How are Plastics Formed?
A good place to start thinking about this process is this video.
1. Crude oil (raw material) is pumped out of oil wells. For example from the North Sea. 2. Then the crude oil is transported to an oil tanker or to the oil refinery by oil tanker or pipeline. 3. The oil is then refined at an oil refinery. This process means that fuel and chemicals can be distilled from the crude oil and also Naphtha. 4. Naphtha is used to produce a range of plastics, to do this the Naphtha is sent to a processing plant. 5. Most plastics are sent from the processing plant in granule form. The granules are then transported to the manufacturing plant to be made into a range of different products or may be made into sheet form ready for users. Example products might be polystyrene cups, chairs, mobile phone casings, car components and many more are the result. These are manufactured by injection moulding, blow moulding, extrusion, compression and vacuum forming machines. Watch an animation? |
Stock Forms
The Two Types of Plastic
As it says at the top of the page there are two types of plastic, Thermoplastics and Thermosets.
The easiest way to remember them is this;
Thermo = Heat
Plastic = Ability to Reshape
Therefore; Thermoplastic means Heat Ability to Reshape.
Thermoplastics under Heat can be Reshaped, if put under Heat again they can be Reshaped again.
So a Thermoset = Heat and Set.
Thermoset plastics are Set with Heat and cannot be changed.
It is mostly because of the different polymer structures in Thermosets and Thermoplastics.
The easiest way to remember them is this;
Thermo = Heat
Plastic = Ability to Reshape
Therefore; Thermoplastic means Heat Ability to Reshape.
Thermoplastics under Heat can be Reshaped, if put under Heat again they can be Reshaped again.
So a Thermoset = Heat and Set.
Thermoset plastics are Set with Heat and cannot be changed.
It is mostly because of the different polymer structures in Thermosets and Thermoplastics.
Thermosets have a strong, rigid, cross link structure, this is why they are so difficult to reshape again.
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Thermoplastics have a looser polymer structure, this is why they can be reshaped with heat easily.
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Thermoset Plastics
Urea Formaldehyde
P: strong, good electrical insulator A: electrical fittings, handles |
Melamine Formaldehyde
P: hard, strong, resists some chemicals and stains A: laminates for work surfaces, tableware, electrical insulation |
Epoxy Resin
P: resists chemicals, good electrical insulator A: casting, encapsulation, usually as an adhesive |
GRP - Glass Reinforced Plastic
P: lightweight, high strength to weight ratio, good thermal insulation A: structural pieces, boat bodies |
Thermoplastics
HIPS
P: good impact resistance but low strength A: vacformed containers or trays |
Expanded Polystyrene
P: lightweight, good sound and heat insulation A: packaging and prototype modelling |
Acrylic
P: stiff, brittle, easily formed by machine A: lasercut signage, car light covers |
PET
P: fairly high strength A: mostly bottles and food containers |
Try a quick test on BBC Bitesize.
Additives
Additives can be added into plastics during the processing stage, these additives can make the plastic perform better.
For example biobatch additives can make the plastics biodegradable. Some additives can make the plastic easier to recycles or can increase properties like rigidity or reduce weight or insulation. |