Study On The Weathering Resistance Of Poplar Wood Treated With Silane-TiO₂

Poplar wood in plantation is one of the most commonly used fast-growing species in China,which is prone to aging behavior when used outdoors due to climatic conditions such as sunlight exposure,rain,temperature changes and oxygen,resulting in limitation of its use and shortening of its service life.In order to avoid or reduce the harm of aging on poplar wood,therefore,it is treated with aging resistance.In this study,poplar wood was firstly modified with different concentrations of isocyanate propyltriethoxysilane（IPTS）,and the changes of chemical structure,microscopic morphology and aging properties of the modified wood were analyzed;IPTS-TiO₂treated wood was prepared by adding different crystalline forms of titanium dioxide（TiO₂）as UV shielding agent with IPTS-modified poplar wood as the base material at the optimal modification concentration,and it was subjected to The wood was subjected to a 480 h artificial accelerated aging test to test the changes of surface color,microscopic morphology and chemical structure before and after aging,and to explore the effects of different crystalline forms and different additions of titanium dioxide on the aging resistance of the wood;the chemical components of the wood were treated separately by IPTS-TiO₂ and combined with Fourier infrared spectroscopy（FTIR）,electron paramagnetic resonance spectroscopy（EPR）and X-ray photoelectron spectroscopy（XPS）.Photoelectron spectroscopy（XPS）and UV absorption spectroscopy were used to analyze the aging mechanism.The main research contents and results of this paper are as follows:（1）Firstly,different concentrations of IPTS-modified poplar wood were prepared,and the different degrees of carbamylation of IPTS in poplar wood were demonstrated by FTIR,SEM,XPS,contact angle and other characterization methods.At the modification concentration of 0.5mol/L,the weight gain of the treated wood reached 27±3.48%,the content of Si and N elements were 5.93 and 7.01,respectively,and the contact angle reached 78±4°with some hydrophobicity.The treated materials were subjected to 480 h aging test and analyzed by FTIR and SEM.The results showed that IPTS could not retard the photodegradation of wood components,but prevented the surface cracking of wood;the color change analysis showed that the maximum color difference change during the aging process of control group was 24.66,and the degree of cracking of wood grain and surface color difference change was the least when the modification concentration of IPTS was 0.5 mol/L,which indicated that the IPTS treated wood had certain aging resistance.（2）The FTIR analysis showed that after 72 h of aging,the control group and the WIA_X（X=0.05、0.10、0.15）group showed complete degradation of lignin and hemicellulose,while the WIR_X（X=0.05、0.10、0.15）group showed no degradation of lignin and hemicellulose.No degradation of lignin and hemicellulose was observed in the WIR treatment group.When WIR_0.05aged for 120 h,WIR_0.10 aged for 168 h and WIR_0.15 aged for 192 h,the characteristic peak of lignin disappeared and hemicellulose was slightly degraded.The UV shielding mechanism was analyzed by EPR and UV absorption spectroscopy,and the order of change of phenoxy radical concentration by mercury lamp irradiation was UW>WI>WIA>WIR,and the UV absorption capacity was UW>WI>WIA>WIR.The above results showed that TiO₂-treated poplar had better color stability,and TiO₂ achieved UV shielding by scattering reflecting UV light to achieve the effect of UV shielding,and rutile TiO₂ can delay the degradation of poplar wood components to a certain extent.（3）To further analyze the aging resistance mechanism of IPTS-TiO₂ treated poplar wood,alkali lignin（lignin model compound）,microcrystalline cellulose（cellulose model compound）,and xylan（hemicellulose model compound）were modified by using 0.5 mol/L IPTS.FTIR and XPS characterization of IPTS-modified alkali lignin（IL）,IPTS-modified microcrystalline cellulose（IMCC）,and IPTS-modified xylan（IX）showed that the IPTS modification efficiency was cellulose>lignin>hemicellulose.IL,IMCC,and IX were modified with different crystalline TiO₂ and subjected to UV aging.FTIR and XPS analysis showed that rutile TiO₂ was better than anatase TiO₂ in protecting lignin,anatase TiO₂ would promote the degradation of cellulose,and rutile and anatase TiO₂ would not affect the degradation of hemicellulose.