A simple methodology for improving the performance and sustainability of rigid polyurethane foam by incorporating industrial lignin

Abstract

Lignin, an inexpensive renewable biopolymer that offers both aliphatic and aromatic hydroxyl (OH) functional groups, is a potential raw material for the polyurethane industry. Contemporary approaches for incorporating lignin in rigid polyurethane foam (RPUF) involve mechanical mixing of microscale lignin powder under ambient conditions or at high loading levels, resulting in the RPUF with inferior compressive mechanical and thermal conductivity properties compared to petrochemical-based controls. Herein, we demonstrate a significant improvement in the dispersion of an industrial grade kraft lignin in a polyol mixture (96% sucrose/glycerine initiated polyether polyol and 4% glycerol) by dispersing at high-temperature (120 °C, 12 h) resulting in RPUF with enhanced performance. Through this methodology, the polyol/lignin dispersion with 5 wt.% lignin has afforded a simultaneous improvement in thermal insulation (by 5%) and compressive strength (by 4%) of RPUF compared to the control and such a property profile, to the best of our knowledge, has not yet been achieved in lignin substituted RPUF systems.