Eur. J. Wood Prod. (2012) 70:37-43 DOl 1O.1007/s00107 -0 10-0494-y OSB as substrate for engineered wood flooring Costel Barbuta . Pierre Blanchet· Alain Cloutier· Vikram Yadama . Eini Lowell Received: 26 August 2009 / Published online: 13 November 2010 © Springer-Verlag 2010 Abstract Oriented strand board (OSB) is a commodity sheathing, OSB web stock and ponderosa pine OSB sub­ product subject to market fluctuation.Development of a spe­ strates showed higher distortion. The PYA type I adhesive cialty OSB could lead to a better, and more stable, market led to weak bonding with high-density OSB surface.The re­ segment for OSB. It was demonstrated in a previous study sults of this study demonstrate the potential of OSB panels (Barbuta et al. in Eur. 1. Wood Prod. 2010), that OSB may to be used as substrate for EWF. be designed to obtain a high bending modulus of elasticity in the parallel direction, close to Baltic Birch Plywood (BBP) OSB als Tragerplatte ffir Doppelboden in its strongest direction. This study focused on the use of such specialty OSB in the manufacturing of engineered Zusammenfassung OSB ist ein Massenprodukt, das wood flooring (EWF) prototypes,a product that widely uses Marktschwankungen unterliegt. Die Entwicklung spezieller BBP as substrate in Canada. The performance of these two OSB-Platten konnte zu besseren und stabileren Absatzmog­ prototypes (aspen/birch and ponderosa pine) was studied. lichkeiten flir OSB flihren. In einer frliherenStudie (Barbuta Five types of substrates: BBP, sheathing OSB, web stock et al. Eur. J. Wood Prod. 20 I 0) wurde die Moglichkeit auf­ OSB and the two specialty OSB prototypes were used to gezeigt, OSB herzustellen, dessen Biege-Elastizitatsmodul manufacture EWF. A 3-mm thick sugar maple plank was se­ in Faserrichtung nahezu gleich dem von Birkensperrholz lected as the surface layer for all constructions. A polyvinyl (BBP) in seiner sUirksten Richtung ist. acetate (PVA) type I adhesive was used to bond the com­ In der vorliegenden Studie wird die Verwendung von spe­ ponents. The tests in conditioning rooms showed that BBP ziellen OSB zur Herstellung von Doppelboden (EWF) un­ substrate constructions present the lowest distortion between tersucht, flir die in Kanada liberwiegend BBP als Trager­ humid and dry conditions as well as aspen/birch specialty platte verwendet wird. Die Eigenschaften von zwei Prototy­ OSB, according to ANOVA. The construction with OSB pen (EspelBirke und Ponderosa Kiefer) wurden untersucht. Zur Herstellung der Doppelboden wurden flinf verschiede­ ne Tragerplattentypen verwendet, namlich BBP, OSB flir C. Barbuta . P. Blanchet (181) . A. Cloutier Wand- und Deckenelemente, OSB flir Stege von I -Tragem Sciences du bois et de la foret, Universite Laval, Quebec, QC, und die zwei speziellen OSB-Prototypen. FUr aIle Konstruk­ Canada mm e-mail: [email protected] tionstypen wurde eine 3 dicke Deckschicht aus Zucker­ ahom ausgewahlt. Zur Verklebung der Komponenten wur­ P. Blanchet de Polyvinylacetat (PVA) vom Typ I verwendet. Klima­ Value-added wood products, FPlnnovations, Quebec, QC, Canada tisierungsversuche zeigten gemaB ANOVA, dass sich bei V. Yadama Prtifkorpem mit BBP als Tdigerplatte sowie bei speziellen Wood Material and Engineering Laboratory, Washington State OSB aus EspelBirken-Mischung die geringsten Formande­ University, Pullman, WA, USA rungen zwischen feuchten und trockenen Bedingungen er­ gaben. Bei den anderen Prlifkorpem ergaben sich groBe­ E. Lowell USDA Forest Service, Pacific Northwest Research Station, re Formanderungen. Der PVA-Klebstoff vom Typ I fUhrte Portland, OR, USA zu einer schlechten Verklebung bei OSB-Oberflachen hoher � Springer 38 Bur. J. Wood Prod. (2012) 70:37-43 Dichte. Die Ergebnisse dieser Studie belegen das Potential these adhesives are commonly used in the construction of von OSB-Platten fUr Tragerplatten von Doppelboden. EWF today. He found that epoxy was weaker than the other adhesives. The adhesives PVA type II, polyurethane hot melt and EPI showed the best behaviours in terms of aging per­ 1 Introduction formance and they were not significantly different. Engineered wood flooring strips are unbalanced compos­ Since the introduction of engineered wood flooring (EWF) ite constructions. Their deformation is caused by the specific to the market in the 1970s, the popularity of these products reaction of each layer to changes in moisture content (MC) has grown steadily. According to the Floor Covering Weekly and temperature near the top surface. Blanchet et al. (2006) (2008), in 2007, 37.5% of the wood flooring installed in the used a finite-elementanalysis to study the hygromechanical United States was EWF. In this period, the North Ameri­ behaviour of EWF. The analysis showed that the mechanical can EWF market has been negatively influenced by the eco­ properties of the substrate and its thickness have a signif­ nomic decline. The average square foot price of EWF has icant impact on EWF deformation. Furthermore, they con­ jumped by 6% from 2006 to 2007. The development of low cluded that enhancing the mechanical properties of the core cost components would be of interest to EWF manufactur­ layer does reduce EWF deformation. Blanchet et al. (2006) ers. indicate that the bending modulus of elasticity (MOE) of Generally, EWF has 3 components: a surface layer, the the substrate affects the cupping deformation. The mini­ substrateand a backing layer. The surface layer is manufac­ mum bending MOE in parallel direction, required by the tured from high-quality hardwood. Its thickness determines CSA 0437.0 (CSA 1993) standard for OSB class 0-2 is the number of sandings (i.e., refinishings) it can tolerate. In 5500 MPa. Blanchet (2008) suggests the necessity to in­ EWF, a surface layer thickness higher than 3 mm is con­ crease OSB bending MOE in one direction to reach a per­ sidered to be a high-quality product. The substrate is the formance level comparable to Baltic Birch (Betula pendula) core layer. Its main function is mechanical since it restrains plywood (BBP) currently used for EWF manufacturing in surface layer deformation. This layer makes it possible to Canada. According to the Handbook of Finnish Plywood achieve the desired flooring strip thickness. Generally, the (Anonymous 2002), the BBP bending MOE in parallel di­ substrateis made of wood composite materials, such as high rection should be 11400 MPa. density fiberboard(HDF), plywood or wood sticks. The bot­ The objective of this study was to evaluate the behaviour of EWF made with two specialty OSB panels (100% pon­ tom layer enhances the appearance of EWF backing, but it derosa pine (Pinus ponderosa) and 90%/10% aspen/birch also reduces cupping (Blanchet et al. 2(06). Generally, the (Populus tremuloideslBetula papyrijera) strands) as sub­ use of a backing layer is linked to the use of a HDF or a strate and benchmark them with three other construction laminated solid wood strip as substrate. materials used as substrate in EWF (Sheathing OSB, Web Using the French standard NF B54-011 (AFNOR 1980), stock OSB and BBP). Blanchet et al. (2003b) developed a method for testing en­ gineered flooring strips adapted to North American climate conditions. Flooring strip assemblies were subjected to al­ 2 Material and methods ternatively dry and wet cycles. It was assumed that, in North America, a dry environment of 20DC and 20% RH corre­ 2.1 EWF prototypes manufacturing sponds to winter conditions and a humid environment of 20DC and 80% RH corresponds to summer conditions. The constructions used in this study are presented in Fig. 1. Blanchet et al. (2003a) present a comparative study on the The geometry of the EWF strip considered was 85 mm wide, use of four types of adhesives in EWF manufacturing: urea 12 mm thick and 610 mm long. The EWF prototypes were formaldehyde (UP), melamine-urea formaldehyde (MUF), produced using five different materials as substrate: Baltic type III polyvinyl acetate (PVA) and polyurethane (PUR). plywood, sheathing grade OSB, web stock OSB, specialty These adhesives were used to bond a 4 mm thick, 65 mm aspen/birch OSB and specialty ponderosa pine OSB. The wide and 600 mm long sugar maple wear layer over a set physical and mechanical properties of these substrates are of cross-grain 8 mm thick, 22 mm width and 65 mm long presented in Table 1. These properties were determined ac­ sticks. The PUR adhesive gave the best results, followed cording to ASTM standard D 1037-06a (ASTM 2006). by UP, MUF and PVA. The authors explained these results A combination of three optimum parameters was selected by the molecular reaction between the isocyanate groups in for the manufacturing of the two types of specialty OSB the PUR adhesive and the moisture in the wood. Blanchet panels (aspen/birch and ponderosa pine) as determined by CW08) compared four other cold-set adhesives: polyvinyl Barbuta et al. (2010): 6.5% phenol-fOIroaldehyde resin con­ acetate (PVA) (type I), epoxy, polyurethane hot melt, and tent, steep density profileand a percent weight-base between emulsion polymer isocyanate (EPI). Except for epoxy, all of the layers of 0.45/0.1010.45. � Springer Eur. J. Wood Prod. (2012) 70:37--43 39 Surfacelayer mended for the installation of EWE The edges of the Adhesive 610 mm x 1220 mm (2' x 4') assemblies were sealed with a bead of silicone in order to limit edge effects. In order Composite substrate to determine the MC of the surface layer and the substrate, 3 supplementary EWF strips for each type of substrate were prepared by sealing the edges and backs of the strips with aluminum foil to reproduce non-homogeneous water vapour transfer. The flooring strips were subjected to a three-week cycle of alternating dry (20°C and 20% RH) and wet con­ Fig. 1 Cross-section diagram of an engineered wood flooring strip ditions (20°C and 80% RH).