Wood finish durability

The adverse effects of weather on wood and wood finishes and resultant chemical and physical changes on wood surface will be reviewed and discussed in this work. In addition, recent research findings on surface pretreatment of wood for enhancing durability of applied finishes will be presented. 

Many aspects of wood weathering are not completely understood. A complete understanding of the mechanisms involved in outdoor weathering would aid in developing new pretreatments and finishes to enhance wood durability. The ever-changing commercial wood supply and the introduction of previously unused species at increasing frequency pose particular challenges to the use of modern wood finishes. A detailed study of the various interactions that affect the performance of wood materials is needed to protect wood products when they are used outdoors. 

Alkyds are used for finishing metal and wood products but not to the degree previously used. Their durability to interior exposure is good, but their durability to exterior exposure is only fair. Because of their formulating flexibility, they are used in fillers, sealers, and caulks for wood finishing. They are still used for finishing by the machine tool and other industries. Alkyd-modified acrylic latex paints are excellent architectural finishes. 

Uses Crosslinking agent, hand builder adding durability and resilience to fabrics (cellulosics, synthetics) adds durability to fluorochem. and water repellent finishes crosslinking agent for hydroxyl-contg. emulsion polymers for top coat systems, waterborne wood finishes, nonwoven binders... 

Common resins in use are rosin esters, such as ester gum, which is used for its low cost maleic resin, used in wood finishes for its good sanding properties and alkyds, employed for their good resistance and durability. Alkyds modified with coconut oil are often used these may be ftirther modified with other resins, such as terpenes, for good heat-sealing properties and phenolics, for good water resistance. 

Developments in glued laminated structures and panel products such as plywood and chipboard raises the question of the durability of adhesives as well as wood. Urea-formaldehyde adhesives are most commonly used for indoor components. For exterior use, resorcinol adhesives are used for assembly work, whilst phenolic, tannin and melamine/urea adhesives are used for manufactured wood products. Urea and casein adhesives can give good outdoor service if protected with well-maintained surface finishes. Assembly failures of adhesives caused by exudates from some timber species can be avoided by freshly sanding the surfaces before glue application. 

Pizzi, A. (1990). Extended durability by the chemical fixation of unsaturated alkyd finishes to wood. Holzforschung und Holzverwertung, 42(6), 107-109. 

Campbell, G. G. "An Investigation of Improving the Durability of Exterior Finishes on Wood", M. S. Thesis, Dept. Wood and Paper Sci. North Carolina State Univ, Raleigh, N. C. (1966). 

Little is understood of the mechanism involved in the improvement of a wood surface after treating with chromium-containing chemicals and the subsequent durability of applied finishes (5). The data in Table II show that the reduction of the rate of weathering (as measured by loss of springwood) is directly related to chromium concentration. 

M. A. Kalnins, in Surface Characteristics of Wood as They Affect Durability of Finishes, US Forest Serv. Res. Pap. FPL 57 (1966). 

Uralkyds have superior adhesion, hardness, abrasion resistance, durability, and chemical resistance to the unmodified alkyds. They find major applications in wood floor finishes, marine coatings, metal primers, and maintenance paints. 

Varnishes. The most natural appearance for wood is obtained by use of clear varnishes or lacquers. Other treatments either change wood color or cover it up completely. Unfortunately, clear varnish finishes used on wood exposed to sun and rain require frequent maintenance to retain a satisfactory appearance. Durability of varnish on exposed wood is limited and many initial coats are necessary for... 

A great store of information has been accumulated on the effectiveness of WRPs in protecting exterior wood (J, 117-119, 121, 122, 124-129). The treatments can be applied by vacuum impregnation, by immersion (which is preferred), by brush, or by spray application. They improve the performance of many finishes applied over them and add greatly to the durability of exposed wood. Even chipboard or particleboard, which is very susceptible to moisture, can be protected quite effectively against the effects of outdoor exposure by using a WRP pretreatment followed by a diffusion-resistant coating 126, 130-133). 

FINISH (FINISHING). Wood products such as doors, stairs, and other fine work required to complete a building, especially the interior. Also, coatings of paint, varnish, lacquer, wax, etc., applied to wood surfaces to protect and enhance their durability or appearance. 

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