Laminate Veneer lumber

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. 

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. 

Figure 10.18. Three examples of structural composite lumber (top to bottom) laminated veneer lumber (LVL), parallel strand lumber (PSL), and oriented strand lumber (OSL).

Figure 10.19. Prefabricated I-joists with laminated veneer lumber flanges and structural panel webs, (a) With an experimental hardboard web. (b) With commercially produced oriented strandboard web. (c) With a plywood web.

Veneers - for plywood, laminated veneer lumber (LVL), and parallel strand... 

The intrinsie effieieney of peeling logs to yield veneer has suggested that the same proeess should be applieable to the manufaeture of laminated struetural members. Laminated veneer lumber (LVL) was first produeed in the early 1970s, and sinee then has been eommereially available in many eountries. It is now the most widely used struetural eomposite lumber produet in the US residential housing market. 

Laufenberg TL, Rowlands RE and Krueger GP (1984) Economic feasibility of synthetic fibre reinforced laminated veneer lumber. Forest Products Journal, 34(4) 15-22 Lavers GM (1969). The strength properties of timbers. Princes Risborough Laboratory Bulletin 50, HMSO, London... 

For the high-resin-content formulation (Table 12), a partial addition of the PF resin can be made just after the initial mix and before sodium hydroxide addition if more fluidity is needed for propeller-type stirring. This formulation is more properly termed a blood-fortified exterior PF resin adhesive for hot-pressing plywood or laminated veneer lumber [52]. Even in quantities this small, the effect of the animal blood is to reduce the hot-press curing time by 2(%30% over that of phenolic resins used alone. For purposes of adhesive solid, calculation, the blood content can legitimately be included with the phenolic resin solids. 

As mentioned previously, neat pMDI does not have gap filling capability for wood bonding because of its low viscosity and propensity for deep penetration. Consequently, neat pMDI is not used for applications such as plywood, laminated veneer lumber, etc. However, gap filling properties may be achieved by modifying pMDI with a wide variety of difunctional or polyfunctional polyols. Viscosity and NCO content are easily tailored to meet many application requirements. 

Wood and biomass are raw materials (Figure 9.4.1) for traditional building products like sawn timber, prefabricated timber elements and systems as well as wood-based materials in the form of boards (e.g. particle- and fibreboards), but also as construction elements from glued products like laminated beams, plywood, oriented structural boards or laminated veneer lumber. ... 

I-beams are glued very similarly to finger joints but with different joint profiles. The most common wood type for the upper and lower parts in the I-beam (flench) is spruce or laminated veneer lumber (LVL) or Douglas fir (Fig. 14). In the middle part (web) oriented strain board (OSB) is most common medium density fiberboard (MDF) can also be used. 

Plywood panels produced in Europe for building purposes use urea-formaldehyde (UF), melamine-urea-formaldehyde (MUF) and phenol-formaldehyde (PF) adhesives. Standards requirements are not focused on direct properties of these adhesives but properties of the end-products (closely linked to adhesive properties and process parameters). Nevertheless, EN 314-1 (2005) [1] defines a test method for the evaluation of the bonding quality of plywood panels, but also blockboards, laminated boards and laminated veneer lumbers (LVL), by shear testing before and after ageing treatments. Relevant requirements are specified in EN 314-2 (1993) [5] which also defines the ageing treatments required for the intended service class of the tested panel as shown in Table 1. 

Laminated veneer lumber (LVL) a flat pressed multilayer wood panel similar to plywood composed of oriented wood veneers but differently from plywood oriented all in the same direction in all the layers and bonded by hot-pressing by using thermosetting adhesive resins. 

Construction and industrial plywood Softwood veneer, some hardwood PP S Roof, floor, wall sheathing, single-layer floor, siding, floor underlayment, preserved wood foundations, laminated veneer lumber 6-31.5 (i-li) 450-500(28-31)... 

Laminated veneer lumber (LVL) Softwood veneer PP, pMDI S Floor and roof joists, roof ridge beams, roof truss chords, window and doorheaders, wood I-joist flanges, concrete form, scaffold planking, window and door joinery 19-75 (f-3 in.), 27-50 in. wide, up to 24.4 m (80 ft) long ... 

The principal wood composite products currently in use in the United States and Canada, based on volume, are plywood (17.5 million cubic meters), oriented strandboard (16.8 million cubic meters), particleboard (10.3 milHon cubic meters), medium density fiberboard (3.4 million cubic meters), hardboard (2.0 million cubic meters), hardwood plywood (1.0 million cubic meters), and laminated veneer lumber (1.2 million cubic meters) (13). These products are described below. While all of these composites occupy an important place in the market now, some of these products are gaining in importance while others appear to be losing market share to other composite products. 

Structural pre-fabricated engineered wood composites (e.g., FiRP reinforcement technology used to produce structural members, beams and I-beams, made from derived wood products, such as glulam and laminated veneer lumber (LVL) with an internal bonded passive reinforcement, like CFRP, GFRP or AFRP). The reasoning behind its development was to allow the use of smaller cross-sections, to obtain more homogeneous... 

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