what does happen when i make flexible polyurethane foam, it does not enough rise ? it has big bubbles on the top part of the foam.
thank you!
This problem can happen due to a variety of reasons. Most probable causes of insufficient rise are (1) not enough mixing of the reactants – try to mix quickly and aggressively if you mix by hand, (2) wrong release agents used – silicone based release agents can lead to collapse and insufficient rise, (3) temperature – try to mix and cast your foam in room or slightly above room temperature. Make sure your mold is also in room temperature or above when you poor the mixture in.
Dear all, I think the gas release is faster than the polymerization reaction, it escapes easily from the matrix. This may be due to the inadequate choice of either the foaming agent and/or its operating conditions. My Regards
Dear Khadijeh Ghassemi, the following two links and the two attached files provide the major reasons behind the PU collapsing. My Regards
https://www.smooth-on.com/support/faq/164/
https://doi.org/10.1016/j.polymdegradstab.2010.02.019
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