Study On Acoustic Vibration Performance Of Modified Wood Based On Extraction And Impregnation Treatment

In order to achieve the inferior material utilise and functional improvement of the wood resources for the instrument soundboard and slow the contradiction between supply and demand,the chemical functional improvement were used in this study.In this paper,the broad-leaved paulownia wood used in national musical instruments was taken as the research object,and the extraction treatment of four different extraction solvents,the immersion treatment of dimethylol dihydroxyethyl ethylene urea and the combined treatment of post-extraction immersion treatment were adopted.In the way of improving the acoustic vibration performance of the test piece,the results show that:(1)After the paulownia and spruce wood were extracted by deionized water,ethanol,dichloromethane and benzyl alcohol,the acoustic vibration performance changed,and the extraction effect of dichloromethane and benzyl alcohol was the best.The overall performance was as follows,the acoustic performance parameters of Chinese fir and Paulownia were changed after being treated with deionized water,dichloromethane,benzyl alcohol and ethanol.The specific dynamic elastic modulus E/ρ of Chinese fir increased by 6.92%,12.97%,14.52%and 11.57%,respectively;the acoustic radiation quality constant R increased by 11.20%,18.11%,17.42%and 14.89%,respectively;the modulus E/ρ increased by 4.41%,13.92%,7.57%and 5.24%,respectively;the acoustic radiation quality constant R increased by 9.85%,17.82%,10.36%and 7.95%,respectively;the extraction effect of organic solvent was higher than that of water,so the extract of organic matter was not conducive to the acoustic properties of the wood.(2)After immersion treatment with dimethylol dihydroxyethyl ethylene urea,the dimensional stability of paulownia wood was significantly improved.From the perspective of acoustic vibration parameters,the acoustic impedance ω of the modified material,the acoustic radiation quality constant R,and the acoustic performance parameters such as the dynamic elastic modulus E/ρ had all been changed.From the vibration sound evaluation index E/G,when the immersion concentration of dimethylol dihydroxyethylethylene urea was about 20%,it can contribute to the improvement of the tone quality of wood.At this concentration,the specific elastic modulus of wood increased by 22%,the acoustic radiation quality constant increased by 23.3%;the hydroxyl and carboxyl content of wood decreased,the moisture absorption rate of wood increased,and the sound stability improved;The number of C4 was reduced,and the amount of C2 was increased,indicating that the valence state of C in the treated wood had been exchanged,converting the hydroxyl group of the hydrophilic portion into a hydrophobic ester bond and an ether bond.(3)Compared with the immersion treatment with organic matter,the SiO2 sol-gel immersion treatment method improved the dimensional stability of the paulownia wood,that was the sound stability of the wood was improved.From the physical and acoustic properties of wood,it was known that the acoustic impedance ω,moisture absorption resistance and WPG of SiO2 wood composites were significantly improved,but the acoustic radiation quality constant R and specific dynamic elastic modulus E/ρ of composite materials and extraction treatment with the decreased of the SiO2 were more obvious with the higher water content,and the decrease was more obvious.Scanning electron microscopy and FTIR analysis proved that the SiO2 of the nano-particles in the SiO2 wood composite was filled on the cell wall,which was also the main reason for the change in material properties.Summarizing the above treatment methods,we can find some methods to improve the acoustic vibration performance of wood.The main means and purpose are to improve the acoustic vibration parameters such as E/ρ and R,which are closely related to the density of wood and the the acoustic vibration performance.Therefore,the extraction treatment method,especially the organic solvent extraction treatment,had certain advantages for improving the acoustic vibration characteristics of wood.Through comprehensive comparison,the order of improving the vibration performance of Paulownia wood was:organic solvent extraction>electrodeless solvent extraction>extraction+impregnation DMDHEU resin treatment>extraction+impregnation SiO2 treatment.Impregnation of organic/inorganic materials was a complex physical and chemical reaction.If the modification,the catalyst,reaction time,chemical reagent selection,etc.can be further studied,new chemical substances are introduced to improve the corresponding acoustic vibration parameters.It is believed that organic and inorganic chemical treatment methods can be an effective means to improve the acoustic vibration performance of wood.