# Question about plastics



## BeeAMaker (Nov 18, 2017)

I can't remember my plastic acronyms, Is there a plastic that resin (any resin) won't stick to ? I know resin usually won't stick to a very smooth surface like glass, but is there are plastic that Resin won't adhere to at all?


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## TattooedTurner (Nov 18, 2017)

HDPE is the only one that I know of.


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## PatrickR (Nov 18, 2017)

I think Polypropylene qualifies. Most trash cans are made of it. It has to be flame treated before printing inks will stick to it, including epoxy.


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## BeeAMaker (Nov 18, 2017)

HDPE is Polypropylene so your probably right!


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## Woodchipper (Nov 18, 2017)

Excuse me please, High Density Poly Ethylene?


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## mark james (Nov 18, 2017)

Not sure what application you are going for, but I use silicone a lot.  No, not a plastic, but still useful

The kitchen cutting mats (upstairs, left side, top right drawer... when Wifey is not looking) are excellent to glue segmented stuff on with wood glue, epoxy, CA.  Bend the mat it pops off, bend it some more all the glue pops off.

Makes excellent casting molds also (i.e., silicone sets of flexible measuring cups).


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## duncsuss (Nov 18, 2017)

Not many things stick to PTFE (polytetrafluoroethylene). Perhaps better known under it's brand name, "Teflon".


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## bmachin (Nov 18, 2017)

Acetal (Delrin) maybe?

Bill


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## duncsuss (Nov 18, 2017)

bmachin said:


> Acetal (Delrin) maybe?



I wondered about that, but remember seeing a kitless pen that used acetal as finials on the barrel and cap. (They might have been threaded, of course.)


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## BeeAMaker (Nov 18, 2017)

Thought about Silicone, but need something non flexible.
McMaster has good pricing, Proto-type time


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## PatrickR (Nov 19, 2017)

McMaster.... I love that place. i always have stuff in my cart. I looked through the plastics and there seems to be several options for you.


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## Sylvanite (Nov 19, 2017)

bmachin said:


> Acetal (Delrin) maybe?


Delrin works quite well.  I bought a box of Delrin pieces several years ago and have used it for molds (PR, Alumilite, and silicone), bushings, gluing jigs, and custom mandrels for CA build-ups.  Nothing sticks to it.

That said, any mold (of any material) that gets scuffed over time will eventually become difficult to demold from.  A good mold release agent will help tremendously.  So well, in fact, that the actual mold material becomes less important.  I use UMR mold release.  With it, you can even cast silicone in a silicone mold (without it, the two will fuse permanently).

I hope that helps,
Eric


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## chartle (Nov 19, 2017)

Certain HDPE plastics can be melted into blocks. Its any thing made from HDPE thats been injection molded not blown like milk bottles. HDPE for bottles is just a slightly different mix and doesn't melt nicely. The injection molded stuff melts down like thick wax. 

I've been making blocks upto breadpan loaf size. Luckily I have an endless source of HDPE from work.


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