Paper-Based Laminates Impregnated with a Hybrid Lignin-Phenol-Formaldehyde Resin.

Area of Science:

• Materials Science
• Polymer Chemistry
• Sustainable Materials

Background:

• High-pressure laminates (HPL) are widely used composite materials.
• Phenol-formaldehyde (PF) resins are common binders in HPL production.
• There is a growing interest in incorporating bio-based additives to enhance material properties and sustainability.

Purpose of the Study:

• To develop novel high-pressure laminates (HPL) using phenol-formaldehyde (PF) resins modified with kraft lignin.
• To investigate the effect of different kraft lignin concentrations (1% and 5%) on the mechanical and physical properties of HPL.
• To evaluate the structural integrity and failure mechanisms of the developed lignin-modified HPL.

Main Methods:

• Kraft lignin was pulverized and incorporated into commercial PF resin at 1% and 5% (solid to solid) ratios.
• Laminates were fabricated using pressure impregnation of the modified resins into paper followed by hot pressing.
• Mechanical properties (bending strength, Brinell hardness, impact bending) and physical properties (moisture uptake, thickness swelling) were tested.
• Scanning electron microscopy (SEM) was used to analyze the microstructure and failure modes.

Main Results:

• HPL with 1% kraft lignin (L-LPF-1) exhibited the highest bending strength (72.42 MPa) and Brinell hardness (9.41).
• L-LPF-1 also showed optimal moisture uptake (9.61%) and thickness swelling (3.32%) after water immersion.
• While L-LPF-5 properties were generally worse, differences were often not statistically significant and comparable to commercial PF resins.
• SEM analysis revealed homogenous structures and cohesive failures in L-LPF-1, with additional adhesive failures observed in L-LPF-5.

Conclusions:

• Incorporating 1% kraft lignin as an additive to PF resin positively impacts the properties of the produced HPL.
• Kraft lignin shows potential as a sustainable bio-based additive for enhancing HPL performance.
• Further research may explore optimizing lignin content and processing for improved material characteristics.