Note that boots are often used in snow and slush,
so you need a plastic that won't become too brittle
at low temperature -- it should have a glass
transition temperature significantly lower than the
lowest temperature the boots would be used at.
Plastic isn't the best choice for this. All of the
ones I've seen are metal. If you want it to look
like plastic, you can powder coat a metal core,
or injection mold around a metal core.
You don't say why you want to use plastic here.
If you're planning to injection mold it, you can't
use most thermoset plastics. (Integrated circuits
are molded in thermoset plastics, but those are
very special formulations.)
The strength of the plastic will be highly dependent
on the filler. You might want a chopped glass fiber
filler for good reinforcement. The filler may need
to be treated with a silane coupling agent or some
other modifier to promote adhesion between the
filler and the matrix. The epoxy-fiberglass
used in printed circuit boards usually has a
characteristic green color because of the copper
used to promote adhesion.
A problem with any non-spherical filler is it will
entrain to the direction of flow during injection
molding. Clever design of the mold can take
advantage of this to increase strength in the
desired direction. In a buckle, you'd want the
fibers to be aligned along the length of the spokes,
but you may create a weak spot where the streams
flow together. There won't be any fibers bridging
this spot, so that's where it's going to crack,
unless you do something about that.
Was this a microwave dryer? If not, why would plastic
not do the same thing?
If you used the metal part as a core for powder coating
or injection molding, you would not electroplate it.
You might pickle it shortly before coating or molding
to improve adhesion. After coating or molding, it would
be sealed againt the environment and not discolor or rust.
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