oriented strand board

Image:LSFosb05.jpg house construction.]]

OSB's mechanical properties make it suitable for load-bearing applications in construction.{{cite web |url=http://www.osb-info.org/technical.html |title=Technical Information |publisher=Osb-info.org |access-date=2016-05-02 |archive-date=2016-05-09 |archive-url=https://web.archive.org/web/20160509234841/http://www.osb-info.org/technical.html |url-status=dead }} In North America, it is more popular than plywood, commanding 66% of the structural panel market in 2016.{{cite news|last1=Marotte|first1=Bertrand|title=Toronto's Norbord riding the rising wave of OSB sales|url=https://beta.theglobeandmail.com/report-on-business/forest-products-firm-norbord-riding-the-rising-wave-of-osb-sales/article30985989/|access-date=20 September 2017|work=The Globe and Mail|date=19 July 2016}} The most common uses are as sheathing in walls, flooring, and roof decking. For exterior walls, panels are available with a radiant-barrier layer laminated to one side; this eases installation and increases energy performance of the building envelope. OSB is also used in furniture production.

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Oriented strand board is manufactured in wide mats from cross-oriented layers of thin, rectangular wooden strips compressed and bonded together with wax and synthetic resin adhesives.

The adhesive resins types used include: urea-formaldehyde (OSB type 1, nonstructural, nonwaterproof); isocyanate-based glue (or PMDI poly-methylene diphenyl diisocyanate based) in inner regions with melamine-urea-formaldehyde or phenol formaldehyde resin glues at surface (OSB type 2, structural, water resistant on face); phenol formaldehyde resin throughout (OSB types 3 and 4, structural, for use in damp and outside environments).{{citation| url = https://sciencing.com/types-glue-used-osb-8615640.html |first = Tony| last = Oldhand | title = Types of Glue Used in OSB| date = 25 Apr 2017 | work = sciencing.com }}

The layers are created by shredding the wood into strips, which are sifted and then oriented on a belt or wire-mesh caul (a heated, ventilated support) and coated with the resin.{{cite book |last1=Koch |first1=Peter |title=Utilization of hardwoods growing on southern pine sites |date=1985 |publisher=U.S. Dept. of Agriculture, Forest Service |location=Washington, DC |oclc=13459178 |page=2423}} The layers thus built up are transferred to a forming line and cross-oriented so that strips on the external layers are aligned to the panel's strength axis, while the internal layers are perpendicular.{{cite book |last1=Hedges |first1=Keith E. |title=Architectural Graphic Standards |date=2017 |publisher=Wiley |location=Hoboken, NJ |isbn= 9781119312512 |chapter=Oriented Strand Board|edition=12}} The number of layers placed is determined partly by the thickness of the panel, but is limited by the equipment installed at the manufacturing site. Individual layers can also vary in thickness to give different finished panel thicknesses; typically, a {{convert|15|cm|1|abbr=on|adj=on}} layer will produce a {{convert|15|mm|2|abbr=on|adj=on}} panel thickness{{cn|date=April 2016}}. The mat is placed in a thermal press to compress the flakes and bond them by heat activation and curing of the resin that has been coated on the flakes. Individual panels are then cut from the mats into finished sizes. Most of the world's OSB is made in the United States and Canada in large production facilities.

Materials other than wood have been used to produce products similar to OSB. Oriented structural straw board is an engineered board made by splitting straw and formed by adding P-MDI adhesives and then hot compressing layers of straw in specific orientations.{{cite journal |url=http://www.ncsu.edu/bioresources/BioRes_07/BioRes_07_3_2986_Han_CME_Zn_Borate_OS_Straw_Bd_Termite_Trial_2741.pdf |journal=BioResources |title=Performance of zinc Borate Treated Oriented Structural Straw Board against Mold Fungi, Decay Fungi, and Termites - A preliminary trial |author=Han, Guangping, Cheng, Wanli, Manning, Mark, and Eloy, Pierre |date=2012 |volume=7 |number=3 |pages=2986–2995 |doi=10.15376/biores.7.3.2986-2995 }} Strand board can also be made from bagasse.

In 2005, Canadian production was {{convert|10500000|m2|sqft|abbr=on}} ({{convert|3/8|in|mm|2|abbr=on|disp=or}} basis) of which {{convert|8780000|m2|sqft|abbr=on}} ({{frac|3|8}} inch) were exported, almost entirely to the United States.{{cite web|url=http://www.fordaq.com/fordaq/news/Canadian_structural_panel_market_13586.html |title=Review of the Canadian structural panel market |date=24 August 2006 |publisher=Fordaq.com |access-date=2016-05-02}} In 2014, Romania became the largest OSB-exporting country in Europe, with 28% of the exports going to Russia and 16% to Ukraine.{{Cite news |work = Fordaq |publisher = Fordaq S.A. |title = Romania has become the largest OSB exporting country in the EU |url = http://www.fordaq.com/fordaq/news/Romania_OSB_exports_EGGER_Kronospan_36635.html |date = 7 April 2014}}

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Adjustments to the manufacturing process can affect thickness, panel size, strength, and rigidity. OSB panels have no internal gaps or voids, and can be water-resistant, although they do require additional membranes to achieve impermeability to water and are not recommended for exterior use. The finished product has properties similar to plywood, but is uniform and cheaper.{{cite web|url=http://www.umass.edu/bmatwt/publications/articles/osb_vs_plywood.html |title=UMass Amherst: Building and Construction Technology » Choosing Between Oriented Strandboard and Plywood |publisher=Umass.edu |date=2015-09-04 |access-date=2016-05-02}} When tested to failure, OSB has a greater load-bearing capacity than milled wood panels.{{cite web|author=Chaya Kurtz |url=http://www.networx.com/article/experts-talk-about-engineered-wood |title=Experts Talk About Engineered Wood - Articles |publisher=Networx.com |date=2010-05-12 |access-date=2016-05-02}} It has replaced plywood in many environments, especially the North American structural panel market.

While OSB does not have a continuous grain like a natural wood, it does have greater strength on its long axis because more of the component grains are oriented in this direction. This can be seen by observing the alignment of the surface wood chips.

All wood-based structural use panels can be cut and installed with the same types of equipment as for solid wood.

The resins used to create OSB have raised questions about their emission of volatile organic compounds such as formaldehyde,{{cite journal |last1=Mantanis |first1=George I. |last2=Athanassiadou |first2=Eleftheria Th. |last3=Barbu |first3=Marius C. |last4=Wijnendaele |first4=Kris |date=2018-03-15 |title=Adhesive systems used in the European particleboard, MDF and OSB industries |journal=Wood Material Science & Engineering |volume=13 |issue=2 |pages=104–116 |doi=10.1080/17480272.2017.1396622 |issn=1748-0272}} although industry trade groups assert that formaldehyde emissions from North American OSB are "negligible or nonexistent".{{cite web |title=Oriented Strand Board Educational Bulletin, Frequently Asked Questions |url=http://osbguide.tecotested.com/pdfs/en/el814.pdf |url-status=dead |archive-url=https://web.archive.org/web/20160304041656/http://osbguide.tecotested.com/pdfs/en/el814.pdf |archive-date=4 March 2016 |access-date=2 May 2016 |website=OSBGuide |publisher=TECOTested.com}} Urea-formaldehyde is more toxic and should be avoided in home use. Phenol-formaldehyde products are considered to be relatively hazard free. Some newer types of OSB, so-called "new-generation" panels, use isocyanate resins that contain no formaldehyde and are considered nonvolatile when cured.{{cite web|last1=MacLeod|first1=Ian|title=I'm concerned about toxic offgassing from OSB subflooring and roofing|url=http://www.greenhomeguide.com/askapro/question/i-m-concerned-about-toxic-offgassing-from-osb-subflooring-and-roofing-are-safer-products-available|website=Green home guide|access-date=2015-11-14|archive-date=2016-06-05|archive-url=https://web.archive.org/web/20160605121604/http://www.greenhomeguide.com/askapro/question/i-m-concerned-about-toxic-offgassing-from-osb-subflooring-and-roofing-are-safer-products-available|url-status=dead}}

Some manufacturers treat the wood chips with various borate compounds that are toxic to termites, wood-boring beetles, molds, and fungi, but not mammals in applied doses.

Five grades of OSB are defined in EN 300 in terms of their mechanical performance and relative resistance to moisture:

• OSB/0 – No added formaldehyde
• OSB/1 – General-purpose boards and boards for interior fitments (including furniture) for use in dry conditions
• OSB/2 – Load-bearing boards for use in dry conditions
• OSB/3 – Load-bearing boards for use in humid conditions
• OSB/4 – Heavy-duty load-bearing boards for use in humid conditions

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Category:Composite materials

Category:Engineered wood