Comparative screening of natural resins, gums and waxes as bio-based binders for lignocellulosic paper composites

The properties of lignocellulosic composite materials are in general largely influenced by the binder used in their production. Binders ensure mechanical strength, extend the product’s lifespan, and significantly impact its environmental footprint. Traditional petrochemical-based binders are not sustainably sourced. Furthermore, they are often a major source of formaldehyde exposure and are mostly poorly biodegradable. Therefore, more environmentally friendly solutions are necessary. To serve as a viable replacement, a new binder system must achieve a balance between mechanical performance, moisture resistance, and environmental compatibility. This work focuses on selected natural waxes, resins, and gums, which are grouped under the term natural binders. In a screening approach, they were evaluated for their potential as bio-based binders for wood fiber composites in form of bound wood paper. Before utilization, the materials were characterized regarding their chemical composition, solubility for application, and thermal behavior. Binder-coated wood paper sheets were produced by solvent application and hot pressing, followed by tensile testing under standard conditions and after accelerated hygrothermal weathering. Moisture stability was assessed by water absorption measurements. Biodegradation was investigated under aerobic soil conditions via CO₂ evolution. All investigated natural binders improve the tensile strength and stiffness of the wood paper substrate compared with the unbound reference. Polysaccharide-rich gums show the strongest mechanical reinforcement. In contrast, waxes and several resin-based binders provide the highest water repellency. Biodegradation behavior also varies strongly with binder chemistry. Polysaccharide-rich gums exhibited the highest mineralization to CO 2 , with up to 77.4% after 91 days. Highly hydrophobic waxes and resins showed only limited degradation. Overall, the results show a trade-off among reinforcement, moisture protection, and biodegradability, indicating that natural binders should be selected based on use-case requirements rather than as a universal replacement for synthetic binder systems.