[gvdm]

Hello to all!

First I'm so sorry for my bad chemistry technical language.

Anyway, I'm searching for a material similar to plexyglass. In particular I'd like to find a non-toxic plastic material that I'll use for building the central part of an Harmonica (this -> http://www.harpelite.com/catalog/images/deluxe_comb1.JPG).
So it should be stiff but I should be able to make the holes and the slots by hand-instruments (I cannot use industrial or professional tools)...

I found the Polymorph (aka "Utile's plast"), which is a plastic which, if heated, becomes very malleable until it gets cold and strong....
an example of Polymorph is this:
http://www.youtube.com/watch?v=ZFXySiLZDOQ&feature=player_embedded

do you know if this plastic is non-toxic?

thanks
Giulio

[Enthalpy]

If your plastic must be transparent there is very little choice: PC=polycarbonate, PMMA (including the trademark plexiglass), and very few expensive ones like PMP.

PET, PETP are fairly transparent (water and soda bottles), nontoxic (be vigilant on additives!), tough, easy to process.

Now, if you don't need transparency, the choice gets huge. The most common plastics are PE (polyethylene) and PP (polypropylene), nontoxic without additives, tough, easy to process, fairly resistant. Still much choice within PE and PP. Stay away from PVC and PVA, be careful with PA (polyamides). You should prefer other plastics only if these don't fit.

Stiffer: sure, but I ignore how little toxic they're. Typical plastics for mechanical engineering include POM and PBTP. Processed faster with a file or a saw than PE, PP and PA.

Do you need some vibrational properties?
Resistance to humidity?
Heat, soap...?

And if you want to identify a plastic, the best method without a lab is to burn it and sniff it. Ask an experienced nose if yours isn't, or compare with known plastics. Density measurements also tell a lot. But the only two common transparent ones are easy to distinguish: a shock sounds duller in PC, scratching with a needle gives a softer feeling, solvents crack its surface, and it deforms prior to breaking.

[gvdm]

I prefer it a transparent plastic, but even a semi-trasparent or a opaque plastic is good.

So, you are telling me that polycarbonate, PMMA, PET, PETP, polyethylene, polypropylene, POM, PBTP are all examples of non-toxit plastic (without additives) which can fit my answer? It's a hard and huge choice! 

Let's add some details: it should be resistant to humidity (because it will stay at direct contact with mouth) and will not require a resistance to soap and solvents (because it is usually water-cleaned). It should be resistant to body heat (but I think all of them fit).

I found that Teflon is used to make cutting boards for cooking...can it be useful too?

Thanks a lot. I'm not expert about plastic materials and you are helping me very much!

Giulio

[AWK]

Search for MSDS

[hugh111111]

I don’t think you need worry about toxicity. I have never known anyone to die from occasionally licking a piece of plastic. You should survive.

[gvdm]

I don’t think you need worry about toxicity. I have never known anyone to die from occasionally licking a piece of plastic. You should survive.

yes, sure, I will survive. But after playing harp 30 minutes per day, every day in ten years, perhaps something will go bad, not because of licking the plastic but because of drawing  and blowing air through it...

[Enthalpy]

For the mentioned reason, I'd go the safe way about toxicity in a music instrument.

The choice is huge, and I only mentioned a few ones, because there are so many plastics. Within each basic composition (PE, PA...) you have variants depending on the molecular mass, the way it was produced, the additives... These variants are distinguished by trademarks which depend on each producer. That's the common life of every plastic buyer.
http://en.wikipedia.org/wiki/Thermoplastic

Some plastics are legally allowed to contain food. This would be the (exaggerated!) safe option. They include PE, PP, PET, PETP and more - though PET is meant to be injected, I doubt you find it as thick plates.

I wouldn't take PTFE (Teflon is one trademark), because it's mechanically so weak. It creeps over time. And it's so expensive. Worse, its fumes are toxic, and fast rotating hand tools can produce them.

I'd would take no PA nor PVC in a humid environment.

Here they explain the most common PC contains bisphenol-A
http://en.wikipedia.org/wiki/Poly%28methyl_methacrylate%29
whose danger is uncertain but may give a bad image of your product in the future.
This would leave PMMA as the only really transparent option. Easy to saw, file as well. But I don't like PMMA too much, as I felt its fumes made me cough after processing it with hand tools.

Do NOT use any resin you cast by yourself. You would always leave some unhealthy monomer and catalyst in it.
Don't heat-process (hot bend, weld etc) any functionalized plastic, as this would create new small molecules. Only PE and PP then.
Don't use any glue (and certainly not MMA!).

Nice, I just read that some POM have been approved for food contact
http://en.wikipedia.org/wiki/Polyoxymethylene
this is the one plastic for mechanical engineering. Strong, easy to process. Not transparent, but can be any colour.
Edit: susceptible to cracking by HCl, and breathe contains some. Oops.
Ask for the experience of flute makers.

Here they suggest some possible toxicity of PET should be investigated, that's new to me
http://en.wikipedia.org/wiki/Polyethylene_terephthalate

"PMMA has a good degree of compatibility with human tissue" they say
http://en.wikipedia.org/wiki/Poly%28methyl_methacrylate%29#Uses
this would make it better than PE and PP which are harder to saw and file

I'd suggest that you find samples of PE, PP, PET, PMMA, POM and try to process them by yourself: differences are big. And check their Material Safety Data Sheets, yes - of the very precise material you plan to use: the exact trademark of the exact producer.

[typhoon2028]

HDPE

[Enthalpy]

PE (without additives) is excellent for health, cost, price, humidity...

It's not comfortable to work. It creeps, slips, and resists abrasion, so it uses to escape from your vice unless you squeeze it into permanent deformation. Filing and sawing it requires more efforts than for mechanical plastics, though PE isn't hard.

The same holds for PP and is much worse with PTFE.

Other plastics are designed for mechanical processing, especially POM and PET, which most people prefer to pay after having had unpleasant time processing PE. Hence my suggestion to find some samples and try how comfortable they're to put into the desired form.

PMMA being favourable in this aspect.

[gvdm]

ok, thanks all of you for your advices! I'll take a closer look to the plastics you mentioned

[Enthalpy]

And now it's my turn... I'm making a Pan flute of plastic tube, it begins to work nicely (I mean, easy to play and damned loud).

It may well be used for hours and hours, and condensation is strong, but at least the musician is not supposed to inhale from this instrument.

I've made my experiments from PVC tube because it's available... Rationale:
- Plasticizers in PVC would be bad, but they're absent from rigid PVC (aren't they?)
- PVC pipes are allowed as drinking water adduction pipes at many North American places
- These pipes are originally ducts for electric cables, not for water adduction...

Your opinion please? Does it make sense? Or is that plain fool?
Can I hope that banal PVC, which I don't heat nor glue nor dissolve, is benign to the musician?

Thanks!