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Plastic Selection

I'm going to have an online machine shop build a part for me using a CAD drawing that I specify.

Typically, these parts are made of Aluminum, but this manufacturer also mills parts out of these plastic materials:

  • Polypropylene (PP)
  • Polystyrene (PS)
  • High impact polystyrene (HIPS)
  • Acrylonitrile butadiene styrene (ABS)
  • Polyethylene terephthalate (PET)
  • Polyester (PES)
  • Polyamides (PA) (Nylons)
  • Poly(vinyl chloride) (PVC)
  • Polyurethanes (PU)
  • Polycarbonate (PC)
  • Polyethylene (PE)

Polypropylene, I know, is the plastic used in Water Bottles, so I know that is not what I want.

This fabricated part will be used for the Clutch Cover on a motorcycle transmission and will have a raised section that needs to be tapped to allow attaching a gear shifter to, like in the Aluminum version below.

Clutch Cover with Shift Mount

I'd like something rigid and strong. Plexiglass comes to mind, but there could be a better alternative that I am unaware of, as long as I am not getting into something exotic that would cost more than Aluminum.

Is there a Chemical guy on here who could suggest a good plastic for me?

Naturally, the material would need to be oil resistant and withstand typical engine transmission temperatures.

Location on Transmission

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1  
If you have a vague idea, it would probably be helpful to say what 'typical engine transmission temperatures' are. Most of these materials have melting points around 100-150 degrees Celsius but may soften before that. –  Aesin Feb 22 '13 at 0:03
    
There is an oil temperature guage for the transmission. Theoretically, the oil can get hotter, but I've never seen it get over 210°F. I'm starting to lean towards a Vinyl. –  jp2code Feb 22 '13 at 1:29
1  
Most plastics melts too easy. The only you mentioned having a chance are polyuretanes and polyamides. And I will recommend aluminum anyway as it is much harder to screw things with aluminum. –  permeakra Feb 22 '13 at 20:08
    
@permeakra: Maybe you could expand that into an answer by explaining why they "have a chance"? :) –  ManishEarth Feb 24 '13 at 7:11
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@permeakra: Ah. Again, you really could put all that into a short answer to the question. Comments aren't meant to be permanent. –  ManishEarth Feb 24 '13 at 11:34
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1 Answer

up vote 3 down vote accepted

Most plastics consist of linear molecules with little inter-molecular interactions, so most plastics melts too easy. The only ones you mentioned having a chance are polyuretanes and polyamides. They have (CO)(NH) fragments, that forms strong intermolecular hydrogen bonds. So, they are ones of the strongest polymeric materials

And I will recommend aluminum anyway as it is much harder to screw things with aluminum.

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Thanks! Now I can vote something as an answer. Thanks to @Manishearth for the suggestion, too. I gave you a +1 for those so you'd get some "points". –  jp2code Feb 24 '13 at 15:33
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