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Indoor Air Quality
Published in Mary K. Theodore, Louis Theodore, Introduction to Environmental Management, 2021
Mary K. Theodore, Louis Theodore
The superior bonding properties and low cost of formaldehyde polymers make them the resins of choice for the production of building materials. Plywood is composed of several thin sheets of wood glued together with UF resin. Particleboard (compressed wood shavings mixed with UF resin at high temperatures) can emit formaldehyde continuously from several months to several years. Medium density fiberboard was found to be the highest emitter of formaldehyde.
Timber and timber products
Published in Arthur Lyons, Materials for Architects and Builders, 2019
Considerable quantities of plywood are used by the construction industry because of its strength, versatility and visual properties. The strength of plywood in shear is used in the manufacture of plywood box and I-section beams in which the plywood forms the web. Increased stiffness can be generated by forming the plywood into a sinusoidal web. Plywood box beams can be manufactured to create pitched and arched roof forms, as illustrated in Figure 4.37. Stiffened and stressed skin panels, in which plywood and softwood timbers are continuously bonded to act as T- or I-beams, will span greater distances as floor structures than the same depths of traditional softwood joists with nailed boarding. Such structural units can also be used to form pitched roofs or to form folded plate roof structures or barrel vaulting (Fig. 4.37). Plywood of 8–10 mm thickness is frequently used as the sheeting material in timber frame construction and for complex roof forms such as domes. The lower-grade material is extensively used as formwork for in situ concrete.
Composites and Fillers
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Structural composites include laminas that can be sandwich or laminate. At times, there is confusion between which materials are sandwich or laminate laminas. Even so, here we will consider laminate composites as containing layers of material (generally considered the reinforcing agent) bound on one or both sides by an adhesive material. Generally, there are a number of layers of reinforcing material present with the distance between the layers being small compared to those present in sandwich composites. Plywood is an example of a sandwich laminar where layers or plies of wood are bound together using an adhesive such as one of the formaldehyde-related resins. Formica is an example of a laminate where paper, cloth, or other material is impregnated with the continuous phase material. Sandwich laminas are widely used in the textile industry where foam, plastic, and fabric are bound together into new textiles. Many electronic boards are laminas. Examples of laminates include surfaces for countertops and wall paneling.
The effect of urea-formaldehyde adhesive modification with propylamine on the properties of manufactured plywood
Published in The Journal of Adhesion, 2023
Jakub Kawalerczyk, Joanna Walkiewicz, Magdalena Woźniak, Dorota Dziurka, Radosław Mirski
Plywood is a multilayer composite commonly used e.g. in the furniture making, packing materials, structural applications, made of multiple thin wood veneers. Although it may seem that it is an environmentally friendly product, the formaldehyde-based adhesives are usually used to bond the layers together.[1] The choice of the specific type of a binding agent depends on the conditions of use for the resultant wood-based material. In the case of interior-grade plywood, the urea-formaldehyde (UF) resins are the most widely applied.[2] They are a thermosetting duromers consisting of the branched or linear polymeric and oligomeric molecules.[3,4] UF adhesives accounts for about 85% of the total amino resins produced worldwide with the annual volume of approx. 11 million tons per year.[2,5] Moreover, their use is expected to grow even more, especially in the developing regions.[6] UF adhesives owe their popularity to fast curing, relatively low cost, good strength performance of bond lines, lack of colour, water solubility and ease of handling.[7,8] However, in spite of these advantages there are also a major drawbacks such as low water resistance in comparison with phenolic adhesives and the formaldehyde emission.[9,10]