Study On The Preparation Technology And Dyeing Mechanism Of Wood Imitation Bamboo Scrimber

Wood-imitation dyed bamboo(Phyllostaehys pubescens)scrimber is a new type of material with high performance and high added value,which is made from bamboo bundles of fluffy bleached or heat-treated bamboo bundle through wood-like computer color matching,circular dyeing,and curing processes.In view of the problems of single color,low added value,difficult dyeing of the preparation unit(bamboo bundle)and unclear dyeing mechanism of the bamboo in China,this study firstly systematically studied the bamboo bundle dyeing process and developed a bamboo bundle circular dyeing system.The dyeing mechanism of bamboo bundles was revealed by using dyeing kinetics and thermodynamics and combining the changes of microscopic morphology and chemical structure of dyed bamboo bundles.The effects of different dyeing concentrations and dye ratios on the color characteristics of dyed bamboo bundles were analyzed.According to the color characteristics of solid wood flooring materials,the computer color matching and its controlling technology of bamboo bundle imitating solid wood was established.A series of imitation solid wood dyed bamboo scrimber flooring products have been developed.This study is of great practical significance to realize high-value utilization of bamboo and broaden the application field of bamboo scrimber.The main conclusions of the thesis are as follows:(1)The best bleaching process for bamboo bundles is bleaching agent concentration 5%,bleaching temperature 70 ?,bleaching time 90 min.Acid dye is suitable for bamboo strand dyeing.The optimal process conditions for normal pressure bamboo strand dyeing are modifier dosage 0.3%,dye solution pH 6,dyeing concentration 0.5%,dyeing temperature 90 ?,dyeing time over 8 hours.Compared with normal pressure dyeing process,pressure dyeing can significantly shorten the dyeing time.The optimal dyeing process is: dyeing concentration 0.5%,dyeing temperature 90 ?,pressure 1MPa,and dyeing time 60 min.All the chromatic aberration was less than 1 after 11 times circular dyeing.The developed circular dyeing system can ensure the stability and uniformity of dyed recombined bamboo color.(2)The dye uptake of bleached bamboo bundle and heat-treated bamboo bundle gradually increased with the extension of time.At the initial dyeing stage,the dye uptake increases rapidly,gradually slows down with the passage of time,and finally tends to balance.Based on dynamics research,it is shown that the monochromatic and multi-component dyeing processes conform to the classical hyperbolic absorption equation of Vickerstaff dyeing,and the equilibrium dye uptake of monochromatic dyeing is higher than that of multi-component dyeing.Based on thermodynamic studies,it is shown that the adsorption isotherm of monochromatic dyeing conforms to Freundlich thermodynamic adsorption model.Scanning electron microscopy observed that the inner walls of the vessels and parenchyma cell cavities of dyed bamboo bundles were covered by a large number of dye particles and attached to the inner walls and pit with spheroids.The crystallization characteristics,chemical functional groups and isothermal adsorption curves of bamboo bundles did not change obviously before and after dyeing,indicating that no obvious chemical bond was formed between dye molecules and bamboo fibers.The dyeing mechanism of acid dyes for bamboo bundles is non-localized physical adsorption.The dyes and bamboo bundles are mainly combined by hydrogen bonds and Van der Waals Forces.(3)When dyeing light-colored solid wood,bleached bamboo bundle are suitable for the base materials.Different concentrations of acid yellow,red and blue have significant effects on the L*,a* and b*,and C* of dyed bamboo bundles,and there is overlap in the difference tests of different dyeing concentrations.Based on the theory of three primary colors,dyes with different proportions can spell out most colors.SAS cluster analysis shows that 66 dyed bamboo bundles with different proportions can be divided into 4 categories,of which acid blue contributes the most to the color of dyed bamboo bundles,followed by acid red and acid yellow.(4)The color parameters of 100 kinds of solid wood flooring materials in our country are basically close to normal distribution.In CIE(1976)L* a* b* system,L* is negatively and positively correlated with a* and b* respectively,and positively correlated with hue label value H.SAS cluster analysis showed that the color of 100 kinds of solid wood flooring materials could be divided into 6 types.Using Kubelka-Munk tristimulus method,the computer color matching and its controlling technology for bamboo imitating solid wood color was established.The different dye ratios of bleached bamboo bundle and heat-treated bamboo bundle imitating Brosimum sp.,T.tomentosa,D.celebica,P.macrocarpus,Peltogyne sp.and Myroxylon sp.were obtained.The relative error of tristimulus value between the dyed samples and the target color was less than 9%.(5)Alkaline neutralization treatment after dyeing is beneficial to improving gluing performance.Impregnated resin treatment had no obvious effect on the color of dyed bamboo.The hot-pressing process of dyed bamboo scrimber showed that the dyed bamboo scrimber had the best performance when the concentration of impregnated resin of dyed bamboo bundles was 25%,the temperature was 130 ?,and the time was 1 min/mm.The color difference between the dyed recombined bamboo and the target colors of Brosimum sp.,T.tomentosa and D.celebica is less than 1.5,the simulation effect is good,and the physical and mechanical properties and heavy metal content meet the standard requirements.