PVDF latex foam composites provide high flame resistance. (Materials: Close-Up).* A new patent-pending technology developed by AtoFina Chemicals in Philadelphia creates highly flame-resistant foams of polyvinylidene fluoride Polyvinylidene Difluoride, or PVDF is a highly non-reactive and pure thermoplastic fluoropolymer. It is also known as KYNAR® or HYLAR®. PVDF is a specialty plastic material in the fluoropolymer family; it is used generally in applications requiring the (PVDF PVDF polyvinylidene difluoride ) fluoropolymer A fluoropolymer is a polymer that contains atoms of fluorine. It is characterized by a high resistance to solvents, acids, and bases. Fluoropolymers were discovered serendipitously in 1938 by Dr. Roy J. Plunkett. without the use of blowing agents or melt processing. The new process combines a liquid latex latex, emulsion of a polymer (e.g., rubber) in water (see colloid). Natural latexes are produced by a number of plants, are usually white in color, and often contain, in addition to rubber, various gums, oils, and waxes. of AtoFina's Kynar PVDF copolymer copolymer: see polymer. with glass mat or other fabric reinforcements to produce open-cell foams that reportedly exhibit extremely low smoke and flame generation in fire tests. AtoFina sources describe the Kynar foams as "essentially non-flammable." Kynar PVDF is transparent to uv radiation, weatherable, and chemically resistant at elevated temperatures. Potential applications for the new foam composites include thermoformed sheet for fire-barrier panels in transportation equipment, construction, and petrochemical processing. Others include plenum-cable insulation wrap for high-rise buildings high-rise building Multistory building taller than the maximum height people are willing to walk up, thus requiring vertical mechanical transportation. The introduction of safe passenger elevators made practical the erection of buildings more than four or five stories tall. , coatings on flame-protective clothing for rescue teams, protective sheathing for homes and other structures threatened by wild fires, and coatings on gaskets or other applications where a material is already flame resistant but cannot withstand chemical exposure. AtoFina is considering licensing agreements or other means of offering the technology commercially. No blowing agents Although fluoropolymers can be extruded into foams using chemical blowing agents or direct gas injection, AtoFina's latex process has the advantage of allowing use of long-fiber mats or fabrics. The process starts with soaking the reinforcing mat in a water-based PVDF latex. This is followed by a proprietary method of refrigerating re·frig·er·ate tr.v. re·frig·er·at·ed, re·frig·er·at·ing, re·frig·er·ates 1. To cool or chill (a substance). 2. To preserve (food) by chilling. the mixture and drying it to a solid in a mold. As the water evaporates from the resin mix, it is replaced by air, leaving a highly uniform, open-cell structure of interconnected voids, explains research scientist Ramin Ramin (Gonystylus) is a genus of about 30 species of hardwood trees native to southeast Asia, in Malaysia, Singapore, Indonesia, Brunei, the Philippines, and Papua New Guinea, with the highest species diversity on Borneo. Amin-Sanayei. The details of the chilling process are secret, but it can take 3 to 12 hr. AtoFina sources say it is possible to shorten the cycle to as little as 20 mm by using moderate heating to around 140 F instead of chilling. The density of the resulting foam depends on the concentration of polymer solids in the latex. The density of unfilled, solid PVDF copolymer is around 1.78 g/cc. AtoFina's latex process can yield foam densities of 0.25 g/cc or less. The volume fraction of voids in the foam can be up to 85% or even higher. To generate specific densities and foam textures, certain solvents can be added at low levels to enhance the uniformity of cell structure and distribution. Fire-test results Initial laboratory tests show these foam composites have excellent fire resistance. "Standard tests are now under way to substantiate To establish the existence or truth of a particular fact through the use of competent evidence; to verify. For example, an Eyewitness might be called by a party to a lawsuit to substantiate that party's testimony. fire-resistance performance," says Amin-Sanayei. The technology allows for incorporation of all kinds of reinforcements, including long-glass fibers, carbon fibers, natural fibers, and even electrically conductive conductive having the quality of readily conducting electric current. conductive flooring flooring or floor covering made specially conductive to electrical current, usually by the inclusion of copper wiring that is earthed metal fibers. AtoFina conducted flame tests flame test, test used in the identification of certain metals. It is based on the observation that light emitted by any element gives a unique spectrum when passed through a spectroscope. on a Kynar foam encapsulating one or more plies plies 1 v. Third person singular present tense of ply1. n. Plural of ply1. of random chopped-glass mat. A propane torch A propane torch is a tool for burning the flammable gas propane. The maximum adiabatic flame temperature a propane torch can achieve with air is 2268 kelvins (1995 °C/3623 °F). was placed 2 in. from the 4 x 6 in. flat sample. Several formulations of different densities were exposed to the same flame conditions. Controls of plain glass fiber and 1/8-in.-thick aluminum sheet were also tested. The test measured the time it took for the flame to burn through the flat panel. As shown in the accompanying table, all the reinforced foam samples compared favorably with the controls. Burn-through time increased with foam density and with the number of plies of glass fiber. Also, a slight change in panel thickness led to a large difference in the time it took for complete burn-through. Most notably, the 5/8-in. thick glass-fiber/foam system took more than 2.5 times longer to burn through than a comparable 3/8-in. sample. A thermocouple showed that surface temperature of the foam/glass samples reached more than 1740 F before burn-through occurred. It is notable that the back surface of the samples remained at room temperature for an appreciable time, as shown in the table. NEED TO KNOW MORE? AtoFina Chemicals, Inc., Philadelphia (215) 914-7921, www.atofina.com BURN-THROUGH TESTS OF PVDF/GLASS-MAT FOAMS (4 x 6 in. Panels) Sample Thickness, Sample Density, Burn-Thur Heat-Thru No. in. Structure g/cc Time, sec Time, sec * 1 3/8 PVDF/1 Ply Glass 0.33 80 -- 2 3/8 PVDF/1 Ply Glass 0.26 65 -- 3 3/8 PVDF/1 Ply Glass 0.21 45 -- 4 3/8 PVDF/1 Ply Glass 0.11 40 -- 5 3/8 PVDF/2 Plies Glass 0.27 120 >60 6 3/8 PVDF/3 Plies Glass 0.28 130 -- 7 3/8 PVDF/2 Plies Glass 0.26 >300 >120 8 3/8 Glass Mat 0.0155 4 <4 9 3/8 Aluminum Panel 2.7 90 <10 * Times that the side opposite flame remained at room temperature. |
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