Re: Viewports gobbed on with silicon

["Marsee Skidmore" <heyred@email.msn.com>]

I found some "Apparent Modulus" (Creep) data in the Modern Plastics
Encyclopedia, and it doesn't show any significant difference between Acrylic
and Polycarbonate. I don't think this is an issue. Polishing certainly is.
Polycarbonate is certainly prone to stress cracking, but Acrylic isn't
immune. Caution should be exercised in drawing conclusions from generic
material properties. The world of plastics is awash in additives and
modifiers, so each flavor should be evaluated individually. On the subject
of hot forming, ya know you can cold form Polycarbonate just like sheet
metal. Not recommended as a pressure vessel, but a dynamite process for
ambient pressure canopies with that Stealth/Star Wars look. :-o Joe
-----Original Message-----
From: protek@shreve.net <protek@shreve.net>
To: personal_submersibles@psubs.org <personal_submersibles@psubs.org>
Date: Friday, August 13, 1999 1:33 PM
Subject: Re: Viewports gobbed on with silicon


>Thanks Phil!
>
>    I couldn't think of a better argument than that against polycarbonates!
>
>Gary
>
>At 10:42 AM 8/13/99 -0400, you wrote:
>>Message text written by INTERNET:personal_submersibles@psubs.org
>>><
>>
>>Hi, Gary:
>>        Just a quickie - off for Key West . . .re polycarbonate: soft:
>>(scratches easily) hard to polish ( 'burns' easily) but, worst of all,
cold
>>flows readily under sustained load. Good for protective dome; not good for
>>vision/pressure dome.
>>Regards
>>Phil Nuytten
>>
>>
>