Polystyrene
Polystyrene is a popular plastic, used to package many consumer goods. There are two main methods for manufacturing polystyrene foam, which creates either expanded or extruded polystyrene foam. Both forms of polystyrene can be used in house insulation.
Polystyrene
Polystyrene is a plastic made from styrene, which is an organic compound. Styrene occurs in small amounts in many plants, including the strawberry and coffee plants. Styrene is produced industrially through a series of chemical reactions.
Plastics are polymers, and this means they are made from chains of repeating molecules joined by chemical bonds. Bonds are created between molecules by the sharing of electrons, and it makes these molecules more stable. Polystyrene is made of a long chain of molecules known as hydrocarbons. The polystyrene hydrocarbons also have phenyl groups attached to them, every other carbon atom.
Extruded Polystyrene
Extruded polystyrene is a rigid form of polystyrene which is used in CD jewel cases and Petri dishes, and is created using injection moulding. Injection moulding involves putting the material into a heated barrel and melting it. It is then pushed into a mould, where it hardens. The mould determines the final shape of the polystyrene.
Polystyrene Foam
There are two main types of polystyrene foam: expanded and extruded polystyrene. Expanded polystyrene foam is the cheapest form of polystyrene. Extruded polystyrene foam has higher insulation qualities in comparison to expanded polystyrene foam.
Expanded polystyrene foam is creating by expanding solid beads of polystyrene. A blowing agent, usually pentane, and other chemicals are used to enhance the expansion of the beads. The expansion is caused by heating the polystyrene beads with steam. The beads expand into polystyrene foam cells, which can be up to 40 times larger than the original polystyrene bead. Expanded polystyrene foam is made up of roughly 90% air.
Extruded polystyrene foam is made by adding solid polystyrene and other additives to an extruder. The mixture is melted in the extruder into a plastic fluid. This fluid is passed through a shape known as a die, which determines the dimensions of the foam. The fluid is cooled, and can then be trimmed to more exact specifications.
High Impact Polystyrene
High impact polystyrene is polystyrene which has had rubber added to it. It is also known as high impact plastic, or bextrene. It is less brittle than pure polystyrene due to the addition of rubber, and is therefore more shock absorbent.
Styrofoam
Styrofoam is often used as a common name for all types of polystyrene; however it actually refers to a specific type of extruded polystyrene foam. Styrofoam is usually used for insulation, but can be used in life raft as all polystyrene foams are buoyant.
Polystyrene Insulation
Polystyrene is light, durable and a good insulator. These properties make it useful in a wide variety of applications, including packaging, toy stuffing and protecting medical vaccinations.
The insulating properties of polystyrene mean it is often used in house insulation. It is waterproof and long lasting, and insulates against both noise and extreme temperatures. Both expanded and extruded polystyrene foams can be used in insulation.
Expanded polystyrene insulation is less expensive and of lower density than extruded insulation. However, it has slightly less insulating properties in comparison to extruded polystyrene foam. This is because it is only filled with air, whereas extruded foam contains refrigerant gas.
Extruded polystyrene insulation has other useful properties. It can be cut and shaped to any specification. It has a smooth, uniform surface unlike expanded polystyrene. It can also be easily cut to add electrical wiring.
Both forms of polystyrene insulation require a fire protective coating. They degrade if exposed to sunlight and extremely high temperatures. However, for most polystyrene insulation uses there is little practical risk of this occurring.