The Mad Surveyor

A question a customer asked was: How hot is the polyurethane foam when it is sprayed? Well, the answer is that it varies between about 100 C to 130 C depending on ambient temperature.

The polyurethane foam is sprayed on at this temperature because it sprays well at a high temperature (when it is cold it is very sluggish) and gives a good spray. It also ensures very good bonding to the substrate, typically a slate or tile. Also, the typical pressure for the spray foam is 60 pounds per square inch. In effect, at 120 C and 60 psi the foam welds to the substrate and ensures excellent bonding. To ensure that the foam reaches (via the flexible delivery pipes) the spray gun at a high temperature it is firstly warmed up by a heating block. Additionally the foam delivery pipes to the spray gun have electrical heating elements along the length that can be regulated to maintain the temperature of the foam from its journey from heating block to the spray gun. This is particularly important in winter months when the pipe run would cause the foam to cool down too much before delivery to the spray gun. On very cold days it is also necessary to heat the twin chemical drums to get sufficient low vicosity to enable the pumping process to start.

Now, all this specialist spray foam gear is quite expensive and also very high maintenance but essential if a professional job is to be done.