Decorative plywood

Economic Aspects. The hardwood and decorative plywood industry has decreased in size and production significantly in the past few years. In 1994, there were an estimated 100 mills operating in the United States having a production volume of 1.135 x 10 m (2). The doUar value of this production is extremely difficult to estimate because of the very wide range of prices for the products. 

Hardwood and Decorative Plywood ANSI/HPVA HP-1-1994, American National Standards Institute, New York, 1994. 

Formaldehyde emission and/or formaldehyde space level potential can be related to both construction type and product end use. While the American National Standard for Hardwood and Decorative Plywood (1 ) references eight different types of construction, three are most important in the context of formaldehyde ... 

Standard for Hardwood and Decorative Plywood, ANSI/HPMA HP... 

Decorative plywood Hardwood veneer, some softwoods UP, MF, RP, PVAc Mostly NS Decorative wall paneling, furniture, cabinetiy, decorative flooring 6-19 (H> 400-880(25-55)... 

Veneer and solid wood composite products are manufactured for building and construction commodity markets and for specialty markets such as marine applications and aesthetic decor. Bonding systems vary based upon the service demands placed upon the final product, interior versus exterior. Construction and decorative plywood are veneered panel products. Laminated veneer lumber (LVL) is a veneer product which competes with lumber. Lumber laminates form majestic beams often for dual structural and aesthetic applications. 

Construction plywood is primarily phenolic bonded for an exterior rating. Decorative plywood is primarily bonded with UF resins for interior applications such as wall panels and hardwood flooring tiles. Both types of plywood are composed of layers of veneer or wood with alternating grain orientations that are bonded with heat and pressure. 

Adhesive systems for construction plywood, decorative plywood, LVL (laminated veneer lumber), and lumber laminates are a heterogeneous mixture consisting primarily of resin with extenders, fillers, and catalysts. The adhesive mixture allows for a better matching of adhesive with mill operating parameters than would easily be obtained solely with the use of neat resin. 

Fig. 1. The hardwood plywood process using sHced decorative veneers.

Lay-up proceeds by laying down the veneer which is to be the back surface of the panel. Then a sufficient number of pieces of core veneer are passed through the glue spreader to form the next layer of cross-oriented veneer. The glue spreader commonly used in hardwood plywood manufacture is a roU coater in which a pair of opposing mbber roUs are coated with a thin layer of adhesive. As the veneer is passed between the roUs, the adhesive is transferred to the surfaces of the veneer. Adhesive is appHed only to the cross-pfles and in sufficient quantity to provide a continuous layer on both opposing faces of veneer. Thus, in the case of a three-ply panel, only the core layer is spread with adhesive and in that of a five-ply panel, the second and fourth layers both of which are cross-pfles, are spread with adhesive. Then the top surface veneer, which is normally the decorative surface, is placed on the assembly. 

Plywood furniture core panels, also about 19 mm (3/4 in.) thick, were normally made of a number of layers of relatively thick, 1.5—3.0 mm (1 /16—1 /8 in.) lower value wood veneers combined with thin surface pHes of the decorative veneer. These assembhes were laid-up from glued veneers and then pressed while the bonding occurred. Both lumber core and plywood core have been almost totally displaced in recent years by particleboard or medium-density fiberboard, both discussed herein. This change resulted from the increasing availabiHty and improved finishing characteristics of composites and from decreasing suppHes of core lumber or veneer of suitable quaHty. 

Thin hardwood plywood in the range of 4.5—6.0 mm (3/16—1 /4 in.) was normally a three-ply constmction with a thin, medium-quaHty back ply, a thicker lower value core, and another thin, high quaHty decorative face veneer. These panels were used as wall paneling, door facings, or for fumiture/cabinet appHcations requiring thin panels. Currently, only relatively small quantities of these types of panels are produced in the United States. 

Wood (qv) is arguably the oldest building material used by humans to constmct their dweUings. It is a natural product obtained from trees, used in both stmctural and decorative appHcations. The chemical composition of wood is largely cellulose (qv) and lignin (qv). Today there are a variety of composite or reconstituted wood products, such as plywood, particle board, wood fiber boards, and laminated stmctural beams, where small pieces of wood or wood fiber are combined with adhesives to make larger sheets or boards (see Laminates). 

Plastic laminated sheets produced in 1913 led to the formation of the Formica Products Company and the commercial introduction, in 1931, of decorative laminates consisting of a urea—formaldehyde surface on an unrefined (kraft) paper core impregnated with phenoHc resin and compressed and heated between poHshed steel platens (8,10). The decorative surface laminates are usually about 1.6 mm thick and bonded to wood (a natural composite), plywood (another laminate), or particle board (a particulate composite). Since 1937, the surface layer of most decorative laminates has been fabricated with melamine—formaldehyde, which can be prepared with mineral fiUers, thus offering improved heat and moisture resistance and allowing a wide range of decorative effects (10,11). 

By far the bulk of amino resins are used in the woodworking industry for the manufacture of chipboard, plywood and as general glues and adhesives. Melamine-formaldehyde is an important component of decorative laminates. The amount of amino resins used for moulding applications is only of the order of 5% of the total. 

Used in molding applications, appliances, TVs, automotive parts, filler, impregnating paper, varnishes, decorative laminates, electrical parts, countertops, toilet seats, adhesive for plywood, sandpaper, brake linings, abrasive wheels No large industrial applications... 

Another proposed composite product, this one strictly non-structural, was a decorative interior panel consisting of a pressed bark overlay on a base material such as plywood, hardboard,... 

Hardwood plywood is distinguished from softwood plywood in that the former is generally used for decorative purposes and has a face ply from a deciduous or broad leaf tree. Softwood plywood is generally used for construction and structural purposes, and the veneers typically are of wood from evergreen or needle-bearing trees. 

Historians have described how Greeks and Romans used plywood in their culture to achieve beautiful decorative effects. Articles of furniture overlaid with veneers in these times were highly treasured articles. There is little reference to the use of veneer in the years that followed these cultures until the 17th and 18th centuries, when a revival of the art occurred in Western Europe. 

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