Polystyrene (PS) is a synthetic aromatic hydrocarbon polymer made from the monomer styrene. PS can be solid or foamed. General-purpose polystyrene is clear, hard, and rather brittle. It is an inexpensive resin per unit weight. PS can be naturally transparent but can be colored with colorants. Uses include protective packaging (such as packing peanuts and CD and DVD cases), containers, lids, bottles, trays, tumblers, disposable cutlery and in the making of models.

Properties of polystyrene

This material is a clear, amorphous, nonpolar commodity thermoplastic that is easy to process and that can be easily converted into a large number of semi-finished products like foams, films, and sheets. It is one of the largest volume commodity plastic, comprising approximately seven percent of the total thermoplastic market. PS is a very good electrical insulator, has excellent optical clarity due to the lack of crystallinity, and has good chemical resistance to diluted acids and bases.

Some of its weaknesses can be overcome by copolymerization with other monomers.

One of the most important styrene copolymers is poly (styrene-co-acrylonitrile) (PSAN). It has much-improved chemical resistance, better heat stability, and improved mechanical properties. However, these copolymers often yield yellow products.

Probably of equal importance are poly (styrene-co-butadiene) (SBR, SBS) and poly (styrene-co-acrylonitrile-co-butadiene) (ABS). Both copolymers have very high stress and impact resistance and ABS has higher tensile strength than pure PS.

To increase the heat resistance, styrene is sometimes copolymerized with small amounts of maleic anhydride or it is copolymerized with this monomer to an alternating structure.

Many styrene derivatives have been synthesized on a laboratory scale and some have been extensively investigated. However, no other styrene polymer has become a large-volume commodity thermoplastic.

PS is not biodegradable plastic and resistant to photolysis. It is a major contributor to the debris in the ocean. Although recyclable, polystyrene is not recycled in many parts of the world. The biggest problem is expandable polystyrene (EPS); due to its low density, it takes up a relatively large amount of space in landfills.

Commercial grades of polystyrene

This polymer is one of the most important commodity plastics. The production volume of polystyrene and styrene copolymers is several million tons per year. It is sold under various trade names, including Styrofoam™, Styropor®, and Styron™

The three most important grades of styrene are:

• GPPS: General purpose polystyrene, also known as crystal-clear polystyrene, is a fully transparent, rigid and rather brittle low-cost thermoplastic made from styrene monomer. GPPS is a solid product manufactured in the form of 2-5 mm pellets.
• HIPS: High impact polystyrene contains usually 5 to 10% rubber (butadiene) and is used for parts that require high(er) impact resistance. HIPS is a graft copolymer having polystyrene sidearms. The grafting occurs when some of the radicals react with the double bonds of the polybutadiene.
• EPS: Expandable polystyrene consists of micro-pellets or beads containing a blowing agent (usually pentane). The expanded or foamed polystyrene is thermally insulating, has high impact resistance and good processability.

Styrenic copolymers and their blends are considered engineering thermoplastics because their properties can be tailored over a wide range for a large number of applications with a broad range of processing methods which permits the manufacture of high quality, very durable plastic products suitable for many demanding applications.

Applications of polystyrene

PS is a polymer that is cheap and easy to process. It is the material of choice for many applications including food packaging, disposable consumer plastic goods as well as parts for optical, electronic/electrical, and medical applications. A large variety of products are formed by injection molding including dining utensils, plastic cups, housewares, toys, CD cases, cosmetic containers, covers, and fixtures.

Expandable polystyrene, either crystal polystyrene or styrene copolymers soaked with a blowing agent (usually pentane), are used to produce various foamed products, like disposable drinking cups, egg cartons, trays, fast-food containers, cushioned packaging, and thermal insulation for the construction market.

Medical applications include pipettes, Petri dishes and medicine containers.

Fillplas use PS to make filler masterbatch (HIPS filler). You could visit our website to have more information.