Quote:
Originally Posted by Lil' Lavery
Plastics, by their nature, tend to fail in a brittle fashion.
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OK, I let it go when the first few people said it, but I can't let it go any more.
Sean,
Your above statement is factually vague and incorrect when talking about plastics on Earth (I say on Earth only because of your last name).
Generalizing the material properties of all plastics is as appropriate as generalizing the materials of all metals. Better yet, even generalizing the material properties of a given plastic (like Nylon, for instance) is completely inappropriate. I don't expect many people are plastics experts, except for the chemical engineers that design the plastics; however, I have vast experience in the field of plastic material properties and their failure modes.
General use Polypropylene is very brittle. Color additives and clarifying agents can significantly change that behavior. For example, many companies use PP bags to hold small parts. They also may use clarifying agents that make the PP bag really clear. This makes the bags even more brittle.
It is possible to mix in additives to make PP very ductile. I am certain this is what Pneuaire has done. PP is desirable because it is used for many approved devices for use in food handling equipment. The Pneuaire tanks are also FDA approved.
Polyethylene is also a very ductile plastic.
PTFE (or Teflon) is extremely ductile, so much so that is it really malleable and hold a deformation if stressed too far.
The bottom line is that to make the claim that plastics are brittle is factually incorrect.