Polymers

The following page of notes will cover:

• Thermoforming Plastics
• Thermosetting Plastics

Using these general rules will help you answer most questions relating to Polymers:

• Thermoplastics can be reheated and reshaped where as thermosets only burn with heat, this gives them a wide range of applications
• Both types of polymer can be recycled but thermoplastics are easier to recycle
• Thermosetting polymers are heat resistant and more durable, they retain their shape when heated
• Both types of polymers can be easily pigmented (coloured)
• Thermoplastics are prone to UV degradation
• Both polymers are heat and eletrical insulators
• Both polymers are hygenic, easily cleaned and waterproof

Acrylic (PMMA):

Advantages	Disadvantages
Stiff Hard Durable Good electrical insulator	Very brittle Scratches easily Splinters easily Poor fatigue properties

Uses: CD cases, Car light cases, Baths

High Impact Polystyrene (HIPS):

Advantages	Disadvantages
High impact resistance Good rigidity Easy to process and fabricate Excellent dimensional stability	Poor UV resistance Low chemical resistance Flammable Not suitable for high temperatures

Uses: Refrigerator liners, Packaging, Toys, Point-of-purchase displays

High Density Polythene (HDPE):

Advantages	Disadvantages
High strength-to-density ratio Excellent chemical resistance Lightweight yet durable Good impact resistance Recyclable	Poor UV resistance (unless treated) Susceptible to stress cracking Limited high temperature use Difficult to bond

Uses: Milk jugs, Water pipes, Plastic bottles, Toys, Cutting boards

Polypropylene (PP):

Advantages	Disadvantages
Lightweight Hard Impact resistant Chemical resistant	Can discolour from UV light Oxidation can cause problems Not heat resistant Difficult to paint

Uses: Medical syringes, carpets, kitchenware

Polyvinyl Chloride (PVC):

Advantages	Disadvantages
Good chemical resistance Weather resistant Stiff/tough/hard Available in a range of colours	Can discolour from UV light Brittle Easily scratched Difficult to recycle

Uses: Pipes, guttering, electrical insulation, floor coverings

Polyethylene terephthalate (PET):

Advantages	Disadvantages
Good alcohol and oil barrier Weather resistant Can be made transparent Inert/non-toxic Stiff/tough/hard Available in a range of colours	Can discolour from UV light Needs to be treated when used for food containers Susceptible to heat degradation

Uses: Fizzy drinks bottles, washing up bottles, fibres for clothing

Epoxy resin (ER):

Advantages	Disadvantages
Corrosion resistant Electrical insulator Good bond qualities	Causes health issues/toxic fumes Brittle

Uses: Adhesives, paints and coatings, electronics

Melamine-Formaldehyde (MF):

Advantages	Disadvantages
Excellent heat resistance Hard and scratch-resistant surface Good electrical insulator Stain and chemical resistant Wide range of colors and patterns	Brittle and can crack under impact Not biodegradable Can release formaldehyde if damaged More expensive than some alternatives

Uses: Kitchenware (plates, bowls), Laminates, Electrical components, Decorative surfaces

Phenol-Formaldehyde (PF):

Advantages	Disadvantages
Excellent thermal stability High mechanical strength Good electrical insulation properties Flame resistant Chemical and moisture resistant	Brittle nature Dark color limits aesthetic options Can release formaldehyde during production Difficult to recycle

Uses: Electrical insulators, Circuit boards, Kitchen countertops, Adhesives, Knob handles

Polyester resin (PR):

Advantages	Disadvantages
Good electrical insulator Heat resistant Hard Cost effective	Short shelf life Emissions are harmful Brittle unless treated

Uses: Glass reinforced boats and cars, garden furniture, castings

Urea formaldehyde (UF):

Advantages	Disadvantages
Strong Hard Heat resistant Good electrical insulator	Can emit toxic vapours during manufacture Brittle

Uses: Electrical fittings, handles, control knobs, domestic appliance components

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