Air bubbles in polyurethane castings

From: Tony Manicom (
Date: Thu Jul 23 1998 - 22:02:25 EEST

A problem with casting polyurethane parts is getting the resin to displace
all the air in the mould. Small air bubbles often ruin the castings. Casting
in vacuum is an option for some moulds but not always practical.

Does anyone in the RP group know of a gas that is soluble in liquid
polyurethane that could be used to flood the mould and displace air before
pouring - trapped gas bubbles would dissolve in the polyurethane.

I know that carbon dioxide or ammonia gas can be used to get water to fill a
container. Has a similar process been tried for resin casting using RTV or
epoxy moulds ?



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