| Wood-based panel products are mainly used in manufacturing furniture and decoration fields in China,which reqired them to be well decorated.Manufacturing artificial wood veneers by fast-growing wood species have become an important way to make up for the lack of resources and to develop wooden decorative materials.In the adhesion technology of manufacturing artificial wood veneers,veneers' bonding quality at high moisture content was one of the key technologies because all of changing the conventional manufacturing process,cancelling veneer drying stage and bonding high moisture content veneers directly with the adhesive were requred.In the course of manufacturing artificial wood veneers,the veneers'surface property was changed by dying and fixing veneers.The veneers were covered by a lot of dyes and fixing agent that caused a direct impact on veneers' adhesion.Compared to bonding higher moisture content raw veneers,bonding effect of dyed veneers and fixed veneers were impacted by chemical group nature of dyes and the fixing agent,including the impact of adhesive interface, wettability,bonding property and so on.One-component moisture-curing isocyanate adhesive was used in the paper for gluing wet veneers dyed and fixed.So the processes of bleaching,dyeing and fixing were studied preliminarily,including the choice of bleach,dyes and the fixing agent,the process parameters selection of bleaching,dyeing and fixing,research of the penetration and adhesion process of acidic dyes to wood using SEM and FTIR analysis tools and the deep research to guarantee the color stability of the artificial veneer.The results showed as follows:the best bleaching process are different for 1.5 mm thick birch and poplar;Only a small part of the dye molecules were penetrated into the core layer of the veneer and absorbed which was physical process mainly proved by the research;The fixing effect of KAl(SO4)2 are the most that made small change to the veneers in six kinds of metal salts fixing agent;The best fixation effect of veneers were got in the way of post-processing veneer with Chitosan solution and the fixed veneers were almost no change.Good water resistance and light resistance of the fixed veneers were achieved after treating with 1 percent chitosan solution.Wettability of one-component wet-curing isocyanate adhesive on the wet surface of raw wood,dyeing and fixing wood was researched respectively.And wettability was characterized by contact angleθand spreading-penetration parameter K.Wetting property of these three different adhesive interfaces was compared and analyzed.The results show that The contact angle of these three interface all reduced significantly with the extension of time,and the higher the moisture content is,the initial contact angle is smaller,the balance contact angle is greater.With the same moisture content,contact angle of raw birch veneer is the smallest, that of fixed birch veneer is the largest,dyed veneer's contact angle is between them.With the increase of moisture content,spreading-penetration parameter K of interface for the raw birch, dyed veneer and fixed veneer were significantly decreased,but the K-value decline of them was different.On the basis of the findings of the wettability study,bonding properties glued dyed and fixed veneers with one-component wet-curing isocyanate adhesive was researched.The major impacts on the adhesive properties such as veneers' moisture content,adhesive spreading volume and pressure time was measured.The best adhesive technology was achieved and the theories were analysed.All of these findings provide guidance to the following manufacture of artificial wood veneers.The results show that dry and wet-shear strength of raw birch specimen has always been the highest in the course of moisture content increasing from 50%to 90% which significantly higher than dyed and fixed specimens.Bonding strength of these three kinds of specimen all gradually increased when the coating is less than 120g/m2,but with the coating more than 120g/m2,these three bonding strength all declined.The intensity pressed 1.5h to three kinds of specimen reached the maximum.With a further increase in pressure time, dry and wet bonding strength have little change.The aging performance of bonding system manufacturing artificial veneer with high moisture content of wood was analyzed.Compared to bonding system change before and after ageing course,its impact on the durability of bonding system was revealed and bonding mechanism was discussed.(1) the bonding joints were repeated by boiled - dry accelerated aging test,then mechanical strength of these joints were measured using of mechanical testing machine.The factors impacted on mechanical strength were analyzed systematically.The results showed that after boiled - drying cycle accelerated aging treatment,compression shear strength of bonding joints showed a sharp decline in one aging cycle.Since the second,third and fourth aging cycle, compression shear strength detected a slight fluctuation.(2) The isocyanate film was treated by boiled - dry accelerated aging test and UV - hot and humid accelerated aging test which change of micro-structure and chemical functional groups was researched and analyzed by SEM, DMA,FTIR and ESCA to try to reveal the aging mechanism of film.The results showed that after the film boiled - drying cycle accelerated aging analyzed by DMA,loss angle tangent(tanδ) had almost no change;storage modulus E' gradually dropped with temperature increasing and tend to balance at 150℃;The initial storage modulus E' of film vary greatly that expressed as E′three cycles＞E′fourcycle＞E′five-cycle＞E′6-cycle;the order of Loss modulus E″was E′′three cycles＞E″four-cycle＞E″five cycle＞E″six cycles before the glass transition temperature,then E″rapidly reduce until tend to 0 after reached this temperature.After film dealt with cycling UV - condensate water,the functional group changes in the ageing film was analyzed by FTIR.The findings showed that -NCO groups characteristic peaks disappeared in the film used CaO as a defoaming agent and -N-CO-O groups characteristic peaks significantly weakened.-NCO groups characteristic peaks disappeared in the film used dimethyl silicone as a defoaming agent and -OH groups characteristic peaks widen markedly.The film was uniformity,meticulous,no porosity in the SEM photos before aging.After dealt with cycling UV - condensate water,the film's surface has undergone great changes.The defoaming effect adding CaO powder and dimethyl silicone oil as a defoaming agent showed significant differences and dimethyl silicone shown a more pronounced role in the anti-foaming.Making use of XPS instrument to analyze the surface chemical state of the isocyanate film before and after aging,its fitting results were consistent with FTIR spectra attribution conclusions.
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