Natural rubber latex (NRL) and lignin are abundant renewable biopolymers with distinct properties, such as NRL's elasticity and lignin's hydrophobicity. These characteristics make them promising candidates for adhesive and composite materials. Despite this potential, their combination remains underexplored in terms of physicochemical synergism. In this work, NRL was functionalized with lignins isolated through different pretreatment routes (organosolv, alkali, and Kraft) [1]. Nanoscale force measurements using lignin-functionalized AFM tips revealed specific interactions between NRL and lignin that are sensitive to the pretreatment method. Density functional theory (DFT) calculations further supported these results by identifying energetically favorable NRL-lignin binding configurations. Macroscale mechanical characterization of NRL-lignin films corroborated the nanoscale findings. The best-performing formulation was then assessed as a water-based adhesive on substrates of varying hydrophobicity, including polypropylene, glass, aluminium, and wood. Shear strength improvements of up to 173% relative to neat NRL were obtained under dry conditions, and adhesion was also retained in underwater conditions. Utilizing this adhesive system, sugarcane bagasse-based composites were formulated with NRL/lignin as a formaldehyde-free binder [2]. The fiber/binder ratio was progressively varied to modulate the composite properties. The resulting materials exhibited tunable mechanical strength, hydrophobicity, and thermal stability, compatible with coating applications. In summary, this work presents a scalable and sustainable route to valorize agricultural residues and renewable biopolymers, providing a greener alternative to petrochemical-based materials for the construction and manufacturing industries.
This study was partially funded by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) – (001); Brazilian National Council for Scientific and Technological Development - CNPq (Research and Productivity grant 303621/2022-2); São Paulo Research Foundation – FAPESP (2020/08651-4, 24/21240-4 and CEMol – Center for Molecular Engineering for Advanced Materials, 24/00989-7) and by Federal University of ABC (UFABC).
[1] SILVA, Juliana Martins et al. Adhesion performance from nano and molecular—To macro insights for bio-based adhesives. Chemical Engineering Journal, vol. 523, p. 168732, 2025.
[2] SILVA, Juliana M. et al. Formaldehyde-Free Binder of Natural Rubber Latex and Lignin for Sugarcane Bagasse Fiber Composite Plates. Industrial Crops and Products, vol. 241, p. 122807, 2026.
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Pedro Alves da Silva Autreto
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