Synthesis of polyurethanes from CO2-based polyols: A challenge for sustainable adhesives

Raw materials used in adhesive polyurethane formulations for the footwear industry come from non-renewable fossil resources. This strong dependence of the chemical industry with regard to fossil fuels, such as oil, contributes negatively to the environment. For this reason, there is a trend towards sustainable products that minimise the use of oil resources.Previous studies demonstrated the feasibility of replacing polyols, one of the essential components of polyurethanes, as vegetable oils, a sustainable alternative to sustainable polyurethanes. However, they compete with food production for humans or animal feed. In this sense, the use of carbon dioxide as a feedstock for the chemical industry is an interesting alternative to oil because CO2 is useful, versatile, non-flammable and its presence is abundant in the atmosphere. Specifically, carbon dioxide could be used for the synthesis of polyurethanes, one of the most polymers produced worldwide, currently dependent on fossil fuels.This work focused on the synthesis of polyurethane adhesives containing polyols from CO2. They were synthesised with 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol as a chain extender. The sustainable polyurethane adhesives derived from carbon dioxide were characterised by Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetric tests (TGA). Finally, the adhesion properties were measured from a T-peel test on leather/polyurethane adhesive/SBR rubber joints, in order to establish the amount of CO2-based polyol that could be added to polyurethane adhesives satisfactorily to meet the quality requirements of footwear joints.