Foam Density
When describing any specific polyurethane system whether it is used for slab-lifting, void-filling, leak-sealing, etc. the system is typically referenced in terms of its density. For example, for slab-lifting, the foam system Poly-Mor uses is a 2 ½ lb. expanding polymer density system. What does this mean? The meaning of density is simply that it takes 2 ½ lbs. of liquid material which will expand into 1 cubic foot of solid polyurethane material. Similarly, if you had a 3 lb. polyurethane system it would take 3 lbs. of liquid material to give you 1 cubic foot of solid material.

Closed Cell Content
It is noted that in order to maximize the closed cell content of any foam system it must have a minimum density of 2 lbs. or more. The low density foams typically used for insulation purposes is well below the 2 lb. density requirement for closed cell material. The polyurethane foam you can purchase at a hardware store is very low density and hence open celled material which will nor stand up to exterior environmental conditions, especially freeze/thaw cycling.

Structural Characteristics

Effect of Density on Compressive Strength

There is a direct relationship between the density of the foam system and its engineering or structural characteristics such as compressive strength, elongation strength, flexural strength and tensile strength. The adjacent chart demonstrates this relationship and the impact of density upon compressive strength. The other relationships can be viewed on our web site at



I would like to take this opportunity to express my thanks and pleasure with the slab treatment Poly-Mor recently completed at my home. I want to express what a pleasure it has been to deal with Uretek. Right from the first contact with Harry, through dealing with the crew at my home, to receiving the bill. You should be proud and comforted to know that such a top-notch bunch of guys represent your company.
Next Time
Next time we will briefly review other characteristics of polyurethane foam like exothermic reaction, R-Value, etc.

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