Aluminum trihydrate

ATH came into wide use as a flame retardant in the 1960s, primarily as a result of demands of consumer-driven safety legislation for carpet backing and fiberglass-reinforced polyester products. For these applications, ATH imparts flame retardance and smoke suppression. End-use markets for ATH include transportation, construction, cast polymers, electrical/electronic, wire and cable, leisure and appliances. Specific polymer applications range from thermosets such as solid surface, sheet molding compounds (SMCs) and bulk molding compounds (BMCs) to wire and 

A comparison of the combustion properties of EPDM composites containing wet ground and precipitated ATH (Table 17.4) shows significant differences. It is likely that the lower average heat release rate (HRR) and average mass loss rate for the wet 

Applications In reinforced thermoset applications, the principal properties that ATH imparts are flame retardance, smoke suppression, thermal conductivity, optical translucency, and chemical stability. Aside from the benefits imparted in the above properties, the use of ATH as a resin extender also aflfords lower cost formulations with an acceptable balance of performance properties. 

Finely divided ATH or MOH produced in precipitation processes or finely ground and surface-treated ATH grades can be used in wire and cable applications, most notably in PVC and EPDM. The FR tests that are relevant to this application are UL 94/horizontal burn, VW-1, UL-1685, UL-1666, and UL-910. The ATH imparts the following fire retarding processes  

The so-called solid surface is a solid, nonporous surfacing composite material derived from ATH and a polyester or acrylic resin that is cured either thermally or at 

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At the alumina plant, the bauxite ore is further crushed to the correct particle size for efficient extraction of the alumina through digestion by hot sodium hydroxide liquor. After removal of "red mud" (the insoluble part of the bauxite) and fine solids from the process liquor, aluminum trihydrate crystals are precipitated and calcined in rotary kilns or fluidized bed calciners to produce alumina (AljOj). Some alumina processes include a liquor purification step. 

Reh, L., Calcining Aluminum Trihydrate in a Circulating Fluid Bed, a New Technique of High Thermal Efficiency, Metallurges, Rev. Activ., 1972(15) 58-60 (1972)... 

Hydrated aluminum oxide is a preferred flame refardanf fhaf liberates its water of hydrafion when exposed to flames, in contrast to chlorinated materials, which give off toxic gases as by-products. The paraffin oil is a processing aid that enhances the ability to extrude such materials. The silane is a coupling agent that improves the interaction between the polymers and the aluminum trihydrate. Trimethylolpropane trimethacrylate (TMPT) enhances the radiation response. 

Nano-modified aluminum trihydrate show a good synergistic characteristics for improving the flame retardant properties of HIPS, when combined with red phosphorus (23). 

The vinyl silanized samples from Mr. Robert E. Schultz of J. M. Huber had been prepared as follows liquid vinylmethoxyethoxy silane (Union Carbide A172) was quantitatively added to a known volume of a mixture of 60% de-ionized water and 40% 2-propanol in a polyethylene beaker via a disposable polyethylene syringe. 100 g of ATH (aluminum trihydrate) was stirred into exactly 300 ml of the vinyl silane mixture for 10 min with a polyethylene rod. The resulting slurry was placed in a 100°C oven and allowed to dry for 24 h. 

Alumina trihydrate alumina hydrate alumina hydrated aluminum oxide trihydrate aluminum oxide hydrate aluminum (III) hydroxide hydrated alumina hydrated aluminum oxide3 aluminum hydrate aluminum trihydrate hydrated aluminad... 

Aluminum fluoride is made by heating ammonium hexafluoroaluminate to red heat in a stream of nitrogen by the action of fluorine or hydrogen fluoride gas on aluminum trihydrate at high temperatures, followed by calcining the hydrate formed by fusing cryolite or sodium fluoride with aluminum sulfate or by a reaction of fluosilicic acid on aluminum hydrate (HSDB 1995). 

Additive flame-retardants may be more easily incorporated in polyurethane formulation. Several class of compounds have been used to improve flame retardancy of PU foams such compounds are halogen- (very often chloroalkyl-phosphate) or phosphorous-based compounds, although also other substances, like as EG, melamine, aluminum trihydrate and magnesium hydroxide, may be used. 

Heat absorbers Usually metal hydrates such as aluminum trihydrate (ATH) or magnesium hydroxide, which remove heat by using it to evaporate water in their structure... 

Reagents were alkali hydroxydes and chlorides (all A.R. from Merck or Carlo Erba), Aluminum trihydrate gel Dry Pharm USPXX (Serva), Precipitated silica (BDH), TEPA, purum, 20% soln (Merck), DP, (A.R., Fluka). All chemicals were used without further purification. 

Many chemicals have been evaluated for their effectiveness as FRs. Today most FRs for wood are based on phosphorus, nitrogen, boron, aluminum trihydrate, and a few other compounds. Phosphorus and nitrogen frequently are used together because they behave... 

Journal of Applied Polymer Science 89, No.3, 18th July 2003, p.753-62 MECHANOCHEMICAL IMPROVEMENT OF THE FLAME-RETARDANT AND MECHANICAL PROPERTIES OF ZINC BORATE AND ZINC BORATE-ALUMINUM TRIHYDRATE-FILLED POLY (VINYL CHLORIDE)... 

Aluminum trihydrate also can be used in conjunction with boron compounds, because a synergistic effect between the boron and aluminum trihydrate exists (88). Hardboard, containing 28% aluminum trihydrate and 6% boron, can be produced and has a flame spread of 25 or less. The aluminum trihydrate is added to a slurry of water and wood fiber. The boron solution is added to the surface of the wetlap or as an impregnated solution in a secondary treatment (88). 

Aluminum Trihydrate. The utility of aluminum trihydrate as a flame retardant is based on its endothermic dehydration to aluminum oxide and water. In absorbing some of the heat of combustion and lowering the temperature of the substrate near the flame, the hydrate functions as a chemical heat sink. The water vapor provided by such action dilutes the gaseous reactants in the flame until all the water of crystallization is exhausted. 

Aluminum trihydrate also can be used as the only fire-retardant... 

Other compounds such as aluminum trihydrate and silicate compounds have also been tried as fire retardants for wood. These compounds work best in combination with other chemicals, especially those in which the behavior is synergistic. 

Common flame retardants are aluminum trihydrate, brominated compounds, phosphorous compounds, antimony oxide, chlorinated compounds, and boron compounds. Brominated flame retardants are preferred for thermoplastic resins such as polystyrene, polyesters, polyolefins and polyamides but are also used in epoxies, ABS and polycarbonates. Decabromodiphenyl oxide is the most common brominated flame retardant used. 

Derivation (1) Action of hydrogen fluoride gas on alumina trihydrate (2) reaction of hydrogen fluoride on a suspension of aluminum trihydrate, followed by calcining the hydrate formed (3) reaction of fluosihcic acid on aluminum hydrate. 

Beyer, G. Flame retardant properties of EVA-nanocomposites and improvements by combination of nanofillers with aluminum trihydrate. Fire Mater. 2001, 25, 193-197. 

The addition of aluminum trihydrate improved fire resistance of glass epoxy laminates but, because of the high loading required, it decreased the mechanical properties of the laminate. Various components of formulation were studied to improve performance. It was found that the curing agent and impact modifier help to improve the mechanical properties of the laminates. Other fillers were also studied in order to understand the impact of filler on properties. It was found that all fillers (glass beads, quartz, calcium carbonate, mica) reduce mechanical properties of laminates, not just aluminum trihydrate. " Aluminum trihydrate was found to be one of better performers in this system. 

Fillers are used in these products to improve mechanical properties or impart flammability resistance. Fillers are frequently silane-treated to further improve mechanical properties. Fillers must have a low moisture (below 0.1%), a low absorption of resin, and are expected to impart thixotropic properties. There are special cases. For example, if peroxyketals are used as initiators, basic fillers have to be used because acidic fillers interfere with cure times and the shelf-life of the composition. Shape and particle size distribution must be considered in filler selection to impart the desired rheological properties. Calcium carbonate is the most popular filler but aluminum trihydrate, anhydrous calcium sulfate, and silica are also frequently used. Barite is well suited to this application, especially if acid... 

In both Europe and the United States, aluminum trihydrate, or ATH [Al(OH)3)], has by far the largest share of the mineral flame-retardant market however, magnesium hydroxide presently has the highest growth rate. To date, most of the research using magnesium hydroxide has focused on thermoplastics, including ethylene-vinyl acetate copolymer (EVA), polypropylene, acrylonitrile-butadiene-styrene (ABS) copolymer, and modified polyphenylene oxide (Hornsby and Watson, 1986). 

Asbestos, either powdered or in fiber form, imparts heat resistance aluminum trihydrate and talcum act as flame retarders mica gives excellent electrical properties and aluminum powder improves heat transfer. Powdered minerals such as silica or china clay are often used to Improve water resistance. One novel area is the use of hollow glass spheres in rigid polyurethane foam, known as "diafoam," to achieve 30-70% higher flexural and compression moduli. This foam is used as "structural foam" in furniture. 

Low moisture content of fillers are typically observed in calcium carbonate and wollastonite (0.01-0.5%), talc and aluminum trihydrate, mica (0.1-0.6%). Medium moisture content can be observed in titanium hydroxide (to 1.5%), clay (to 3%), kaolin (1-2%), and Biodac (2-3%). High moisture content is often seen in cellulose fiber (5-10%), wood flour (to 12%), and fly ash (to 20%). Biodac absorbs 120% of water under direct contact with an excess of water. 

This property can be beneficial for hydrophobic plastics, such as polyolefins, as hydrophobic fillers can show a good interaction with the matrix. Also, hydrophobic fillers can very significantly influence the viscosity of the matrix, hence, its rheology and flowability. Fillers typically absorb oil in much higher quantities compared to water. Calcium carbonate absorbs 13-21% of oil, aluminum trihydrate absorbs 12-41% of oil, titanium dioxide 10-45%, wollastonite 19-47%, kaolin 27-48%, talc 22-57%, mica 65-72%, and wood flour 55-60%. Biodac absorbs 150% of oil by weight. 

HDPE filled with a flame-retardant ATH (aluminum trihydrate) showed the ignition temperature of 445°C (833°F). The 10°C delay was caused by ATH, which releases water vapor at about 180-240°C (360-460°E), which that in turn cools down the material. 

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