Chunfeng Li

Bio-based waterborne polyurethane (WPU) coatings are renewable alternatives in coating technology, yet their mechanical strength, thermal stability, and barrier properties remain inadequate for demanding applications such as carbon fiber (CF) sizing. Herein, hyperbranched WPU coatings were prepared from a laboratory-synthesized aminated tung oil polyol (ATOP), L-lysine diisocyanate, and two natural phenolic acids, protocatechuic acid (PA) as a chain extender and gallic acid (GA) as an internal cross-linker. The hydroxyls of ATOP, PA, and GA form covalent cross-links with isocyanates, while the aromatic rings originating from the tung oil backbone and the two phenolic acids provide supplementary physical reinforcement through π-π stacking interactions. Varying the PA/GA molar ratio simultaneously regulated the cross-linking density and the extent of aromatic stacking, linking the thermal, mechanical, barrier, and degradation properties of the coatings to network architecture. GPWPU2 (PA/GA = 1:1) delivered the best overall performance, exhibiting a T5% of 283.6 °C, a tensile strength of 45.86 MPa, and robust resistance to water, acid, alkali, and saline environments. Under lipase-catalyzed hydrolysis, GPWPU2 lost 45.7% of its initial mass within 7 days, whereas 40.2% of the mass was retained after 60 days of soil burial, confirming its inherent biodegradability. Applied to CF at 3.5 wt%, the polar functional groups of GPWPU2 elevated the fiber surface energy from 34.68 to 61.32 mN/m, while the coating concurrently infiltrated intrinsic fiber microcracks, a defect-healing effect that improved the single-filament tensile strength by 20.7% to 6.077 GPa. Composites fabricated from the sized fibers achieved a flexural strength of 811.5 MPa and an interlaminar shear strength of 68.9 MPa, both exceeding the corresponding values obtained with a commercial sizing benchmark. The combination of covalent cross-linking and aromatic π–π stacking thus provides a practical route to bio-based WPU coatings that balance mechanical performance with biodegradability for fiber sizing.

Biobased polylactic acid composites show great potential as alternatives to petroleum‐based polymer materials, but their practical use is limited by the difficulty of simultaneously achieving mechanical strength, service durability, and integrated functionality. To address this challenge, we developed a biomimetic interfacial engineering strategy inspired by nacre's rigid‐inorganic/flexible‐organic interfacial composition. The composite exhibits favorable mechanical strength (flexural strength increased by 3.8 times) and durability under harsh environments, and outstanding UV‐blocking properties are imparted by the interior of the composite together with its biomimetic interfacial layer, effectively inhibiting the photodegradation of various water‐soluble organic substances (degradation extent 95%), enabling efficient outdoor deicing/snow removal and stable solar‐driven desalination, combining high evaporation efficiency (>94%) with excellent cycling stability. More significantly, at the disposal stage, the porous and surface‐functionalized residue can adsorb dyes and heavy‐metal ions from water, supporting resource‐oriented end‐of‐life utilization. The composite also shows antifungal rates exceeding 96%, long‐term antifungal behavior, low toxicity in the tested aquatic plant system, and soil‐burial degradation behavior. This work presents an interfacial‐design route for high‐strength, multifunctional, and recyclable bio‐based composites for outdoor and water‐treatment‐related applications, which is anticipated to exhibit significant potential in sustainable polymer materials.

To address the poor mechanical strength and surface color of fast‐growing poplar wood, and to avoid the environmental hazards posed by formaldehyde emissions from resin‐based dyeing modifiers, a composite modifier was formulated in this study. This modifier was fabricated by blending silica sol/melamine glyoxal with three dyes and used for modifying poplar wood. A comprehensive investigation was conducted on the effects of pure dyes and resin‐based dyeing modifiers on the color parameters of poplar wood. The influence of three auxiliaries—NaCl, TiO ₂ and Na ₂ CO ₃ —on the ageing performance of modified poplar wood was analysed. Furthermore, the dyeing and ageing mechanisms of resin‐based dyeing modifiers were examined. The results showed that at a dye mass fraction of 1.0%, the dye uptake reached a maximum of 20.8%. Among the auxiliary additives tested, NaCl gave the best performance for dye retention under ultraviolet (UV) exposure. After 200 h of UV irradiation at 340 nm, the incorporation of resin enhanced the photostability of dyed poplar by 51% compared to the control group. Under the current UV‐ageing conditions, the addition of NaCl further reduced the color difference by 19% compared with SS/MG‐R18. This study provides a theoretical basis and technical guidance for developing non‐toxic resin‐based dyeing modifiers for modifying poplar wood.

Fast‐growing poplar is a renewable hierarchical porous material; however, its low mechanical strength, poor toughness, and high moisture affinity limit its application in structural fields. In this work, a hyperbranched epoxy resin/modified silica sol hybrid system was developed as an organic–inorganic reinforcing phase and introduced into poplar wood via vacuum‐pressure impregnation. An in situ hybrid network was constructed within the cell walls and lumens through epoxy ring‐opening reactions, Si‐O‐Si inorganic condensation, Si‐O‐C covalent bonding, and interfacial interactions with wood hydroxyl groups. The synergistic combination of flexible hyperbranched epoxy segments and rigid silica frameworks improved interfacial compatibility, pore filling, and stress transfer within the wood‐based composite. Consequently, the modified wood exhibited an impact toughness of 73.75 kJ/m ² and a modulus of rupture of 150.43 MPa, representing increases of 50.51% and 110.6%, respectively, compared with the control material (49 kJ/m ² and 71.43 MPa, respectively). Meanwhile, the water contact angle increased significantly from 82.3° to 125.5°, indicating reduced moisture affinity and improved hydrophobicity. This work provides an effective organic–inorganic hybrid network strategy for developing high‐performance wood‐based polymer composites with improved mechanical performance and environmental stability.

Shifting from petroleum-based feedstocks to renewable biomass for high-performance waterborne polyurethane (WPU) coatings is critical for promoting sustainability within the coatings industry. In this work, castor oil (CO) was chemically modified with cinnamic acid (CA) to produce a customized polyol featuring precisely three hydroxyl groups, three benzene rings, and three carboxyl groups per molecule. This functionalized-CO was employed as the soft segment and was combined with L-lysine diisocyanate as the hard segment, protocatechuic acid (PA) as the chain extender, and gallic acid (GA) as an intramolecular cross-linker to synthesize a series of bio-based WPU coatings intended for application on oak wood (Xylosma congesta). The benzene ring of GA functions as a 3D cross-linking node, transforming the quasi-one-dimensional π–π stacking interactions between the CA and PA benzene rings along the polymer backbone into an interconnected 3D aromatic conjugated network. This synergistic interaction between covalent cross-linking and physical π–π stacking enhances multiple material properties simultaneously, including tensile strength (30.9 MPa), thermal stability (T5% = 289.4 °C), storage modulus (3815.6 MPa), toughness (87.9 MJ·m⁻3), solvent resistance, and microphase separation, while maintaining significant biodegradability under both soil burial and enzymatic degradation conditions. When applied to oak wood substrates, the coatings reduced abrasion-induced mass loss from 117 mg to 13 mg and lowered the water vapor transmission rate to 35.2 g·m⁻2·24h⁻1, outperforming two commercial WPU products used as benchmarks across evaluated parameters. This research establishes a comprehensive structure–property framework based on the interplay between covalent cross-linking and supramolecular π–π stacking, providing molecular-level design guidelines for the development of fully bio-based, high-performance wood coatings.

Through precise molecular engineering, a fully bio-based, high-performance hyperbranched tung oil-type waterborne polyurethanes (GPWPUs) was designed and developed as an efficient sizing agent for carbon fibers (CFs). First, a highly functional aminated tung oil-based polyol (ATOP) containing multiple active sites was prepared using renewable tung oil as the raw material via epoxidation, amination, and hydroxylation reactions. ATOP was employed as the soft-segment core, and L-lysine diisocyanate was used as the hard-segment component. Two natural phenolic acids, protocatechuic acid (PA) and gallic acid (GA), were introduced as a functional chain extender and an intramolecular cross-linker, respectively. This approach constructed a hyperbranched polymer network with controllable cross-linking density and comprehensive properties. Synergistic regulation of the ATOP/PA/GA mixture resulted in a GPWPU with an elevated initial thermal decomposition temperature of 283.6 °C, tensile strength of 45.86 MPa, and excellent tolerance to water, acids, alkalis, and salt solutions. When applied as a CF sizing agent, the GPWPU formed a uniform and dense coating on the fiber surface. This coating effectively repaired surface microcracks via a "defect-healing" mechanism, thereby improving fiber roughness. GPWPU sizing increased the surface energy of the CF to 61.32 mN/m and significantly enhanced the single-filament tensile strength by 20.7%, reaching 6.077 GPa. Consequently, GPWPU2-sized CF reinforced epoxy composites achieved exceptional interfacial adhesion, with flexural strength and interlaminar shear strength reaching 811.5 MPa and 68.9 MPa, respectively. This study presents an innovative approach to developing sustainable, high-performance composites, from molecular design to interfacial reinforcement.

Phenolic resin-modified materials partially reduce the toughness of the wood. In this study, organic–inorganic composite modifiers were used to modify the wood. Silica sol/phenolic resin was prepared through in-situ polymerization, and poplar wood was modified using a vacuum pressure impregnation process, enhancing its toughness. Orthogonal experiments were conducted, and the impact toughness of the modified poplar wood was used as the evaluation index. Through orthogonal experiments, using the impact toughness of modified poplar as the evaluation indicator, it was found that when the average particle size of the silica sol is 8–15 nm, the pressure is 1.2 MPa, and the pressurization time is 3 h, the impregnation-modified poplar’s impact toughness reaches its optimum, improving by 84.1% and 135.4% compared to the raw material and phenolic resin impregnated wood, respectively. The Fourier Transform Infrared Spectroscopy (FT-IR) results indicated that the characteristic absorption peak of Si-O-Si appears in the poplar wood after impregnation, confirming the formation of new silicon-oxygen (Si-O) chemical bonds. X-ray Photoelectron Spectroscopy (XPS) analysis revealed that a chemical reaction occurs between the impregnation liquid and the wood, generating Si-O-C. Subsequently, through Dynamic Mechanical Analysis (DMA) and Thermogravimetric (TGA) analysis, it was understood that this chemical reaction significantly enhances the thermal stability and toughness of the impregnated material, making it superior to the original poplar material. The TGA further unveiled that, compared to untreated poplar, the thermal stability of the impregnated material has been notably improved. Lastly, Scanning Electron Microscopy (SEM) analysis demonstrated that the composite impregnation liquid successfully permeates and fills the interior of the poplar cells.