Preparation of bio-based phenol formaldehyde foams using depolymerized hydrolysis lignin

Bio-based phenol formaldehyde (BPF) foams with high phenol substitution ratios (30-50 wt%) were successfully prepared using depolymerized hydrolysis lignin (DHL, Mw ≈ 2000 g/mol) obtained via a proprietary low-temperature/low pressure depolymerisation process. FTIR measurements indicated that the foamable BPF resoles and foams had structures very similar to the phenol formaldehyde (PF) resole and foam. The prepared 30% BPF foam had similar apparent density (40 kg/m3), compressive strength (0.152 MPa), elastic modulus (2.16 MPa) and thermal conductivity (0.033 W/m/K) with the PF foam. However, 50% BPF foam showed higher apparent density (108 kg/m3), higher compressive strength (0.405 MPa) and elastic modulus (7.56 MPa) than the PF foam. All BPF foams exhibited satisfactory thermal conductivity (0.033-0.040 W/m/K) and cell structure. TGA analysis demonstrated that the BPF foams had excellent thermal stability at temperatures less than 200 °C. Thus, the BPF foams could be utilized as the insulation and fire resistant materials.