film extrusion the polymer is heated until it melts. It is then forced through a die to produce thick sheet, thin film or fibres. Depending on the thickness of the film, it can then be used to produce anything from lightweight food packaging wrap to much heavier film for agricultural use.
- The moulding process involves heating and compressing the polymer in a barrel. It is then forced (blown or injected) into a mould and cooled. The plastic items that are made in this way can be anything from crates and boxes, to bottles and food containers
Did you know?
- Polyolefins represent more than 50% of all polymers consumed in South Africa.
- Polyolefin raw materials are cost-effective. Their densities are the lowest of all plastics – meaning more products per kilogram of material.
- Polyolefins are successfully recycled into new plastic products.
- Polyolefins recycling rates can increase if consumers separate their recyclables from the rest of their waste.
Identification guidelines for polyolefins
How do I recognise them?
- Look out for the polyolefin recycling numbers on your packaging. The material identification codes for polyolefins are numbers 2, 4 and 5. These numbers are used when sorting for recycling and will also tell you that the item should go into your recycling bin or bag!
- Polyolefins will float in clean water (because they have a specific gravity of less than one – they are lighter than water).
- They become soft and pliable when heated and hard when cooled (they are ‘thermoplastics’). This means they are recyclable and can be cooled and heated multiple times.
- Polyolefins are extremely suitable and safe for packaging. This is because they are ‘chemically inert’ materials, which means they do not interact with other materials. The contents of polyolefin packaging – including foodstuffs – cannot absorb harmful chemicals, additives or by-products from the container.
Click here to view the guidelines to identify polyolefins.
Polyolefins – recycling codes 2, 4 and 5 – are some of the most popular plastics. They are used extensively in packaging and are recyclable as per the table BELOW :
Polyolefins and safety
- Polyolefins are chemically inert materials and do not react with the contents. This makes them ideal materials for food packaging. There are no harmful chemicals, additives or by products that can be absorbed by the contents and therefore consumed by the user of the packaging. Polyolefins are extremely safe in contact with food.
- Polyolefins soften at temperatures below that of boiling water and should not be used at high temperatures as the material will soften and may even melt. Molten plastics can cause serious burns. Do not use polyolefins for the cooking of food or the boiling of water as it will soften. The material will still not release harmful chemicals into the contents, even at melting temperatures.
- Polyolefins also do not maintain their strength at extremely low temperatures. Care should be taken when polyolefin packaging is taken from the freezer as it may crack open when dropped whilst frozen.
- Polyolefins are safe to use at ambient temperatures.