Expanding spray foams, such as spray foam insulation are these created through a chemical process (where two chemicals react and foam up) or just a mechanical (pressurized with gas) process?

If a chemical one, what are the chemicals involved.

Sorry I tried 'How is self expanding foam made' and got loads of how it is used, but not how it is made or the chemicals involved.

its kinda like pressurized in the can till you let it out. its premixed but when it hit the out side air it expands. like whipped topping in a can. something with the air helps it solidify.

I think best i can do

I think what you start with it must be liquid under pressure.

But when you release the pressure, one component vaporizes. But because the pressurized material was a mixture, part of it (after a chemical reaction caused by the change of temperature due to the lowered pressure, produces a gas) expands. But some of the material stays solid (or semi-solid, like a fluid plastic).

So the gas molecules trapped in this "fluid" cause expansion; but the 'fluid' begins to harden , trapping the gas. So as it cools, the entire material becomes a solid-gaseous foam. (No longer fluid.)

This is just a guess. I didn't find a site either. But I have used those pump things.

There are two methods.

Professionals use a two part mixture. Part A mixes with part B and a chemical reaction cause it to foam up. This also starts the hardening process. This is preferred so it can harden in a closed space. No air curing or air drying needed.

Foam in a can is more like a shaving cream. The foam comes from gas under pressure in the can. When released, it causes the foam mix to expand. Kind of like shaking up a soda. These air cure or dry to harden.

Hm. I'm interested in learning more about the chemical kind. I guess nobody is able to find out what the two chemicals are. I had no luck.

I was kinda wondering if it was possible that natural ingredients, tree sap, plant material, something could do the same thing.

While I can not tell you what chemicals cause the foaming, here is a site for soy based foam or "Green Foam".

Foam

The early years of sprayed on or in, foam had formaldehyde in it and was taken off the market as a carcinogen. It was OK after it cured out but for the first several years, it would "Gas Off" putting formaldehyde in the air.

Formaldehyde

Foaming can be as simple as an acidic water and baking soda. When mixed to gether the give off CO2. Like old water based fire extinguishers. The water had baking soda in it and there was a vial of acid in the top. When tipped over, the acid would mix with the soda water and pressurized the can with CO2 pushing the water out.

I will continue to research this.