Spectroscopic study of the morphology development of closed-cell polyurethane foam using bio-based malonic acid as chain extender
Weiwei Zhao, Bradford Nolan, Harry Bermudez, Shaw Ling Hsu, Umesh Choudhary, Johan van Walsem
Abstract
In this study the advantages of using bio-based multi-functional malonic acid salt as chain extender in preparing closed cell polyurethane foams is demonstrated. We found that the presence of malonic acid salt can alter the reaction kinetics, segmental mobility and hence the relative kinetics of polyurethane and polyurea formation. By analyzing the infrared active vibrations, it is demonstrated that the formation of urethane and urea linkages is accelerated at the initial stage of reaction, resulting in enhanced viscosity build-up attributed to the catalytic activity of the triethylamine complexed with malonic acid. The relative kinetics in formation of different morphological features thus can be used to control the cell opening process. These results, combining information on polymerization kinetics, gas evolution and phase separation, illustrate the capability of using malonic acid salt as the chain extender to manipulate polyurethane foam morphology and its potential application in polyurethane closed cell foam systems.