“Quenching” and “zapping” are the two usual methods for opening the cells of PU foams, thus leading to reticulated foams. Quenching corresponds to a chemical edging in caustic soda, whereas zapping is the method by which cell walls are destroyed with an explosive gas in an autoclave.
Can anyone answer to the following questions, please?
1. What are the exact experimental conditions for these methods (concentration and time for quenching, pressure and nature of the gases for zapping)? Can anybody suggest some literature providing such details?
2. Do other methods exist for producing reticulated foams?
3. What are the chemical mechanisms involved in quenching, which may explain why quenching is not effective in polyether polyurethanes, whereas zapping works with both polyester and polyether polyurethanes?
4. Anybody knows if such methods were already successfully tested with other kinds of thermoset foams, such as phenolic foams?
5. It seems that zapping is becoming the prevailing method for producing reticulated foams, but quenching produced different interesting properties, such as hydrophilicity. Can anybody provide a list of suppliers of quenched PU foams?
Thank you very much for reading until the end. Please don’t hesitate to provide only a few answers if you can’t answer everything !!
Alain
Dear Alain, Polyester segments will be hydrolytically degraded by caustic solutions, while ethers are quite stable to hydrolysis. This may explain why quenching is only used for polyether urethanes. The surfaces of the remaining struts will also be hydrolysed to form carboxylic acid and alcohol groups, which will account for the increased hydrophilicity. Hope this partial answer helps. I do not have experience with zapping equipment. Regards. Deon
An interesting article ,about reticulated PU foams, was released by UFP Technologies, Inc. (U.S.A) this year & its link is given below. The same link gives more information that you look for. I hope that it will help.
A simple note: when there is an ether linkage, neither the acid HCl nor the base NaOH are effective in hydrolyzing it & so the very strong HI is usually used for this purpose. My regards.
http://www.ufpt.com/materials/foam/reticulated-polyurethane-foam.html
I recommend to read the patent literature - only a first glimpse into it lead to 329 named patents among which the following should be of interest:
US 3,425,890
US 3,622,435
US 3,718,613
US 3,753,756
As the process to reticulate polyurethane (and other, including ceramic ertc.) foams is old and has been developed in the 60ies and 70ies literature of that time should be consulted.
Best wishes for suc cess
Gerhard
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