Plastics that once heated can be formed into a variety of different shapes, using technique like blow moulding, injection moulding and vacuum forming.
Once the polymer has cooled down, the shape remains permanent. The same shape can then be reheated, softened, shaped and cooled many times over and over again. We call this the Thermoplastic Heating Cycle. These materials can be easily recycled.
Thermoplastics are used in a wide range of graphic products, from Styrofoam models to signs in the high street and injection moulded casing on many electrical products such as games consoles.
Polymers have a number of advantages over metal casings.
- less expensive to produce in large quantities
- thermoforming processes can produce more intricate shapes
- non conductive
- excellent heat proof properties (for when games consoles get warm)
- usually cast into sheets
- also available in rods and tubes
- self finishing so no need to be painted.
- making models-signs
- easily cut and bent using strip heater
- thinner sheets can be vacuum formed just like polystyrene or PVC
IN shop signs, a higher quality acrylic must be used as i has to be abble to:
- withstand weather conditions from heat in the summer to cold in the winter.
- chemical resistant to pollution and detergents.
- durable by resisting long term stresses such as being outdoors for a long time.
- easy to fabricate
- has to have excellent aesthetic properties to attract customers attention and give a high quality look for the business' reputation.
Styrofoam is a polystyrene made for insulating buildings. Also make excellent modelling material.
- great rigidity
- high compressive strengths so it cannot be bent easily
- easy to cut and shape with a variety of hand tools (files etc)
- sheets can be glued together with PVA to form larger blocks
- a smooth surface finish when sanded.
- can be painted to give good quality finish if desired.
Polymers in commercial packaging
- lightweight and versatile
- strong, tough, rigid, durable, impact and water-resistant
- easily formed and moulded.
- easy to print on
- low cost
Polymers can be identified by code, usually stamped on the back of the product or printed onto the label.
An internationally recognised coding system means that you can easily identify polymers and sort them, making it suitable for recycling.
Each polymer has its own useful properties, making it usable in different areas of the packaging industry.
Expanded polystyrene is used in the fast food industry because it is:
- strong, yet lightweight
Expanded polystyrene is also used in the protective packaging of many delicate products such as electrical products, as it is shape moulded it fits snugly around products which are placed inside corrugated board boxes.
Disadvantages of polymers
The main disadvantage if the widespread use of plastics are concerns about how sustainable they are. They are made from oil, which is a finite resource that requires a lor of energy to process, producing high levels of pollution.
Manufacturing techniques for plastic 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 regarding landfill sites.