Identifying plastics

I am restoring a couple of accordions, dating from the 1950-60s. They contain some components that appear to be moulded material of some sort. I'd like to be able to identify the material. I'm aware that 'hard rubber' (whatever that is - it's hard and black...) was/is used for saxophone mouthpieces, but don't know much about what plastics were around in my childhood. Accordions have traditionally been covered in moulded sheet celluloid, but the things I'm interested in are thicker-section items like feet and moulded key facings, which I doubt are lumps of celluloid (although the key facings might be...).

OK, I know there were thermosetting materials like Bakelite, and some thermoplastics, like acrylic, polystyrene, polyethylene, nylon and possibly ABS, but what else? Are there practicable ways of identifying plastics from this era? From plastic kit-making days, I could tell polystyrene by its smell, but my sense of smell is poor now, and, although a childhood pyromaniac, I've forgotten the burning characteristics of those plastics the identity of which I knew. Also what is 'hard rubber'?

Edited By Kiwi Bloke on 04/09/2023 11:28:52

Oh, sorry, I'm guilty of a sin that's all too common: not making an effort to help myself before seeking help. Now I know what 'hard rubber' is, thanks to Wikipedia...

British Plastic Federation have a website that may be of interest bpf.co.uk I believe

Regards Mike

Sometimes a photo helps, when you see the part you can start to guess as to how it was made (injection moulding ejector marks, witness lines etc..) else solubility, does it melt, feel (dry waxy?). For most of his working life my father worked with phenolic resins which used to turn up in brake pad, billiard balls, rosary beads, cutting disc for jewels and lamp capping cements amongst others. I worked with high temperature thermoplastics PEEK and PES..

Sometimes if you can describe the part you will get lucky and an internet search will give you a match and a clue what something is made of. If is a small volume part, this may also be a clue. Sometimes just a filled epoxy, well cured, will do as a substitute.

Regards,

Dick.

Degradation/ageing is a big issue with plastics. I've seen examples that bear little resemblance to the originals. So straight identification might be a problem.

Just don't burn test suspected celluloid without a lot of care, it burns very fast

Hard Rubber may well be an alternative (? colonial) term for Ebonite - as used for the cases of car batteries until this century. (=/-). Another description is hard vulcanised rubber - in which more sulfur* than usual is used, so the rubber loses its springy nature. The black is carbon.

And a further warning re celluloid - it is only a smidgeon different from nitro-cellulose (gun cotton). So don't hit it. Old cellulose is hard because the plasticiser (? camphor, from memory) slowly evaporates. That is why the coating on pre-war steering wheels is fragile.

* yes, that is the correct modern spelling. It derives from a country where ass doesn't mean donkey.

Regards, Tim

Yes Tim but on an English site the correct ENGLISH spullin is preferable.

Regards Ian.

I give the 'correct' spelling for the UK - according to the latest info from the New Scientist.

Cheers - from an old scientist

Tim