Research On Properties And Mechanism Of Rubber Wood Treated By MUG Resin In Combination With Silica Sol

In this dissertation,we take the tropical economic tree rubber wood as the research object,and report a green and environmentally friendly resin modified solution（MUG resin）for rubber wood via a combined treatment with glyoxal,melamine,urea,and additive in the different dosage of additives,reaction temperature and treatment time.MUG resin penetrates well into the interior of the wood,and evenly distribute in the wood lumen and cell wall after curing,so that the wood can achieve the effect of increasing density and strength.On this basis,rubber wood was treated by MUG resin combined with silica sol can improve the dimensional stability and mechanical properties,and give the wood good flame retardant,weather resistance and durability.The main result-s are as follows:（1）MUG resin was synthesized by controlling the molar ratio of glyoxal:melamine:urea:additives=1:0.08:0.6:0.5 at 70℃ for 150 min.There was a reaction between glyoxal,melamine and urea of MUG resin.The results showed that the weight percent gain and density of treated wood increased with increasing MUG resin concentration,while water uptake and leachability decreased with the increase of resin concentration;the anti-swelling effect first increased and then decreased.Considering the basic properties of the treated wood,25%～35%MUG concentration can be selected to impregnate rubber wood.（2）S-MUG treated wood were prepared by a combined treatment with different amounts of MUG resin（25,30 and 35 wt%）and 10%silica sol,and compared and analyzed the physical and mechanical properties of MUG resin treated wood and silica sol treated wood.The results showed that the physical and mechanical properties of the S-25%MUG treated wood,S-30%MUG treated wood,and S-35%MUG treated wood were not significantly,between the MUG resin treated wood and silica sol treated wood.MUG resin functions as covering and fixing agent to anchor silica sol in wood,thus reducing its leaching into water.The bulking effect of S-MUG treated wood was about 20.0%;the density was about 0.755 g/cm³,which increased by21.2%than control wood;the equilibrium moisture content decreased by 23.9%than control wood;the anti-swelling effect at about 50.0%;the water uptake after immersion for 60 d decreased by 38.7%than control wood;theΔE^*was about 3.0;the weight loss percent after immersion for 4 h,12 h,24 h and 48 h were respectively around 2.0%,8.0%,16.0%and 20.0%;the end hardness,plane hardness quartered hardness increased by 17.7%,21.0%,and 30.8%than control wood;the end nail holding power,plane nail holding power,and quartered nail holding power increased by 20.0%,9.4%,and 14.0%than control wood;the MOR and MOE increased by 22.8%and 50.0%than control wood;the compressive strength parallel of grain increased by53.0%and 13.0%than control wood.（3）The S-25%MUG treated wood（S-MUG）was prepared by a combined treatment with25%MUG resin and 10%silica sol,and compared and analyzed the flame retardancy,thermal stability,ageing resistance,and corrosion resistance of MUG resin treated wood.The results showed that the oxygen index increased by 17.4%and 45.3%of MUG resin treated wood and S-MUG treated wood.The ignition time of MUG treated wood and S-MUG treated wood increased by 22.7%and 50.0%than control wood.The total heat release,total smoke release,CO and CO₂ yield peaks of MUG treated wood increased 13.9%,30.3%,0.4%,and 4.9%than control wood.The total heat release,total smoke release,CO and CO₂ yield peaks of S-MUG treated wood increased 39.6%,55.0%,44.7%,and 29.6%than control wood.The residue of MUG treated wood and S-MUG treated wood increased by 28.3%and 96.8%than control wood.There was a photochemical reaction after irradiated with ultraviolet light.TheΔE^*of MUG resin treated wood and S-MUG treated wood decreased by 19.1%and 29.4%than control wood.The mass loss rate of MUG resin treated wood decreased by 76.1%and 76.7%achieved decay resistance grade.The mass loss rate of S-MUG treated wood decreased by 83.0%and 83.8%achieved a strong corrosion resistance grade.S-MUG treated wood had a better flame retardancy,thermal stability,ageing resistance,and corrosion resistance than MUG treated wood.（4）The wood can basically maintain the natural porous structure after treated.The absorption peaks of C-N bond and Si-O-Si bond appeared in the FT-IR spectra of the treated wood and the modifier could penetrate the wood,filled the cell lumen and cell wall,and distributed evenly on the cell wall along the cell contour.The crystallinity of the treated wood increased,and the crystal structure was not destroyed,which indicated that the treatment did not damage the physical structure of the wood,and mainly entered the amorphous area of the wood.With the increased of N and Si elements,the relative contents of C and O elements decreased,and the O/C ratio increased.The unstable end group in wood undergo oxidation reactions during the treatment and low molecules of acid were generated,resulting in a decreased in C1 content and an increased in C4 content.