Overdrying PC

[brentb]

Can OVER PC drying lead to splay in PC?

Keep on molding!

brent

[Suhas]

Hi Brent,
For our readers let us first define 'overdrying'. Overdrying is a misnomer but it has been widely used and so I guess we will keep it that way. A better explanatory phrase would be exposing the resin the drying temperature more that recommended.
Having said that, I think if you expose any resin to an extended period of time there is a danger of the additives first breaking down. Additives such as flow promoters, heat stabilizers, plasticizers are all lower molecular weight additives and cant take heat for a longer period of time. (Keep a candle outside in your yard for a month in the sun and then look at it, it is now become powder like.) Once these break down and you start melt processing these they degrade further. If it was a heat stabilizer that degraded, then the polymer may break down. Splay is caused because of any gaseous product that gets between the mold surface and the polymer. The polymer cannot touch the mold and so so you see shiny streaks and sometimes the flaky surfaces.
So there you have it, chances are you will get splay if you over dry the PC.
Hope this helps.
Suhas