This is a thermoplastic polymer, commonly known as PMMA or acrylic. It is a hard, rigid and lightweight material with good optical properties.
PMMA was developed in 1932 by John Crawford and produced by ICI as a cast sheet of material which could be thermoformed or fabricated. It was regarded as being tough and an unbreakable alternative to glass. Having excellent optical qualities it was famously used for the bubble canopy of the Supermarine Spitfire offering good all round visibility and reducing weight.
Its good optical qualities and rigid and lightweight characteristics means that it has many uses including spectacle lenses, windows in commercial aircraft, jewellery, furniture, tableware and decorative objects.
PMMA can be industrially recycled by depolymerisation by heating to about 400°C. This breaks it down into its component parts which can be used to produce new material.