Carbon dioxide as “blowing agent

The reaction of NCO groups and carboxylic acid groups resulted in the formation of amide linkages and carbon dioxide as blowing agent. This reaction has led to the invention of urethane foam preparation, and the polyurethane industry has become one of the biggest plastic industries. A model reaction of a polyamide foam formation is shown below ... 

Polyurethanes are manufactured by addition of polyols (polyether or polyester) with polyvalent isocyanates. Polyether-polyols are sensitive to oxygen. Thermal-oxidative degradation typically occurs during the manufacture of flexible foams when water is used to form carbon dioxide as blowing agent. Large PUR slab stock... 

Zhu, B., Zha, W., Yang, J., Zhang, C., and Lee, L. J., 2010. Layered-silicate based polystyrene nanocomposite microcellular foam using supercritical carbon dioxide as blowing agent. Polymer5 2177-84. 

---