In Situ Transformation of Natural Bark into Additive-Free, Self-Adhesive Composites

Abstract

Lignocellulosic plastic composites are widely used in many industries for their excellent mechanical strength and durability owing to the synergistic effect of lignocelluloses and polymers. However, the polymer content severely limits their recyclability and environmental sustainability. Here, a self-adhesive lignocellulosic composite is designed directly from forestry residue Eucommia ulmoides bark (EUB), which is rich in Eucommia ulmoides gum (EUG) and lignin. The fabrication consists of a two-step process of in situ epoxidation and self-adhesive technique. In situ epoxidation transformed the intrinsic EUG into an excellent viscoelastic epoxidized EUG (EEUG). The self-adhesive technique relies on hydrogen bonding reinforcement promoted by pressure-assisted densification and thermal-assisted flow of EEUG, and further enhanced by epoxy ring-opening. This process converts the raw materials into a fully natural self-adhesive composite without any additional polymers. The demonstrated composite exhibits enhanced mechanical strength, notable flexibility, high hydrophobicity (contact angle at 104.55°), remarkable water resistance, improved thermal stability, and biodegradability (52.96% mass loss in 5 months). In addition, the life cycle assessment reveals a carbon emission factor of 3.28 kg CO₂ eq/kg, which can be reduced to 1.56 kg CO₂ eq/kg under renewable-energy production. This work demonstrates a practical route for transforming forestry residue into high-value lignocellulosic materials and provides an environmentally benign alternative to conventional plastic-bonded systems.

Graphical Abstract

Keywords

Eucommia ulmoides bark / Eucommia ulmoides gum / Self-adhesive / Lignocellulosic composite

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Funding

National Natural Science Foundation of China(32571985)

National Science Fund for Distinguished Young Scholars(32225034)

Fundamental Research Funds for Central Universities of the Central South University(QNTD202507)

RIGHTS & PERMISSIONS

Donghua University, Shanghai, China

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