Bio-Based Rigid Polyurethane Foams for Cryogenic Insulation

Abstract

Cryogenic insulation material rigid polyurethane (PU) foams were developed using bio-based and recycled feedstock.Polyols obtained from tall oil fatty acids produced as a side stream of wood biomass pulping and recycled polyethylene terephthalate were used to develop rigid PU foam formulations.The 4th generation physical blowing agents with low global warming potential and low ozone depletion potential were used to develop rigid PU foam cryogenic insulation with excellent mechanical and thermal properties.Obtained rigid PU foams had a thermal conductivity coefficient as low as 0.0171 W/m•K and an apparent density of 37-40 kg/m 3 .The developed rigid PU foams had anisotropic compression strength properties, which were higher parallel to the foaming direction.Moreover, the compression strength was also influenced by the type of applied bio-based polyol.The bio-based polyols with higher OH group functionality delivered higher crosslinking density of polymer matrix; thus, the mechanical properties were also higher.The mechanical strength of the foams increased when materials were tested at liquid nitrogen temperature due to the stiffening of the polymer matrix.The thermal properties of the developed materials were determined using differential scanning calorimetry, dynamic mechanical analysis, and thermogravimetric analysis methods.Lastly, the developed rigid PU foams had good adhesion to the aluminium substrate before and after applying cyroshock and an excellent safety coefficient of 4-5.Rigid PU foams developed using Solstice LBA delivered adhesion strength of ~0.5 MPa and may be considered for application as cryogenic insulation in the aerospace industry.