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Clear Plastic

Clear Plastic

Clear Plastic

(OP)
Is there any CLEAR plastic (in sheet form) that won't degrade in moderate acid or base pH environments?

RE: Clear Plastic

That depends on some specifics:

HOW clear?  Optically clear, transparent, or translucent?  What level of transmissibility (% of light transmitted) would be okay?

What pH and what temperatures?

The (partial) list below proceeds in a decreasing chemical resistance as you read down:

ECTFE can be had in translucent to near-transparent sheets.  PFA is similarly clear, but don't know of anybody supplying it in sheet form.  Both are pretty much as chemically resistant as you can get in a "clear" product at high temperatures.

PVC, ABS and similar vinyl compounds can achieve transparency, and have good acid/base resistance.  Think of clear vinyl tubing.  Both are limited to below-boiling temperatures.

Cellulose-based plastics (used for a lot of "blister" packaging) have "moderate" acid and base resistance, and good transparency.  Temperature limits for these are pretty low ("warm water")

Polycarbonate and acrylic are commonly used as "window" substitutes; both have pretty lousy chemical resistance.

RE: Clear Plastic

Polysulfones are amorphous, transparent materials with excellent thermal and chemical resistance.

Pierre Coat
Material Analyst

hi_performance_polymers@yahoo.com

RE: Clear Plastic

Whoops.  Add PET to that list too, somewhere above cellulose plastic for chem/temp resistance.

Add FEP to the top list.  PVDF between PFA and PVC.

There are "clear" nylons, which should have good alkaline resistance, but not so good in acids.

And add disclaimer "by all means this list is not complete".

RE: Clear Plastic

(OP)
btrueblood,

Thanks for the quick response.  I'll look into the materials you have suggested.

The application is for a window/door for a plastic lens polishing chamber.  The opperation is at room temperature.

The chemistry of the polishing slurry is unknown and secret-we will test the plastic in a bucket of the slurry.

RE: Clear Plastic

Why not glass?  That is the standard for this application.

How about epoxy - it can be clear and chemically resistant.  The "sheet" requirement would need a creative interpretation.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Clear Plastic

I'd agree with CoryPad, glass would be best - the slurry is going to abrade whatever you use, glass will give a longer lifetime.

RE: Clear Plastic

Glass sounds good to me.

Acrylic is not so good to acid, but is very good to abrasion.

PC is lousy to abrasion but pretty good to acid, not so good to alkali, especially if hot.

Ally (?spelling) resin (CR39) is probably the best, but might not be avaliable or cost effective

Regards

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RE: Clear Plastic

Does anyone know of a source of optical quality clear acrylic camera domes which truely are of optical quality?  I need a size ranging between 14 and 16 inches in diameter.  They would be hemispherical and  significantly superior to typical security camera domes.
Thanx.

RE: Clear Plastic

I agree glass is best. If you are fixed on plastic then try SAN. It's cheap, chemically resistant and transparent. And it has the highest modulus and therefore good scratch resistance compared to many other transparent polymers. For extra chemical resistance get a grade with higher acrylonitrile content.

You might look at cellulose acetate proprionate too (from Eastman). It's not that scratch resistant but has a special property that with a hair drier you can heat it and the scratches anneal out.

RE: Clear Plastic

What has modulus got to do with scratch resistance. Take diamond and rubber for example. both have good scratch resistance.

Acrylic also has very good scratch resistance as does all cellulosics like acetate, butyrate and propionate

Regards

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RE: Clear Plastic

Hi Pat,

I really enjoyed your excellent answers to a broad range of topics.

You are right, there are many ways to measure scratch resistance and they give different answers. From working for several of years on that subject at a major appliance manufacturer I have some experience. In fact your comment is right on the mark, the two extremes give the best performance. Soft elastomeric materials like PU are excellent and so are very hard materials like diamond. Materials in between are poor, i.e. most plastics. Also it depends on what you make the scratch with and the type of test. However, if you cannot have diamond or PU then I have seen results for transparent plastics (made with Taber Abrader) and the material with highest modulus was best (SAN).

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