Materials can be selected based upon their working properties. It is important to know and understand which materials can be used for a specific purpose:
Most polymers are synthetic, meaning they are man-made and have been designed by chemical engineers. Different polymers are created all the time so that the demands of the consumer can be met. Polymers fall into two categories:
‘Thermo’ indicates that heat will be involved in the way the polymer is shaped, and ‘set’ means that once the polymer has been set in that shape, heat will not alter the form.
Thermoforming plastic, however, can be heated and shaped, then heated and shaped again. These polymers are also often referred to simply as ‘thermoplastics’.
A popular polymer to use in schools is acrylic. This can be heated and bent using a line bender and, as it is a thermoforming polymer, it can then be reheated and reshaped. For example, a hairdryer would not be made from acrylic as it would not withstand the heat and would deform when used.
Four popular polymers used in schools are:
There is possibly a near infinite selection of polymers, with new ones being created to meet new demands. Colour, texture, opacity and function can all be altered by chemical engineers.
Most polymers are made from a product of crude oil. There is a drive to reduce the use of plastics as they don’t biodegrade quickly and can pollute oceans. Some bioplastic alternatives are available and will be used more as the availability of non-bioplastic diminishes.
Many prototypes are now made on 3D printers as more complex, intricate and curved shapes can be produced quickly and cheaply in comparison to traditional modelling methods such as Styrofoam modelling. The most common 3D printer filament is PLA, and many additives are now combined with PLA to give a greater range of material choice. Some PLA filaments are combined with carbon fibre, different wood fibres and even metal.
The costs of polymers vary depending on how specialised they are.
If a roll of carbon fibre 3D printer filament costs £45.00 for 750 g and a 25 g part for a prototype needs to be 3D-printed, what will the cost of the print be?
Find the cost per gram of the filament:
45 ÷ 750 = 0.06
= 0.06p per gram
Find the cost for the part:
0.06 × 25 = 1.5
If a roll of carbon fibre 3D printer filament costs £56.00 for 700 g, how much would a 250 g carbon fibre print cost?
Cost per gram = 56 ÷ 700= 0.08
Cost of the print = 0.08 × 250 = 20