Understanding the interfacial changes of wood during heat treatment can facilitate the improvement of the bonding and coating processes of heat-treated wood. Steam was used as the medium to modify Pinusmassoniana wood through heat treatment at 160, 180, 200, and 220 °C. Changes to the surface characteristics after heat treatment were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM) and contact angle measurement. The results showed that: (1) hemicelluloses were the first to experience degradation at 160 °C, and this degradation was the most intense at 200 °C. The cellulose started experiencing obvious degradation at 200 °C, while there was less degradation of lignin at this temperature. (2) Oxygen-containing groups like hydroxyl and carbonyl were gradually reduced as temperature increased with deepened color and passivated surface. (3) Cellulose crystallinity presented a variable trend of increasing–decreasing–increasing. (4) Surface porosity and roughness of Pinus massoniana wood both increased after heat treatment. (5) The Pinus massoniana wood interface turned from hydrophilic to hydrophobic, and 180 °C was a turning point for the wettability of the Pinus massoniana wood interface.

A flame retardant composition was prepared by using phosphoguanidine, guanidine sulfamate, disodium octaborate tetrahydrate and dodecyl dimethyl benzyl ammonium chloride. Veneers were immersed in such flame retardant mixture to prepare plywood. The combustion characteristics and thermal stability of plywood were assessed using a cone calorimeter and TG. Results showed that: (1) High concentration and loading of flame retardant were beneficial for the fire resistance of the plywood. (2) The limiting oxygen index (LOI) and residual mass of plywood processed using the flame retardant was increased by 87.52% and 58.66% compared to those of the untreated plywood, while the average heat release rate (av-HRR), total heat release (THR), effective heat of combustion (EHC), total smoke release (TSR), CO yield (COY), CO2 yield (CO2Y) and oxygen consumption were decreased by 44.3%, 82.9%, 47.0%, 86.0%, 89.9%, 50.1% and 83.1%, respectively. (3) Treated plywood which had a low fire growth index (FGI) displayed a later combustion heat release rate peak and slower flame spread than observed for the untreated material. Combustion of treated plywood displayed a higher fire performance index (FPI), indicating a longer time to ignition. This suggests that burning structures from this material would be subject to a longer time for escape from the structure and would present lower fire risk than similar structures containing treated plywood. (4) TG results demonstrated that the presence of the flame retardant can decrease the pyrolysis temperature for hemicellulose and cellulose, change the decomposition and reaction progress for plywood degradation and promote dehydration carbonization and accelerated charformation. Moreover, the formed char was more stable than that combustion of untreated plywood. (5) The flame retardant contains nitrogen (N), phosphorus (P), boron (B), chlorine (Cl) and guanidine (Gu) compounds. The adhesive also contains N and P compounds. These substances display flame resistance and supplement each other to generate flame retardance than any one used alone. By changing the thermolysis and thermal decomposition processes, the heat release and smoke release from plywood, undergoing combustion was reduced. This controlled generation of combustible substances and promoted dehydration and carbonization to form char. As a result, the flame resistance of plywood was improved significantly. The probability of smoke asphyxia or poisoning death of those trapped in structures containing treated plywood during fire accidents can be decreased dramatically.

(1) A compound protectant was prepared using manganese chloride, phosphoric acid, boric acid and ammonium chloride, and then a veneer was immersed in the prepared protectant to prepare plywood in this paper. Great attention was paid to discussing influences of such protectant on fire resistance, decay resistance, anti-mold property and bonding performance of plywood. Results demonstrated that after protectant treatment, the plywood showed not only good fire resistance and smoke inhibition, but also strong char-formation ability, slow flame spreading, long time to ignition, small fire risk and high safety level. (2) The mass loss rates of plywood with protectant treatment after infection and erosion in wood-destroying Coriolus versicolor and Gloeophyllum trabeum were 19.73% and 17.27%, reaching the II-level corrosion grade. (3) There is not a significant difference with Aspergillus niger V.; however, it was possible to observe a strong difference with Trichoderma viride Pers. ex Fr., indicating that the protectant acted as a good anti-mold product for plywood. (4) The protectant influenced the bonding interface of wood and bonding conditions of the adhesive. The bonding strength of plywood was weakened, but it still met the requirements on bonding strength of GB/T 9846-2015. (5) The protectant changed the thermal decomposition and thermal degradation of plywood, inhibiting the generation of inflammable goods, blocking transmission of heats and lowering the thermal decomposition temperature of plywood. These promoted dehydrations and charring of wood and the generated carbon had a high thermal stability. (6) Compared with untreated plywood, the prepared protectant treatment significantly enhanced the fire resistance of plywood, reduced its biodegradability by wood-decaying fungi and showed good mold resistance.

To study the static bending creep properties of glass fiber reinforced wood, glass fiber reinforced poplar (GFRP) specimens were obtained by pasting glass fiber on the upper and lower surfaces of Poplar (Populus euramevicana, P), the performance of Normal Creep (NC) and Mechanical Sorptive Creep (MSC) of GFRP and their influencing factors were tested and analyzed. The test results and analysis show that: (1) The MOE and MOR of Poplar were increased by 17.06% and 10.00% respectively by the glass fiber surface reinforced composite. (2) The surface reinforced P with glass fiber cloth only exhibits the NC pattern of wood and loses the MSC characteristics of wood, regardless of the constant or alternating changes in relative humidity. (3) The instantaneous elastic deformation, viscoelastic deformation, viscous deformation and total creep deflection of GFRP are positively correlated with the stress level of the external load applied to the specimen. Still, the specimen’s creep recovery rate is negatively correlated with the stress level of the external load applied to the specimen. The static creep deflection and viscous deformation of GFRP increase with the increase of the relative humidity of the environment. (4) The MSC maximum creep deflection of GFRP increased by only 7.41% over the NC maximum creep deflection, but the MSC maximum creep deflection of P increased by 199.25% over the NC maximum creep deflection. (5) The Burgers 4-factor model and the Weibull distribution equation can fit the NC and NC recovery processes of GFRP well.