Plastics

Most of the plastics we use today are obtained from crude oil.

There are two main groups of plastics:

Thermoplastic

Thermoplastics soften when heated and can be shaped. On cooling, they harden. This process of softening and hardening can be repeated over and over again.

Example of Thermoplastic

Acrylic

Properties: light, hard-wearing, strong, easily scratched or cracked; can be formed at temperatures between 160ºC – 170ºC; can be joined using special solvents such as chloroform and tensol cement; transparent, coloured; comes in the form of a sheet, rod or tube

Uses: spectacle lenses, goggles, car light units, signboards, baths,  shower trays

Nylon

Properties: most common type is in the form of fibres that are woven into a fabric; tough, durable, low frictional properties, easy to machine, can withstand high temperatures

Uses: gears, nuts, bolts, hinges, zips, clothing, bags, tents, ropes, brush handles, fan blades

Polyvinyl chloride (PVC) – Plasticised PVC

Properties: plasticised PVC is soft, flexible, good electrical insulation properties

Uses: waterproof clothing, inflatable air beds, electrical cables, garden hoses

Polyvinyl chloride (PVC) – Rigid PVC

Properties: rigid PVC is light, stiff, hard, resistant to abrasion, resistant to chemicals and solvents

Uses: water pipes, liquid containers, electrical trunking

Polyethylene (polythene) – High Density

Properties: high density polyethylene is strong, stiff, tough, resistant to chemical attack

Uses: liquid containers, buckets, garbage bins, crates, gas pipes, plumbing components

Polyethylene (polythene) – Low Density

Properties: low density polyethylene is weaker, softer and more flexible

Uses: squeeze bottles, garbage and carrier bags, rainwear, drinking cups

Polystyrene – General Purpose

Properties: very brittle

Uses: packaging trays, modelling kits, tape casings, low cost disposable items such as cups and spoons

Polystyrene – High Impact

Properties: tough, flexible, can withstand rough handling

Uses: television and hi-fi casings, refrigerator linings

Polystyrene – Expanded

Properties: light, buoyant, shock-absorbant, good insulator of heat and sound

Uses: swimming float, packaging, thermal insulation, ceiling tiles, beads for bean bags

Thermosetting Plastics

Thermosetting plastics cannot be reshaped by heating once formed.

Example of Thermosetting Plastics

Polyester Resin

Properties: good electrical insulator, good heat resistance, stiff; hard and brittle alone; strong and resilient when laminated

commonly combined with glass fibre to produce glass-reinforced polyester (GRP)/fibreglass -> light, very strong, durable, weather-resistant, easily moulded, coloured

Uses: outdoor structures such as bus-stop shelters, playground equipment, waterslides, boat hulls, car body panels, garden furniture

Melamine

Properties: stiff, hard, strong, heat resistant; clear material but can be coloured by adding pigments, cannot be stained or scratched easily

Uses: laminates for kitchen worktops and dining tables, non-breakable tableware such as plastics bowls, plates and cups

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s