Mass transport and physical properties of polymeric methylene diphenyl diisocyanate/CO2solutions

Polyurethane foams are typically obtained by reacting a polyisocyanate with a polyol and the foamed structure derives from a blowing reaction concurrent to the polymerization reaction. The blowing stage makes use of chemical and physical blowing agents, among which ozone-depleting or flammable gases are being substituted with eco-friendly and safe ones, such as CO2. To allow a more educated use of CO2 as a physical blowing agent in polyurethane foams, we herein investigate the CO2 sorption in polymeric methylene diphenyl diisocyanate (PMDI), by using a fully experimental, coupled gravimetry-Axisymmetric Drop Shape Analysis. Solubility, mutual diffusivity, specific volume and interfacial tension of PMDI/CO2 solutions in contact with CO2 have been measured at 35 deg C and at CO2 pressures up to 6500 kPa. Effects of CO2 on PMDI were also evaluated by using Gel Permeation Chromatography and Fourier Transform Infrared spectroscopy.