Biotechnology- Plastics

Additives in plastic Plastics can become composites or smart materials when their properties are altered by the addition of additives. Without additives the application of plastic products would be very limited. Additives makes plastic: Easier to process Enhance their aesthetics Makes them safer Reduces their impact on the environment

Plasticisers These are added when plastics need to be soft and flexible; for example PVC on an electrical cable. Plasticisers are added as liquids to improve the flow of plastics for moulding. They also lower the softening temperature and make them less brittle. The most common plasticisers are organic compounds known as phthalates. As they are organic they also decompose and bio degrade relatively quickly. Plasticisers are also added to aid injection moulding and ensure the free flow of plastic within the machine.

Fillers & Foamants Fillers are an economic measure to allow plastic to be bulked up. By adding them the manufacturer reduces the overall cost of the plastic being produced. Foamants have much the same use; The volume of the plastic increases however the elasticity of plastic also increases making it appear more springy. This means the plastic can be pushed or pressed and it will spring back to its original shape. Plastics that contain foamants are also used as buoyancy aids. The cell structure allows air to get trapped within the cells thus making it lightweight and float. Other applications include heat/sound insulation.

Fibres Plastics on their own are sometimes not strong or stiff enough to carry out the task needed. For this reason GRP or carbon fibre is used. These are composite materials that use a polymer matrix reinforced with glass or carbon strands and bonded with an epoxy or polyester resin. The result is an extremely strong plastic composite. Applications of GRP: Boats/ventilation systems Applications of Carbon Fibre: Golf club shafts/ F1 cars

Stabilisers Over time polymers can deteriorate for example when they are exposed to ultraviolet light (reactions occur that cause the polymer to degrade). For this reason stabilisers are added that help to stop or slow down the degradation of polymers. Stabilisers consist of: Heat stabilisers Light stabilisers Bio stabilisers

Stabilisers continued Heat stabilisers are put into plastic to stop plastics decomposing during any manufacturing process that uses heat (i.e. injection moulding). Light stabilisers are put into plastic as exposure to sunlight or UV light can make plastics go brittle or break down (sometimes seen in uPVC windows). Bio stabilisers stop the break down of plastic due to microbiological attack. Plastic can become stained, discolour and even smell. Plastic under biological attack also loses its mechanical properties.

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