Plastics advice needed.

[dfariswheel]

I need to buy some plastic for a project, and need advice on the best for my needs.

These are side guards for an equipment seat.
It needs to be.........

12 inches by 8 inches.
1/4 inch thick.
Black in color.
STIFF and as inflexible as possible.
Won't crack after drilling holes and bolting mounting tabs on it.

The tabs will bolt to the bottom of the plate and up at least 4 inches.
The tabs fit in a slot with the plates sticking straight up.

This will be subject to side loading against the plates.

What plastic?? Delrin??

[Schuetzenman]

Delrin maybe. https://www.mcmaster.com/#standard-p...heets/=1bxzqxt Check Mc Master Carr I've put one link in.

[NAPOTS]

UHMW Poly?

[dfariswheel]

I thinks it's down to Delrin and HDPE.

Both sound pretty good for the purpose.
I contacted an online seller and asked which.

[Krupski]

Delrin maybe. https://www.mcmaster.com/#standard-p...heets/=1bxzqxt Check Mc Master Carr I've put one link in.

UHMW Poly?

I suggest Lexan (polycarbonate).

Delrin absorbs moisture like nylon does and gets brittle in cold temperatures.

Polyethylene exhibits cold flow (things bolted to it go loose as the plastic "flows" out under the pressure. HDPE is rather soft, but strangely also brittle. If bent beyond it's plastic deformation limit, it shatters.

These plastics are also degraded by UV radiation from sunlight.

Lexan costs quite a bit, but it's the most rugged plastic out there (a 1/2 inch thick pane of Lexan will stop a 5.56 bullet!).

[Schuetzenman]

Lexan aka Polycarbonate also absorbs moister and what is worse is gasoline and other solvents will kill it in 30 seconds. Very poor choice IMO says the guy with 35 years as a Molding Process Engineering career.