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Polyurethane block voids

Polyurethane block voids

Polyurethane block voids

(OP)
Hello,
I'm a relatively new chemical engineer, and am attempting to pour a Urethane part A and B system into a hot mold at 200F.
We are routinely seeing "air pockets" if you will as if the urethane is sucking back into itself during the curing process.

Do you have any tips for me?
Thank you

RE: Polyurethane block voids

If it is a room temperature foaming resin why are you heating the mold to 200F? At 200F the resins may over expand and collapse as a result.

RE: Polyurethane block voids

(OP)
Hello,
It is common practice to drive the urethane reaction and maintain a uniform reaction; typically you want the mold temperature to be the same temperature as the reaction.
The voids I'm seeing are normal if on the surface or exposed to air, these voids are not on the surface and nowhere near the atmosphere.
There is no air entrapment.... I'm thinking I may have leaky molds.

Thanks,

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