Polystyrene Properties

Polystyrene, commonly known as 'Styrofoam' is one of the most widely used type of plastics. It is an inexpensive and hard plastic that finds use in a number of applications. The outside housing of your computer, housings of most kitchen appliances, model cars and airplanes, toys, molded parts in your car are all made of polystyrene. It is also made in the form of foam that is used for packaging and insulating.

Polystyrene
Polystyrene is actually an aromatic polymer that is made from the monomer styrene. It is a long hydrocarbon chain that has a phenyl group attached to every carbon atom. Styrene is an aromatic monomer, commercially manufactured from petroleum. Polystyrene is a vinyl polymer, manufactured from the styrene monomer by free radical vinyl polymerization.

Polystyrene is a rigid, transparent thermoplastic, which is present in solid or glassy state at normal temperature. But, when heated above its glass transition temperature, it turns into a form that flows and can be easily used for molding and extrusion. It becomes solid again when it cools off. This property of polystyrene is used for casting it into molds with fine detail. Pure polystyrene polymer is colorless and hard with limited flexibility. It can be transparent or can be made to take on different colors.

Properties of Polystyrene
The unique physical and chemical properties of polystyrene are responsible for its use in a wide range of applications. Polystyrene is hard and brittle and has a density of 1.050 g/cm³. It is represented by the chemical formula, C₈H₈. It is made up of three chemical elements, carbon, hydrogen and oxygen. Most of the polystyrene properties are as a result of the unique properties of carbon. It is highly flammable and burns with an orange yellow flame, giving off soot, as a characteristic of all aromatic hydrocarbons. Polystyrene, on oxidation, produces only carbon dioxide and water vapor. Have a look at the physical properties of polystyrene given below:

• Density - 1.05 g/cc
• Dielectric constant - 2.4 to 2.7
• Thermal conductivity - 0.08 W/(m.K)
• Young's modulus - 3000 to 3600 Mpa
• Tensile strength - 46 to 60 Mpa
• Melting point - 240 ºC
• Water absorption - 0.03 to 0.1

Polystyrene is chemically nonreactive and hence, used to make containers for other chemicals, solvents and even food items. The transformation of carbon-carbon double bonds into less reactive single bonds in polystyrene, is the main reason for its chemical stability. Polystyrene is flexible and can be made into moldable solid or thick viscous solids. This is mainly because of the Van der Waal's forces of attraction, that exist between the long hydrocarbon chains. However, when heat is applied, the chains can slide over each other. This property of intermolecular weakness along with the intramolecular strength, due to the strong hydrocarbon backbone, allows polystyrene to be flexible and stretchable. Polystyrene is soluble in solvents that contain acetone, such as most aerosol paint sprays and cyanoacrylate glues.

Copolymers of polystyrene, that have improved properties, are made by adding other polymers with desired properties such as polybutadiene rubber, during the process of polymerization. Some examples of copolymers include high impact polystyrene and acrylonitrile butadiene styrene.