Identifying sustainable alternatives to dimethyl formamide for coating applications using Hansen Solubility Parameters

The toxicity of certain organic solvents utilized in industrial processes has been a major concern in the last few decades. The stricter regulations and increased public awareness around the use of toxic solvents are driving industries towards safer alternatives. Dimethyl formamide (DMF) is an important industrial solvent used to solubilize several polymers used in the coating industry (more than 200 thousand tons globally), especially polyurethanes (PU). However, DMF is toxic and can potentially create an unsafe work environment for workers, and therefore safer alternatives are needed. The Hansen Solubility Parameter (HSP) theory is one of the accepted methodologies used for predicting the solubility of polymers. Using the HSP principles and the Hansen Solubility Parameters in Practice (HSPiP) software, alternative solvent blends are identified for two commercial polyurethanes - Desmopan® and Desmocoll®. The alternative solvent blends dissolve the polymers at 25% w/w loading and have comparable costs to DMF. They are also less toxic in comparison to DMF. In addition, other physical properties like evaporation rate and boiling point are also matched. Coating trials are carried out using an industrial pilot coating line to ensure that the solvent system is a ‘drop-in’ replacement for DMF. This research establishes a methodology for rapidly identifying safer alternatives for various toxic solvents.