A semi-conductive rigid polyurethane foam derived from kraft lignin polyol and a PEDOT: PSS coating

Rigid polyurethane foams (RPUF) are mainly used as thermal insulators materials. These materials are drawing the attention of the emerging sector of the Internet of Things (IoT) due to their features such as good chemical resistance, lightweight, and tunable mechanical properties. Yet, for IoT applications, the electrical conductivity of this type of materials should be increased substantially. To address this challenge, as well as the urgency to use renewable and sustainable resources, semi-conductive RPUF were synthesized using crude lignin-based polyol (LBP) doped with multi-walled carbon nanotubes (MWCNT) and coated with PEDOT: PSS, using the dip coating technique. The ensuing semi-conductive RPUF has low density (33–34 kg/m³), high electrical conductivity (in the order of magnitude of 10⁻⁵ S/m), and a stretchability enhancement of almost 50 % upon coating with PEDOT: PSS. Furthermore, the mechanical performance of RPUFs can be adjusted using MWCNT and fine tuning of the formulation. Lignin being an abundant natural aromatic polyol allows the partial replacement of fossil derived polyols in the production of RPUFs and its aromatic structure contributes to the thermal and mechanical stability of the ensuing foams.