Dimensional stability boards

Epoxies Powder, one and two-part liquids and paste Many types of resins available, providing wide spectrum of properties. Easy to compound. Low shrinkage and excellent dimensional stability. Good to excellent adhesion. May be cast or molded. Coatings, sealants, adhesives, solderless PC boards. 

In the production of wet process hardboards and serai-hardboards the press-dried boards are usually tempered or "cured" in hot air to increase their water resistance, dimensional stability, strenght and stiffness. A curing for 5 hours or more in hot air of 165°C is common. Higher curing temperatures reduce the period needed for each batch and thus increase the capacity of the heat treatment chamber, but they increase the auto-ignition risks. 

PEN is a good candidate for labels where temperature tolerance is required, such as multi-layer labels for automobile bodies when being painted and dried at high temperatures. PEN is ideally suited for bar code labels where dimensional stability and registration are required at elevated temperatures. PEN labels have dimensional-excellence performance on printed circuit boards, in solvent- and aqueous-based painting operations, and in under-the-hood applications. PEN labels also provide substantially improved performance over PET or vinyl labels when the label must survive in harsh chemical environments. PEN performs extremely well in applications where the label must be in contact with organic solvents, such as acetone, ethers, toluene and phenol, as well as strong bases (30 % NaOH) and moderate acids. 

Research on resin-bonded boards has used wood chips, or fibres, that are acetylated prior to composite manufacture. In almost all cases, acetylation has been achieved by using uncatalysed acetic anhydride. Significant improvements in dimensional stability proportional to the WPG of the wood particles have been reported when acetylated wood is used, and there is also a reduction in irreversible swelling (e.g. Bekere etal., 1978 Arora etal., 1981 Rowell etal., 1986a-e, 1989, 1990, 1991,1995 Yoshida etal., 1986 Youngquist etal., 1986a,b, 1988 Larsson and Tillman, 1989 Subiyanto etal., 1989 Vick etal., 1991 Clemons etal., 1992 Kajita and Imamura, 1993 Sasaki and Kawai,... 

Fuwape, J.A. and Oyagade, A.O. (1999). Strength and dimensional stability of acetylated Gmelina and Sitka spruce particle board. Journal of the Timber Development Association of India, 45(1/2), 5-10. 

Rowell, R.M., Kawai, S. and Inoue, M. (1995). Dimensionally stabilized, very low density fibre-board. Wood and Fiber Science, 27(4), 428—436. 

We are in the process of producing fiberboards from various types of acetylated lignocellulosic fibers. Most of our research has been on pine or aspen particleboards or flakeboards, so the data presented here on dimensional stability and biological resistance come mainly from these types of boards. 

U.S. market is about 20 million pounds per year. The applications are those where one needs very high flame resistance (clothing for firefighters and welders, welder s protective shield, upholstery and drapes), heat resistance (ironing board covers, insulation film for electrical motors and transformers, aerospace and military), dimensional stability (fire hose, V- and conveyor belts), or strength and modulus (circuit boards, bulletproof vests, fiber optic and power lines, ship mooring ropes, automobile tire cord, puncture-resistant bicycle tires). 

Commercial applications have been identified primarily in the electronics industry where requirements for dimensional stability, mechanical properties, and high temperature resistance make these systems attractive in advanced circuit board technology. Other commercial applications include high temperature membranes and filters where these materials offer performance improvements over glass, Kevlar, and graphite composites. Industrial development of these types of materials will most likely be dependent on monomer cost and advances in various product properties requirements. 

Ultem polyetherimides have applications in areas where high strength, dimensional stability, creep resistance, and chemical stability at elevated temperatures are important. Uses include electrical connectors, wave guides and printed circuit boards for electronic equipment, food applications (microwaveable containers, utensils, and films), aircraft interior materials, and sterilizable medical equipment. 

Specifications, Standards, Quality Control, and Health and Safety Factors. Formerly, there was an Insulation Board Institute representing the insulation board industry, but the decline in the market and number of producers has led to its demise. Currendy (ca 1997), the industry is represented by the American Hardboard Association (AHA). Specifications and standards are found in American National Standards Institute (ANSI) standard for CellulosicFiberboard (7). The standard includes descriptions of the various types and classes of fiberboard, as well as requirements for physical and dimensional stability properties. Quality control tests are limited to a few basic strength and stability tests, including bending strength, bond strength, and moisture resistance. 

Common grades of laminates tend to be thin materials ranging from 0.5—1.5 mm in thickness, therefore for most applications they must be supported. In the manufacture of furniture, cabinetry, and countertops the laminates are bonded to particle board or plywood. Since the laminates consist largely of cellulosic paper, their dimensional stability is similar to wood, particularly to particle board. 

Ultem PEI resins are amber and amorphous, with heat-distortion temperatures similar to polyethersulfone resins. Ultem resins exhibit high modulus and are stiff yet ductile. Light transmission is low. In spite of the high use temperature, they are processible by injection molding, structural foam molding, or extrusion techniques at moderate pressures between 340 and 425°C. They are inherently flame retardant and generate little smoke dimensional stabilities are excellent. Large flat parts such as circuit boards or hard disks for computers can be injection-molded to maintain critical dimensions. 

The book opens with a paper on the structure and composition of wood to define the material under discussion and then considers molds, permeability, wood preservation, thermal deterioration and fire retard-ance, dimensional stability, adhesion, reconstituted wood boards such as fiberboard and particleboard, plywood, laminated beams, wood finishes, wood-polymer composites, and wood softening and forming. A final paper treats the common theme of wastewater management. Only one of the papers presented at the meeting is not included in this volume, and its subject of conventional wood preservation methods is adequately treated in detail elsewhere (e.g., Nicholas, D. D., Ed Wood Deterioration and Its Prevention by Preservative Treatments, 2 vols., Syracuse University Press, 1973). 

By increasing furfuryl alcohol usage to 20, an exceptionally high internal bond and good dimensional stabilization were realized. Also, an amount of hydrochloric acid lower than any usage reported in Table VII, used with 10 furfuryl alcohol, gave board properties approximating those of the phenol formaldehyde control listed in Table II. 

Boards exhibiting excellent dimensional stability and internal bonds vie re produced using 3 and % NO, Once again it appears that splinter-type particles rather than flakes give highest internal bonds. Densities of all boards reported ranged from 0 73 to 0.78, Molar ratios of furfuryl alcohol to formaldehyde used vieve approximately 3 2. 

A report from West Virginia University by Koch and Hall (57) discussed the use of hardwood bark as particleboard furnish, with and without added binders. Species included red oak, soft maple, and black birch. Initial studies indicated no-binder boards had to be compressed to 70 pounds per cubic foot to maintain their integrity. Both strength and dimensional stability were enhanced by pressing boards at 400°F instead of 300°F. Longer press times (15, rather than 10 minutes) also helped. Later, boards were made with 5% added starch powder. One potential use of this product was for expandable horticultural planting containers. Both raw and composted barks were tried, with promising results. 

In dry conditions decorative laminates will shrink, and in damp they will expand unless suitable precautions are taken the associated movements can give rise to stress cracking of laminates and the bowing of composite boards. Since the phenol-formaldehyde resins are more stable in this respect than melamine-formaldehyde, laminates with phenolic kraft cores have dimensional stability better than those with melamine core papers—and thick laminates incorporating many plies of phenolic core paper are more stable than thin laminates with fewer plies. 

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