I want to prepare PU foam in my lab with very large pore size (possibly up to 1-2 mm in diameter pore size). Which method will be suitable? Etching treatment or air blowing?
Well, it depends on how you prepare the foam. If you use pentane as blowing agent for example, just increase the amount: the foam will be lighter, but the cells will be much bigger. If not enough, then change the blowing agent and use for example diethyl ether. I have many articles about foams in my RG profile, with different cell sizes, you should have a look there. Air blowing can be a possibility, provided that you find the suitable surfactant for stabilizing the cells.
Alain
Dear S. Ajit
In addition to what correctly stated by Dr Alain Celzard, I suggest to control the amount of the surfactnts/tensides used to stabilize the foam. The higher the amount of tensides the smaller the pore size. The choice of the tenside has to be built on the HLB value of your reactive mixture. Let us suppose that the HLB balance of your reactive mixture equals 12 (polar reactants), in this case it is better to choose tween 80 or tween 85. If the HLB of your reactants is quite low, as for example 4 or 5, it is better to use span 85, etc. Remember to use the lowest necessary amount of surfactants, otherwise they will reduce the pore size.
Bests,
Irini
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