Polystyrene is synthetic aromatic thermoplastic polymer made of long chain hydrocarbons with alternating carbon centres attached to phenyl groups ( derivative of benzene). Polystyrene can be made into a foam material, called expanded polystyrene (EPS) or extruded polystyrene (XPS), which is valued for its insulating and cushioning properties. The expanded polystyrene (EPS) is commonly associated with trade name Styrofoam, in which this foam is made of more than 95% air. The General Purpose Polystyrene, also called GPPS, is an option when polymer clarity is required even if it is very brittle.
Polystyrene is made from polymerization of styrene monomer that is produced by replacing one of the hydrogen atoms in ethylene by a benzene ring (C6H6). Steps involved in Polystyrene manufacturing are:
1. Styrene production
Styrene monomer is achieved by an two-fold reaction of Ethylene and benzene, in the presence of a catalyst such as aluminum chloride to form ethylbenzene. The ethylbenzene is then dehydrogenated at 1,112- 1,2020 0 F (600-6500 0 C) to form styrene monomer (C 8 H 8 ).
2. Suspension polymerization
Little drops of styrene monomer are completely surrounded by water and a mucilaginous substance. Supporting and surrounding the styrene globules, the suspension agent produces droplets of polystyrene.
Polymerization initiator is added to the droplets, which are suspended by heat radiation of about 2120F (1000oC). This results in free radicals that are combined randomly to form chains of polystyrene.
4. Polymerization termination
Polymer Terminators are introduced to the process to end it at the appropriate time. Though variable, chain length must fall within a certain range, because polystyrene with overly long chains won't melt readily, and polystyrene with short chains will be brittle.
5. Beads preparation
After polymerization is complete, the mixture—consisting of beads made up of polystyrene chains—is cooled. These beads are then washed out and dried. Uniform bead size is achieved by sorting the beads through meshes which filter out over- and undersized beads.
Building and Construction
Polystyrene resins are one of the most popular materials used for roofing, plumbing, and insulation in the building industry. When applied with reinforced concrete, polystyrene provides protection against harsh environments.
Blocks of polystyrene are used as an energy efficient means for both industrial and homes as it prevents drafts and evens temperatures, which in turn reduces the cost of electricity.
Polystyrene can be painted, coloured and printed on, making it ideal option for packaging. Packaging food in polystyrene has proved to be more hygienic as opposed to plates that are washed and reused.
Polystyrene is shatterproof which makes it an excellent choice for electrical insulation.
GPPS is an option for IT equipment, CD cases and other packaging application.
The General Purpose Polystyrene can also be used for disposable medical products such test tubes.
Some gardening equipment and toys can also be made from GPPS.