Hi Rezvan Sharifi,

When you say it does not remain stable - it may be due to many factors on the foaming properties of the polyurethane; Temperature used, the type of polyol, the type of isocynate, mixing, adding methods etc.

For an example different types of polyols can facilitate different foaming of polyurethane. 

Hello Rezvan Sharifi ..... I don’t believe that the problem is because your polyol or isocyanate if the temperature profile of the gel is high enough and it sets in reasonable time.

What is your surfactant? And what is your blowing agent? I bet your foam fails because one of the followings:

1.     You may use very small amount of surfactant.

2.     You may use the wrong surfactant for your blowing agent.

3.     You are using too much PBA in the recipes.

 One of my papers studied the effect of surfactants and modes of failure. Check it please. 

Another reason is that the maximum reaction temperature of your foaming reaction is not high enough to set the urethane polymer. Check my paper “Impact of maximum reaction temperature ….. ”

 Thanks for your suggestions.

I use the temperature, ambient temperature is the winter and the state. And for  surfactant i use  polydimethylsiloxane and  foam agent is water. I have to get density 33kg / m3.

Thanks a lot

 Dear Harith,  unfortunately I can not download your paper!

If you use only water as a foaming agent you have to make sure that the start time to rise does not exceed 30 s and that your stabilizer is adjusted to the formulation, your PDMS definitely is not. I recommend to use TEGOSTAB B8433 with about 0.2 to 0.5 % based on the A component mix. Which isocyanate do you use? Did you check the quality (NCO content, clearness, viscosity)?

Isocyanate M 143 ,% NCO 29,1 and F=2,2 Gardner 8 

Viscosity  at25°c is 40 mPa.s .

thank you Gerhard