Dispersion engineering of cellulose nanofibres in polyols: for controlled microstructure of high-performance polyurethane foam

Cellulose nanofibres (CNF) with hydroxyl functional groups are among the most attractive types of functional additive candidates being explored to improve the mechanical and thermal insulation performance of rigid polyurethane foams (RPUF). However, in practice, the poor dispersion of CNF in polyols has hindered the potential enhancements to RPUF using this approach. In this study, CNF/polyol dispersions with a good distribution of CNF in polyol at loadings from 0.03% to 1.12% w/w were used to prepare the CNF/RPUF nanocomposites (CNF/RPUF) containing 0.01% to 0.40% w/w CNF loading. This series of true RPUF nanocomposites represents a better platform to investigate the effect of the CNF on the microstructure, thermal and mechanical properties of RPUF. A CNF/RPUF nanocomposite (0.01% w/w CNF in RPUF) prepared from a dispersion of 0.03% w/w CNF in polyol afforded a 20% reduction in thermal conductivity and a 25% and 56% improvement, respectively, in specific compressive strength and specific modulus. This scale of thermal insulation and mechanical performance improvement for low-density (39 kg m-3) CNF/RPUF systems has not previously been reported. An efficient control over the microstructure and physical properties of polyurethane foam is demonstrated through dispersion engineering of cellulose nanofibre, a biosourced nanoadditive, in polyols with a broad range of rheological characteristics.