Using “Plastex” for molding?

A Make reader is wondering about using “Plastex” – “Have you heard of ‘Plastex’? I’m interested in the home casting materials of plastex and friendly plastic – the former, in particular, anecdotally seems like it make have enough structural integrity to actually make useful items from and not just use it for gap-filling repair work as it is sold, yet seems much easier to work with than the entry-bar for other types of molding. I have not experimented with these items on my ‘to do’ list. (actually I did use friendly plastic as a kid – it melts however at high temperatures which could be a liability).” Have any Makers out there used this stuff? I’ve only see it here and here.