Styrene, the building block of polystyrene, can turn into plastic by itself
Leave pure styrene warm and it starts linking into polystyrene with no help at all, releasing heat that speeds the reaction further. That runaway has caused tanker and factory explosions, so the liquid must be dosed constantly with inhibitors. Chemists first spotted the trick in 1839, in resin from an American tree.
The compound takes its name from storax, the fragrant resin of sweetgum trees. In 1839 the German apothecary Eduard Simon distilled a sweet-smelling liquid from it and called it styrol. He noticed that air, light or heat slowly turned it into a hard, rubbery mass. Nobody then understood what had happened; only in 1866 did the French chemist Marcelin Berthelot recognise that mass as a polymer, the material now called polystyrene.
A second puzzle took longer. Chemists made what looked like the same liquid from cinnamic acid, another component of storax, yet the resin version bent polarised light and the other did not. In 1876 the Dutch chemist van 't Hoff showed the difference came from a contaminant. Small natural traces of styrene turn up in cinnamon, coffee beans and peanuts.
Industry now makes it on a vast scale, around 35 million tonnes in 2018. Most comes from ethylbenzene, itself made from benzene and ethylene, stripped of hydrogen by superheated steam at up to 600 degrees over an iron oxide catalyst. Separating the two afterwards is tricky because their boiling points differ by only 9 degrees, and the hot styrene keeps trying to polymerise inside the columns. The results end up in rubber, insulation, fibreglass, pipes, car and boat parts, food containers and carpet backing.
Its effects on people remain debated. The International Agency for Research on Cancer calls it probably carcinogenic, and the US National Toxicology Program says it is reasonably anticipated to cause cancer, while the Danish environment agency concluded in 2012 that the data did not support a cancer concern. Studies also link it with hearing problems, particularly in combination with noise.
Source: Styrene
