To further improve the preparation efficiency and properties of bamboo fiber reinforced polymer composites (BFRPs) fabricated by the vacuum-assisted resin transfer molding (VARTM) process. Here, the bamboo fiber/glass fiber mesh reinforced polymer hybrid composites (BGRPs) were fabricated by VARTM to determine the effects of three fiber stacking sequences (namely, GBBGBBG, BGBGBGB, and BBGGGBB; B: bamboo fiber, G: glass fiber mesh) on the physical and mechanical properties, as well as void characteristics of BGRPs (i.e. BGRP-1, BGRP-2, and BGRP-3). The results showed that the incorporation of glass fiber meshes could shorten the injection time of epoxy resin and improve the mechanical properties of BFRPs. BGRP-1 exhibited the lowest water absorption (1.31%) and the highest shear strength (15.55 MPa). Glass fiber meshes on the surface and bottom of BGRP-1, respectively, served as buffer layers to retard mechanical damage, so that BGRP-1 had the best drop hammer impact properties. BGRP-2 represented the highest flexural strength and flexural modulus of 92.22 MPa and 6.69 GPa, respectively. The mechanical properties of BGRP-3 were inferior to those of BGRP-1 and BGRP-2, and more voids were observed in the middle of BGRP-3 in micro-CT slices induced by inadequate epoxy resin impregnation on bamboo fibers.

In order to improve the flame-retardant properties of bamboo scrimber, chitosan (CS) and polyvinyl alcohol (PVA) were used as the film-forming substances, and hexagonal boron nitride (h-BN) was used as the flame-retardant substance to prepare h-BN flame-retardant coatings, which were coated on the surface of the bamboo scrimber. The effects of the h-BN flame-retardant coatings with different quality concentrations on the flame-retardant properties of the bamboo scrimber, as well as on the morphology of the residual carbon, were investigated using the analytical methods of FTIR, environmental scanning electron microscopy, thermogravimetric analysis, combustion test, and coating adhesion test. The results showed that the h-BN flame-retardant coating could improve the thermal stability of the bamboo scrimber and that the higher the mass concentration, the better the thermal stability of the h-BN. Compared to the control, the time to ignition (TTI) of the 5% h-BN flame-retardant-treated specimens increased by 56%; the peak heat release rate (Pk-HRR), total heat release (THR), and total smoke production (TSP) decreased by 9.92%, 7.54%, and 32.35%, respectively; however, due to the presence of PVA, the peak smoke production rate (Pk-SPR) increased by 17.78%. The 5% h-BN coating had very good adhesion, with an adhesion grade of zero. In conclusion, the h-BN coating could be well-adhered to the surface of the bamboo scrimber, and the 5% h-BN flame-retardant coating had a better flame retardancy compared to other treatments, meaning that it could provide a new strategy for improving the flame-retardant properties of bamboo scrimber for construction use.

Bamboo pretreatment is a key technology for the preparation of bamboo fibers (BFs) for composites. This study examined the properties of BFs prepared by steam explosion (SE) BFs following pretreatment by enzyme, alkali, and salt. The microstructure, functional groups, crystallinity, and surface chemical elements of BFs were characterized by environmental scanning electron microscope (ESEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicated that bamboo could be separated into fiber bundles through SE after pretreatment. The separation of BFs pretreated by enzyme and alkali were better, but colloid remained and was able to stick the fibers together. Through performing different pretreatments before SE, the lignin and hemicellulose of BFs were partially removed, and alkali pretreatment had the best effect on lignin removal. The crystal structure of the BFs did not change significantly, and the crystallinity of BFs was highest at 2 MPa and 6 min when pretreated by alkali. The XPS results showed that the effect of alkali pretreatment at 2 MPa for 6 min was the best.

Bamboo was carbonized and further modified via co-doping with graphene oxide (GO) and polyaniline (PANI) to prepare microwave absorption composites (GO/PANI/CB) by in situ polymerization of 1R-(-)-Camphorsulfonic acid (L-CSA). The conductivity of GO/PANI/CB reached 2.17 ± 0.05 S/cm under the optimized process conditions. The oxygen-containing group of GO reacts with PANI to form hydrogen bonds and thus polymerize. The GO and PANI particles covered the carbonized bamboo (CB) surface in a disordered aggregation form. Based on the measuring method of the vector network analyzer (VNA), the microwave-absorption performance of GO/PANI/CB was investigated. With 30% addition of GO/PANI/CB, the minimum reflection loss (RL_min) at 7.12 GHz with a thickness of 3.5 mm of samples reached −49.83 dB. The effective absorption bandwidth (<−10 dB) is as high as 4.72 GHz with a frequency range of 11.68–16.40 GHz and a thickness of 2 mm. Compared with many PANI based electromagnetic wave absorbing materials reported in recent years, GO/PANI/CB provides improved microwave-absorption performance while maintaining high absorption bandwidth. GO/PANI/CB exhibited the advantages of simple preparation, low cost, renewability, light texture, thinness, wide absorption bandwidth, and strong absorption ability, and can be used for new microwave absorption materials.

This study aimed to examine the effect of epoxy resin (EP) systems on the impregnation of bamboo fibers (BFs) by EP and the properties of BF/EP composites prepared by vacuum-assisted resin transfer molding (VARTM) process. BF preforms obtained by solution suspension method were used as reinforcement, and epoxy/anhydride system (EP-1), epoxy/amine system (EP-2) and two-component epoxy system (EP-3) were employed as matrix; on this basis, BF/EP-1, BF/EP-2 and BF/EP-3 composites were prepared by VARTM. The physical, mechanical and thermal properties and void characteristics of BF/EP composites were characterized. The results showed that EP-1 with a viscosity of 265 mPa·s at 23°C and an operating time of room temperature without curing was beneficial for the EP-1 to impregnate BFs adequately and uniformly. The incorporation of BFs into EP-1 significantly improved the flexural, shear and impact properties, thermal properties and interface properties of EP-1. Moreover, the properties of BF/EP-1 composites were better than those of BF/EP-2 and BF/EP-3 composites. Three-dimensional X-ray microscopy scans revealed that the volume and distribution of voids in the BF/EP composites differed significantly depending on the EP systems, and the percentage of void volume in the BF/EP-1 composites was only 0.14% in 3D reconstruction models.

In order to improve the interface compatibility of HDPE/bamboo fiber composites, O₂ and N₂ plasma were used to treat the HDPE surface, the effects of plasma treatment power, time, and different flow rates on HDPE surface wettability were analyzed, the optimal process of plasma to improve HDPE surface wettability was determined, and a mathematical model between HDPE surface energy and the plasma treatment process was established. The effect of plasma treatment on the mechanical properties of HDPE/bamboo fiber composites was further studied, and the surface morphology and surface chemical structure of the materials before and after plasma treatment were analyzed. The results show that the surface wettability of HDPE can be significantly improved after O₂ and N₂ plasma treatment, which can further enhance the interface compatibility of HDPE/bamboo fiber composites and improve the impact and tensile strength of the composites (impact strength increased by 19.91% and 19.55% after O₂ and N₂ plasma treatment, respectively; tensile strength increased by 16.47% and 12.48%, respectively). The optimal process parameters for enhancing the interface compatibility of the two plasma composites are 1100 W, 13 s, and 1.75 L/min (O₂ plasma), and 1100 W, 13 s, 2.5 L/min (N₂ plasma); between the two, N₂ plasma has a better effect on the surface wettability of HDPE than O₂ plasma treatment.