cfharris at erols.com
Thu Apr 28 14:36:35 UTC 2011
The only real way to tell with plastics is to subject them to the test
of time and environment. The basic problem is one of plasticizer migration.
Many plastics have an added goo that improves the way they flow in molding,
and softens the plastic so that it is suitable for use. The plasticizer
evaporates slowly out of the plastic making it shrink, and leaving it very
brittle. Some plasticizers migrate to the surface leaving the plastic very
sticky... vinyl (PVC), particularly soft vinyl, which is heavy in plasticizer,
has that problem. That plasticizer migration is what makes xerox'd pages
stick to vinyl binders, leaving the lettering behind on the vinyl...
Some of the ancient plastics aren't really plastic at all... bakelite is an
example.... and they hold up incredibly well. The common characteristic,
in my opinion, no plasticizer. The much fabled BPA is one of the plasticizers
that causes problems if it isn't used just right.... It also causes breast
development in men, but that is another story.
Marvin E. Gozum wrote:
> Is there a way to decipher plastics potential longevity in a finished
> I'm impressed plastic parts on many HP equipment endure intact over 20+
> years, some barely discoloring. I can't tell what type they are, but the
> more durable plastics often feel hefty and solid. Likewise, Fluke DMM
> have the same 'feeling' and endure for decades.
> On a side note, casing of some iPhones barely 2-3 years old are
> spontaneously cracking, so it can be made quite badly too.
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