Polyolefins are produced from oil or natural gas by a process of polymerisation, where short chains of chemicals (monomers) are joined in the presence of a catalyst to make long chains (polymers). Polymers are solid thermoplastics that can be processed in two ways – by film extrusion or moulding. During film extrusion the polymer is heated and forced, in a molten state, through a die to produce thick sheet, thin film or fibres. The thickness of the film can be varied 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 an extruder, and then forcing it into a mould where it solidifies into the required shape.
Benefits of polyolefins
Because of their versatility, Polyolefins are one of the most popular plastics in use today. Their many applications include:
- LDPE: cling film, carrier bags, agricultural film, milk carton coatings, electrical cable coating, heavy duty industrial bags.
- LDPE: stretch film, industrial packaging film, thin walled containers, and heavy-duty, medium- and small bags.
- HDPE: crates and boxes, bottles (for food products, detergents, cosmetics), food containers, toys, petrol tanks, industrial wrapping and film, pipes and houseware.
- PP: food packaging, including yoghurt, margarine pots, sweet and snack wrappers, microwave-proof containers, carpet fibres, garden furniture, medical packaging and appliances, luggage, kitchen appliances, and pipes.
Polyolefins (family) includes:
