On 2 Sep, 2004, at 12:02, [EMAIL PROTECTED] (Martin Westbeek) wrote:
AFAIK the diff between Poly and Antron is that Poly floats. That's why it is so suitable for parachute posts. Antron does not float, so I wouldn't sub it for poly in all cases.
I hear this often, but given the fact that polypropylene ('poly' yarn) and nylon 66 (antron) are quite similar types of polymer, I was always wary of said claims. So today I decided to look it up, and lo and behold, most polypropylenes (though not all) indeed have a specific gravity lower than 1 (less dense than water, around 0.95) and most nylons have a specific gravity higher than 1 (denser than water, around 1.05). The differences are of such small magnitude, however, that I doubt if it makes much practical difference for fibrous material. For solid objects, you'd of course readily observe that a poly object would float and a nylon object would sink.
Reference: http://www.plasticsusa.com/specgrav2.html
Henk
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