Study On Flame Retardant And Anticorrosive Properties Of Pinus Radiata Wood

Wood is a renewable and degradable material.It has the characteristics of easy processing,beauty and environmental protection,and can provide good strength and sustainable life cycle.Therefore,it is widely used in architectural decoration industry.However,wood has the disadvantages of flammability and perishability,which is greatly limited in use.In order to increase the fire-retardant and anti-corrosion properties of wood,the vacuum atmospheric pressure impregnation method was used to impregnate radial pine with ammonium polyphosphate（APP）,silica sol and copper azole preservative.The flame-retardant properties,dimensional stability,mechanical properties and pyrolysis characteristics of radial pine material and wood treated with different concentrations of flame retardants were compared and analyzed,combined with scanning electron microscope（SEM）,Fourier infrared spectroscopy（FTIR）X-ray diffraction（XRD）and other technical means revealed the internal mechanism of the effect of impregnation modification on the properties of radial pine wood.The main research conclusions of the test analysis are as follows.（1）The test results of flame retardant characteristics show that the limit oxygen index（LOI）of Pinus radiata material is 23.6%,and the combustion grade is B2,which belongs to combustible material;The LOI value of the test material impregnated with app and silica sol alone is higher than that of the material,and increases with the increase of the concentration of flame retardant.The LOI value of the material treated with app silica sol is 63.5%,and the combustion grade reaches B1,which is a flame retardant material.The heat release rate（HRR）of the material treated with silica sol alone is not lower than that of the material,but the time to reach the peak is prolonged;When the concentration of silica sol is 15%,the total heat release（THR）is lower than that of the material,indicating that the flame retardancy of silica sol with the concentration of 15%is relatively good.The effective heat of combustion（EHC）of the material is 17.38 MJ/kg,and the EHC of the flame retardant impregnated material is less than that of the material.The smoke release rate（SPR）of the material treated with silica sol alone is higher than that of the material,while the SPR of the material treated with app is lower than that of the material.The SPR peak of the combined impregnated material is 0.019 m²/s,which is 17.4%less than that of the material.Compared with the materials,the total smoke emission（TSP）of flame retardant impregnated materials decreased in varying degrees,and the app treated materials with a concentration of 10%had the best smoke suppression effect.Therefore,the THR,HRR and EHC of APP treated materials were significantly reduced;App treated materials will increase the output of CO and reduce the output of CO₂;The result of silica sol treatment is opposite.The combination of the two treatments showed a good smoke suppression effect.Therefore,APP silica sol combined treatment can improve their shortcomings and achieve the effect of flame retardant and smoke suppression.（2）The number of hydroxyl groups of the test material impregnated with flame retardant is reduced,the active groups of the flame retardant react with the hydroxyl groups of the wood,and the polar groups and the chemical components of the wood produce hydrogen bond association.Due to the addition of flame retardants,the relative content ratio of wood components was reduced,and hemicellulose and cellulose were reduced.The flame retardant impregnated material reacts with the hydroxyl groups on the cellulose in the amorphous region while rearranging the microfibrils and transfers them to the crystalline region to increase the crystallinity of the cellulose.The analysis of thermogravimetric results shows that the residual carbon rate of the material is 18.9%,and the residual carbon rate of the test material impregnated with flame retardant is 30.5%-150%higher than that of the material.APP has better heat resistance than silica sol,and to a certain extent It inhibits the pyrolysis of wood.（3）The weight gain rate,compatibilization rate and absolute dry density of the flame retardant impregnated material increased with the increase of the concentration of the flame retardant;compared with the raw material,the water absorption rate of the impregnated material decreased;With the increase of the ratio,the equilibrium moisture content（EMC）of the APP-treated material increases,while the addition of silica sol reduces the EMC of the test material.between.The mechanical properties such as flexural modulus of elasticity（MOE）,flexural strength（MOR）,and compressive strength along the grain of the silica sol treated material are all improved relative to the material,and increase with the increase of the concentration of silica sol;APP reduces the MOE and MOR of the wood,but increases the along-grain compressive strength.Compared with the raw material,the mechanical properties of the joint-treated wood are reduced.（4）The decay test results showed that the mass loss rate of Pinus radiata was 23.2%after the flame-retardant test material with copper azole preservative was eroded by brown rot fungus,while the mass loss rate of the treated test material was only 7.4%,which effectively reduced the mass loss rate of the test material;Through the SEM image,it can be seen that the interior of the rotten wood is full of hyphae,while the interior of the test material added with preservative can hardly see the existence of hyphae,which indicates that the copper azole preservative has a strong antibacterial effect on brown rot fungi.