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Importance of Drying
> Fabrication Process >
Purging & Using Regrinds > Finishing
Polycarbonate resins are hygroscopic
and absorb water from surroundings. At elevated temperatures,
even very small amounts of moisture can attack the carbonate
linkage of the polymer and bring about chain scission,
lowering the molecular weight, resulting in the loss of
physical properties. As a result, resins should be pre-dried
at 120กษ for at least three to four hours in order to limit
moisture content to 0.01 percent to 0.02 percent before
use.
If regrinds are used, the drying time
should be even longer. Re-drying pre-dried resins is necessary
if they are exposed to air for longer than 15 minutes.
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