Fractionated lignin as a polyol in polyurethane fabrication

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomass Valorization

Background:

• Lignin, a complex biopolymer, presents challenges in its application due to heterogeneity.
• Developing sustainable polyols from renewable resources like lignin is crucial for eco-friendly materials.
• Polyurethane foams (PUF) are versatile materials with widespread industrial applications.

Purpose of the Study:

• To investigate the impact of lignin molecular weight fractions on polyurethane foam properties.
• To evaluate lignin as a polyol component in PUF production using green solvents.
• To correlate lignin structure with foam performance metrics like mechanical strength and thermal stability.

Main Methods:

• Fractionation of lignin into different molecular weights using green solvents.
• Incorporation of lignin fractions as polyols in polyurethane foam synthesis.
• Characterization of foam morphology (pore structure), mechanical properties (tensile strength, elongation at break), density, and thermal stability.

Main Results:

• Lower molecular weight lignin resulted in uniform pore structure and enhanced mechanical strength.
• Higher molecular weight lignin improved foam density and thermal stability but compromised mechanical properties and pore uniformity.
• At 2%-30% substitution, the lowest molecular weight lignin achieved 99.13% reaction participation, boosting elongation at break to 834% and tensile strength to 0.90 MPa.
• Increased lignin substitution enhanced thermal stability and the amount of unreacted lignin.

Conclusions:

• Lignin molecular weight significantly influences polyurethane foam characteristics.
• Tailoring lignin fractions allows for targeted optimization of PUF properties for specific applications.
• Sustainable polyurethane foams can be produced using fractionated lignin, offering a pathway to valorize biomass waste.