To improve the flame-retardant performance of bamboo fiber (BF) reinforced polypropylene (PP) composites, melamine pyrophosphate (MPP) and aluminum hypophosphite (AP) at a constant mass ratio of 2:1 were added. The influence of the MPP/AP mass fraction on the mechanical and flame-retardant properties of the BF reinforced PP composites were evaluated by mechanical testing, limiting oxygen index (LOI) and cone calorimetry. Mechanical tests demonstrate that tensile properties of BF/PP decreased with the increase of MPP/AP mass fraction, while flexural properties of composites exhibited very different tendencies. Both flexural strength and modulus increased slightly with the addition of MPP/AP at first, and then decreased significantly after a relatively high content of MPP/AP was loaded. This was due to the poor interfacial compatibility between PP and MPP/AP. The flame retardancy of BF/PP composites has been greatly improved. When 30% MPP/AP was loaded into the composites, the LOI increased to 27.2%, which was 42.4% higher than that of the composite without flame retardant addition. Cone calorimetry results indicated that MPP/AP worked in both gas and condensed phases during the combustion process. Peak heat release rate, total smoke production and mass loss of the composites were significantly reduced because of the addition of MPP/AP.

When thermoplastic resins such as polyethylene (PE) and polypropylene (PP) are selected as wood adhesives to bond wood particles (fibers, chips, veneers) by using the hot-pressing technique, the formaldehyde emission issue that has long existed in the wood-based panel industry can be effectively solved. In this study, in general, thermoplastic-bonded wood-based panels presented relatively higher mechanical properties and better water resistance and machinability than the conventional urea–formaldehyde resin-bonded wood-based panels. However, the bonding structure of the wood and thermoplastic materials was unstable at high temperatures. Compared with the wood–plastic composites manufactured by the extruding or injection molding methods, thermoplastic-bonded wood-based panels have the advantages of larger size, a wider raw material range and higher production efficiency. The processing technology, bonding mechanism and the performance of thermoplastic-bonded wood-based panels are comprehensively summarized and reviewed in this paper. Meanwhile, the existing problems of this new kind of panel and their future development trends are also highlighted, which can provide the wood industry with foundations and guidelines for using thermoplastics as environmentally friendly adhesives and effectively solving indoor pollution problems.

The practical problem of free formaldehyde pollution in the plywood industry is that polyethylene films have been shown to be able to replace some urea–formaldehyde resins for wood adhesives. To broaden the variety of thermoplastic plywood, reduce the hot-press temperature, and save energy consumption, an ethylene–vinyl acetate (EVA) film was selected as a wood adhesive to manufacture a novel wood–plastic composite plywood via hot-press and secondary press processes. The effects of the hot-press and secondary press processes at different levels on the physical–mechanical properties of EVA plywood (tensile shear strength, 24 h water absorption, and immersion peel performance) were evaluated. The results showed that the properties of the resulting plywood using the EVA film as an adhesive could meet the type III plywood standard. The optimum hot-press time was 1 min/mm, the hot-press temperature was 110–120 °C, the hot-press pressure was 1 MPa, the dosage film was 163 g/m², the secondary press time was 5 min, the secondary press pressure was 0.5 MPa, and the secondary press temperature was 25 °C. EVA plywood can be used in indoor environments.

The flexible modification of decorative veneer by plastic film is an effective method to broaden its applications. In order to understand the effect of initial veneer moisture content on the performance of plastic film reinforced decorative veneer, Fraxinus mandshurica veneers with different initial moisture contents were composited with polyethylene film. The overlaying performance of the decorative veneer and its interface morphology with MDF substrate were evaluated. The results showed that when the initial moisture content increased from 10% to 50%, the cavity proportion of PE film reinforced decorative veneer increased from 7.23% to 18.48%, while all of the minimum steel rod diameters remained at 7.6 mm. When the initial moisture content fluctuated between 10% and 20%, the optimum surface bonding strength (1 MPa) and immersion peel strength (0 mm) of the decorative veneer could be obtained. The strength of the decorative veneer significantly decreased when the initial moisture content was more than 20%, which was caused by the cavities and the poor interfacial bonding. The veneer surface was easy to crack under low moisture content conditions. Based on the overall performance and the cost of decorative wood-based panels, initial veneer moisture content was suggested to be 15% to 20%.

In order to further improve the performance of impregnated paper decorated blockboard (ecological board), high-density fiberboard (HDF) was selected as the equilibrium layer to replace the commonly used poplar veneer. Results showed that the performance of HDF ecological board can be comparable to that of poplar veneer ecological board. It had good appearance quality, and its surface scratch resistance, surface wear resistance, water resistance and mechanical properties met the requirements of National Standard GB/T 34722-2017. The surface cracking resistance of the ecological board prepared with HDF as the equilibrium layer reached the highest level (grade 5), far better than that of the poplar veneer ecological board. This was because HDF was a relatively homogeneous material, and its dry shrinkage in both the transverse direction and along the grain direction was much lower than that of the poplar veneer. This characteristic of HDF made it possible to improve the dimensional stability and bending resistance of blockboard substrates under dry and hot conditions. The formaldehyde emission of the HDF ecological board was higher than that of the poplar veneer ecological board, but it met the formaldehyde emission requirements of indoor materials according to GB 18580-2001.