| As a green and sustainable material,bamboo has been paid more and more attention by researchers.In recent years,multifunctional bamboo composites have aroused great interest.In the case of wood shortage,its utilization value and economic value are continuously improved.Therefore,it is necessary to study the functionalization of bamboo composites.This paper studies the influence of metal(silver / copper)electrochemical treatment on the physicochemical properties of bamboo,systematically analyzed the anti-fungal performance of treated bamboo,explored the catalytic principle and action law of nano metal particles for adhesive,revealed the aggregation effect of high-voltage electric field and metal particles on the bonding interface,and finally explored a preparation method of bamboo composites.The main research contents are as follows:(1)Based on the excitation of high voltage electric field,metals(silver / copper)existed as ions and moved towards the cathode under the action of Coulomb force.The main interaction positions between metal ions and bamboo were the carboxyl group of hemicellulose,phenolic hydroxyl group and aromatic alcohol in lignin.After treatment,the O / C ratio and-OH content of bamboo decreased,the number of-CHO groups decreased,and the number of C= O groups increased.The content of metal(silver / copper)particles was the best when the treatment process was 60 k V / 24 h,and the average particle size was less than 50 nm.The study found that silver migrated more easily than copper.There were great differences in the microstructure of different bamboo sections,resulting in different effects of metal electrochemical treatment.It was found that the action intensity of different sections was as follows: bamboo cross section(BC)< bamboo radial section(BR)< bamboo skin(BS)<bamboo pith(BP).(2)The anti-fungal performance of the samples treated with metals(silver / copper)were significantly improved.Comprehensive consideration can be found that the treatment parameter of 60 k V / 24 h was the optimal treatment process.Under the same treatment process of 60 k V /24 h,the mass loss rate was 2.3 %(brown rot fungi)and 2.8 %(white rot fungi)respectively after the indoor corrosion resistance test of copper electrochemical treatment of bamboo;the mass loss rate of silver electrochemical treated bamboo was 0.33%(brown rot fungi)and the quantity loss rate was 0.6%(white rot fungi)respectively.According to the decay of different bamboo sections,the BC was the most vulnerable to corrosion,and the mass loss rate of treated BS and treated BP was less than 1%.The electrochemically treated bamboo can effectively maintained the microstructure of the material,and was not damaged by white rot fungi and brown rot fungi.Under the same treatment process,the concentration of silver electrochemical treatment was higher and the penetration depth was larger.Both treatment methods had excellent fixation performance.The permeability of different bamboo sections were different,and the strengths were BC > BR > BP > BS,which was mainly related to the microstructure of bamboo.(3)For the study of metal electrochemical treatment of bamboo composites,it is found that the maximum mechanical properties can be obtained when the treatment process was 60 k V/ 06 h,which were 8.1 MPa for copper treatment and 8.3 MPa for silver treatment respectively.The mechanical properties of bamboo composites after silver electrochemical treatment were better than those of copper treatment.When the materials were the same,the bonding strength of BS-BS was the lowest and that of BP-BP was the highest.The average growth rate of viscosity,storage modulus and loss modulus of phenolic resin(PF)adhesive under different treatment parameters was Ag < HVEF < Ag + HVEF.In the nano silver / phenolic resin composite system,nano silver particles were easy to combine with phenoxy anions to form phenolic resin silver complex with ortho substitution characteristics.During HVEF treatment,many water molecules and oxygen molecules in the air were strongly ionized,resulting in a significant increase in new chemical groups,which improved the polarity and charge density of the adhesive,which was conducive to increasing the content of hydroxymethyl.The intersection of storage modulus(E’)and loss modulus(E’’)can reflect the polycondensation reaction of PF adhesive.The intersection of Ag + HVEF treatment was the lowest,at 57.9 Hz,E’ = E’’ = 9867.8 Pa.This showed that PF had the highest molecular weight and the strongest polycondensation reaction.Under the synergistic action of silver electrochemical treatment and HVEF,the distribution of bonding interface was orderly and continuous,and the effective penetration depth of the adhesive increased from 78 μm(control)to 167 μm.This was due to the synergistic effect of silver electrochemical treatment and HVEF treatment,which can improve the polymerization speed of adhesive,increase the crosslinking degree of adhesive and effectively inhibit the ineffective penetration of adhesive at the bonding interface.(4)Combined with the above research contents,a preparation method of bamboo composites was explored.The bamboo composite prepared by using silver electrochemical treatment(60k V / 24h)BS as the surface of the composite,silver electrochemical treatment(60k V / 06h)bamboo BP as the bonding surface of the composite and adding 60 k V high-voltage electrostatic in the hot pressing process had excellent properties.One year after the field durability test,the damage rate was only 4.92 %,reaching the C4 A grade of the service grade.The bonding strength increased by 50.67% compared with the untreated.The aging test showed that the bonding strength of the control material decreased by 36.0%,and the bonding strength of the new composite decreased by 14.2 %,which had better weather fastness.The surface hydrophobicity of the composite was increased,and the contact angle was 115.9 °.The surface resistance of bamboo was about 5 lg / Ω,reaching the conductor level,so that the treated bamboo had antistatic properties.After 204 h UV irradiation,the △E remained at about2.0,and the stability of the surface color of the new bamboo composite was significantly enhanced. |
PDF Full Text Request