Pinus massoniana Lamb. wood particleboards processed by inorganic and organic fire retardants of two densities were prepared by isocyanate and MUF resin. Variations of internal bonding strength (IB), modulus of rupture (MOR), modulus of elasticity (MOE) and thickness swelling rate (TS) of particleboard were observed. Results demonstrated decreasing of IB from 0.81 MPa to 0.42 MPa and 0.36 MPa, MOR from 17.3 MPa to 12.5 MPa and 12.3 MPa, MOE from 1840 MPa to 1328 MPa and 1117 MPa, and increasing of TS from 5.2% to 15.1% and 11.2%, respectively, for the treated MUF particleboards of density 0.65 g.cm-3. Similarly, decreasing of IB from 0.93 MPa to 0.66 MPa and 0.64 MPa, MOR from 16.2 MPa to 10.6 MPa and 12.1 MPa, MOE from 1246 MPa to 1573 MPa and 1466 MPa, and increasing of TS from 6.7% to 7.1% and 6.0%, respectively, when isocyanate adhesive was used. The similar changes were showed when the density of particleboard was 0.75 g.cm-3. Improving density of particleboard appropriately and decrease density difference between the surface to chip layers could make the profile density curve tend to be stable, which could get a relatively high mechanical strength and water resistance. Synergistic effects between isocyanate and fire retardants was confirmed. The particleboard prepared with isocyanate was obviously superior to that prepared with MUF resin in all performances.
A high-efficiency fire retardant composition was prepared with dicyandiamide, phosphoric acid, boric acid, borax, urea and magnesium sulfate and it was used to process veneers which were then to prepare the plywood. Meanwhile, heat release and smoke release from combustion of plywood were tested by a cone calorimeter, including heat release rate, mass loss rate, CO yield, CO2 yield and oxygen consumption. Results showed that the plywood with this fire retardant treatment had the better flame-retardant performance and smoke suppression effect as well as the stronger char-forming capability compared to plywood without fire retardant treatment. The average heat release rate, total heat release, average effective heat of combustion, total smoke release, CO yield and oxygen consumption of the plywood with fire retardant treatment were decreased by 63.72%, 91.94%, 53.70%, 76.81%, 84.99% and 91.86%, respectively. Moreover, the fire growth index of plywood treated by fire retardant was relatively low (3.454 kW·m-2·s-1) and it took longer time to reach the peak heat release rate, accompanied with slow fire spreading. The fire performance index was relatively high (0.136 s·m2·kW-1) and it took longer time to be ignited, thus leaving a long time for escaping at fire accidents. The fire hazard of plywood with fire retardant treatment was low, and its safety level was high.
Heat-treatment woods of Betula alnoides were prepared by using vapor as the heat-conducting medium. Effects of heat-treatment time and heat-treatment temperature on equilibrium moisture content, density, pH value, contact angle and bonding performance of Betula alnoides were discussed in this paper. The results indicated that: (1) With the increase of heat-treatment temperature, the equilibrium moisture content, density and pH value of Betula alnoides decreased gradually. (2) With the increase of heat-treatment temperature, the contact angle of Betula alnoides increased from 70.08° to about 100°, resulting in the reduction of bonding strength gradually. Bonding strength of Betula alnoides after heat-treatment was related with the used adhesive. Bonding strength of different adhesives decreased to different extents. The bonding strength of Betula alnoides wood with polyvinyl acetate (PVAC) resin was generally higher than that of melamine-urea-formaldehyde (MUF) resin. The former were 6.35-4.56 MPa, and the latter were 5.60-3.00 MPa. (3) Heat-treatment time influenced equilibrium moisture content, density, contact angle, pH value and bonding strength of Betula alnoides less than heat-treatment temperature. (4) Heat-treatment could affect strength and surface performance of Betula alnoides greatly and the processing medium should be extended.
In this study, wood protectants were prepared by using manganese chloride, potassium carbonate, borax and nano colloidal silica sol. Effects of the wood protectants on decay resistance, anti-mold property and fire resistance of Pinus massoniana Lamb. were discussed. The results indicated that the optimal formula of the protectant was composed of 20% colloidal silica sol and 8% modifier (manganese chloride + potassium carbonate + borax). Under this formula, the protectant had good permeability and fluidity, accompanied with synergistic effect between colloidal silica sol and modifier. Pinus massoniana Lamb. treated by the protectant with this formula showed good decay resistance, and its mass loss rates after corrosion by Gloeophyllum trabeum and Coriolus versicolor were respectively about 21% and 19%, lower than those of the control group. This indicated that the preferred samples reached I-level decay resistance according to Chinese Forestry Industrial Standards LY/T 1283-2011. Moreover, Pinus massoniana Lamb. under this formula had good anti-mold property, manifested by 100% resistance to Aspergillus niger V. Tiegh and Trichoderma viride Pers. ex Fr. The treated Pinus massoniana Lamb. also showed good fire resistance with the oxygen indexes before and after leaching respectively at 20.45% and 13.64%, higher than those of the control group. It was concluded that the formulated protectant of this research had not only multiple functions of one dose, but also comprehensive resistances to decay, mold and fire, as well as strong leaching resistance.
A process for the delignification of poplar wood using lactic acid-based deep eutectic solvents (DESs) with different hydrogen bond acceptors (choline chloride, glycine) was studied. The effect of operational parameters on the yields of the pulps and the regenerated lignins, the chemical compositions of the pulps and the delignification extent was investigated with respect to several factors, such as the types of hydrogen bond acceptor, reaction temperature and time. The maximum delignification extent of approximately 90.4% was achieved with lactic acidcholine chloride DES at 120°C for 12 h, however only about 58.4% of lignin was removed with lactic acid-glycine DES under the same reaction condition. The structural characteristics of the pulps were subsequently investigated by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric Analysis (TGA) and compared with original wood sample and microcrystalline cellulose.