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View Full Version : Not mystery metal but mystery PLASTIC? Help..



JRouche
09-15-2012, 01:20 AM
Ok, ok. I know the mystery metal posts get on some folks nerves. I get it, why work with mystery metal? Well as a home shop hobbyist I need to get inexpensive materials. I dont have alot of money to buy clean stock. I have my fair share of saw drops that I scrounge from the local shops that work with metal. And I have my honey pots that I frequent. I try to see what they are working with at the time when I dig through the "scrap" metal cut off box and try to get some idents of the metal from the shop. And they sell it off at about 9-13 cents a pound. I love my scrap metal...

But a new company is in town and its plastics they work with. UHMW, Teflon, Acetal and some other identifiable plastics.

My question? How can I tell the diff between Acetal, UHMW and Teflon? I picked up some drops and they are all white or off white. The thing is I know what these plastic parts are. So its not a big deal with these cuts. But I started thinking. What if there is no ident for the plastic that I might buy. Mainly the Acetal and UHMW. The Teflon is a bright white so its pretty much noticeable.

How can I tell the diff from UHMW and Acetal? And for that matter Teflon?

I know. Its hard to give advice with mystery materials. There is no firm determination. For metal maybe (there are at least some spark tests) how bout plastics?

The Acetel seems "stiffer and harder". The UMHW seems softer and more gummy when cutting.

So my question? Is there a simple but not complete test (like the spark test with steel) to get me close to what type of scrap plastics I buy? Thanks in advance, JR....

Frank Ford
09-15-2012, 02:33 AM
I believe it's been posted before - here's a cool flow chart for identifying plastics by "spark test" (burning):

http://www.recycleduklimited.com/files/burning-1.pdf

customcutter
09-15-2012, 08:47 AM
Great info. Posted to my "favorites". I would just suggest using caution if burning any plastics in enclosed areas.

Ken

Evan
09-15-2012, 11:47 AM
I've posted that chart here several times in a more printable size. I surprised that anybody hasn't seen it.

customcutter
09-15-2012, 01:51 PM
I've posted that chart here several times in a more printable size. I surprised that anybody hasn't seen it.

Evan:

Gotta remember some of us are fairly new, or maybe we missed it. Also sometimes you have to see a "treasure" several times before you recognize it.

Ken

JRouche
09-15-2012, 02:07 PM
Thanks guys. Great info..... JR

Evan
09-15-2012, 03:21 PM
Ken,

Last posted on 08/12/2012 http://ixian.ca/pics9/biggrin.gif

http://bbs.homeshopmachinist.net/threads/55515-Plastic-gloat

customcutter
09-15-2012, 08:33 PM
Ken,

Last posted on 08/12/2012 http://ixian.ca/pics9/biggrin.gif

http://bbs.homeshopmachinist.net/threads/55515-Plastic-gloat

I remember it well, now that you brought it up. At the time I didn't "recognize it for the treasure" that it was.;) Since then I've acquired a few small pieces. Hoping to machine some blocks to hold AR uppers/lowers in the bench vise. I'll save that one also in my favorites, so that I can print it off first chance I get.

Ken

morehelium
09-16-2012, 05:09 PM
Quick test to distinguish Plexiglass and Lexan (acrylic / polycarbonate)

-cut a small ~1/2" square piece and whack it with a hammer on a hard surface.

Acrylic will shatter, polycarb won't...

Chris

Evan
09-16-2012, 06:43 PM
Regarding the burn testing and in keeping with the caution by Ken take note that if the plastic "initialism" such as PTFE has an "F" in it anywhere it probably contains Fluorine. Any plastic that contains Fluorine will produce extremely toxic gases of decomposition when heated above the decomposition temperature. PTFE (Teflon) is notable for generating exceedingly toxic gases when heated above about 550 to 600 degrees F.

Many plastics generate toxic gases when they burn but the fluorine based plastics can cause life threatening toxicosis in just a few breaths. The general name for the syndrome is PFF or Polymer Fume Fever.

customcutter
09-16-2012, 08:47 PM
Evan:

Just an educated guess on my part, but I remember from my early fire fighting training. I was told that regular foam rubber burning in a house fire was extremely toxic, 1 breath you were unconcious, the next you were dead. In the phosphate mines we had hydrogen sulfide in low lying spillways, caused by rotting vegetation. At around 2% you would get a wiff of rotten eggs, stronger concentrations you wouldn't even smell it. Again 1 breath and you were unconcious, 2nd breath and you were dead. There was one incident were there were like 4-6 people down in a spillway only 1 survived. The first person went down to adjust spillway boards, went down due to gas, safety watch tried to retrieve him without backup, several minutes later others arrived and continued down the ladder.

Ken

hitnmiss
09-18-2012, 03:10 PM
back when I bought scraps from the local plastic guy he showed me to rap the pieces on the concrete floor.

Acetal and PVC had distinct sound differences. One would ring and the other would thud. Can't remember which was which.


Teflon I could tell apart by being slick and shiny where it was cut even.