Properties Of Poplar And Radiata Pine Wood Treated With High-melting-point Waxes

Wax impregnation treatment can effectively improve water resistance,mechanical properties and decay resistance.Previous studies have used low-melting-point wax emulsions to impregnate wood.The treated wood cannot resist high temperatures and has bad machining performance.This study addresses the above deficiencies by treating wood with high-melting-point and high hardness Fischer-Tropsch waxes.Two high-melting-point Fischer-Tropsch waxes,2120 and 3105H,were delivered at molten state into the fast-growing poplar and radiata pine under vacuum/pressure condition.The weight gain,moisture sorption,density change,and mechanical properties of the treated wood were analyzed.The combustion performance of treated wood was analyzed by cone calorimetry.1.Thermogravimetric analysis and differential scanning calorimetry showed that the melting point of Wax 2120 was 112℃ and that of Wax 3105H was 101℃.There was only one weight loss peak in the two thermal decomposition processes of waxes and only one endothermic peak in the heating and melting process,indicating that the two waxes have a narrow molecular weight distribution and low oil content.From the relationship between the molecular weight and melting point of the linear alkanes,it can be seen that the average molecular weight of Wax 2120 is greater than that of Wax 3105H.Considering the shrinkage of the volume of the two waxes during cooling from the molten state to room temperature,which may affect the water resistance of the treated wood.The volumetric shrinkage of waxes for cooling from the experimental temperature of 115℃ to room temperature was examined.The results show that both waxes volume shrinkage is at 15%.The weight gain rates of poplar and radiata pine of various sizes were larger and the weight gain rate of radiata pine was higher than that of poplar wood.Under the same process conditions,the size,species,and species of wax had an effect on the rate of weight gain.The densities of modified poplar wood and modified radiata pine were similar,and they all ranged from 0.8 g/cm3 to 1.0 g/cm3.There is a gap between the wax in the cell lumen and the cell wall due to the volume shrinkage of the wax and the wax treatment does not completely close the cell lumen.2.Wax treatment can significantly reduce the wood’s water absorption,hygroscopicity,and surface hydrophobicity,but does not significantly improve the dimensional stability of the wood.The water-repellent efficiency of the two kinds of wax treated materials was between 94.15%and 96.6%when soaked in water for 6 hours and the water-repellent efficiency of the treated materials after soaking in water for 32 days was between 71.3%and 77.8%.Under the condition of 93%RH,the highest moisture-blocking efficiency of the treated wood after 15 days of moisture absorption was Radiata pine treated with the wax 2120 of 64.9%.Wax 2120 was superior to Wax 3105H in reducing wood moisture sorption and improving wood surface hydrophobicity.With the same type of wax,the modified radiata pine had higher water absorption and hygroscopicity and the surface hydrophilicity was also stronger.3.Wax treated wood improved the bending strength,flexural modulus and hardness of the wood;the impact properties of the treated wood do not decrease significantly.The flexural strength of radiata pine and poplar treated with Wax 2120 increased from 78.85 MPa and 101.71 MPa to 128.31 MPa and 125.5 MPa,an increase of 62.7%and 23.8%,respectively.Two waxes treated poplar and radiata pine flexural modulus(MOE)also improved.Relative to untreated poplar and radiata pine material,Wax 2120 treatment caused an increase by 9.7%and 50.2%;Wax 3105H treatment had an increased by 12.4%and 29.2%,respectively.Wax treatment not only improved the mechanical strength of wood,but also reduced the difference in the material properties of wood between the early wood and latewood.The difference in the hardness of radiata pine material from early wood to latewood was reduced from 15.8HD to about 8.5HD of treated material.The hardness and stiffness of the treated material increase,the brittleness increases,and the impact strength of the treated material slightly decreases.The abrasion resistance of the wood surface is significantly improved during long-term frictional processes.4.By cone calorimetry experiments,it can be found that incorporation of Wax 2120 and Wax 3105H in wood resulted in a prolonged burning time,reduced ignition time and fire performance index of wood.The heat release rate,total heat release rate,smoke release rate,total smoke emission,and CO and CO2 concentrations of the treated wood were higher than the untreated controls.Wax treatment not only increases the fire risk of wood.In summary,the water resistance and stiffness of poplar and radiata pine treated with Fischer-Tropsch Wax 2120 and Wax 3105H are improved and the treated wood is highly waterproof.However,the treatments results in a higher fire risk than the untreated wood.