Plastics are man-made organic materials which can be moulded into required shapes by the application of heat and pressure. There are more than 50 basic types of plastics in industrial use today. Each plastic has different material properties. The artefacts in this group have been made from eight different plastics.
Polyethylene is one of the simplest and most commonly encountered plastics. It is light, and has a good balance between impact strength and flexibility. As a result it was used to make the first squeezable packaging. It also accepts print easily allowing the application of product names etc. The fact that it is also cheap and easy to process made such packaging economically viable. It is also food safe, has good chemical resistance, low moisture permeability, and can cope with moderately hot and cold temperatures. It is therefore suitable to be used as food containers. Its flexibility aids the extraction of frozen contents. Its capacity to be translucent can allow a hint as to the contents.
The characteristics of polypropylene are similar to those of polyethylene except that it has greater rigidity and is therefore, for example, capable of holding several litres of water as in the watering can. It also has better fatigue resistance and can be folded like paper as in the case of the colander, which is sold in a flat pack. The fact that it can withstand very hot temperatures means that it can go in the oven, as in the case of the casserole.
Silicone rubber has outstanding heat and flame resistance and is food safe. It can therefore be put in the oven. The fact that it is soft and flexible means however that it is not suitable for cooking, say casseroles, but it is, by contrast, ideal for baking cakes, and, being, in addition, anti-adhesive, it is a material that facilitates their extraction from the mould. The sensuous feel of silicon means that the oven mitt is a delight to wear and its slightly transparent vibrant blue is a result of the grades of transparency in which the material can be produced. Silicone rubber is however expensive: such products are thus aimed at the luxury market.
PMMA or acrylic (often known by the trade name of Perspex) is hard, rigid and light-weight, all characteristics appropriate to the use of this product. The characteristic, however, that it utilizes in particular is the sparkling clarity of acrylic showing off the blue liquid and silver glitter enclosed within the toilet brush handle and base.
PVC comes in different grades of rigidity & flexibility and strength & softness. The base and top of the sandals utilize these characteristics appropriately. It is cheap, durable and easy to process and thus a suitable material for the mass-production of inexpensive footwear. PVC is also weatherproof. Thus it is a good material for exposure to the sun. It also takes up colour beautifully, as this example demonstrates.
Polystyrene can be transparent or opaque. It is always rigid, and easy to mould and colour. Note how it has taken up the different colours in the egg cups. The material also has low water permeability, hence its use to make the watering-can. It is also cheap and thus an ideal material for products being made in very large numbers as in the case of the pen.
ABS is another low cost rigid material and is characterized by outstanding impact strength. This means that it is an excellent material for telephones, which so often get dropped, and for the Freeplay Radio which was designed to have an active life. Its glossy, scratch resistant qualities give such products a long lasting attractiveness. Important for Lego also is its good dimensional stability. The bricks would not work if they warped and the studs did not fit.
Melamine is another rigid plastic but of middle cost. Thus it is not used for products to be produced in vast numbers. Both these examples are life-style products by designers of repute. It is not only heat and flame resistant but also self-extinguishing and thus a very good choice for an ashtray. It is also non porous and has no smell or taint and is thus suitable for eating and drinking vessels. In addition it is stain resistant.