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Heading 3903 : Polymers of styrene, in primary forms.
This heading covers polystyrene and copolymers of styrene. The most important copolymers of styrene are styrene‑acrylonitrile (SAN) copolymers, acrylonitrile‑butadiene‑styrene (ABS) copolymers and styrene‑butadiene copolymers. Most of the styrene‑butadiene copolymers with substantial amounts of butadiene comply with the requirements of Note 4 to Chapter 40 and are therefore classified in Chapter 40 as synthetic rubber. For the classification of polymers (including copolymers), chemically modified polymers and polymer blends, see the General Explanatory Note to this Chapter.
Unexpanded polystyrene is a colourless, transparent, thermoplastic material which finds extensive use in the electrical and radio industries. It also has packaging applications, for example, in the packaging of foodstuffs and cosmetics. It is also used in the manufacture of toys, clock cabinets and gramophone records.
Expanded (cellular) polystyrene contains gases from the expanding process and has a low bulk‑density. It is extensively used as a thermal insulent for refrigerator doors, air‑conditioner housings, cold storage facilities, freezer display cabinets, and in the construction industry. It is also used in disposable packaging and in food serving articles.
Certain chemically modified copolymers of styrene are ion‑exchangers (heading 39.14).
Styrene‑acrylonitrile (SAN) copolymers, which have high tensile strength, good mouldability and chemical resistance, are used for making cups, tumblers, typewriter keys, refrigerator parts, oil‑filter bowls and certain kitchen equipment. Acrylonitrile‑butadiene‑styrene (ABS) copolymers, which have high shock and weather resistance, are used in the manufacture of parts and accessories of bodies for motor vehicles, of refrigerator doors, of telephones, of bottles, of shoe heels, of cases for machines, of water pipes, of building panels, of vessels, etc.
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