Design & Tech - Unit 2 - Polymers

Thermoplastics definition

A material which can be repeatedly reheated and reshaped

Examples of thermoplastics:

PMMA, LDPE, HDPE, PET, PVC, uPVC, PP, ABS

Properties of PMMA

THERMOPLASTIC - Tough, hard, good chemical resistance, can be translucent

Uses of PMMA

Car light casings, CNC laser cut items, lighting units, baths

Properties of LDPE

THERMOPLASTIC - Very tough, good chemical resistance, weatherproof, can be translucent, low level of rigidity

Uses of LDPE

Carrier bags, bin liners, food wrap film, squeezy detergent bottles

Properties of HDPE

THERMOPLASTIC - Tough, good chemical resistance, weatherproof, transparent

Uses of HDPE

Chemical drums, jerry cans, toys, bags for life, buckets

Properties of PET

THERMOPLASTIC - hard, tough, available in transparent form, good chemical resistance

Uses of PET

Single use drink bottles, food packaging, detergent bottles, shampoo bottles, food trays.

Properties of PVC (flexible polyvinyl chloride)

THERMOPLASTIC - Tough, flexible, can be translucent, good weathering resistance, good chemical resistance

Uses of PVC

Hose pipes, cable insulation, medical grade tubing, inflatable products, imitation leather, seat coverings

Properties of uPVC (Rigid polyvinyl chloride)

THERMOPLASTIC - Rigid, opaque, tough, hard, good weathering resistance, good chemical resistance

Uses of uPVC

Window frames, external doors, guttering and downpipes for buildings, water service pipes, bank cards

Properties of Polypropylene (PP)

HERMOPLASTIC - Available in translucent or transparent, good chemical resistance, tough, good fatigue resistance (hinge property)

Uses of PP

Rope, folders, hinged food containers, folio cases, medical equipment

Properties of ABS

THERMOPLASTIC - Tough, hard, available in opaque

Uses of ABS

Telephone handsets, domestic appliances, computer housing, rigid luggage. Used in extrusion moulding.

Thermosetting plastics definition

A material which, when heated, undergoes a chemical change whereby the molecules form rigid cross links.

They cannot be reheated or reshaped, even at very high temperatures.

Examples of thermosetting plastics:

Epoxy resin, Urea formaldehyde, Polyester resin

Properties of Epoxy Resin

THERMOSET - rigid, clear, hard, tough, chemical resistant

Uses of Epoxy Resin

Adhesives, surface coatings, encapsulation of electrical components, cardiac pacemakers, aerospace applications

Properties of Urea Formaldehyde

THERMOSET - Hard, heat resistance, chemical resistant, brittle

Uses of Urea Formeldahyde

Electrical fittings, adhesives

Properties of Polyester Resin

THERMOSET - Rigid, heat resistant, chemical resistant, brittle

Uses of Polyester Resin

Castings, used in lay-up process for glass reinforced plastic (GRP) for boat hulls, car parts, chair seats

Elastomers definition

Materials which, at room temperature, can be deformed under pressure, and then upon release of the pressure, will return to their original shape

Elastomers examples

Natural rubber, neoprene

Properties of natural rubber (polyisoprene)

ELASTOMER - High tensile strength, low elongation, good hardness, tough, electrical insulator, good cold resistance

Uses of natural rubber

Automotive industry such as tyres, tubes, hoses, gaskets, belts, balloons, toys, footwear

Properties of neoprene

Good thermal resistance, tough, good oil and chemical resistance, excellent weather resistance, good abrasion resistance, electrical insulator

Uses of neoprene

Wetsuits, laptop cases, shock absorbing seals, car door seals, industrial wire insulation, hose covers, transmission bellts, gaskets and door seals

Stock forms of polymers:

Sheet, Film, Granules, Rod, Foam, Powder

More detailed notes on stock forms are available in the 2.3 ppt

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Biodegradable definition

Capable of being decomposed by bacteria or other living organisms and thereby avoiding pollution.

Categories of biodegradable polymers

- Those that are made from renewable raw materials including sugar and plant starches such as Polylactic acid (PLA)​

- Those that are manufactured from ​petrochemicals with the addition ​of biodegradable additives ​(bio batch) which aid degradation​

Types of biodegradation

Oxy-degradation

Photo-degradation

Hydro-degradation

Examples of biodegradable polymers

PotatoPak, Biopol, PLA, PHA, lactide, glycolide

More detail on biodegradable polymers in the 2.5 ppt

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