Polyurethane foam is a rigid polymer, a type of plastic, formed when two liquid components react, expand, and cure into a lightweight, high-strength, water-resistant material used to lift and support concrete.
In depth
The foam is created by mixing an A-side (isocyanate) and a B-side (polyol blend). When combined in the correct ratio the two react within seconds, generate heat, and expand rapidly into a closed-cell structure, reaching about 90% of final volume almost immediately and fully curing in 15 to 30 minutes. Once cured it is rigid, dimensionally stable, and capable of supporting significant weight.
Although raw isocyanates are hazardous, cured polyurethane is non-toxic, chemically inert, and classified as non-hazardous; it can even go into standard construction-debris landfills. One caveat: the foam is not UV-stable, so it must stay buried under concrete or soil and never be left exposed to sunlight.
How Acme applies it. The foam Acme uses has a compressive strength of roughly 100 PSI at a typical density of 4 lb/ft3, suitable for residential, commercial, and highway-grade lifting.
Related terms: Two-Component Polymer, Closed-Cell Foam, Hydrophobic Foam, High-Density Foam, Compressive Strength
Frequently asked questions
Is polyurethane foam safe once cured?
Yes. In its cured form it is non-toxic, chemically inert, and non-hazardous. It is water-resistant and will not leach into soil.
Does polyurethane foam break down over time?
Not underground. It is dimensionally stable for decades. Its one weakness is UV light, which is why it is always injected beneath concrete or soil.