PolymersPolymers or ’plastics’ are a relatively modern material. They were firstproduced in the early twentieth century; their use grew rapidly duringthe second half of the century, and continues to grow today. Polymershave provided alternatives to many packaging requirements previouslycarried out by metal, glass and boards, and have often completelyreplaced these materials.

ThermoplasticsThermoplastics are polymers that, once heated, can be formed into avariety of interesting shapes using different forming techniques suchas blow moulding, vacuum forming and injection moulding (see pages44-46 for more on these techniques). Once the polymer has cooleddown, the shape then remains permanent. The same thermoplasticcan be heated, softened, shaped and cooled many times over, whichmeans these materials are ideal for recycling. Thermoplastics are used in a wide range of graphic products, from the Styrotoam models that you make in the classroom, to the shop signage you see on the high street and the injection-moulded casings of many electrical products, such as games consoles.

Polymers in electrical productsMany electrical products make use of polymers to form their protectivecasings. Polymers have a number of advantages over metal casings:

• They are less expensive to produce in large quantities andthermoforming processes, such as injection moulding, can produceextremely intricate shapes• They are non-conductive — they do not conduct electricity — soproducts are safe to handle• They have excellent heat—resistant properties, which is an advantagewhere electronic components can become quite hot with prolongeduse (just think about your games console when you have beenplaying a game tor a long time).

Polymers

AcrylicAcrylic is usually cast into sheets but is also available in rods andtubes. It is self—finishing, so it does not need to be painted. Acrylic hasa wide range of uses within graphic products, from making models toshop signage.

When making a model, acrylic is a versatile sheet material as it can beeasily cut and bent using a strip heater. Thinner sheets of acrylic canalso be vacuum-formed just like polystyrene or PVC. Acrylic is availablein a Wide range of colours, and has an excellent surface finish, whichadds a quality feel to any model.

In shop signage, a higher quality acrylic is used which must satisfyseveral high performance requirements. it has to be able to:

•Withstand extreme weather conditions, such as heat in the summerand cold in Winter.•Be chemical—resistant to pollution and detergents•Be durable by resisting |ong—term stresses, such as being. outdoorsfor prolonged periods•Be easy to fabricate and to make relatively complicated shapes out of•Have excellent aesthetic properties, to attract a customer’s attentionand give a high-quality look for the business.

Polymers

Styrofoam

”Styrofoam" is a polystyrene foam manufactured for the constructionindustry for insulating buildings. It also makes an excellent modellingmaterial. The process of making the foam results in a material withuniformly small, closed cells, which gives it all of the properties that amodelling material should have, including:

• Great rigidity and high compressive strength so it cannot be bent outof shape easily• Easy to cut and shape with a range of hand tools• Sheets can be glued together using PVA to form larger blocks• A smooth surface finish when sanded• Can be painted to give a good quality finish if desired.

Polymers

Expanded polystyreneExpanded polystyrene is used in fast—food packaging because it is:• hygienic — disposable cups and plates mean germs and bacteria aresimply thrown away with the rubbish instead of multiplying in achipped coffee mug, for instance.

• strong, yet lightweight- protects against moisture and keeps itsstrength. Containers and lids close tightly and prevent any leakage ofthe contents. it can be moulded into a variety of structural packageswhich complement its excellent cushioning properties in protectingy the contents of the package.

• efficient- provides excellent insulation. Therefore, hot food can bekept warm for longer periods. It also means that the package doesnot become so hot that it cannot be held in the hand.

• economical- products are generally cheaper to buy than disposablepaper products and much cheaper than reusable service ware (e.g.china). This is because only about five per cent of the foam packageis actually plastic — the rest is simply air

• convenient- with today’s busy lifestyles people want food to beavailable instantly, and polystyrene is an economical way of servingpeople with their fast food.

•Expanded polystyrene is also used in the protective packaging ofmany delicate products, such as electrical products; shape—molded,it fits snugly around products which are placed inside corrugatedboard boxes.

Polymers

Polymers in commercial packaging

Polymers are widely used in commercial packaging because they are:•lightweight and versatile•strong, tough, rigid, durable, impact and water—resistanteasily formed and moulded• easy to print on• low—cost• recyclable.

Polymers can be identified by a code, usually stamped onto the base of the package or printed onto the label. An internationally recognised coding system means that you can easily identify polymers and sort them for recycling. Each polymer has its own useful properties, making it suitable for use in different areas of the packaging industry.

Disadvantages of polymers - Environmental concernsThe main disadvantage for the widespread use of polymers centres on concerns about how sustainable they are. They are made from oil, which is a finite resource that requires a lot of energy to process, producing high levels of pollution. Manufacturing techniques for polymer-based packaging, such as blow moulding, also consume a lot of energy. Then comes the problem of disposal. Polymers are durable and degrade slowly, which is a problem for landfill sites.