Polystyrene

Polystyrene homopolymer, known as “crystal" polystyrene in the trade, is an amorphous, colorless, and transparent commodity thermoplastic. It is rigid, brittle, relatively hard and has excellent gamma radiation resistance, good electrical properties but has poor chemical and UV resistance. It can also be radiation sterilized.

When modified by incorporating elastomers, polystyrene homopolymer turns into (high) impact polystyrene or HIPS, which is usually opaque. As a result, a wide variety of commercial polystyrene grades are available.

Polymer Type

Thermoplastic

Advantages

Advantages of Polystyrene include:

Cheap, rigid, transparent, easy to mould and good dimensional stability.

Good electrical properties, low dielectric loss.

Excellent resistance to gamma radiation.

Disadvantages

Disadvantages of Polystyrene include:

Brittle, poor chemical resistance especially to organics.

Susceptible to UV degradation.

Flammable.

Applications

Applications include toys, light diffusers, beakers, cutlery, general household appliances, video/audio cassette cases, electronic housings, refrigerator liners, housewares, containers, glazing, packaging and for HIPS.

Structural foam polystyrene moldings are used for business machine housings, tools, cases and boxes. Expanded polystyrene beads are used for packaging and cushioning. Foamed polystyrene is used for food trays, dishes, and egg boxes.

Typical Properties

Property Value

Density (g/cm3) 1.07

Surface Hardness RM80

Tensile Strength (MPa) 34

Flexural Modulus (GPa) 3

Notched Izod (kJ/m) 0.02

Linear Expansion (/°C x 10-5) 7

Elongation at Break (%) 1.6

Strain at Yield (%) 1.4

Max. Operating Temp. (°C) 50

Water Absorption (%) 0.05

Oxygen Index (%) 18

Flammability UL94 HB

Volume Resistivity (log ohm.cm) 16

Dielectric Strength (MV/m) 20

Dissipation Factor 1 kHz 0.0002

Dielectric Constant 1 kHz 2.6

HDT @ 0.45 MPa (°C) 90

HDT @ 1.80 MPa (°C) 80

Material. Drying hrs @ (°C) 2 @ 70

Melting Temp. Range (°C) 200 - 250

Mould Shrinkage (%) 0.5

Mould Temp. Range (°C) 20 - 50

Source : Abstracted from Plascams

Polystyrene is produced by the polymerization of the monomer styrene, which is a derivative of petroleum. If you look at the chemical structure of polystyrene, you'll see that it is composed of carbon and hydrogen atoms only. Thus, it is classified as a hydrocarbon. Now, if you observe the bonds in its chemical structure, you'll see that the carbon atoms are linked to one another by covalent bonds. Every alternate carbon atom on the polystyrene chain has a phenyl group (name given to benzene ring) attached to it. It is a long-chain hydrocarbon, and its chemical formula is C8H8)n. Given below is the chemical structure of polystyrene.