Shuangbao Zhang

An investigation was conducted of the modification of bamboo fibers (BF) by nano-hydroxyapatite (N-HA) and its impact on the mechanical and thermal properties of BF/PLA composites. The functional groups, and crystallinity of the N-HA modified BF were investigated with Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD), respectively. The effects of different N-HA contents on the properties of the BF/PLA composites were evaluated using mechanical testing (bending, tensile, and impact properties), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The results showed that the most suitable N-HA content was 7.5 wt.%. Treating BF with an optimum concentration of N-HA decreased the polarity of the bamboo fiber, while maintaining the crystal structure of the cellulose. Compared with the control group, the mechanical properties and the crystallinity of the modified BF/PLA composites were improved, and the flexural, tensile, and impact strengths increased by 10.2%, 11.6%, and 28.1%, respectively. The thermogravimetric analysis results indicated modified BF/PLA composites has higher thermal stability.

As a bamboo processing residue, bamboo green (B) was evaluated as an additive to wood fiber (W) for developing composite panels. According to a Box-Behnken design, urea-formaldehyde resin-glued panels were fabricated from blends of B and W, with three preparation variables: B weight percentage in fibrous material (20%, 40%, and 60%), hot-pressing temperature (160 °C, 180 °C, and 200 °C), and hot-pressing duration (60, 120, and 180 s). The panels were tested for water uptake, thickness expansion, bending strength, and bending modulus. The results showed that the physical-mechanical properties of panels satisfied the strictest requirements of GB/T 11718 (2009). Four quadratic models were established to predict the four properties using the three variables. All models were statistically significant, with coefficients of variation below 5% and coefficients of determination beyond 0.96. An analysis of variance revealed that all variables significantly influenced panel properties. Their effect mechanisms were discussed. A response surface analysis demonstrated that, for different properties, the optimum B percentage, hot-pressing temperature, and hot-pressing duration ranged from 35% to 49%, 173 °C to 198 °C, and 111 s to 134 s, respectively. When all four properties were simultaneously optimized, the optimum preparation conditions were 42%, 179 °C, and 119 s, respectively.

The purpose of this paper is to discuss the influence of different proportions of bamboo pulp residue on the bending strength, the static bending strength, the water absorption rate, and the microstructure of wood flour/phenolic resin composites. The level of bamboo pulp residue ranged from 0 to 30 percent. According to the optimum technological parameters of the pretest, the resin content, the molding temperature, and the molding time were controlled within 51 to 54 percent, 152°C to 160°C, and 51 to 60 s/mm, respectively. Compared with the control group, there were remarkable improvements in the mechanical properties, indicating that the bending strength, the static bending strength, and the water absorption rate increased by 39, 31, and −6 percent, respectively. The greatest level of bamboo pulp residue was 20, 20, and 10 percent for the bending strength, the static bending strength, and the water absorption rate, respectively. All of the above proved that the wood flour/phenolic resin composites can be modified by adding bamboo pulp residue.

To develop construction and building materials from low-quality fast-growing wood, poplar laminated veneer lumber composites reinforced by E-glass fiber cloths (GFC) were prepared with phenol-formaldehyde adhesives. The GFCs were modified with gamma-aminopropyltriethoxysilane solution (concentration: 0.8%, 1.3%, and 1.8%). Between each veneer, 260, 330, or 400 g/m(2) adhesives were spread on one or both sides of veneers. The composites were hot-pressed under different temperatures (130, 145, and 160 degrees C) and gauge pressures (0.7, 1.2, and 1.7 MPa). The GFC dosages and positions in composites were varied. To evaluate the effects of variables on composites, analytical methods included the contact angle, scanning electron microscopy, and physical-mechanical measurements (flexural strength, flexural modulus, horizontal shear strength, internal bond strength, thickness swelling, and dip peel). The results showed that gamma-aminopropyltriethoxysilane made GFC more hydrophilic and compatible with adhesives, enhancing their interfacial adhesion. Considering most of the physical-mechanical and interfacial properties, the optimum parameters for preparing composites were determined to be 1.3% (gamma-aminopropyltriethoxysilane), 330 g/m(2) (adhesive, double-sided gluing), 160 degrees C (temperature), and 1.2 MPa (pressure). Varying GFC dosages and positions in composites had positive or negative effects on different physical-mechanical properties. Models were developed to correlate flexural data with GFC dosages and positions.

New plywood composites for furniture and interior decoration were developed with eucalyptus veneers using polyethylene films as formaldehyde-free adhesives. To enhance the interfacial adhesion, the veneers were modified with an oven treatment (temperature: 100, 120, 140, and 160 °C; time: 0.5, 1.0, 1.5, and 2.0 h) or by soaking in a sodium hydroxide (NaOH) solution (concentration: 3%, 7%, and 11%; time: 12, 24, and 36 h). The effects of these treatments on the mechanical properties (flexural strength, MOR; flexural modulus, MOE; wet shear strength, WSS) of the composites were studied. Both treatments improved the three properties of the composites. The heat treatment was better at improving the shear property, while the alkali treatment was better at improving the flexural properties. For the heat treatment, the highest WSS was 81.1% higher than the untreated group. The optimum conditions for the heat treatment were 140 °C and 1.0 h. For the alkali treatment, the highest MOR and MOE were 267.5% and 173.7% higher than the untreated group, respectively. The optimum conditions for the alkali treatment were 3% and 36 h. The changes to the veneer surfaces were determined by scanning electron microscopy.

A bio-inspired approach to coating polydopamine (PDA) onto bamboo fiber (BF) was developed to enhance the poor interfacial bonding of BF/polybutylene succinate (PBS) biocomposites. The macroscopic features, functional groups, nanoscale topography, and crystallinity of the PDA-coated BF (D-BF) were investigated with digital photography, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and X-ray diffraction (XRD), respectively. The effects of the PDA loading rate on the performance of the D-BF/PBS biocomposites were also evaluated through the mechanical properties tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). Treating BF with an optimum concentration of dopamine (DOPA) decreased the polarity of the bamboo fiber, while maintaining the crystal structure of the cellulose. The thermal stability, mechanical properties, and storage modulus of the D-BF/PBS biocomposites were noticeably enhanced because of the good interfacial compatibility. Moreover, the glass transition temperature (Tg) and crystallinity of the biocomposites increased with higher DOPA loading rates. The best properties were observed with a DOPA concentration of 1.0 mg/mL. These findings exhibited the feasibility for the application of PDA in the biomass fiber-reinforced biodegradable polymer composites industry.