Production of Bio-based Polyol from Oxypropylated Pyrolytic Lignin for Rigid Polyurethane Foam Application

Abstract

A recent trend in ecofriendly product development is the use of added-value lignin residues. This study aimed to assess the potential use of pyrolytic lignin (PL) for producing rigid polyurethane foam (RPUF). For this purpose, PL was recovered from bio-oil using water as extraction solvent. The PL was then subjected to oxypropylation in the presence of KOH and under mild temperature and pressure (482 K; 14 Bar). FTIR and hydroxyl number quantification was used to confirm and assess the occurrence of oxypropylation reaction. Thus, oxypropylated lignin (OL) was successfully used to produce RPUF. Results revealed a lignin recovery yield of 30 ± 4% relative to the bio-oil weight. FTIR and NMR showed that the PL retained its aromatic structure after pyrolysis cracking. The weight ratio obtained after oxypropylation was 50/50/5 lignin/propylene oxide/KOH with a hydroxyl number of 703 mg KOH/g. Gradual substitution of polyol with OL ranged from 10 to 50%, and the ensuing foams were characterized in terms of chemical, physical, and morphological properties. Modulus of elasticity and insulation performance of 20% OL-based foam increased by 17% and 5.5%, respectively, compared to the commercial rigid polyurethane foam (CRPUF). SEM micrographs for OL-based polyurethane foams showed smaller cell structure, which is desirable for increasing rigidity. These findings demonstrate the potential use of pyrolytic lignin in the manufacturing of high performance biobased insulation materials.