Moisture resistant boards

The standard sized sheets are four ft (1.22 m) wide and from 8 to 16 ft long. Sheets are available in thicknesses from j up to 1 in. (0.63 to 2.5 cm), but the most common thicknesses are S and 5/8 in. (1.3 and 1.6 cm). There are special products for bathrooms, such as moisture-resistant board (3% of market) and sheathing appHcations (2% of market), but the vast majority of the product sold is either standard board (60% of market) or the fire-rated Type X board (29% of market). Type X (1.6 cm thick) is the basis of most of the one-hour fire walls in buildings built since the 1960s. 

The tested products were bonded with formaldehyde containing resin and used indoors. Most of the woodbased panels and other materials were manufactured during 1984. The panels were not coated. If nothing else is stated the test objects were manufactured with UF-resin and of Swedish origin. As the most common UF-bonded material the particleboards dominated the investigation. The selected boards included both ordinary UF-bonded (V-20) and moisture resistant boards, (V-313) and were received from eleven factories. 

Moisture resistant boards are manufactured of UF with some melamine added (MUF-bonded). If these boards are excluded from the calculations the correlation factor between the perforator values and emission values increases from r=O,76 to r=0,82. 

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. Currently (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 ftberboard, as well as requirements for physical and dimensional stabiUty properties. QuaUty control tests are limited to a few basic strength and stabiUty tests, including bending strength, bond strength, and moisture resistance. 

Expanded polystyrene bead mol ding products account for the largest portion of the drinking cup market and are used in fabricating a variety of other products including packaging materials, iasulation board, and ice chests. The iasulation value, the moisture resistance, and physical properties are inferior to extmded boardstock, but the material cost is much less. 

Plastic laminated sheets produced in 1913 led to the formation of the Formica Products Company and the commercial introduction, in 1931, of decorative laminates consisting of a urea—formaldehyde surface on an unrefined (kraft) paper core impregnated with phenoHc resin and compressed and heated between poHshed steel platens (8,10). The decorative surface laminates are usually about 1.6 mm thick and bonded to wood (a natural composite), plywood (another laminate), or particle board (a particulate composite). Since 1937, the surface layer of most decorative laminates has been fabricated with melamine—formaldehyde, which can be prepared with mineral fiUers, thus offering improved heat and moisture resistance and allowing a wide range of decorative effects (10,11). 

The production of moisture resistant particleboard by treatment with a maleic anhydride -glycerol mixture and using phenol formaldehyde as the matrix material has been investigated (Fujimoto etal., 1987). Boards prepared from modified wood showed considerable improvements in modulus of elasticity and internal bond strength when compared to control boards. Composites made from aspen fibres modified with SA, MA or acetic anhydride using phenol-formaldehyde (PF) or polypropylene as binder have also been studied (Clemons etal., 1992 Rowell etal., 1993b). The reaction of wood with MA was found to proceed at a slower rate than with SA. The volume increase due to modification... 

Properties of the HDA boards prepared from the activated substrate may be compared to the phenol-formaldehyde (PF) boards prepared using 6 resin solids. Comparison may also be made to the property requirements from commercial standard CS 236-66, type 2 medium density (below 0.8 g/cc), Class 1 particleboard fabricated using durable and highly moisture resistant and heat resistant binders suitable for interior and certain exterior applications. Specifications of this class of particleboard, generally prepared from PF resins, are MOR, minimum = 2,500 psi M0E, minimum =... 

The next series of reports based on use of bark for wet process hardboard were published over a 7-year span from 1950-1956 by Anderson and Runckel. In the first report (22), the results included laboratory boards made from Douglas-fir slabwood containing bark, which varied between 15 and 45% of the total furnish. Bending tests indicated adequate strengths were obtained, and addition of bark enhanced moisture resistance of the boards. Acceptable boards also were made when white fir and western hemlock barks made up a portion of the furnish. No binder was added to the Asplund-type fiber. 

Anderson contributed a paper to the 1956 International Consultation on Insulation Board, Hardboard and Particle Board (26). In addition to a good review of the literature, the paper contained results of further experimentation using the barks of several more species as furnish for wet-process hardboard. New species included ponderosa pine, sugar pine, southern pine, pinyon pine, lodgepole pine, noble fir, and red oak. Ponderosa pine bark produced hardboard comparable to Douglas-fir bark in both strength and moisture resistance. The other species varied widely in these properties. 

Up until 1952, all references found on bark in composition board were based upon wet-process softboard or hardboard. The first mention of a dry process came in a one-page article published by the British Columbia Research Council (30). The brief report indicated a dry process had been developed for making an interior wallboard possessing good strength and moisture resistance. No binder was necessary for the cedar mill residues, which included bark. Apparently, the process never was tried commercially. 

The nine MDF-boards that were tested were from five different manufacturers in Europe and have been commercially available in Sweden. One of the boards was moisture resistant and another flame resistant. Two of the boards were treated with formaldehyde reducing agents. 

The product proposed in this invention is designed to replace laminate flooring composed of medium density fireboard or particle board and PVC laminate. The weakness of this flooring method is its moisture resistance (particularly moisture resistance of particle board). This product of invention may have three layers (core layer (as given by formulation in the table above), print layer, and wear layer). 

Uses Moisture-resist., protective films for outdoor use, transportation industry, pkg., building laminates, decorative applies. release film for printed circuit boards, thermosetting resins, epoxies, phenolics, polyester, rubber compds. in food-contact coatings Reguiatory FDA 21CFR 175.270 Trade Name Synonyms Tedlar Series [DuPont... 

PPE was also blended with some commercial epoxy resins (Chao et al. 1993) to improve the dielectric properties (lower the dielectric constant), toughness, and moisture resistance of the cured thermoset. These formulations with fiberglass reinforcements were used for the printed circuit boards and other electronic applications. In one formulation of epoxy resin (Epon 825, Shell) cured with aluminum alkoxide, incorporation of 30 % PPE increased the tensile elongation at break for the epoxy thermoset from <2 % to 17 %. The HOT was increased from 60 °C to 195 °C. The dissolution of PPE in the epoxy raised its viscosity from 0.2 to 400 Pa.s. (Anonymous 1991). 

Melamine-formaldehyde They are rarely used alone because of iheir high price. However, combining with urea-formaldehyde, either by mixing the two resins or preferably by producing as a co-condensate, gives a very substantial improvement in the durability of urea adhesives (see step polymerization). A melamine content of at least 40% is needed to satisfy a standard method of accelerated ageing for moisture-resistant grades of particle board and MDF. " ... 

Applications. Due to retention of their excellent electrical, mechanical, and chemical properties at elevated temperature and very high moisture resistance, the high-pressure Mil spec, molding compoimds have found their market niche in high-performance military and commercial applications such as connectors, potting shells, relays, printed circuit boards, switches, coils, and bobbins. 

Cyanate esters are used in circuit boards because of their low dielectric constant of 2.91 and a high Tg of 290°C. Prepregs and laminates are made with conventional technology, and they are tougher and more moisture resistant than FR-4 copper clad. Laminates are also used in radomes, antennas, and aerospace structures. 

Performance and durability of wood products bonded with isocyanate and urethane adhesives have been the subject of several investigations. The strength of composition board is generally determined by its modulus of rupture (MOR), which is a flexure to break test its modulus of elasticity (MOE), or stiffness and its internal bond strength (IB), or tensile strength. These tests are run on dry and on water-soaked or wet samples, and are described in ASTM test method D 1037. As compared to phenol-formaldehyde adhesives, composition boards prepared with isocyanate or urethane adhesives are reported to display similar or superior initial strengths. Moisture resistance of isocyanate-bound par-... 

Melamine-fortified resins with a melamine content of up to approximately 10% based on liquid resin are used for various applications where straight UF resins cannot provide the desired combination of processing tolerance, formaldehyde emission, and specific board properties such as a low thickness swelling. MUF resins with higher content of melamine (up to 30% based on liquid resin) find applications in enhanced performance grade boards for use in hiunid conditions (moisture-resistant application). 

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