PLASTIC TYPES

Plastics

There are two main types of plastics –

Thermoplastics which are softened by heat and can be moulded. (Injection moulded, blow moulded or vacuum formed). Good examples are acrylic, polypropylene, polystyrene, polythene and PVC.

Thermosets which are formed by ha heat process but are then set (like concrete) and cannot change shape by reheating. Good examples are melamine (kitchen worktops), Bakelite (black saucepan handles), polyester and epoxy resins.

Composites are made by mixing materials together to get enhanced properties. Polyester resin is mixed with glass fibre to make GRP used for boatbuilding and fishing rods. Epoxy resin plus carbon fibre is stronger than steel but lighter.  
   
Nylon Very strong, nylon can be machined and will take a fine thread. It is also slippery and can be used to make washers, spacers and bushes.

Nylon was originally developed as a textile but is available in many forms with vastly different properties. Engineering nylon grades are easy to machine with good resistance to biological attack. Unfortunately nylons can absorb moisture from the atmosphere and can degrade in strong sunlight (they are unstable in ultraviolet light) unless a stabilizing chemical is added at the initial manufacture of the plastic. Nylons are easy to mold. Nylons also have a natural 'oily' surface that can act as a natural lubricant. Nylons are used for everything from clothes through to gears and bearings.
 
Acrylic Comes in a range of thicknesses, colors and can be opaque or transparent. There are two type of acrylic extruded which is cheaper and very "plastic" and cast which machines better but is harder and less flexible.
Acrylics are available in a range of colours and can be opaque, translucent or transparent. They are available in sheet, rod, and tube for use in injection moulding, extrusion and vacuum forming. Acrylics withstand weather and are stable in sunlight. Almost any colour can be produced. Transparent acrylic can be as clear as the finest optical glass, this led them to be used in optical equipment such as cameras. It is possible to significantly strengthen the acrylic when it is being made, these high grade acrylics are used use for aircraft windows.

PVC and uPVC Stiff, hard,tough lightweight plastic. uPVC is established for outside use ans is used for plastic windows and plastic pipes. Plasticized PVC is used for flexible applications such as insulating - cables.
 
Polythene This plastic has a range of uses from food packaging to gas pipes. The plastics can be injection molded or extruded and is available in two forms. High-density polyethylene (HDPE) is a hard rigid plastic. A low-density grade ( LDPE )is tough and flexible.
 
Polypropylene Polypropylene is a tough, cheap plastic, it has a slightly waxy feel. It can be bent repeatedly without breaking. Used for Medical equipment such as syringes, stacking chairs (chair shell is polypropylene), suitcases with integral hinges,
 
Polycarbonate Used for making eye protection, machine guards and riot shields. It is not as hard as acrylic and can be cut easily but it will absorb impacts.
 
Bakelite A thermosetting plastic. Dark brown. Used as a composite reinforced with paper or cloth. Used to make circuit boards and heat proof insulated parts in the electronics industry.
 
Epoxy resin A two part mix which can be used as a glue (ARALDITE) or be reinforced with carbon fiber to produce a very strong and light composite materials which is used in aerospace and Formula 1  

Melamine A thermoset very tough and heat resistant. White but can be produced in a full range of colours.