What are Polyolefins? - PolycoPolyco

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 :

Polymer Identification Code
Polyolefin Name	High-density polyethylene (HDPE)	Low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE)	Polypropylene (PP)
Definition	Packaging made from HDPE has very good chemical resistance, and can therefore be used for bottles and drums for a wide range of chemicals. HDPE can also be made into opaque (not clear) film for packaging.	Film made from low-density polyethylene (PE-LD) and linear low-density polyethylene (PE LLD) is strong and tough and is used for general packaging and wrapping of consumer goods.	The inherent stiffness of polypropylene (PP) makes it ideal for thin-walled packaging items. Various kinds of film from polypropylene are used for different applications. They are different in the way they look and behave. Film-extruded clear PP films are very strong, the biaxially orientated PP (BOPP) films are shiny, clear and crackle when handled. It is therefore ideally suited for integral lid closures and containers like tablet vials. The bulk of bottle caps and closures are made of PP.
Identification	Translucent and identified by a crackling sound when handled.	Translucent or foamed.	Translucent and very (glass-like) clear.
Examples	Crates and boxes, bottles (for food products, detergents, cosmetics), food containers, industrial wrapping, carrier bags and drums for food, drinks and chemicals.	PE-LD: shrink film, carrier bags, and heavy duty refuse bags. PE-LLD: stretch film, industrial packaging film, thin walled containers, and heavy-duty, medium- and small bags.	Food packaging, including yoghurt and margarine tubs. Buckets made of PP packaging are used for detergents, peanut butter, paint and animal feed. Stationery items, confectionery and even clothing. PP film is also used to manufacture tapes for woven tape applications as cement, bulk and feedbags. Non-woven textile applications for PP include personal hygiene products.

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.