Thermosoftening plastics and thermosetting plastics
There are two main categories of plastic:
- Thermosoftening (also called thermoplastics) are plastics which will soften when heated and can be reshaped.
- Thermosetting plastics are plastics do not soften on heating. They are used when resistance to heat is important (eg kettles, plugs, laptop chargers etc).
The properties and uses of some common thermosoftening plastics are shown in the table below.
| Name | Properties | Principal uses |
| Polyamide (Nylon) | Creamy colour, tough, fairly hard, resists wear, self-lubricating, good resistance to chemicals and machines | Bearings, gear wheels, casings for power tools, hinges for small cupboards, curtain rail fittings and clothing |
| Polymethyl methacrylate (Acrylic) | Stiff, hard but scratches easily, durable, brittle in small sections, good electrical insulator, machines and polishes well | Signs, covers of storage boxes, aircraft canopies and windows, covers for car lights, wash basins and baths |
| Polypropylene | Light, hard but scratches easily, tough, good resistance to chemicals, resists work fatigue | Medical equipment, laboratory equipment, containers with built-in hinges, 'plastic' seats, string, rope, kitchen equipment |
| Polystyrene | Light, hard, stiff, transparent, brittle, with good water resistance | Toys, especially model kits, packaging, 'plastic' boxes and containers |
| Low density polythene (LDPE) | Tough, good resistance to chemicals, flexible, fairly soft, good electrical insulator | Packaging, especially bottles, toys, packaging film and bags |
| High density polythene (HDPE) | Hard, stiff, able to be sterilised | Plastic bottles, tubing, household equipment |
| Name | Polyamide (Nylon) |
|---|---|
| Properties | Creamy colour, tough, fairly hard, resists wear, self-lubricating, good resistance to chemicals and machines |
| Principal uses | Bearings, gear wheels, casings for power tools, hinges for small cupboards, curtain rail fittings and clothing |
| Name | Polymethyl methacrylate (Acrylic) |
|---|---|
| Properties | Stiff, hard but scratches easily, durable, brittle in small sections, good electrical insulator, machines and polishes well |
| Principal uses | Signs, covers of storage boxes, aircraft canopies and windows, covers for car lights, wash basins and baths |
| Name | Polypropylene |
|---|---|
| Properties | Light, hard but scratches easily, tough, good resistance to chemicals, resists work fatigue |
| Principal uses | Medical equipment, laboratory equipment, containers with built-in hinges, 'plastic' seats, string, rope, kitchen equipment |
| Name | Polystyrene |
|---|---|
| Properties | Light, hard, stiff, transparent, brittle, with good water resistance |
| Principal uses | Toys, especially model kits, packaging, 'plastic' boxes and containers |
| Name | Low density polythene (LDPE) |
|---|---|
| Properties | Tough, good resistance to chemicals, flexible, fairly soft, good electrical insulator |
| Principal uses | Packaging, especially bottles, toys, packaging film and bags |
| Name | High density polythene (HDPE) |
|---|---|
| Properties | Hard, stiff, able to be sterilised |
| Principal uses | Plastic bottles, tubing, household equipment |
The properties and uses of some common thermosetting plastics are shown in the table below.
| Name | Properties | Principal uses |
| Epoxy resin | Good electrical insulator, hard, brittle unless reinforced, resists chemicals well | Casting and encapsulation, adhesives, bonding of other materials |
| Melamine formaldehyde | Stiff, hard, strong, resists some chemicals and stains | Laminates for work surfaces, electrical insulation, tableware |
| Polyester resin | Laminated, good electrical insulator, resists chemicals well | Casting and encapsulation, bonding of other materials |
| Urea formaldehyde | Stiff, hard, strong, brittle, good electrical insulator | Electrical fittings, handles and control knobs, adhesives |
| Name | Epoxy resin |
|---|---|
| Properties | Good electrical insulator, hard, brittle unless reinforced, resists chemicals well |
| Principal uses | Casting and encapsulation, adhesives, bonding of other materials |
| Name | Melamine formaldehyde |
|---|---|
| Properties | Stiff, hard, strong, resists some chemicals and stains |
| Principal uses | Laminates for work surfaces, electrical insulation, tableware |
| Name | Polyester resin |
|---|---|
| Properties | Laminated, good electrical insulator, resists chemicals well |
| Principal uses | Casting and encapsulation, bonding of other materials |
| Name | Urea formaldehyde |
|---|---|
| Properties | Stiff, hard, strong, brittle, good electrical insulator |
| Principal uses | Electrical fittings, handles and control knobs, adhesives |