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Exterior Structural Grade Flakeboards from Southern Woods

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Exterior Structural Grade Flakeboards from Southern Woods dJrl qGi'7 I= EXTERIOR STRU- GWFw<EBDAIIDS FROM SOCTTHERN WIX - 32236 pop A TECHNICAL AND ECONOMIC ASSESSMENT Peter Vajda, President Colmhia Engineering International Ltd. Vancower , Canada Abstract "strands" are flakes hose length is at least 3 to 4 tines greater than their %is paper sumMlrizes the history and tech- width (the slenderness ratio is essen- nology of structural flakeboard IMnufacture and tial for orientation) the currently ongoing research work aimed at bpmving and/or reducing the axt of the pre- Saw sources refer to structural particle- sently marketed products. !Ihe basic mqara boards as stnlctural flakeboards mainly tive emnanics of the product, or its ampti- because the use of flake-type particles is tive position against softwood plywocd are dis- thought to be essential for the manufacture of used and evaluated. It is concluded that an exterior structural grade product. The structural flakebards present a good opportu- term structural particleboard is used by those nity to supplement the diminishing softwood who do not wish to pre-judge the ned for a plywood supply in the housing construction and specific kind of particle in order to acfiieve saw industrial markets. structural properties. First, let m make an attempt to clear up As the term "particleboard" is closely SOE uncertainties as to the terminology of associated with the industrial gra& and "structural grade particleboards" or "flake underlayrnent grade particleboards manufactured boards". at present by the industry wit!! uF resins, for interior applications, for the purposes of Structural grade particleboards are called differentiation 1 will use in this paper the by saw sources "particleboards" by others term structural flakeboards as designating a "flakeboards" and still by sm others as product which is made with exterior grade "waferbard" or "stranM". All these terms resins (PF or other) and having properties refer mainly to the types or kinds of particles suitable for structural and exterior applica- which are being used in the manufacture of an ticms. This terminology is not intended to exterior grade reoonstituted wood panel product. exclude the possibility that structural pro- We will therefore have to agree on terminology perties may be achieved by using either "semi- before atknpk-ing to analyze the technology and flakes" or even "randm particles" in say the emanics of manufacturing these products. axe of a structural grade panel. In the follming paper, I propose to use History the follming terns: Structural grade flakeboard or the idea of particles are used as a generic term for structural grade flakeboard has been mund any kind of wccd particles be they randan for a long time. or of specific length, width, thickness parallel to the grain or at right angles Almost all the original particleboards in to the grain Europ in the late Forties and early Fifties were made with flakes and were aired at flakes are particles which are cut para- optimizing bending strength and stiffness. llel to the grain (that is, tk cutting They were hawever manufactured with urea knife is parallel to the grain) resins and were therefore interior rather than exterior grade products. The use of smller "semi-flakes" or "chip flakes" are flakes flakes or randan particles or semi-flakes and cut fran pulp chips by a ring type flakec the enphasis on surface cfiaracteristics and sine the pulp &ips are essentially cut 3ntemal bond properties cam at a later date, across the grain, the resulting flakes probably after 1960. will also have a cross-grain feature In North America, one of the first par- randcm particles are particles cut fran ticleboards introduced was "Novoply" which shavings, sawdust and other mill residue, used flakes in the surface layers of the or even chips, by a hamwrmill or hog board and had potentially structural proper- type macfiine ties with the exception that it was again made with urea resins. "wafers'' are large, square flakes as used in "waferboard" 427 In the early Fifties, Dale Turner working approval in the construction of haws and 2 ' at the Forest Products Laboratory in Madison, Story apartment buildings. Wisconsin, explored the effect of flake am- figuration cm board properties and shaed that In 1969, MaMillan Bloedel doubled its structural or plymod-like properties are capacity at Hudson Bay, Saskatchewan. In the adievable with suitable flake canfiguraticm. 1971 to 1974 period, four mre waferbard His paper published in 1954 is probably one of plants =re built in Canada - three in the classics in North Amrican particleboard Bay, Ontario and one at Ti.", Ont. literature. At the present, waferboard in Canada is In 1954, Jim d'Arcy Clarke presented a produced at a rate of about 500 to 550 PMsf paper to an mseting in Seattle introducing 3/8" per annun rate. About half this pro- the concept of a "waferboard" product and a duction is sold in Canada while half is waferboard plant. The research and pilot plant exported to the northeastern and northcentral mrk on this project was carried out at United States. The Canadian mnsmption of Washin- State University Wood Products waferboard is about 12%to 13%of Canadian Laboratory at Pull.", Washingbn and, by 1958, softwood plywood consmption. a waferbard plant was in operation at Sand- point, Idaho. The developent of a structural flake- board, or a substitute for plywoodr proceeded The introduction of a waferboard or struc- in the united States at a much slaver pace tural flake!xard product in 1958, haever, was than in Canada, in spite of the fact that the not timly. North An-erica had an abundant expansion potential of the U.S. plyklwa supply of law cost peeler logs and sheathing industry in tenus of available sof-twood peeler grade plywd. ?he cost advantage of wafer- log supply in the U.S. is mu& mre limited board against sheathing grade plywood was and is probably approaching its ultimate level. marginal, especially sine the Sandpoint plant was located in the northwest region along with In the early Seventies, Potlatch Forests all the plymod plants. As a result, the Inc. built a pilot plant to prove the techni- Sandpint plant did not succeed in petrating cal and marketing feasibility of Oriented the structural sheathing grade plywlooa market Strandwad based on the Elmendorf process. and the pmduct was sold mainly for deaxative Using this technology, Potlatch opted for the end uses. manufacture of a cross-oriented core board for use in the "facture of a ccmposite The late Fifties and early Sixties also saw flakeboard/plywcod product nmd Plystran. the experinentation and pilot plant work Also in the early Seventies, Blandin Paper at carried out by Armin Elmendorf, attapting to Grand Rapids, Minnesota built a waferboard work out a process for the manufacture of plant based on the Clarke process. This plant oriented flakeboard or, as it is nw called had considerable start-up difficulties but is "Oriented StranM". John Talbot at now reported to be in full production and is Washington State University also carried out marketing the product successfully. sminvestigations on flake orientation and the properties of such an oriented flakeboard Time and spa= do not permit the enwr- product. ation here of all the research and pilot plant work that has been carried out in relation to In 1963, another waferboard plant was built structural board during the past 10 years by in Hudson Bay, Saskatchewan, based on Jim various institutions in North Amrica. All Clarke's process and concept. This venture of these mncepts hmever would require con- also failed under its initial mership and siderable additional work in order to be management. It was first taken over by the jumed as fully practical and qel-ational. In Govenwnt of Saskatchewan and eventually sold view of the expected increase in North Ameri- to Madillan Blcedel Ltd. of Vanmver, B.C. can dernand for structural grade wood p-1 Under MacMillan Bloedel's magmnt and sales prcducts coupled with the impending shortage efforts, the wafertx>ardprcduct found its way of softwood peeler log supplied in the U.S. r into the structural sheathing grade markets in the demnd for structural flakebard products ccanpetition with plywood, mainly based on its in the U.S. should accelerate in the next 5 freight advantage against West Coast plywoOa years resulting in increased plant con~tru* in Canada' s mi&estern Prairie markets. tion and the introdudion of ww structrual products and prcduct variations into the U.S. The first applications penetrated by markets. waferkmard in the Prairies were in the con- struction and rermdelling of farm buildings, The Properties and Technology of C-cially fences and other general utility applications. Produced Structural Flakeboards In these applications, the pmduct proved itself to be satisfactory as an exterior Just what dc we mean by structural flake- grade parel. As a result, it received Cock board? In sinple terms, vie are aiming at a 428 prdducrt which auld replace exterior sheathing It should be mted here that waferboard as grade (mnstruction grade) plywoOa or the stan- it is produced at the present has a powdered dard CDX grade plywWa marketed in the U.S. phenolic resin content of about 2.5% to 3.0%. Other applications and end uses are possible, A sliFpltly higher resin mtent (3.5%) pawder- even probable, but in all Likelihood the ed resin or 6% resin solids in liquid form initial market penetration will have to be made wuld improve all strength properties by at sinply as plywood replamt. least 20%. The product hmever has performxl and sold well in its present fop and the It is of interest therefore to s"rize mufacturers did not see any need to umrade here the significant praperties of "CDX" or improve.
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