To optimize the bamboo heat treatment process, the corresponding evolution rules under various heat treatment conditions must be determined. When the heat treatment time and temperature remained constant, the effects of different heat treatment pressures on the equilibrium moisture content, dimensional stability, mechanical properties, and chemical composition of bamboo were systematically investigated. In this experiment, bamboo without heat treatment was used as the control group. The experimental findings demonstrate the following: (1) The equilibrium moisture content of heat-treated bamboo gradually decreases with increasing treatment pressure. When the heat treatment pressure was set at 0.1, 0.15, 0.2, and 0.25 MPa, the bamboo’s equilibrium water content decreased to 12.1%, 11.7%, 9.9%, and 8.6%, respectively, while that of the control group was 13.8%. (2) The dimensional stability of bamboo was enhanced with increasing heat treatment pressure. At pressures of 0.1, 0.15, 0.2, and 0.25 MPa, the radial air-dry shrinkage rates of the heat-treated bamboo decreased to 3.4%, 3.4%, 2.6%, and 2.3%, respectively, while the tangential air-dry shrinkage rates reduced to 5.6%, 5.1%, 3.3%, and 3.0%. In comparison, the radial and tangential air-dry shrinkage rates of the control group were measured as 3.6% and 5.8%, respectively. Similarly, the radial and tangential full-dry shrinkage of bamboo exhibited a similar trend. (3) With the increase in heat treatment pressure, the bending strength and longitudinal compressive strength of bamboo exhibited an initial rise followed by a decline. When it was at heat treatment pressures of 0.1, 0.15, 0.2, and 0.25 MPa, the corresponding bending strengths of the heat-treated bamboo were measured as 41.2, 26.7, 22.4, and 20.4 MPa, respectively; while the longitudinal compressive strengths were recorded as 42.6, 38.1, 29.1, and 25.3 MPa. In comparison, the bending and longitudinal compressive strengths of the control group were measured as 39.8 and 38.5 MPa, respectively. It is evident that the optimal heat treatment pressure for bamboo is 0.1 MPa, resulting in a significant increase of 3.5% and 10.6% in bending strength and longitudinal compressive strength, respectively, compared to the control group. (4) Based on the FTIR and XRD patterns of bamboo samples, a range of physical and chemical transformations were observed during the heat treatment process, including cellulose adsorb water evaporation, hemicellulose and cellulose degradation, as well as acetyl group hydrolysis on the molecular chain of hemicellulose. These changes collectively impacted the physical and mechanical properties of bamboo.

Microcrystalline cellulose (MCC) possesses important attributes, including high crystallinity, a large surface area, excellent mechanical strength, chemical stability, and biodegradability. This study aims to research MCC extraction from bamboo (Phyllostachys edulis (Carrière) J. Houz.) fiber by assessing the impact of key processing variables such as acid concentration, temperature, and hydrolysis duration. Experimental results indicate that hydrolysis time and hydrochloric acid (HCl) concentration significantly influence yield. After evaluating the effects of various hydrolysis conditions, the optimal parameters were determined to be a 2.0 M HCl concentration, 90 °C, and 10 min of reaction time. The MCC produced under optimal conditions displayed improved crystallinity (77.2%) while retaining functional groups similar to those found in raw bamboo. Morphological analysis revealed an irregular rod-like shape with rough surfaces. This optimized hydrolysis process offers a viable approach for MCC production from raw bamboo and holds potential as a precursor for developing environmentally friendly biodegradable fiber materials.

In this research, a urea–formaldehyde (UF) resin was modified with nanocrystalline cellulose (NCC) and nanofibrillated cellulose (CNF), and the properties of the modified resin were comprehensively evaluated by combining the techniques of infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that (1) the introduction of NCC and CNF significantly changed the hydrogen bonding network of the UF resin, in which CNF enhanced the internal hydrogen bonding of the resin through its long-chain structure and elevated the cross-linking density. NCC increased the crystallinity of the resin, while CNF enhanced the overall performance of the resin by improving its dispersion. (2) The composite curing agent system significantly reduced the curing temperature of the resin, resulting in a more homogeneous and efficient curing reaction, and the CNF-modified UF exhibited better thermal stability. (3) The addition of NCC and CNF significantly improved the dry and water-resistant bonding strengths of the resins. In addition, the use of complex curing agent further enhanced the bonding strength, especially in the CNF-modified system; the addition of complex curing agent increased the dry bonding strength to 1.60 MPa, and the water-resistant bonding strength reached 1.13 MPa, which showed a stronger cross-linking network and structural stability. (4) The addition of NCC and CNF led to a significant reduction in the free formaldehyde content of UF resins, resulting in respective levels of 0.17% and 0.14%. For plywood bonded with the CNF-modified UF resin, formaldehyde emissions were measured at 0.35 mg/L, which were markedly lower than the 0.54 mg/L of the unmodified sample. This further highlights CNF’s effectiveness in minimizing formaldehyde release. (5) Overall, CNF is superior to NCC in improving the thermal stability, bonding strength, water resistance, formaldehyde release, and overall performance of the resin. The use of complex curing agents not only optimizes the curing process of the resin but also further enhances the modification effect, especially for CNF-modified resins, which show more significant performance advantages.

Sustainable polymer stabilization requires renewable antioxidants that combine efficient radical scavenging with clear structure–performance relationships. Diphenylamine antioxidants are widely used in rubber protection, but their conventional production depends on petrochemical feedstocks and hazardous aniline chemistry. Lignin valorization research largely targets model compounds; native lignin’s complexity makes direct conversion challenging. Here, we report a two-step tandem strategy that converts raw lignin into diphenylamine compounds without intermediate purification. PtFe/NiAl₂O₄ and phosphotungstic acid first depolymerize lignin selectively to p-substituted phenols, which are then converted into diphenylamine derivatives with ammonium formate, Pd/C and LiOH. The process affords p-substituted phenols in 35 wt% yield and final diphenylamine compounds in 23 wt% yield from birch lignin. When incorporated into natural rubber at 1 wt%, the lignin-derived diphenylamines suppress thermo-oxidative aging: after treatment at 140 °C for 24 h, the mass loss decreases from 10% for the untreated rubber to 1% for the stabilized material. The stabilized rubber also withstands harsher aging conditions and shows performance comparable to commercial EPDM rubber. Mechanistic experiments indicate that lignin demethoxylation supplies in situ hydrogen for depolymerization, while the diphenylamine N–H group interrupts radical chain oxidation in the rubber matrix. This work links lignin valorization chemistry with polymer-aging control and provides a renewable route to high-performance rubber antioxidants.