Thermoforming is a technique that involves taking a plate-like material (glass, plastic ...) then heating it to soften it, and to take advantage of this ductility to shape it with a mould. The material hardens when it cools, keeping this form.
Many plastic parts are thermoformed: plastic cups, yoghurt pots, most packaging (blister), etc. Hard cover protection for electronic components, machinery, or even automotive body parts (ex. bumpers). For the thermoforming of thermoplastic we use materials that have a rubbery plate (the difference between the softening temperature and the melting temperature) to a greater or lesser extent. Ideally, this plate should be as broad as possible to provide the best options for thermoforming. It is mainly influenced by the crystallisation rate and the molecular weight (chain length). This is why some thermoplastics are difficult to thermoform, PA, for example.