Effects Of Hydrophobic Formula,Flame Retardant Formula,and Treatment Process On Properties Of Rubberwood

Rubberwood is favored by the furniture and construction industry because of its superior properties such as clear texture,elegant color,and good mechanical performance.Meanwhile,it faces unavoidable disadvantages of the absorption of water,mildew,and combustion.Therefore,it is necessary to improve the flame retardancy and hydrophobicity of rubberwood.Three kinds of O/W microemulsions(HSAS,MSAS,MSHS)were prepared by using high hydrogen silicone oil(MS),hydroxyl silicone oil(HS),and amino silicone oil(AS)as main hydrophobic materials and water as the continuous phase.The stability of microemulsion was investigated,and results showed that the stability of HSAS in the three silicone oil microemulsions was the best,followed by MSAS,and MSHS was the worst.Rubberwood was treated by silicone oil microemulsion formulation and flame retardant formulation through the pressure impregnation process,and the hydrophobic and flame retardant properties of the modified rubberwood were investigated.The research results are shown as follow:(1)Although the silicone oil microemulsion formulation can improve rubberwood hydrophobicity,and the water contact angle(WCA)arrived at 58.39°,it does not effectively improve the flame retardancy of treated samples.Besides,the results show that the flame retardancy of rubberwood can be significant improved by using the flame retardant formulation(boric acid:Borax:diammonium hydrogen phosphate=1:1:1,mol/mol)and that it obtained the Limiting oxygen index(LOI)value of 33.7%,but the hydrophobicity of the material is not improved.(2)The flame retardant formulation and silicone oil microemulsion formulation were impregnated into rubberwood by a twice pressure impregnation process.The test results showed that rubberwood hydrophobicity was significantly improved,and the maximum WCA arrived at 128.07°.Furthermore,the microemulsion system of MSAS and HSAS has a remarkable effect on rubberwood hydrophobicity compared with MSHS.The water absorption efficiency,volume expansion efficiency,air dry shrinkage efficiency,and absolute dry shrinkage efficiency of rubber wood treated with MSAS decreased by 35.35%,45.05%,49.65%,and 24.58%,respectively,while those treated with HSAS decreased by 49.04%,53.56%,50.69%,and 31.18%,respectively,compared with pure rubberwood.(3)The treated rubberwood obtained by a twice pressure impregnation process,which had a remarkable flame retardancy and that it reached the maximum LOI value of 29.7%.The cone calorimeter(CONE)test results showed that the second heat release peak(pk-HRR₂),the total heat release(THR),the total smoke emission(TSP)of rubberwood decreased by39.84%,7.77%,and 21.90%,respectively.And the yield of carbon residue increased by45.48%,which showed that the above-modified formulation had good heat and smoke suppression performance and carbonization.(4)The three modified systems have a significant flame retardant effect on the gas phase and condensed phase.However,the modified system containing amino silicone oil can promote forming carbon residue with better continuity,higher graphitization,higher silicon,and stable chemical bond content.Besides,this system treated materials produce non-combustible gases such as NH₃and NOx during decomposition,and the gaseous flame retardant effect is more pronounced.(5)Under the air atmosphere,the decomposition rate of the modified materials was significantly reduced,which means that modified formula can play an irreplaceable role in the inhibition of rubberwood decomposition,reduce combustible gas release,and inhibiting fire diffusion.