Wood strength

Entry Fortifier Percentage Fortifier On Resin Adhesive Strength (% Wood Failure) ... 

Full strength wood alcohol for the lamp can be bought at the drug store. Rubbing alcohol, although 30% water will bum in the lamp but not so well. You can distill the pure alcohol off the water from nibbing alcohol. 

Adhesive properties are listed in Table IX. Shear strength, wood failure, and swelling data for two wood species, southern pine and hard maple, illustrate excellent performance properties of lignin-based urethane products. 

Comparison of Adhesive Properties--Strength, Wood Failure, Swelling of Several Types of Adhesives1... 

Shear strength Wood failure Shear strength Wood failure... 

Testing is performed at a rate of 600 to lOOOlb/min until failure. Strengths are recorded as pounds per square inch of shear area. At least thirty representative samples should be tested to obtain an average strength. Wood failures should also be recorded as well as sample preparation and conditioning. 

The controller has to operate within specific constraints, which include limits on available steam and continuously varying heat transfer area in addition to unmeasured disturbances associated with liquor strength, wood chip composition, moisture content etc. 

Fig. 35 Relationship between bending strength, wood powder content and LSD/MLS content of PU composites...

Plywood has essentiahy equal stability in both panel directions and is almost as stable as the parent wood in the direction of the wood grain. Strength properties in bending are roughly proportional in each panel direction to the amount of wood in those layers closest to the surface which are parahel to the wood grain direction. Thus as the number of phes increases, these bending properties become more equalized in both panel directions. 

Nonwood fibers are used in relatively small volumes. Examples of nonwood pulps and products include cotton Enters for writing paper and filters, bagasse for cormgated media, esparto for filter paper, or Manila hemp for tea bags. Synthetic pulps which are based on such materials as glass (qv) and polyolefins also are used (see Olefin polymers). These pulps are relatively expensive and usually are used in blends with wood pulps where they contribute a property such as tear resistance, stiffness, or wet strength which is needed to meet a specific product requirement. 

Aqueous dispersions are used in fiber bonding, paper coating, friction and abrasive appHcations, and laminates and wood bonding. PhenoHc dispersions improve the strength of latex-contact adhesive appHcations. Epoxy-modified phenoHc dispersions are prepared by dispersion of the phenoHc epoxy resin. The systems are used for baked primer appHcations and bonding requirements. Minimum baking conditions are 20 min at 150°C (25). 

Different phenoHc resins are used for different types of wood for example, plywood adhesives contain alkaline-catalyzed Hquid resole resins. Extension with a filler reduces cost, minimizes absorption, and increases bond strength. These resins have an alkaline content of 5—7% and are low in free phenol and formaldehyde. Because many resins have a high water content and limited storage stabiHty, they are frequently made at or near the mill producing the plywood product. The plywood veneers are dried, coated with resin, stacked for pressing, and cured at 140—150°C. 

Waferboard, a more recent wood constmction product, competes more with plywood than particle board. Waferboard and strand board are bonded with soHd, rather than Hquid, phenoHc resins. Both pulverized and spray-dried, rapid-curing resins have been successfully appHed. Wafers are dried, dusted with powdered resin and wax, and formed on a caul plate. A top caul plate is added and the wafers are bonded in a press at ca 180°C for 5—10 min. Physical properties such as flexural strength, modulus, and internal bond are similar to those of a plywood of equivalent thickness. 

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