The use of cellulose nanocrystals to enhance the thermal insulation properties and sustainability of rigid polyurethane foam

The enhancement of thermal insulation performance of rigid polyurethane foam (RPUF) achieved through a cost-effective and sustainable approach still remains an ongoing interest in both industry and academia. This study reports an efficient approach of reducing thermal conductivity and enhancing mechanical properties of RPUF without affecting the density, by incorporating a very low fraction of cellulose nanocrystal (CNC) through an optimised solvent-free ultrasonication method. A 5% reduction in thermal conductivity of RPUF afforded by the addition of 0.4 wt.% of CNC without any further surface chemical modification is almost double the effect of any other unmodified nanoparticulate nucleating agent reported so far. This reduction in thermal conductivity is attributed to the better compatibility of the CNC with the polyol and the foam to allow maximum nucleation and therefore the lowest initial thermal conductivity. Further, the Young's modulus of an optimised nanocomposite foam was also enhanced to the control RPUF perpendicular to foam rise.