I think I know what you mean. It sounds very similar to the type of material pvc foam sandwich blanking panels they use in uPVC doors. Seems to be a bit of a thinner capping though. I can see it has it uses for some trim parts and stiffeners.
Dibond has also been used for ages and is very good for certain things. Sam at CSP has made some FOHP back plates that are fully machined. This is, I believe, more a stiffener and primarily a silencing board for the otherwise hollow sounding switch movements and the flexing.
Difficult to beat metal for the MIP fascia though. With the cost of laser or water jet cutting then steel is a great option. It is dirt cheap to have cut.
The PVC board will be really nice to work with I would presume. ?
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