Reinforced lignin-based polyurethane foams with improved heat-insulating performance by using cellulose fibers

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomass Utilization

Background:

• Polyurethanes are versatile materials with broad applications.
• Valorization of biomass, particularly lignin and cellulose, is crucial for sustainable development.
• Developing functional materials from natural polymers offers an eco-friendly alternative to synthetic materials.

Purpose of the Study:

• To synthesize lignin-based polyurethane foam (LPUF) using Kraft lignin.
• To investigate the effect of incorporating cellulose fibers as reinforcing skeletons on the mechanical and thermal properties of LPUF.
• To determine the optimal loading of cellulose fibers for enhanced material performance.

Main Methods:

• Lignin-containing polyol (LP) was prepared from Kraft lignin, polyethylene glycol, and glycerol.
• LPUF was synthesized by reacting LP with polymethylene diphenyl diisocyanate (PMDI) using water as a foaming agent.
• Cellulose fibers were incorporated at various loadings (0-1.0%) to reinforce the LPUF structure.

Main Results:

• A 0.5% addition of cellulose fibers significantly improved compressive strength (72.3%), flexural strength (154.5%), and tensile strength (244.1%).
• Optimal cellulose loading (0.5%) enhanced mechanical properties to 647.6 kPa (compressive), 1.28 MPa (flexural), and 1.17 MPa (tensile).
• Thermal conductivity decreased from 0.0413 to 0.0378 W m⁻¹ K⁻¹ with 0.5% cellulose, indicating improved thermal insulation. Higher loadings (>0.5%) negatively impacted pore morphology and mechanical performance.

Conclusions:

• Cellulose fiber reinforcement, particularly at 0.5% loading, significantly enhances the mechanical and thermal insulation properties of lignin-based polyurethane foam.
• The study highlights the potential of utilizing wood-derived natural polymers (lignin and cellulose) for creating high-performance, sustainable polyurethane materials.
• This approach contributes to value-added biomass utilization, promoting sustainable development and carbon neutrality goals.