Study On The Modification Of Phenolic Resin Wood Adhesive With Eucalyptus Bark Resource

Eucalyptus is rich in resources.The number of eucalyptus bark in Guangxi is 4.16 million cubic meters per year,which has not been effectively utilized for a long time,and most of them are used as fuel.Eucalyptus bark is rich in chemical composition and contains a lot of polyphenols,which can partly replace phenol to prepare phenolic resin.Because of this,eucalyptus bark,a kind of biomass resource,has attracted the attention of researchers.In this paper,Eucalyptus bark resource was taken as the research object,and the chemical composition of Eucalyptus bark extract,Eucalyptus bark powder and Eucalyptus bark ash were analyzed.The modified phenolic resin adhesive was prepared from Eucalyptus bark extract,ball milled Eucalyptus bark powder and coupling treated Eucalyptus bark ash.The main research contents and achievements are as follows:?1?A method for the determination of total phenol content and condensed tannin content in Eucalyptus bark was established.Under the maximum absorption wavelength of 755nm,the standard curve of gallic acid content absorbance was drawn with the experimental data.The regression equation was y=123.86x-0.0173,and the linear correlation coefficient was 0.9997.Under the maximum absorption wavelength of 500nm,the standard curve of catechin content absorbance was drawn with the experimental data.The regression equation was y=17.96x+0.0286,and the linear correlation coefficient was0.9991.Based on the standard curve,the effects of extraction times and temperature on the content of total phenol and condensed tannin in the extract were investigated,the results showed that the contents of total phenol and condensed tannin were 18.43mg/g and 3.01mg/g under the condition of extraction temperature of 60? for one time;The total phenol and condensed tannin content of the extract were 20.39mg/g and 3.54mg/g under the condition of extraction temperature of 60? and three times;The extraction temperature was 100?,the total phenol and condensed tannin content of the extract were39.29mg/g and 13.81mg/g.The results showed that the increase of extraction times had little effect on the content of total phenol and condensed tannin,and the extraction temperature had a greater effect.?2?The modified phenolic resin wood adhesive?TPF?was prepared by partially replacing phenol with Eucalyptus bark extract.The results showed that the viscosity of TPF increased,the storage period shortened,and the content of free formaldehyde and free phenol decreased with the addition of extract;When the phenol substitution rate is 15%,the adhesive strength is 1.45MPa?unmodified PF is 1.36MPa?.The results of FT-IR,¹H-NMR and ¹³C-NMR showed that tannins in the extract may dehydrate and condense with hydroxymethylphenol to form methylene bond and methylene ether bond.DSC results showed that the curing of TPF and PF was exothermic reaction,With the increase of phenol substitution rate,the peak value of curing exothermic decreased from 131.7? to 124.7?.?3?FT-IR results showed that the absorption intensity of the peaks at3420cm^-1,2930cm^-1,1630cm^-1,1340cm^-1,1250cm^-11 and 1044cm^-1 increased under the action of ball milling,which indicated that the connection structure between cellulose,hemifiber and lignin in bark was destroyed and new groups were formed;SEM results showed that the ball milling bark powder formed uniform and fine powder.?4?BPF-a1 and BPF-b1 were used to prepare modified phenolic resin adhesive respectively,the results showed that BPF and TPF had similar rules:the viscosity increased with the addition of BPF,the content of free formaldehyde and free phenol decreased,and the bonding strength of BPF-b1and BPF-a1 reached 1.49MPa and 1.56MPa respectively.The results of DSC showed that the curing peak temperature of PF-a1 and BPF-b1 were 129.6? and 125.8??the curing peak temperature of PF was 133.6??.?5?The results of XRD and XRF showed that the contents of Ca and Si in Eucalyptus ash were 50.35%and 12.52%,which were the main elements of Eucalyptus ash,including Al,K,Mg,Fe,Cl,Mg,Mn,and a small amount of P,S,Ti,which existed in the form of CaCO₃,SiO₂,KCl.The ash of Eucalyptus bark was treated by coupling agent Z6011,and was blended with phenolic resin adhesive.The results showed that when 25%of the total amount of coupling Eucalyptus bark ash was added,the bonding strength could reach 1.65MPa?unmodified PF was 1.36MPa?,which increased by 0.29MPa.DSC results showed that the curing peak temperature of the coupling treatment of Eucalyptus ash modified phenolic adhesive was 125.9??PF curing peak temperature132.6??,which indicated that the blending had a certain promoting effect on curing,which may be due to the metal ions in the coupling treatment of Eucalyptus ash and the introduction of amino acids.