Bien que les produits de finition à base d’eau constituent une avenue prometteuse pour les manufacturiers de meubles et d’armoires de cuisine, ces produits semblent provoquer l’apparition non désirable des joints de colle reliant les composants de bois. Ce projet de recherche avait pour objectif d’analyser ce phénomène. L’apparence des lignes de colle de panneaux lamellés-collés a été analysée suite à l’application de produits de finition à base d’eau dans le but d’identifier les combinaisons de colle/produit de finition causant l’apparition de cette problématique.
Six colles fréquemment utilisées en industrie et quatre systèmes de finition, dont trois à base d’eau et un à base de solvant, ont été testés sur des panneaux de bois massif lamellés-collés et sur des panneaux particules. L’apparence des lignes de colle a été analysée visuellement et aussi à l’aide d’un profilomètre afin de mesurer de façon précise la topographie de surface des échantillons vis-à-vis les joints de colle.
Ces manipulations n’ont toutefois pas permis de recréer la problématique des joints de colle trop apparents rencontrée par certains industriels. Suite à la fabrication des panneaux et à l’application des produits de finition, les lignes de colle n’étaient pas plus visibles qu'ordinairement en industrie avec l’utilisation des produits de finition à base de solvant. Les échantillons ont été conditionnés à un cycle d’humidité dans le but de constater l’effet de l’humidité sur la finition des panneaux. Ce traitement a engendré une augmentation de l’apparence des lignes de colle sur plusieurs échantillons, mais ce, autant sur les échantillons traités avec les systèmes à base d’eau que sur ceux traités avec le système à base de solvant.
This study relates to technology for tailor-making PF resin with molecular weight and size distributions beyond those now available for commercial processing. Consequently, adhesive mobility and cure speed can be adjusted through use of a two-component resin system comprised of continuous and dispersed phases. Current studies specifically concern two-component alkaline plywood formulations suitable for bonding veneer at 12 plus or minus 2% m.c.
The objectives of this study were to produce and modify phenolic dispersion based adhesives using technology recently developed at Forintek and to further characterize the physical properties and bonding properties of these systems for veneer and composite board applications with emphasis on faster cure speed potential. Data developed in this study indicate opportunities to improve waferboard and plywood PF adhesives in terms of color, cure rate and application properties. Further research work is recommended to improve techniques for producing and characterizing appropriate powder disperson-like formulations for wood bonding.
Further data on flow, viscosity-solids and veneer bonding at dry and 11 plus or minus 2% wood m.c. conditions are provided for heated PF powder systems. This information is intended to supplement the main report issued in March 1987.
A series of dispersion-resin plywood formulations were prepared in the laboratory and their bond performance assessed on incised spruce veneer at 10% m.c. Excellent bond quality results were achieved in these laboratory experiments as indicated by high average % wood failure values of over 90%. To further develop the plywood dispersion resin, a pilot plant trial at a gluing company was conducted and again excellent bond quality results were achieved. A large quantity of the plywood dispersion resin was prepared and a successful mill trial at Cantree Plywood was carried out. This trial demonstrated that more dimensionally stable panels can be prepared from high m.c. veneer. The waferboard dispersion technology developed in this study helped facilitate a mill trial using high moisture content face wafers.
A pilot plant apparatus was built to electrostatically spray phenolic resin on strands. To evaluate the resin distribution on these strands, an image analysis method was developed. The experimental conditions in this study made it difficult to compare electrostatic treatments to control (non- electrostatic) treatments. Although not statistically significant, there were notable differences between these treatments which indicate that electrostatic resin application may improve panel properties and is therefore worth further investigation. First of all, the electrostatic treatment produced panels with a 10% higher internal bond than the control. Secondly, the resin distribution results show that the electrostatic spray, on average, covered a 30% greater area of the strands than the control even though both treatments applied resin at the 2% resin solids level. Further experiments using alternative test procedures are planned to compare electrostatic treatments to control treatments that simulate industrial conditions.
The major defining characteristic of lumber cut from trees that have been infected with the mountain pine beetle is the extent of fungal bluestain in the sapwood. It is reported that bluestained wood has shown increased permeability, and questions arose as to whether the application of an adhesive or a finish coating may be adversely affected. Laminating of wood is a key value-added process and one that is very dependent on the quality of the bond between two or more components. Bluestain is a common phenomenon in the secondary wood processing industry where finishing is part of the value-adding process. The finishing evaluations made in this study were intended to benefit these processors.
Pieces of bluestained and non-stained 2 x 4 in. lodgepole pine lumber were dried to a moisture content typically targeted by the furniture sector — i.e., much drier than lumber used for structural purposes. From this lumber, specially constructed edge-glued panels were made which exhibited bluestained to bluestained joints and non-stained to non-stained joints. This construction method provides bluestained and non-stained joints for the laminating tests, as well as providing a good representation of what will really happen in an industrial setting where bluestain most likely will not be separated from non-stain. Each panel was cut in half, with one half being used for the laminating tests and the other half for the finishing evaluations. The strength and durability of the glue lines were measured. Various finish coatings either used alone or in combinations with others were subjectively evaluated.
The laminating tests show that gluelines in lodgepole pine that contains beetle-transmitted bluestain were not significantly different in strength from gluelines in unstained wood when PVA and PRF adhesives are used. The durability of the bluestained beetle-killed wood gluelines easily met the requirements specified by the ASTM D1101 standard.
Where desired, the appearance of bluestained wood can be enhanced or highlighted by a simple standard clear furniture finish. Bluestain in parts of edge-glued panels can be masked if certain types of finishes are employed. The finishes that gave more consistently good masking results were those containing blue, red, and charcoal tints in the stain, toner, or glaze coatings. Increased permeability of the bluestain did not affect the adherence of any of the finishes.
While the finishing evaluations indicate the possibilities for finishing pine, whether it has bluestain or not, market research is recommended, using the best performing finishes on full-scale furniture pieces, to test consumer acceptance.