Lumber laminate

Weatherproof and permanently mold-resistant casein-based laminating glues. (This would include both low-staining formulations for door and millwork assembly and more highly alkaline lumber-laminating adhesives.)... 

Straight casein lumber laminating adhesives for their superior open and closed beam assembly time tolerance and gap-filling properties. 

Pressure and heat are applied in the process of curing a thermosetting adhesive resin. The resin viscosity typically decreases initially in a thermoplastic response to the heat. The viscosity then increases in response to crosslinking of the polymer molecules in the resin, the kinetics of which are influenced by heat. The resin becomes solid and the heat and pressure are removed as the process is completed. The duration of the thermoplastic phase controls the amount of flow into the wood and must be carefully manipulated for each process. In the case of bonding at ambient temperatures, such as in lumber laminating, the resin is typically catalyzed chemically and cured under pressure. 

Applications. PRFs and RFs are used primarily in lumber laminating and ambient temperature bonding applications. PFs are used primarily in hardboard, plywood, oriented strand board (OSB), and wafeiboard. It is used to a small extent in particleboard. Because PFs generally do not develop the tack of UFs, they are not easily used on caulless particleboard lines. 

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. 

As the thickness of the wood members to be bonded increases, heat transfer from the hot press becomes limiting, and a more reactive resin system is required. Radio frequency (RF) curing processes may also be used. Laminated veneer lumber may be heat cured if the composite thickness allows heat transfer. Alternately, PRF resin systems are used which will cure at ambient temperature. PRF resin systems are used in lumber laminating applications and are cured at ambient temperature under pressure, generally with a catalyst to promote cure. 

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. 

Laminated Strand Products. The most recent developments in the family of wood-based composites are a group of laminated strand products, made with strands oriented in the long direction of the product and marketed as stmctural composite lumber. One product is made with long, narrow strips of softwood veneer. The strips or strands are about 2.5 x 13 x 600 mm (0.1 x 0.5 x 24 in.), coated with a PRE adhesive, and pressed under heat and pressure into large blocks. After the resin is cured the blocks are resawn and planed into lumber dimension stock. 

Melamine or melamine—ureas are used in the manufacture of tmck and railroad flooring, laminated lumber, beams, exterior doors, marine plywood, toilet seats, and school furniture. The bonds in these products meet a variety of commercial, military, and federal specifications for exterior waterproof adhesives. 

Typical features of a plywood resole formulation are a formaldehyde-to-phenol molar ratio in the 2.0 1 to 2.5 1 range, programmed formaldehyde, an alkali content from 4 to 8 wt% (calculated as sodium hydroxide), and pan solids of 40-50%. Resins used for laminated veneer lumber (LVL) tend to be similar to plywood resins in composition and molecular weight, though they are often designed for high-end cure speed. 

Parallam, or laminated strand lumber (LSL) is a beam made by a continuous manufacturing process composed of bigger-size wood needles (very elongated wood particles) reassembled with a structural exterior grade adhesive, the favorite adhesive being isocyanates (pMDI) when heat-curing and PRFs when cold-curing. 

Adhesives based on isocyanate (especially PMDl, polymethylene diisocyanate, more exactly polymeric 4,4 -diphenylmethane diisocyanate) have been used for more than 25 years in the wood-based panel industry [88], but still have a low market value in the wood-working industry compared to systems based on UF-, MUF- or PF-resins. The main application is the production of waterproof panels, but also the production of panels from raw materials that are difficult to glue, like straw, bagasse, rice shells or sugar cane bagasse. They can be used as adhesives for wood-based products like particleboard, oriented strandboard (OSB), laminated strand lumber (LSL), medium-density fiberboard (MDF) or... 

Kawai, S., Wang, Q., Sasaki, H. and Tanahashi, M. (1992). Production of compressed laminated veneer lumber by steam pressing. In Pacific Rim Bio-Based Composites Symposium Chemical Modification of Lignocellulosics, Plackett, D.V. and Dunningham, E.A. (Eds.). FRI BuUetin, 176, pp. 121-128. 

Particleboard (waste wood chips or dust plus a resin) panelling, subflooring, general plywood and lumber replacement Paper-base laminates (plies of wood plus a phenolic, urea, or melamine resin) structural and machine parts... 

The types of adhesives suitable for laminating beams are restricted by the conditions of application and by their end-use requirements. A wider choice of adhesives for plywood depends on whether softwoods or hardwoods are used, whether they are required for internal or external exposures, or whether they are to be used for ornamental or structural purposes. Thus phenol-formaldehyde types would be used for marine or exterior construction uses urea-formaldehyde types would be advantageous for cold pressing, or melamine-urea adhesives might be preferred for hardwood plywood, or lumber-core panels used in furniture production. 

D 5751 Standard Specification for Adhesives Used for Laminate Joints in Nonstructural Lumber Products... 

If lumber were used to do to the same job as OSB, an excess of 8 billion more board feet of lumber would be needed annually, and this lumber would have to come from laiger, higher quality, more expensive trees. It is easy to understand why OSB is considered as the wood product of future in the construction business. Veneer lumber, parallel strand lumber, and laminated strand lumber are also rapidly moving into the market as engineered wood products.25,26... 

From about 1930 to the present, casein glues have been used successfully for bonding high-strength softwood lumber into glued laminated beams and arches for interior or covered exterior service. Even earlier, until perhaps 1900, casein... 

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