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I just looked at a microscopic cross section of sprayed polyurethane foam (SPF) and see that the cells are very irregular and the cell walls appear glassy and brittle. Is this OK?

April 26, 2017cells cross foam irregular looked microscopic polyurethane section SPF sprayed

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I just looked at a microscopic cross section of sprayed polyurethane foam (SPF) and see that the cells are very irregular and the cell walls appear glassy and brittle. Is this OK?

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No. What you have observed is foam that is “off ratio”. Sprayed polyurethane foam is manufactured by mixing 2 components, A and B, at equal proportions. If the proportions are incorrect, the foam can have the appearance you describe. What you’ve described is characteristic of off ratio form where the A component is greater than the B component.