Physical blowing agent efficiency for polyurethane foams?

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Asit Baran Samui

Both nitrogen and mafron (banned) function as physical blowing agent.

Alain Celzard

As far as I know, pentane is widely used because of its low cost, despite its flammability. Other blowing agents have been developed by Dupont, some of them having quite low thermal conductivity, low greenhouse effect and zero depleting ozone action. But they are quite expensive ... Please check the link below.

Alain

http://www2.dupont.com/Formacel/en_US/assets/downloads/h75349_Formacel.pdf

Mike Bender

Dear Harith,

I believe that efficiency in blowing with a blowing agent also (A) relates to whether the introduced (or liberated gas) has solubility in the polymer. Likewise (B) the viscoelasticity of the polymer solution/melt is very important because as the bubble distends the polymer solution/melt it may fracture or strain stiffen and not reach a maximal distension that could have occurred. (B) means at the minimal that prepolymer visocosity/molecular weight must matter.

Use of azodicarbonamide in PVC foaming for architectural uses or pipe used to be common, but as the other writers are suggesting with some other blowing agents it too is being viewed a little dimly in parts of the world, I believe.

Best regards,

Dear Asit and Mike, please don't forget that PU are thermosetting polymers in this context, not to be extruded like PVC or PE with a gas saturating the molten polymer before the pressure falls abruptly down. Harith's question was very specific, hence my answer.

Dear Alain,

Thanks for your insight. I had indeed not taken in that Harith's systems would be thermosetting.

Mike B.

Harith Hasoon Al-Moameri

Hello...

I want to thank everyone answer my question.

I want to give more clarification to my question. The system I have is PU rigid foam and the goal is to find out if there are some research that address the efficiency of the liquid physical blowing agent (LPBA) that is used in the formulation (not specific one).

I define the efficiency of LPBA as: the number of moles of LPBA that is evaporated and went to foam cells divided by the initial amount in the recipe.

For the viscosity effect, I did a research to include its effect.