Aromatics, so called because of their distinctive perfumed smell, are a group of hydrocarbons that include benzene, toluene and the xylenes. These are basic chemicals used as starting materials for a wide range of consumer products. Almost all aromatics come from crude oil, although small quantities are made from coal.
Xylene and polyester chain
One of the forms of xylene, paraxylene, is used to make polyesters which have applications in clothing, packaging and plastic bottles. The most widely-used polyester is polyethylene terephthalate (PET), used in lightweight, recyclable soft drink bottles (30% of production), as fibers in clothing (60% of production), as a filling for anoraks and duvets, in car tire cords and conveyor belts. It can also be made into a film that is used in video and audiotapes and X-ray films.
Polyester makes up about 18% of world polymer production and is the third most-produced polymer; polyethylene (PE) and polypropylene (PP) are first and second, respectively. Metaxylene is an isomer of mixed xylene. It is used as an intermediate in the manufacture of polyesters for coatings, inks, reinforced plastics and packaging applications. Unsaturated polyester is used over a broad spread of industries, mainly the construction, boat building, automotive and electrical industries. In most applications, they are reinforced with small glass fibers. Hence, these plastics are commonly referred to as glass reinforced plastics (GRP). Initially a liquid, the resin becomes solid by cross-linking chains. A curative or hardener creates free radicals at unsaturated bonds, which propagate in a chain reaction to adjacent molecules, linking them in the process. Styrene is often used to lower viscosity and evaporates during hardening, where the cross linking releases heat.
Orthoxylene is an isomer of mixed xylene. It is primarily used in plasticizers (primarily in flexible polyvinyl chloride (PVC) material to make it more flexible), medicines and dyes. Alkyd resins are a group of sticky synthetic resins used in protective coatings and paints.
