Aluminum trihydroxides

Bayerite (P-Aluminum Trihydroxide). Bayerite is rarely found in nature. It has been synthesized by several methods A pure product is prepared by the Schm b method (3) in wliich amalgamated aluminum reacts with water at room temperature. Other methods include rapid precipitation from sodium alurninate solution by CO2 gassing, aging of gels produced by neutrali2ation of aluminum salts with NH OH, and rehydration of transition rlio alumina. 

Alumina - Alumina forms a variety of oxides and hydroxides whose structures have been characterized by X-ray diffraction (16). From the catalytic viewpoint y-alumina is the most important. This is a metastable phase that is produced from successive dehydration of aluminum trihydroxide (gibbsite) to aluminum oxide hydroxide (boehmite) to y-alumina, or from dehydration of boehmite formed hydrothermally. y-alumina is converted into a-alumina (corundum) at temperatures around 1000 C. 

Aluminum trifluoride trihydrate, 2 361 a-Aluminum trihydroxide. See Gibbsite P-Aluminum trihydroxide. See Bayerite Aluminum trihydroxides, 2 421 classification, 2 422... 

P-aluminum trihydroxide. See Bayerite P-amino alcohols, 2 113 P-amylases, 10 288... 

Alumina is a porous, high-surface-area form of aluminum oxide. The surface has more polar characteristics than silica gel does therefore, it has both acidic and basic characteristics, reflecting the nature of the metal. Alumina has a high melting point, slightly over 2000°C, which is also a desirable property for a support due to its thermal stability. Alumina is composed of aluminum trihydroxides, Al(OH)3 aluminum oxyhydroxides, AIO(OH) and aluminum oxide, Al203n(H20). 

The commercial alumina and silica gel sorbents are mesoporous, i.e., with pores mostly larger than 20 A (see Fig. 1). Activated alumina is produced by thermal dehydration or activation of aluminum trihydroxide, A1 (OH)3 (Yang, 1997), and is crystalline. Commercially, silica is prepared by mixing a sodium silicate solution with a mineral acid such as sulfuric or hydrochloric acid. The reaction produces a concentrated dispersion of finely divided particles of hydrated Si02, known as silica hydrosol or silicic acid ... 

Dando, N.R., Clever, T.R., Pearson, A., Stinson, J.M., Kolok, P.L., and Martin, E.S., Aluminum trihydroxide (ATH) as a filler for polymer composites Improvements in thermal stability by controlled precipitation, Proceedings from 50th Annual Technical Conference, Composite Institute, Society of Plastics Industry Inc., Washington D.C., Session 1-D, 1995, pp. 1—4. 

Boric acid in conjunction with APP was reported in epoxy intumescent coating.30-31 Boric acid and its derivatives were used in phenolics to impart thermal stability and tire retardancy. For example, Nisshin steel claims the use of boric acid and aluminum trihydroxide (ATH) in phenolics for sandwich panel.32 It was also reported that the small amounts of boric acid (around 0.25% by weight) in polyether imide (PEI) and glass-filled and PEI can reduce peak HRR by almost 50% in the OSU Heat Release test for the aircraft industry.33 In applications where high modulus and high strengths are needed, boric acid can be added without the softening effects of other additives such as siloxanes. 

SYNS AF 260 ALCOA 331 ALUMIGEL ALUMINA HYDRATE ALUMINA HYDRATED ALUMINA TRIHYDRATE a-ALUMINA TRIHYDRATE ALUMINIC ACID ALUMINLLM HYDRATE ALUMINUM(III) HYDROXIDE ALUMINUM HYDROXIDE GEL ALUMINUM OXIDE HYDRATE ALUMINUM OXIDE TRIHYDRATE ALUMINUM TRIHYDRAT ALUMINUM TRIHYDROXIDE ... 

For consistency, pseudopotentials should be based on the same functionals as used for the valence states. This point has been illustrated by Gale and coworkers in their study of aluminum trihydroxides [47]. Table 8.3 compares their results of cell optimizations using various mixtures of psuedopotential and valence state functionals with the experimental structure of gibbsite [48]. LDA pseudopotentials in an LDA optimization of the cell gives underestimated cell parameters, consistent with the usual expectation that LDA gives over-binding in chemical bonds. 

Flame-retardants are used as additives in the preparation of fire retardant paints. They are decomposed by heat to produce nonflammable components, which are able to blanket the flames. Both inorganic and organic types of flame-retardants are available in the market. The most widely used inorganic flame-retardants are aluminum trihydroxide, magnesium hydroxide, boric acid, and their derivatives. These substances have a flame-retardant action mainly because of their endothermic decomposition reaction and their dilution effect. The disadvantage of these solids is that they are effective in very high filler loads (normally above 60 percent). 

For hundreds of years sticky surfaces have been dusted with powder (e.g., talc) to keep them separated. Talc is broadly used in cable and profile extrusion to obtain a smooth surface. Similarly, in injection molding, the application of aluminum trihydroxide gives a better surface finish. Talc, CaCOs, and diatomite provide anti-blocking properties. Graphite and other fillers decrease the coefficient of friction of materials. PTFE, graphite and M0S2 allow the production of self-lubricating parts. Here, PTFE, a polymer in powder form, acts as a filler in other polymers. Matte surfaced paint is obtained by the addition of silica fillers. 

Names aluminum trihydroxide, aluminum hydroxide, hydrated alumina... 

Figure 2.2. SEM of aluminum trihydroxide decreasing viscosity. Courtesy of Alcan Chemical Europe, Gerrards Cross, UK.

Magnesium hydroxide is an emerging filler for fire retardant applieations. In this area, it eompetes with aluminum trihydroxide, antimony oxide, and other fillers based on zine. Magnesium hydroxide has a different deeomposition temperature from aluminum trihydroxide, it is more suitable for polymers with higher decomposition temperature. These aspects and current findings are discussed in detail in Chapter 10. 

Fillers such as magnesium hydroxide and aluminum trihydroxide are used as flame retardants because their decomposition product - water -is an active ingredient in flame retardancy. These fillers are discussed in detail in Chapter 12. 

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