How to Identify a Plastic

I don't think I added anything to what you said. Should have read your post before running off at the mouth.

Hi Jack, Thanks for the links. GA to you. -S

You can test slices of it to determine the dielectric properties of the material.

You could buy what you need and get on with life.

You could take your block of mystery plastic to your local plastics distributor's warehouse and maybe compare materials.

You can burn samples and sniff the smoke.

Do you know what dielectric properties you are looking for?

Which material would you like it to be?

"You can test slices of it to determine the dielectric properties of the material." I am considering that, But I think the best solution is to buy new for the project. "Which material would you like it to be?" Teflon is first choice, Nylon is last choice.

Nylon reacts badly to hydrochloric acid.

Happy New Year Guy,

Forget your plastic! It can be thermoplastic or not, can be good conductor or not. It takes too much time to find it and the waste will not compensate the quality.

Use a clear 2-pack epoxy composition made specially for electrical applications. Ask one of many manufacturers and get what you need, Gil.

This sounds remarkably hypothetical, homeworkish... but I think I know you are not a student.

You can sort plastics to a large extent by physical properties: friction coefficient, tensile strength, impact resistance, density, melting point, etc. and perform those tests. Then, do chemical tests. Obviously, you would also want to test electrically.

Unless you have pretty sophisticated plastics fabrication equipment, getting the very thin film required as a capacitor dielectric from a block of plastic would be troublesome. Why not just buy dielectric film... especially if this is a critical application? You would spend far more in testing costs than the value of the block of plastic (unless, perhaps, your block is 5 meters on each side).

Hi Blink,

Have you all equipment to do the tests? Are qualified to execute all tests? No critics, I work in the paint industry for over five (5) decades and I probably don't know and never executed more than half of tests we use to measure different qualities and characteristics of paints. Also, like I already mentionned, time and energy cost more, so use something as an insulating material like 2-pack epoxy resin as coating. All coils are unsulated with it.

Yes, we can test all you mention but life will be short to find a convenient solution. My suggestion is only one and plausible solution. Wait for another, Gil.

Have you all equipment to do the tests? Are qualified to execute all tests?

Yes, of course. It's not much different than the tests of minerals many of us did as kids. When I pick up a piece of Nylon or Delrin in my shop I can tell the difference instantly, without having to employ any test equipment beyond my hands, eyes, and ears.

Incidentally, all coils are not insulated with epoxy.

Hi Blink,

You are mentionned "friction coefficient, tensil strength", and other tests that require sophisticated and expensive equipment. Kids do analyse? I don't think so but it's your opinion.

I suggest to visit the initiator of the blog and tell him what and how to do! It's simple like you tell us, isn't it? That way, no harm to nobody, no error of judgement, and solution to a problem! Bravo Blink, you help a person in need, Gil.

"getting the very thin film required as a capacitor dielectric from a block of plastic would be troublesome. Why not just buy dielectric film." I don't think I need a thin film to use as a dielectric, I should be able to use any thickness I choose as long as I have the appropriate jig. I may not use it as a film, but as a support for metal plates. Then I can use oil as the dielectric if I choose.

Plastics melt at different temperatures.

1)Put a sample piece in the oven at 200 F and wait 15 mins.

2)Check the sample to see if it is beginning to melt.

3)I sample has not started melting increase the temperature by 50 F wait 15 mins, repeat step 2 and 3 until the sample begins to melt. When the sample has started to melt or soften you have found the melting point of the mystery plastic. Then look it up on a chart. Here is a web sight for a chart, look under melting point. http://www.machinist-materials.com/comparison_table_for_plastics.htm

Hi Victor, I had seen that table and printed it, but didn't realize the printout was truncated. Thanks for listing it. The table, however doesn't have all the choices, but if it doesn't melt before 500 F it's probably Teflon. -S

Some of the suggestions above are very good. You might also try to obtain a copy of a small book published by The Society of Plastics Engineers that is titled(I think) "How To Identify Plastics" It is a small book of simple tests to ID which resin a plastic may be. It is layed out in a step by step flow chart format.

Well, <...Nylon...> can be identified as it decomposes on exposure to dilute hydrochloric acid whereas the others don't. <...Teflon...> burns with difficulty with a lot of sooty, black, acrid smoke. <...Polypropylene...> also produces sooty black smoke as it burns though it melts as well and doesn't smell so bad. <...Delrin...> has the highest mechanical strength of those four.

Does that help?