Bio-Based Polyurethane Foams from Kraft Lignin with Improved Fire Resistance

Area of Science:

• Materials Science
• Polymer Chemistry
• Sustainable Chemistry

Background:

• Rigid polyurethane foams (RPUFs) are widely used as insulating materials.
• Petroleum-based polyols are conventionally used in RPUF synthesis.
• There is a growing demand for sustainable and bio-based alternatives.

Purpose of the Study:

• To synthesize and optimize bio-based RPUFs using exclusively lignin-based polyol (LBP).
• To evaluate the thermal, mechanical, and fire resistance properties of the bio-based RPUF.
• To assess the potential of LBP-based RPUF as a sustainable alternative to conventional RPUFs.

Main Methods:

• Lignin-based polyol (LBP) was synthesized via oxyalkylation of kraft lignin with propylene carbonate (PC).
• Design of experiments methodology and statistical analysis were employed for formulation optimization.
• Thermo-mechanical properties, thermal conductivity, density, cell morphology, and fire resistance were evaluated and compared to commercial RPUFs.

Main Results:

• An optimized bio-based RPUF formulation was achieved with low thermal conductivity (0.0289 W/m·K) and low apparent density (33.2 kg/m³).
• The bio-based RPUF demonstrated reasonable cell morphology and improved fire resistance, with an 18.5% reduction in average heat release rate and a 25% increase in burn time.
• While exhibiting slightly lower thermo-oxidative stability and mechanical properties than conventional RPUFs, the bio-based foam is suitable for thermal insulation.

Conclusions:

• A novel, high-performance bio-based RPUF can be produced using 100% unpurified LBP derived from kraft lignin.
• This bio-based RPUF shows significant potential to replace conventional petroleum-based RPUFs in thermal insulation applications.
• This study represents the first report on utilizing 100% unpurified LBP from LignoBoost kraft lignin for RPUF production.