Bamboo, a natural material, has been widely used in the fields of decoration, architecture and furniture. However, bamboo is easy to mildew and lose its use value. In this paper, the inhibition mechanism and antibacterial activity of a natural antibacterial agent citral on bamboo mould and its anti-mildew effect on bamboo were studied. The results showed that citral could change the shape of mycelium, destroy the integrity of mycelium structure, cell wall and cell membrane structure, thereby causing leakage of nucleic acids, proteins and other substances in the cell, as well as destroy the pH balance of the inside and outside of the cell, to inhibit or kill mould. When the concentration of citral is 100 mg ml ⁻¹ , the antibacterial rates of citral against Penicillium citrinum (PC), Trichoderma viride (TV), Aspergillus niger (AN) and a hybrid fungi group comprising PC, TV and AN (Hun) were more than 100%. However, compared with the direct effect of citral on mould, the antibacterial property of bamboo treated with citral was significantly reduced, the mildew proof effect can be achieved only if the concentration of citral to treat bamboo is increased to more than twice the concentration of citral directly acting on mould.

In recent years, bamboo has been widely used for building materials and household goods. However, bamboo is flammable, so a flame-retardant treatment for bamboo is urgently needed. In this work, nano MgAl-layered double hydroxide (MgAl-LDH) coated on bamboo, which was called MgAl-LB, was synthesized by an in situ one-step method. To determine the optimal in situ time, the effects of different reaction times on LDH growth on the bamboo surface and the flame retardancy of the MgAl-LBs were investigated. The SEM observations show that LDH growth on the surface of bamboo was basically saturated when the in situ reaction time was 24 h. Abrasion experiments show that MgAl-LDH coating has good abrasion resistance. The fire performance of the MgAl-LBs was evaluated by cone calorimeter tests, which indicated that the THR and TSP of the MgAl-LBs were significantly lower than those of untreated bamboo. Taking into account the energy consumption problem, determining the reaction time of 24 h is the optimal reaction time. Compared with untreated bamboo, the THR and TSP of MgAl-LB prepared at 24 h decreased by 33.3% and 88.9%, respectively.

Bamboo is a widely used renewable and degradable biomass material; however, its sustainable utilisation is hindered by its susceptibility to mold. The current bamboo anti-mold technology is mainly based on organic chemical agents; these agents can easily induce mold resistance in bamboo with long-term use, and can even adversely affect human health. In the present study, the poly(N-isopropyl acrylamide) (PNIPAm)/citral nanohydrogel was prepared by encapsulating the natural antibiotic citral in PNIPAm for the anti-mold treatment of bamboo. The results revealed that this nanohydrogel exhibited a core–shell system with citral as the ‘core’ and PNIPAm as the ‘shell’, an average hydrodynamic diameter of 88.1 nm, and a low critical solution temperature (LCST) of 35.4 °C. After the high-pressure impregnation with the nanohydrogel, the bamboo strips showed excellent control effects toward common bamboo molds. Therefore, the nanohydrogel demonstrated high efficiency and it may become an ideal alternative to organic chemical anti-mold agents, thus showcasing its significant potential in the field of mold prevention for bamboo.

The aim of this study was to overcome drawbacks of the inhomogeneous dispersion and facile agglomeration of nano-ZnO/poly(N-isopropylacrylamide) composite hydrogels (nano-ZnO/PNIPAm composite hydrogels) during synthesis and improve the anti-mold property of the nano-ZnO/PNIPAm composite hydrogels. Here, nano-ZnO/PNIPAm composite hydrogels were prepared by the radical polymerization method. Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), differential scanning calorimeter (DSC), and dynamic light scattering (DLS) were used to characterize the effects of different dispersants on the particle sizes, dispersions, and phase transition characteristics of the nano-ZnO/PNIPAm composite hydrogels. The anti-mold properties of nano-ZnO/PNIPAm composite hydrogels were studied. Results revealed that the nano-ZnO/PNIPAm composite hydrogel prepared by the addition of nano-ZnO dispersion liquid exhibited the smallest particle size, the most homogeneous dispersion, and the highest stability. The addition of the dispersant did not change the phase transition characteristics of nano-ZnO/PNIPAm, and the nano-ZnO/PNIPAm composite hydrogels (P_f) exhibited good anti-mold properties to the bamboo mold.

Presently, chemical agents remain the main antimildew agents for bamboo, which has a certain negative impact on the environment and human health. Therefore, it is urgent to develop new environment-friendly antimildew agents for bamboo. Here, citral, an environment-friendly natural antibacterial agent, was used as an antimildew agent for bamboo. The orthogonal test was used to explore the effects of citral concentration, impregnation pressure, and pressurization time on the drug loading capacity of treated bamboo strips. The effect of antimildew-treated bamboo strips on bamboo mold was also discussed. Furthermore, the Fourier transform infrared spectroscopy and ultraviolet spectrophotometer were used to investigate the distribution of citral in bamboo strips. Results showed that the optimum technological parameters of citral mildew-proof treatment of bamboo were as follows: citral concentration: 0.795 mg/ml, impregnation pressure: 0.3 MPa, and pressurization time: 90 min. Also, citral was easy to volatilize, which decreased the citral content of bamboo strips after vacuum drying and showed the trend of a lower surface layer and a higher inner layer. The concentration of citral therefore had a significant effect on the drug loading of the antimildew-treated bamboo strips. Thus, it was difficult to achieve effective prevention and control of bamboo mold when bamboo strips were impregnated with a lower concentration of citral solution. When the concentration of citral reached 200 mg/ml, the prevention and antimold efficiency of antimildew bamboo strips reached over 100%. This study will provide references for the development and application of environment-friendly natural antibacterial agents in the field of bamboo mildew prevention.

In the present study, the sustained-release system loading citral was synthesised by using PNIPAm nanohydrogel as a carrier and analysed its drug-release kinetics and mechanism. Four release models, namely zero-order, first-order, Higuchi, and Peppas, were employed to fit the experimental data, and the underlying action mechanism was analysed. The optimised system was applied to treat a bamboo mould, followed by assessment of the mould-proof performance. Our experimental results revealed that the release kinetics equation of the system conformed to the first order; the higher the external temperature, the better the match was. In the release process, PNIPAm demonstrated a good protection and sustained-release effect on citral. Under the pressure of 0.5 MPa, immersion time of 120 min, and the system concentration ratio of 1, the optimal drug-loading parameters were obtained using the slow-release system with the best release parameters. Compared to the other conditions, bamboos treated with pressure impregnation demonstrated a better control effect on bamboo mould, while the control effect on Penicillium citrinum, Trichoderma viride, Aspergillus niger, and mixed mould was 100% after 28 days. Moreover, the structure and colour of bamboo remained unchanged during the entire process of mould control.