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Study on the Manufacturing Technology of Artificial Wood Veneer with Wet Veneer and the Aging Mechanism of Bonding System

Author: WeiShuangYing
Tutor: GuJiYou
School: Northeast Forestry University
Course: Biological materials engineering
Keywords: Artificial veneer Wet like glue Moisture curing isocyanate adhesive Dyeing Fixative Film aging mechanism
CLC: TS653
Type: PhD thesis
Year: 2008
Downloads: 193
Quote: 1
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Abstract

China's wood-based panel products are mainly used in the field of furniture manufacturing and construction and fitting, its decorative a higher demand, the need for surface decoration. The fast-growing species of wood as raw material to manufacture artificial veneer has become one of the important ways to make up the natural precious tree resources are scarce, the development of wooden decorative materials. Conventional manufacturing processes in the manufacture of artificial veneer bonding technology, change, cancel veneer drying stage, connected to the high moisture content of veneer adhesive glue, causing wet like glue to become one of the key technologies of the artificial veneer manufacturing. Process in the manufacture of artificial veneer, veneer After staining, fixing stage, so that the the veneer surface properties changed veneer surface is covered by the large number of dye molecules, fixing agent molecules, resulting in a direct impact on the bonding. Compared to the high moisture content material veneer glued, glued stained with a high moisture content, fixing veneer subject to the dye group, the influence of the chemical properties of the fixing agent group, including the impact on the bonding interface, the surface tension the impact of wettability on bonding performance, eventually leading to an impact on the bonding effect. This project to start from the adhesive, single component moisture curing isocyanate adhesive bonding high moisture staining, fixing veneer is the entry point for a number of preliminary studies, the first timber bleaching, dyeing and fixing process work, including bleaches, dyes and fixing agents choose; selection of process parameters in the process of bleaching, dyeing and fixing; using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy were investigated by means of acid dyes, dye in wood staining process penetration of wood attached to the process; taking into account the veneer color stability is to ensure that the artificial veneer an important guarantee of the quality of the final product, launched an in-depth study of staining, fixing veneer color stability. The results show that, in the bath ratio is 1:15 hours, pH = 10 under the condition of 1.5mm thick birch and poplar veneer best bleaching process varies; acidic dye penetration and adsorption studies prove in birch, only a very small portion of the dye molecules are able to enter to the board core layer, the dyeing process, Acid Orange II molecules and the binding process of the birch based on physical adsorption; in six kinds of metal salt fixing agent, KAl (SO ₄) ₂ effect of fixing the most significant, after fixing veneer discoloration; chitosan solution dyed veneer processing, you can get the best solid color effects, and treatment the veneers hardly discoloration; mass fraction of 1% chitosan solution enables veneer has good water, light color stability. Followed by in-depth study of a single component moisture curing isocyanate adhesive wetting properties of the material, stained wood and solid color wood surfaces. Mainly studied the solid color under the conditions of the higher moisture content to the birch material, dyed wood and chitosan timber as the bonding material, the use of single-component moisture-curing isocyanate adhesives by measuring the glued interface contact angle θ The determined diffusion - permeability coefficient K permeability coefficient K with a contact angle θ and diffusion - joint characterize the the interface wetting properties of the different glued on comparative analysis of three different interface wetting properties. The results show that the contact angle of the three interfaces are significantly reduced with time, and the higher the moisture content, the initial contact angle is smaller, the larger the equilibrium contact angle; moisture content the same, the contact angle change birch material Minimum solid color birch stained birch than fixative birch slightly reduced; - permeability coefficient K values ??were significantly decreased with increasing moisture birch material, stained birch and solid color birch three interface diffusion, but the value of K changes differ. Next, on the basis of the wetting properties of the results of the single-component, moisture curing isocyanate adhesive glue then stained with high moisture content, fixing veneer glued performance system, determination of veneer moisture content, glue The amount of pressure time main factors affect the bonding performance, come to the best bonding process, and expand theoretical analysis, and to provide guidance for the subsequent manufacture of artificial veneer. The results show that the moisture content is increased from 50% to 90% of the process, material dry, always the highest shear strength in wet state, significantly greater than the two test pieces of the dyeing and fixing; amount of glue is less than 120g / m ^{2 , with the increase of the amount of adhesive bonding strength of the material, dyeing and fixing specimen gradually increases; When the amount of glue over 120g / m ^{2 the bonding strength of the three test pieces for reduced; the strength of the three test pieces in 1.5h after pressure has reached the maximum value, with a further increase of the pressing time, dry, little change in wet strength. Final system analysis glued artificial veneer with a high moisture content of wood glued system aging properties, adhesive joints and isocyanate film before and after aging physical, chemical change, reveals aging glued system before and after the change of the bonding durability explore the effect of the glued system aging mechanism. (1) of the adhesive bonded joints repeated boiling - dry accelerated aging test using a universal mechanical testing machine mechanical strength of adhesive joints before and after aging detection system analysis of the factors affecting the mechanical strength of glued joints. The results show that the glue joint after boiled - drying cycle to accelerate the aging treatment, compression shear strength decreased rapidly after one cycle, after a slight fluctuation in the second, third, detected in the four-aging cycle test compression shear strength. (2) of the film isocyanate repeated boiling - dry accelerated aging tests - hot and humid artificial accelerated aging test, using scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), dynamic mechanical properties analysis (DMA) and ultraviolet photoelectron spectroscopy analysis means isocyanate film microstructure and chemical functional groups change before and after aging research, system analysis isocyanate film before and after aging, physical and chemical changes of the film the aging mechanism. The results show that the film after boiling - the drying cycle accelerated aging were analyzed after treatment with DMA instrument, the loss tangent tanδ almost no change; storage modulus E 'is gradually decreased as the temperature rises, gradually tends after 150 ℃ balance. The film's initial storage modulus E 'very different performance for the E' _{three cycles > E '_{four cycles > E' _{five cycles > E '_{six cycles}; loss modulus E \six cycles, the Sub >> E \- condensing water circulation after the treatment, by Fourier Transform Infrared Spectroscopy film aging functional groups before and after the change, found using CaO as the antifoaming agent of the film after aging-N = C = O groups characteristic peaks disappear; Characterization carbamate The characteristic absorption peak was significantly reduced. The dimethyl silicone oil as a defoamer of the film after aging-N = C = O, characterized in absorption peaks disappear;-OH peak was significantly widened; photos can be seen through a scanning electron microscope (SEM): film uniformly before aging meticulous, no pores. Processing of UV - condensation water cycle, the surface morphology of the film has undergone great changes, adding CaO powder and dimethyl silicone oil as defoamers defoaming effect is a significant difference, dimethyl silicone oil shows more apparent from the defoaming effect. X-ray photoelectron spectroscopy to analyze the chemical state of the isocyanate film surface before and after aging, the fitting result with the film before and after aging FTIR spectral peaks conclusion. Consistent.}}}}}

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CLC: > Industrial Technology > Light industry,handicrafts > Wood processing industry,furniture manufacturing industry > Processing > Wood-based panel production
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