What’s the difference between thermosetting polymers, thermoplastics and composites.
Thermoset plastics undergo a chemical change and cannot be reheated and shaped where as thermoplastics can be reshaped by heat. Composites are made from multiple components.
4 examples of thermosetting polymers
Urea formaldehyde, epoxy resin, polyester and silicone.
3 examples of thermoplastics
Acrylic, high density polyethylene and polyethylene terephthalate.
What is a thermoplastic
Thermoplastics are made up of long chains of molecules held together by small cross links. When a thermoplastic is heated, these bonds weaken and become pliable, meaning the plastic can be shaped and formed. Once the heat is removed, the chains reposition and the plastic is hard.
What is a thermosetting plastic
The molecules in thermosetting plastics link side to side and end to end. This linking is covalent bonding resulting in a very rigid structure.
Urea formaldehyde- properties and uses
High tensile strength, hard, brittle, heat renitence.
Adhesives, plug sockets, desk lamps and fabrics.
Urea formaldehyde- advantages and disadvantages
Low cost, low cure temperatures, water-resistance, resistance to microorganisms and abrasion, lack of colour.
UF can release formaldehyde, a toxic vapour when manufacturing.
Epoxy resins- properties and uses
Resistant to chemicals, heat resistant, adhesion to variety of substances, high tensile compression and bend strengths. Low shrinkage, high electrical insulation and corrosion resistant.
Coating composites for electrical items and filling gaps in materials.
Epoxy resins- advantages and disadvantages
Provide a protective layer that separates food and drinks from the metal used to make their cans.
Long curing time, potential harm to health, can cause allergic reactions, and higher cost compared to other adhesives.
Polyester resin- properties and uses
Strong , durable, resistant to shrinking, stretching, several chemicals, abrasion and heat. Dries quickly.
Bottles, tarpaulin, sails (Dacron), canoes, glass reinforced cars and boats, garden furniture.
Polyester resin- advantages and disadvantages
Strength, flexibility, moisture resistance, ease of care, and low cost.
High energy and water consumption, pollution, and inability to biodegrade. Brittle so can crack.
Silicone- properties and uses
Fine electrical properties, good chemical stability and flame retardancy, and superior resistance to heat and cold.
Sealants, adhesives, lubricants, medicine, cooking utensils, thermal insulation, and electrical insulation.
Silicone- advantages and disadvantages
Last longer, spread better, stay flexible or rigid, and withstand extreme temperatures or humidity.
Tear strength meaning it is susceptible to breakage.
2 examples of composites
Glass reinforced plastic and carbon fibre plastic.
Acrylic- properties and uses
Strong, stiff, transparent and lightweight. Plus hard, durable and a good electrical insulator. Can withstand extreme weather and chemicals.
Shop signage, glass substitute, baths, car lights or CD cases.
Acrylic- advantages and disadvantages
Acrylic is easy to shape, highly transparent, easy to clean and maintain. It is also stronger than glass whilst being lighter, plus an affordable substitute. Acrylic is also 100% recyclable.
Brittle so it can easily break or scratch. Cracks are easily formed and acrylic is prone to splintering.
High density polyethylene- properties and uses
Good impact strength and is resistant to chemicals. Due to its water barrier it can float and the products created from HDPE are very easy to maintain (easily washed). It’s a good electrical insulator and flexible.
HDPE is used for water tanks, water pipes, bowls, thin packaging sheets and household bottles for either edible items or chemicals.
High density polyethylene- advantages and disadvantages
It is highly resistant to chemicals, is tough and hard wearing, lightweight, rigid and 100% recyclable.
HDPE however can break under stress and the colour fades over time. It is also flammable and not very temperature resistant.
Polyethylene terephthalate- properties and uses
Very tough and lightweight due to its low density. It’s a good barrier to things such as alcohol, oil and is chemical resistant. It has high impact and tensile strength.
PET is used for carbonated drink bottles, packaging for flavoured food as it has no effect on their flavour and microwavable food trays.
Polyethylene terephthalate- advantages and disadvantages
It is an easily available polymer and also affordable. Pet has a high strength to weight ratio, is shatter proof and easily recyclable.
Can discolour and needs to be treated when used in the food packaging industry. It also has low heat resistance.
Carbon Fibre Composite- properties and uses
High strength to weight ratio, high chemical resistance and can withstand tensile loads.
Sports equipment, aircraft parts, car bodies, yacht masts and fishing rods.
Carbon Fibre Composite- advantages and disadvantages
Better tensile strength than steel alloys and can be formed into complex, aerodynamic, one piece structures.
Very expensive, only available in black, difficult to repair, cannot be recycled easily and loses integrity over time.
Glass reinforced plastic composite- properties and uses
Durable, lightweight, non-conductive, high flexural strength. Chemical and UV radiation resistant.
Rotor blades of wind turbines, canoes, fairground rides, fish ponds.
Glass reinforced plastic composite- advantages and disadvantages
Excellent strength to weight ratio, resistant to corrosion, water resistant, wide range of colours, can be repaired easily, long lifespan.
Expensive to produce and purchase, specialised manufacturing process required and high quality moulds are required.
