kayu komposit\

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ORIENTED STRANDBOARD ORIENTED STRANDBOARD (OSB) (OSB) Introduction Introduction Uses and Feature Uses and Feature Composition of OSB Composition of OSB Manufacture Manufacture Sizes Sizes Quality Control Quality Control Storage and Storage and Handling Handling Strength Strength Properties Properties

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Page 1: KAYU KOMPOSIT\

ORIENTED ORIENTED STRANDBOARD (OSB)STRANDBOARD (OSB)

•Introduction Introduction •Uses and FeatureUses and Feature•Composition of OSBComposition of OSB•Manufacture Manufacture •Sizes Sizes •Quality Control Quality Control •Storage and HandlingStorage and Handling•Strength PropertiesStrength Properties

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Armin Elmendorf was the inventor of OSB, Armin Elmendorf was the inventor of OSB, which he first described in 1949 (Elmendorf which he first described in 1949 (Elmendorf 1949). He later patent his invention in 1965 1949). He later patent his invention in 1965 (Elmendorf 1965). A product called (Elmendorf 1965). A product called waferboard appeared on the market in the appeared on the market in the 1970's. It consisted of a random array of 1970's. It consisted of a random array of thin flakes about 50 mm both in length and thin flakes about 50 mm both in length and width (Maloney 1977).width (Maloney 1977).

INTRODUCTIONINTRODUCTION

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The OSB industry evolved from the waferboard The OSB industry evolved from the waferboard industry in the late 1970's as technology and industry in the late 1970's as technology and investors caught up with the concept of it. From investors caught up with the concept of it. From the time of its invention, research has been the time of its invention, research has been conducted into the effect of chip size, the raw conducted into the effect of chip size, the raw material used, the three layer structure, the material used, the three layer structure, the different methods of strand alignment and the different methods of strand alignment and the effects of the alignment itself on the strength of effects of the alignment itself on the strength of OSB (Avramidis 1989).The result has been the OSB (Avramidis 1989).The result has been the development of the commercial OSB produced by development of the commercial OSB produced by industry today. today.

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OSB or waferboard are efficient additions to the family of OSB or waferboard are efficient additions to the family of wood wood

building materials because: building materials because:

• They are made from abundant, fast growing, small diameter They are made from abundant, fast growing, small diameter aspen poplar or pine to produce an economical structural aspen poplar or pine to produce an economical structural panel. panel.

• The manufacturing process can make use of crooked, The manufacturing process can make use of crooked, deformed, small diameter trees which would otherwise have deformed, small diameter trees which would otherwise have little commercial value, thereby maximizing forest little commercial value, thereby maximizing forest utilizationutilization. .

• Many strength-reducing defects are removed during Many strength-reducing defects are removed during manufacturing, and any remaining defects are evenly manufacturing, and any remaining defects are evenly dispersed throughout the panel, resulting in consistent dispersed throughout the panel, resulting in consistent strength properties. strength properties.

• The orientation of strands gives increased strength The orientation of strands gives increased strength properties along the long panel dimension (strength axis) of properties along the long panel dimension (strength axis) of OSB. For waferboard, random alignment of the wafers gives OSB. For waferboard, random alignment of the wafers gives more consistent strength properties throughout the panelmore consistent strength properties throughout the panel

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Why is OSB so special?Why is OSB so special?

OSB is three times as strong as particle boards of the same density and resin content. Its three ply form has been described as comparable with Douglas fir plywood (Elmendorf 1949).

It is an improvement on wafer board as it has its flakes, or strands, aligned. This alignment can take place because the strands are not dimensionally uniform (Maloney 1977), being only a third to a half of the width of those of waferboard though approximately the same length.

The core flakes are aligned at right angles to surface layers. This is intended to mimic the structure, and consequently the strength properties, of plywood. In other words OSB was introduced as an attempt to compete with plywood as a structural material while using a low quality resource (Illston 1994).

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Oriented Strand Board Oriented Strand Board (OSB)(OSB)

•A multi-layered board A multi-layered board made from strands of made from strands of wood bonded with a wood bonded with a binderbinder

•Strands in outer layers Strands in outer layers are aligned and parallel are aligned and parallel to length or width; core to length or width; core random or oriented random or oriented perpendicularly to the perpendicularly to the facesfaces

•Substitute to plywoodSubstitute to plywood

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OSB or waferboard are used in OSB or waferboard are used in construction as roof construction as roof sheathing, wall sheathing, sheathing, wall sheathing, siding, soffits, floor siding, soffits, floor underlayment, subfloors and underlayment, subfloors and combination subfloor-combination subfloor-underlayment. They are also underlayment. They are also suitable for shearwall and suitable for shearwall and diaphragm applications. diaphragm applications.

Uses and FeatureUses and Feature

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Composition of OSBComposition of OSB

Wood:Wood:• One advantage of OSB is that panels constructed from One advantage of OSB is that panels constructed from

relatively weak tree species such as relatively weak tree species such as aspen (once regarded a (once regarded a weed species) and western red cedar have almost the same weed species) and western red cedar have almost the same strength characteristics as those produced from normally strength characteristics as those produced from normally stronger species such as Douglas fir (Maloney 1977).stronger species such as Douglas fir (Maloney 1977).

• As a result industry is able to utilise an almost untapped As a result industry is able to utilise an almost untapped timber resource to produce a high strength, high value timber resource to produce a high strength, high value product. product.

• Another similar advantage is that the size of the round wood Another similar advantage is that the size of the round wood raw wood used is irrelevant in regards to the final size of the raw wood used is irrelevant in regards to the final size of the panel produced. panel produced.

• However, a minimum diameter usually still applies due to the However, a minimum diameter usually still applies due to the mechanical workings of the mechanical workings of the production process. This means . This means that OSB panels can be made from such attractive resources that OSB panels can be made from such attractive resources as bamboo (Yin 1987).as bamboo (Yin 1987).

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Particle size and shapeParticle size and shape

• 0.5 to 0.7 mm thick and 19 to 38 mm wide and 0.5 to 0.7 mm thick and 19 to 38 mm wide and 76mm long(Haupe 1994) There are distinct 76mm long(Haupe 1994) There are distinct increases in strength related to increasing chip increases in strength related to increasing chip size (Illston 1994). size (Illston 1994).

• The particle dimensions are designed to The particle dimensions are designed to optimise efficient resin use (by spot bonding optimise efficient resin use (by spot bonding and lowering of the flakes specific surface area and lowering of the flakes specific surface area (Maloney 1977)) as well as maximising the (Maloney 1977)) as well as maximising the amount of mechanical bonding occurring amount of mechanical bonding occurring between particlesbetween particles.

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Particle alignmentParticle alignment

•OSB consists of long wafers that have been OSB consists of long wafers that have been oriented either by an electrical field or, more either by an electrical field or, more commonly, are mechanically aligned by vibrating commonly, are mechanically aligned by vibrating the particles through fins. the particles through fins.

•There are two main forms of OSB: One form of OSB There are two main forms of OSB: One form of OSB have all the particles aligned in the one direction, have all the particles aligned in the one direction, providing many of the strength properties found in providing many of the strength properties found in solid timber such as high lengthwise strength. solid timber such as high lengthwise strength. However, its widthwise strength is low. In However, its widthwise strength is low. In construction applications it is best used as a load construction applications it is best used as a load bearing member (Maloney 1977). bearing member (Maloney 1977).

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The other form of has two surface layers where the wafers have The other form of has two surface layers where the wafers have a lengthwise orientation and a core of wafers with a widthwise a lengthwise orientation and a core of wafers with a widthwise orientation. orientation.

This type of core orientation is called crossbanding and, as with This type of core orientation is called crossbanding and, as with plywood, gives the board a high lengthwise bending strength. plywood, gives the board a high lengthwise bending strength. Crossbanding also provides the board with a high resistance Crossbanding also provides the board with a high resistance toward 'racking'. This is the tendency for the board to distort toward 'racking'. This is the tendency for the board to distort from a rectangle into a parallelogram. This, combined with high from a rectangle into a parallelogram. This, combined with high overall dimensional stability (including reactions to changes in overall dimensional stability (including reactions to changes in moisture content), makes an important element in providing ), makes an important element in providing support in structural applications. (Kubler 1980). support in structural applications. (Kubler 1980).

Three layers OSB, the top and bottom layers have their strands Three layers OSB, the top and bottom layers have their strands oriented toward the length of the panel to optimise strength, oriented toward the length of the panel to optimise strength, stiffness and spanning ability. The middle layer has its strands stiffness and spanning ability. The middle layer has its strands aligned across the board. aligned across the board.

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Structure of OSB:Structure of OSB:

OSB has its flakes OSB has its flakes aligned, and they are only half this width though , and they are only half this width though their length is the same. Core flakes at right angles to surface layers. their length is the same. Core flakes at right angles to surface layers. This is intended to mimic the structure and of plywood (Illston 1994) This is intended to mimic the structure and of plywood (Illston 1994)

Adhesive:Adhesive:

OSB is generally held together by a phenol formaldehyde resin OSB is generally held together by a phenol formaldehyde resin (Avramidis 1989). (Avramidis 1989).

Trials on the addition of lignin to the adhesive have been undertaken Trials on the addition of lignin to the adhesive have been undertaken to access whether it would make a suitable substitute. The lignin is to access whether it would make a suitable substitute. The lignin is extracted from hardwood wood chips through acid hydrolysis. extracted from hardwood wood chips through acid hydrolysis.

The importance of replacing oil based The importance of replacing oil based resins with substances such as with substances such as lignin is that lignin comes from a renewable resource and also may lignin is that lignin comes from a renewable resource and also may eventually be produced more cheaply (Haupe 1994). eventually be produced more cheaply (Haupe 1994).

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The process described here is The process described here is general and may vary in detail general and may vary in detail from one manufacturer to from one manufacturer to another but it is always another but it is always comprised of log conditioning, comprised of log conditioning, stranding or waferizing, stranding or waferizing, drying, blending, forming, drying, blending, forming, pressing, and final processing. pressing, and final processing. A schematic representation of A schematic representation of a typical manufacturing a typical manufacturing process is shown in the process is shown in the following figure. following figure.

ManufactureManufacture

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Log Sorting Jackladder Debarking

StrandingWet BinsDrying

Blending

Forming Line Pressing Finishing Line Shipping

OSB Manufacturing OSB Manufacturing ProcessProcess

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• Log Sorting: Log Sorting: After harvest, whole logs are hauled to the mill's wood yard, then After harvest, whole logs are hauled to the mill's wood yard, then

sorted. sorted.

• Jackladder: Jackladder: Logs are soaked, to remove ice and prepare wood for stranding, then Logs are soaked, to remove ice and prepare wood for stranding, then

sent up the jackladder. sent up the jackladder.

• Debarking:Debarking: Logs are run through the debarker to remove bark. Bark is later used Logs are run through the debarker to remove bark. Bark is later used

as fuel in the mill's energy supply.as fuel in the mill's energy supply.

• Stranding:Stranding: The strands are cut from whole logs into precise dimensions of up to The strands are cut from whole logs into precise dimensions of up to

six inches long.six inches long.

• Wet Bins:Wet Bins: Strands are deposited into wet bins.Strands are deposited into wet bins.

• Drying:Drying: Strands are then dried until the appropriate moisture content is Strands are then dried until the appropriate moisture content is

reached.reached.

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• Blending:Blending: Strands are blended with resin binders and a small amount of Strands are blended with resin binders and a small amount of wax, which improves the efficiency of the resin binder and wax, which improves the efficiency of the resin binder and enhances the panel's resistance to moisture and water enhances the panel's resistance to moisture and water absorption.absorption.

• Forming Line:Forming Line: Strands go through the forming line where cross-directional Strands go through the forming line where cross-directional layers are formed.layers are formed.

• Pressing:Pressing: Layers of cross-directional strands are pressed under intense Layers of cross-directional strands are pressed under intense heat and pressure to form a rigid, dense structural panel of heat and pressure to form a rigid, dense structural panel of oriented strand board (OSB). Presses are primarily multiple oriented strand board (OSB). Presses are primarily multiple opening allowing 8 to 16 master panels to be pressed in one opening allowing 8 to 16 master panels to be pressed in one operation for increased efficiency. Since 1997, continuous operation for increased efficiency. Since 1997, continuous presses producing a ribbon of OSB commenced operation on presses producing a ribbon of OSB commenced operation on certain sites.certain sites.

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• Finishing Line:Finishing Line:

Panels are cooled, cut to size, grade stamped, stacked in Panels are cooled, cut to size, grade stamped, stacked in bundles and edge coated. All graded panels bear a bundles and edge coated. All graded panels bear a mandatory certification agency stamp, plus the SBA logo if mandatory certification agency stamp, plus the SBA logo if applicable.applicable.

• Shipping:Shipping: Finally, the panels are ready to be loaded and shipped to Finally, the panels are ready to be loaded and shipped to destinations around the world. Panels can be ordered destinations around the world. Panels can be ordered smooth sanded for special uses or with tongue and groove smooth sanded for special uses or with tongue and groove edges.edges.

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•Freshly cut logs are taken from the log storage yard and Freshly cut logs are taken from the log storage yard and

placed in hot water ponds. The soaking softens the wood to placed in hot water ponds. The soaking softens the wood to facilitate debarking and making of strands or wafers, facilitate debarking and making of strands or wafers, thereby reducing the amount of fines and slivers thereby reducing the amount of fines and slivers generated. To maintain effectiveness, hot pond generated. To maintain effectiveness, hot pond temperatures are increased in cold weather conditions. temperatures are increased in cold weather conditions.

•After conditioning, the logs are debarked and fed into a After conditioning, the logs are debarked and fed into a machine with sharp knives. This strander or waferizer cuts machine with sharp knives. This strander or waferizer cuts the log pieces into strands or wafers along the grain. The the log pieces into strands or wafers along the grain. The strands or wafers are conveyed to wet storage bins and are strands or wafers are conveyed to wet storage bins and are screened after drying to remove fine particles. Most mills screened after drying to remove fine particles. Most mills process core and surface strands and wafers separately process core and surface strands and wafers separately and then deposit them together in layers to form the mat. and then deposit them together in layers to form the mat.

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•The strands or wafers are placed in large cylindrical dryers The strands or wafers are placed in large cylindrical dryers where they are dried to a moisture content of three to seven where they are dried to a moisture content of three to seven percent. While in the dryer, the strands or wafers rotate percent. While in the dryer, the strands or wafers rotate slowly minimizing breakage of the strands while ensuring slowly minimizing breakage of the strands while ensuring consistent moisture content. When dry, the strands or consistent moisture content. When dry, the strands or wafers proceed to the blender where they are mixed with wafers proceed to the blender where they are mixed with resin and wax. resin and wax.

•The small quantity of hot wax (about 1.0 to 1.5 percent of The small quantity of hot wax (about 1.0 to 1.5 percent of the weight of wafers) sprayed on the wafers helps to the weight of wafers) sprayed on the wafers helps to distribute evenly the powdered or liquid phenol-distribute evenly the powdered or liquid phenol-formaldehyde resin or polyurethane binder (2.0 percent to formaldehyde resin or polyurethane binder (2.0 percent to 3.5 percent by weight or more). Resins or binders are of the 3.5 percent by weight or more). Resins or binders are of the thermosetting type, which means they can't be softened by thermosetting type, which means they can't be softened by heat or moisture once fully cured. The strands or wafers are heat or moisture once fully cured. The strands or wafers are continuously weight metered to ensure the proper quantities continuously weight metered to ensure the proper quantities enter the blenders so that the correct resin coverage is enter the blenders so that the correct resin coverage is achieved. achieved.

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The forming machine arranges the strands or wafers in The forming machine arranges the strands or wafers in several layers to form a mat on stainless steel press several layers to form a mat on stainless steel press sheets or on a continuous belt. sheets or on a continuous belt.

For OSB, the strands for the faces are usually oriented For OSB, the strands for the faces are usually oriented parallel with the long direction of the panel (machine parallel with the long direction of the panel (machine direction) and the core layers are either cross-oriented direction) and the core layers are either cross-oriented or laid random.or laid random.

For waferboard, the wafers are randomly deposited. The For waferboard, the wafers are randomly deposited. The size of the mats varies with the press size, but generally, size of the mats varies with the press size, but generally, one mat will be large enough to produce several one mat will be large enough to produce several standard sized panels. standard sized panels.

In multi-opening presses, the mats are placed in the In multi-opening presses, the mats are placed in the press accommodating from 10 up to 24 sheets at a time. press accommodating from 10 up to 24 sheets at a time. Each mat sits between a pair of heated platens. Each mat sits between a pair of heated platens.

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When all the mats have been inserted, the press is closed When all the mats have been inserted, the press is closed under heavy pressure. The layup of the mat and the press under heavy pressure. The layup of the mat and the press operation are important in ensuring proper panel thickness. operation are important in ensuring proper panel thickness.

The duration of the press cycle varies from plant to plant The duration of the press cycle varies from plant to plant and with the desired thickness of the board. For example, a and with the desired thickness of the board. For example, a press cycle of 3-1/2 minutes might be required for 6.35mm press cycle of 3-1/2 minutes might be required for 6.35mm (1/4") thick panels, and eight minutes for 15.5mm (5/8") (1/4") thick panels, and eight minutes for 15.5mm (5/8") panels. The heat and pressure polymerize the resin or panels. The heat and pressure polymerize the resin or binder glueing the strands or wafers together strongly into binder glueing the strands or wafers together strongly into a rigid panel. a rigid panel.

In newer plants, some presses are long and continuous In newer plants, some presses are long and continuous rather than the more conventional stacked multi-opening rather than the more conventional stacked multi-opening presses. In those presses a continuous mat enters the front presses. In those presses a continuous mat enters the front end of the press. Finished board exits the rear end of the end of the press. Finished board exits the rear end of the press, which is then cut to the required size with flying press, which is then cut to the required size with flying cross-cut saws. cross-cut saws.

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2. 2. The logs length are loaded The logs length are loaded onto the production lineonto the production line

3. Logs being debarked by a3. Logs being debarked by a Cambio DebarkerCambio Debarker

4. Logs being sawn into billets4. Logs being sawn into billets

1.1. The Plantation Resource The Plantation Resource (Radiata Pine)(Radiata Pine)

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5. Logs being fed into a waferising machine5. Logs being fed into a waferising machine

6. Drum drier6. Drum drier 7. Strand alignment7. Strand alignment

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8. Mat formation8. Mat formation

9. Prepressing the mat9. Prepressing the mat

10. The final press10. The final press

11. Stacking for storage11. Stacking for storage

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OSB SizesOSB Sizes

•OSB and waferboard are available in a variety of thicknesses and OSB and waferboard are available in a variety of thicknesses and sizes as shown in the following table (for panels meeting CSA sizes as shown in the following table (for panels meeting CSA O437.0). O437.0).

•The most common panel size is 1220 x 2440mm (4' x 8'). Panels The most common panel size is 1220 x 2440mm (4' x 8'). Panels are sized for spacing (3 mm or 1/8" short). Panels may be specially are sized for spacing (3 mm or 1/8" short). Panels may be specially ordered up to 2440 x 7320mm (8' x 24'). For instance, ordered up to 2440 x 7320mm (8' x 24'). For instance, manufacturers of wood I-joists desire larger panel sizes because manufacturers of wood I-joists desire larger panel sizes because the long lengths reduce the need for web splicing. the long lengths reduce the need for web splicing.

•Sizes smaller than the standard size can also be specially ordered. Sizes smaller than the standard size can also be specially ordered.

•Thicknesses are available from 6mm (1/4") to 28.5mm (1-1/8"). For Thicknesses are available from 6mm (1/4") to 28.5mm (1-1/8"). For panels meeting CSA O325.0 or PS 2, the typical nominal sizes are 6 panels meeting CSA O325.0 or PS 2, the typical nominal sizes are 6 mm (1/4"), 9.5 mm (3/8"), 11 mm (7/16"), 12 mm (15/32"), 12.5 mm (1/4"), 9.5 mm (3/8"), 11 mm (7/16"), 12 mm (15/32"), 12.5 mm (1/2"), 15 mm (19/32"), 16 mm (5/8"), 18 mm (23/32"), and 19 mm (1/2"), 15 mm (19/32"), 16 mm (5/8"), 18 mm (23/32"), and 19 mm (3/4") mm (3/4")

•Panels may be sanded on one or both faces on special orderPanels may be sanded on one or both faces on special order. .

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80363/419

67305/815.9

53241/212.7

47217/1611.1

40183/89.5

33155/167.9

27121/46.35

lb.kgin.Mm

Panel Weight 

1220 x 2440mm (4' x 8')Thickness

OSB (O-1) and Waferboard (R-1)

Table 2: OSB and Waferboard - Thicknesses and Weights

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Notes:1.Panel weight calculated on the basis of 640 kg/m^3 (40 lbs/cu.ft.) density and nominal thickness. 2.Panels in thickness of 15.5, 15.9, 18.5 and 19mm (5/8" and 3/4") are available in either square-edged or tongue and groove on the long edges. 3.Other thicknesses are available on special order.

120541-1/828.5

78363/418.5

66305/815.5

52241/212.5

46217/1611

39183/89.5

32155/167.5

26121/46

lb.kgin.Mm

Panel Weight 

1220 x 2440mm (4' x 8')Thickness

OSB (O-2)

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Quality Quality ControlControl

• The quality of OSB and The quality of OSB and waferboard is the waferboard is the responsibility of the responsibility of the individual manufacturer. individual manufacturer.

• Each mill must establish its Each mill must establish its own program of in-plant own program of in-plant quality control to ensure the quality control to ensure the finished product meets or finished product meets or exceeds the requirements exceeds the requirements for the grade specified in the for the grade specified in the applicable standard. applicable standard.

• Panel quality is affected by Panel quality is affected by every process in the plant every process in the plant and by the quality and and by the quality and consistency of the raw consistency of the raw materials used to materials used to manufacture the panels.manufacture the panels.

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• Process control is uniquely designed for each Process control is uniquely designed for each mill and reflects the particular combination of mill and reflects the particular combination of machinery, control devices, materials and machinery, control devices, materials and product mix. Continuous monitoring of all product mix. Continuous monitoring of all process variables by the plant quality control process variables by the plant quality control staff maintains the product as required by the staff maintains the product as required by the applicable standards. applicable standards.

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• Among the factors most carefully monitored and Among the factors most carefully monitored and controlled are the sorting of logs by species, size, and controlled are the sorting of logs by species, size, and moisture content, strand or wafer size and thickness, moisture content, strand or wafer size and thickness, moisture content following drying, the consistent blending moisture content following drying, the consistent blending of strands or wafers, resin and wax, the uniformity of the of strands or wafers, resin and wax, the uniformity of the mat leaving the forming machine, the press temperature, mat leaving the forming machine, the press temperature, pressures, closing speed, thickness control and pressure pressures, closing speed, thickness control and pressure release control, quality of panel faces and edges, panel release control, quality of panel faces and edges, panel dimensions and the appearance of the finished panel. dimensions and the appearance of the finished panel.

• Physical testing of the panels according to standard test Physical testing of the panels according to standard test procedures is necessary to verify that production procedures is necessary to verify that production conforms to the applicable standard. In addition, mills conforms to the applicable standard. In addition, mills monitor panel quality on a continuing basis by carrying monitor panel quality on a continuing basis by carrying out such tests on hot panels right off the production line out such tests on hot panels right off the production line to ensure process control is maintained. These hot tests to ensure process control is maintained. These hot tests are correlated to the standard conformance testsare correlated to the standard conformance tests. .

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Storage and HandlingStorage and Handling

All wood products are hygroscopic in nature and All wood products are hygroscopic in nature and therefore gain and lose moisture in accordance with therefore gain and lose moisture in accordance with climatic conditions. OSB and waferboard change in climatic conditions. OSB and waferboard change in dimension, as do other wood products, as humidity dimension, as do other wood products, as humidity fluctuations change the moisture content. fluctuations change the moisture content.

Panels should be protected from excessive wetting Panels should be protected from excessive wetting during storage and construction. Manufacturers during storage and construction. Manufacturers protect the panel edges with a special coating, and protect the panel edges with a special coating, and recommend a 3 mm (1/8") gap be left between panels recommend a 3 mm (1/8") gap be left between panels during installation to accommodate linear expansion.during installation to accommodate linear expansion.

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Panel products are susceptible to corner and Panel products are susceptible to corner and edge damage from handling and must be edge damage from handling and must be handled carefully to avoid wastage. handled carefully to avoid wastage.

In summary, points to watch for when storing In summary, points to watch for when storing and handling OSB and waferboard are: and handling OSB and waferboard are:

Store bundles indoors or under cover with Store bundles indoors or under cover with enough support to keep panels flat and off the enough support to keep panels flat and off the ground.ground.

On the job site, schedule delivery as close as On the job site, schedule delivery as close as possible to time of use and close in the structure possible to time of use and close in the structure as quickly as practicalas quickly as practical. .

Protect panel edges and corners. This is Protect panel edges and corners. This is especially true for tongue and groove panelsespecially true for tongue and groove panels. .

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Structural Structural stabilitystability

Surface coating the Surface coating the compressive side of an compressive side of an panel significantly panel significantly reduces creep (Bach reduces creep (Bach 1993).1993).

Strength PropertiesStrength Properties

Moisture content of jointed materials is highly influential Moisture content of jointed materials is highly influential of total stiffness of OSB in sheathing applications. High of total stiffness of OSB in sheathing applications. High moisture content results in lower stiffness, and OSB moisture content results in lower stiffness, and OSB jointed to dried lumber up to 3 times as stiff as that jointed to dried lumber up to 3 times as stiff as that jointed to green lumber (Mohammad 1994). jointed to green lumber (Mohammad 1994).

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Bending strength and stiffnessBending strength and stiffness

The progression of wood composite materials to The progression of wood composite materials to structural applications required them to have structural applications required them to have mechanical properties that approach those of mechanical properties that approach those of wood. does this through flake alignment.(Shaler wood. does this through flake alignment.(Shaler 1991). The modulus of elasticity (MOE), Modulus of 1991). The modulus of elasticity (MOE), Modulus of rupture (MOR), internal bonding (IB) and tensile rupture (MOR), internal bonding (IB) and tensile strength (TS) of OSB improves as resin content strength (TS) of OSB improves as resin content increases from 4 to 6% (Avramidis 1989). increases from 4 to 6% (Avramidis 1989).

One of its limitations is its susceptibility to One of its limitations is its susceptibility to moisture as it is not durable in applications moisture as it is not durable in applications where it is subject to prolonged wetting (Illston where it is subject to prolonged wetting (Illston 1994).1994).

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The The spot resin bonds used in manufacture are, in used in manufacture are, in themselves, not strong. Consequently the boards are themselves, not strong. Consequently the boards are particularly weak in tension perpendicular to the flat particularly weak in tension perpendicular to the flat surface of the particles. However, the product is rarely surface of the particles. However, the product is rarely used in a way that would place this kind of stress on the used in a way that would place this kind of stress on the board. The compression of the mat to produce the board board. The compression of the mat to produce the board adds to its strength greatly by interlocking the fibres adds to its strength greatly by interlocking the fibres making up the particles (Kubler 1994). making up the particles (Kubler 1994).

However, the strength properties of (bending strength However, the strength properties of (bending strength and stiffness), while around greater than that of and stiffness), while around greater than that of waferboard, are still not as good as plywood.(Illston waferboard, are still not as good as plywood.(Illston 1994). Norbord Ltd has a MOR parallel to the panel length 1994). Norbord Ltd has a MOR parallel to the panel length of 34N/mmof 34N/mm22 and perpendicular to the panel length of and perpendicular to the panel length of 18n/mm2. It has a MOE parallel to the panel length of 18n/mm2. It has a MOE parallel to the panel length of 5000N/mm2 and perpendicular to the panel length of 5000N/mm2 and perpendicular to the panel length of 2000N/mm2000N/mm22. .

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PULMONARY EFFECTS OF SIMULTANEOUS EXPOSURES TO PULMONARY EFFECTS OF SIMULTANEOUS EXPOSURES TO MDI FORMALDEHYDE AND WOOD DUST ON WORKERS IN MDI FORMALDEHYDE AND WOOD DUST ON WORKERS IN AN ORIENTED STRAND BOARD PLANTAN ORIENTED STRAND BOARD PLANT

A study of respiratory effects associated with exposure to A study of respiratory effects associated with exposure to methylene-diisocyanate (MDI), phenol-formaldehyde, and methylene-diisocyanate (MDI), phenol-formaldehyde, and wood dust in an oriented strand board (OSB) factory was wood dust in an oriented strand board (OSB) factory was conducted. The cohort was comprised of 127 males, conducted. The cohort was comprised of 127 males, mean age 33.1 years, employed in an OSB factory. The mean age 33.1 years, employed in an OSB factory. The comparisons were 165 healthy male and female workers comparisons were 165 healthy male and female workers from the same geographic area. The prevalence of from the same geographic area. The prevalence of respiratory symptoms such as phlegm, dyspnea, respiratory symptoms such as phlegm, dyspnea, wheezing, wheezing with chest tightness, and chest wheezing, wheezing with chest tightness, and chest tightness was significantly higher in the OSB workers tightness was significantly higher in the OSB workers than in the comparisons.than in the comparisons.

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The OSB workers were significantly more likely to The OSB workers were significantly more likely to have a history of asthma than the comparisons. have a history of asthma than the comparisons. The prevalence of atopy, determined from the The prevalence of atopy, determined from the skin prick test responses, was similar in both skin prick test responses, was similar in both groups. The authors conclude that employment in groups. The authors conclude that employment in the OSB factory is associated with definite effects the OSB factory is associated with definite effects on respiratory health. The data emphasize the on respiratory health. The data emphasize the importance of MDI, and possibly formaldehyde importance of MDI, and possibly formaldehyde and wood dust, in producing airway dysfunction and wood dust, in producing airway dysfunction and symptoms in exposed workers in the wood and symptoms in exposed workers in the wood products industry. products industry.

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Thank You