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High Impact Styrene (Polystyrene)

Styrene monomer and the styrene resin made from the monomer were little more than chemical curiosities for eighty years after their discovery in 1845. Commercial production of the plastic began in 1925 in the U.S. and Germany. Today, polystyrene is the third largest selling plastic in the world.

It is difficult to characterize polystyrene in a general sense, because they are so easily tailored to serve in a wide range of mechanical, thermal and chemical environments. Therefore, these properties should only be taken as guidelines.

Mechanical Properties

As a family, polystyrenes are characterized by their hardness and ease of processing. Most hold their dimensions extremely well under conditions of normal use.

While crystal polystyrene has very high strength, it is characterized by brittleness which prevents its use in many applications. However, a rubber-modified polystyrene is available (commonly called High Impact Styrene) with improved toughness.

High Impact Styrene has a specific gravity of 1.05, a tensile modulus of 250,000 to 350,000 psi, and a tensile strength of 2000 to 5000 psi.

Thermal Properties

Styrene's heat resistance is low compared to that of other thermoplastics; maximum continued service use is well under 200° F. Some of the copolymers have a heat deflection temperature about 20° F higher than other polystyrenes.

Chemical Properties

Most foods, drinks and usual household acids, oils, alcohol and vinegar have no effect on polystyrene.

Polystyrene is not recommended for use with citrus rind oils, cleaning fluids, gasoline, turpentine or nail polish and removers (lacquer and lacquer thinners).

Polystyrene is soluble in most aromatic and chlorinated solvents. It is insoluble in alcohols such as methanol, ethanol, normal heptane and acetone.

Environmental Properties

Most polystyrenes are not suitable for continued outdoor use.

Electrical Properties

Electrical properties at room temperature are good, affected only slightly by higher temperatures and varying humidity conditions.