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Expanding Foam - 2-Part

Adjustable Density Expanding Foam
Two-part expanding foam, great for fin encapsulation, securing noseweight, etc. Includes (2) 8-ounce bottles

By combining equal parts of A and B, the foam expands to about 10 times it’s original liquid volume. The result is a 6 lb. density (per cubic foot) rigid foam that is extremely strong and still relatively light weight. This is perfect for filling small spaces where the highest strength is required and weight is not a real issue.

However, as the volumes increase, a lower density (higher expansion ratio) may be desirable. With the increase of volume, surface area also increases so strength and adhesion are less of a factor. In larger volumes, weight may be the over riding concern. Rather than stock several hard to get foam densities, it is much easier to lower the density of a high density foam as needed.

This type of polyurethane foam is highly reactive to small amounts of water. Even the humidity in the air can slightly alter the expansion ratios. The more moisture introduced into the mix, the higher the expansion ratio. By purposefully adding small amount of water to the mixture, we can adjust the expansion (and density).

Most other brands of commercially available 2 part liquid foam expand to about 20 times their original volume and are already near the limit of usefulness. The foam is near it’s lowest density and strength. It cannot be adjusted down. Our new Adjustable Density Foam starts as a denser foam that can easily be adjust up using just a few drops of water.

Below is a photograph showing the results of adding various amounts of water to the mixture of foam. The difference of just adding one drop of water is dramatic. Keep in mind that if you double the batch size, you will need to double the water amount to achieve the same expansion ratio. A little experimentation is highly recommended before actual use in your project.

The Expanding Foam features are:


  • Expands 10 to 25 times it`s liquid volume. (10x expansion mixed in equal parts, adjustable to 25x with water)
  • High temp formula. Perfect for fin root encapsulation.
  • High adhesion rate.
  • Two equal part (by volume) mix ratio.
  • Does not need air contact to cure.
  • Fast curing.
  • Light weight.
  • Easy to cut and sand. Very carvable.
  • Great for strengthening thin wall nose cones or securing nose weight.

Click here for a PDF file showing how to use the foam. WARNING: Do not burn or use hot-wire cutting methods on this or any other urethane based foam product because toxic fumes will be released. (However, the heat of a motor casing next to the foam is not a concern.)

This product was added to our catalog on Sunday 29 November, 2009.
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