Question About Keycap Plastics

[nsrexler]

Forgive me if this is a stupid question, but how come all keycaps seem to be made of ABS, PBT, or occasionally POM? There are hundreds (thousands?) of different types of plastics, so why are we only using these three?

Edit: I looked it up and I was mistaken, there are only a few dozen main types of plastics. Still, why do we only use three of them for keycaps?

[TheGreatAmphibianPling]

A few more types are used - see

http://deskthority.net/wiki/Keycap_construction (VERY good link)

But basically, you want cheap, easily moulded, wear resistant and capable of standing a high temperature for dying. And resistance to yellowing - that's a big one for plastics and it is where PBT scores especially well.