Fillers alumina

In a further attempt to improve properties, Brauer, McLaughlin Huget (1968) examined the use of alumina as a reinforcing filler. Alumina is considerably more rigid than fused quartz. They achieved a considerable increase in strength. The preferred composition was the powder defined in Table 9.4, which had a compressive strength of 91 MPa. This zinc oxide based powder was the one most commonly used in subsequent studies by Brauer and coworkers. We shall refer to it as the EBA powder for it is the one used in commercial formulations and in a number of experimental studies. 

Alumina-Filled Edoxv. A different interfacial geometry and failure mechanisms are provided by particulate fillers. Alumina and silica are incorporated into plastics primarily because of their low cost, and may also improve properties to some extent. In our studies, the EE, phE and RE from neat and alumina-filled Epon 828... 

An investigation was carried out into the fire retardant behaviour of zinc hydroxystannate-coated fillers (alumina trihydrate and magnesium hydroxide) in PVC and EVA cable formulations. Measurements were made of the limiting oxygen index, peak rate of heat release and smoke parameter and the data for unfilled and filled formulations compared. X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier-transform spectroscopy were used to study the filler-coating interaction. 16 refs. 

Fig. 2 Retention of fibers (cellulose) and filler (alumina) during preceramic paper formation.

Combination of the Classical Flame Retardant Filler Alumina Trihydrate with Organoclays... 

Fillers that contain combined water or carbon dioxide, such as alumina trihydrate, Mg(OH)2, or dawsonite [12011 -76-6] increase fire resistance by hberating noncombustible gases when they are heated. These gases withdraw heat from the plastic and can also reduce the oxygen concentration of the air surrounding the composition. 

TrialkylPhosphates. Triethyl phosphate [78-40-0] C H O P, is a colorless Hquid boiling at 209—218°C containing 17 wt % phosphoms. It may be manufactured from diethyl ether and phosphoms pentoxide via a metaphosphate intermediate (63,64). Triethyl phosphate has been used commercially as an additive for polyester laminates and in ceHulosics. In polyester resins, it functions as a viscosity depressant as weH as a flame retardant. The viscosity depressant effect of triethyl phosphate in polyester resins permits high loadings of alumina trihydrate, a fire-retardant smoke-suppressant filler (65,66). 

Though functionally and chemically similar, fillers and pigments ate distinguished from one another in that fillers are added at the wet end of the paper machine, and serve to fill the sheet pigments are added at the size press and serve to alter the surface of the sheet. The most common fillers are mineral pigments, eg, clay, titanium dioxide [13463-67-7] calcium carbonate, siUca [7631-86-9], hydrated alumina [21645-51 -2], and talc [14807-96-6]. 

Spheres. HoUow spherical fillers have become extremely useflil for the plastics industry and others. A wide range of hoUow spherical fillers are currently available, including inorganic hoUow spheres made from glass, carbon, fly ash, alumina, and 2h conia and organic hoUow spheres made from epoxy, polystyrene, urea—formaldehyde, and phenol—formaldehyde. Although phenol—formaldehyde hoUow spheres are not the largest-volume product, they serve in some important appHcations and show potential for future use. 

Dicylopentadiene Resins. Dicyclopentadiene (DCPD) can be used as a reactive component in polyester resins in two distinct reactions with maleic anhydride (7). The addition reaction of maleic anhydride in the presence of an equivalent of water produces a dicyclopentadiene acid maleate that can condense with ethylene or diethylene glycol to form low molecular weight, highly reactive resins. These resins, introduced commercially in 1980, have largely displaced OfXv o-phthahc resins in marine apphcations because of beneficial shrinkage properties that reduce surface profile. The inherent low viscosity of these polymers also allows for the use of high levels of fillers, such as alumina tfihydrate, to extend the resin-enhancing, fiame-retardant properties for apphcation in bathtub products (Table 4). 

Gibbsite is aii important technical product and world production, predominantly by the Bayer process, is more than 50 million metric tons aimuaHy. Alost (90%) is calcined to alumina [1344-28-1 j, Al202, to be used for aluminum production. Tlie remainder is used by the chemical industry as filler for paper, plastics, rubber, and as the starting material for the preparation of various aluminum compounds, alumina ceramics, refractories, polishing products, catalysts, and catalyst supports. 

Bayer aluminum hydroxides in most grades are sold by all major U.S. alumina producers. Other firms offering aluminum hydroxide fillers probably operate reprocessing faciHties to grind or otherwise treat hydroxide obtained from the primary producers. Countries exporting small amounts to the United States are Japan, Germany, Canada, and the UK. 

Flame retardants (qv) are incorporated into the formulations in amounts necessary to satisfy existing requirements. Reactive-type diols, such as A/ A/-bis(2-hydroxyethyl)aminomethylphosphonate (Fyrol 6), are preferred, but nonreactive phosphates (Fyrol CEF, Fyrol PCF) are also used. Often, the necessary results are achieved using mineral fillers, such as alumina trihydrate or melamine. Melamine melts away from the flame and forms both a nonflammable gaseous environment and a molten barrier that helps to isolate the combustible polyurethane foam from the flame. Alumina trihydrate releases water of hydration to cool the flame, forming a noncombustible inorganic protective char at the flame front. Flame-resistant upholstery fabric or liners are also used (27). 

The polysulfide base material contains 50—80% of the polyfunctional mercaptan, which is a clear, amber, sympy Hquid polymer with a viscosity at 25°C of 35, 000 Pa-s(= cP), an average mol wt of 4000, a pH range of 6—8, and a ntild, characteristic mercaptan odor. Fillers are added to extend, reinforce, harden, and color the base. They may iaclude siUca, calcium sulfate, ziac oxide, ziac sulfide [1314-98-3] alumina, titanium dioxide [13463-67-7] and calcium carbonate. The high shear strength of the Hquid polymer makes the compositions difficult to mix. The addition of limited amounts of diluents improves the mix without reduciag the set-mbber characteristics unduly, eg, dibutyl phthalate [84-74-2], tricresyl phosphate [1330-78-5], and tributyl citrate [77-94-1]. 

Composite Resins. Many composite restorative resins have incorporated fluoride into the filler particles. One commonly used material, yttrium trifluoride [13709-49-4] is incorporated as a radiopaque filler to aid in radiographic diagnosis, and is also responsible for slow release of fluoride from the composites (280). This same effect is achieved with a barium—alumina—fluoro-siUcate glass filler in composite filling and lining materials. Sodium fluoride [7681-49-4] has also been used in composites by incorporating it into the resin matrix material where it provides long-term low level release (281-283). 

Minerals Limestone Fillers Paper coatings Flue gas desulfurization Kaolin Gypsum Alumina Precious metals hheration... 

Some inorganic fillers are used as flame retardants in rubber base formulations. Flame retardants act in two ways (1) limiting or reducing access of oxygen to the combustion zone (2) reacting with free radicals (especially HO ), thus acting as terminator for combustion-propagation reaction. The additives most widely used as flame retardants for polymers are antimony oxides and alumina trihydrate. 

Fillers. Addition of fillers is not common in polychloroprene latex formulations. Fillers are used to reduce cost and control rheology, solids content and modulus. However, cohesion and adhesion are reduced. Calcium carbonate, clay and silica are some of the fillers than can be added. Alumina trihydrate is often used when resistance to degradation by flame is important. 

For certain products, skill is required to estimate a product s performance under steady-state heat-flow conditions, especially those made of RPs (Fig. 7-19). The method and repeatability of the processing technique can have a significant effect. In general, thermal conductivity is low for plastics and the plastic s structure does not alter its value significantly. To increase it the usual approach is to add metallic fillers, glass fibers, or electrically insulating fillers such as alumina. Foaming can be used to decrease thermal conductivity. 

After formulation with a flame retardant filler such as alumina trihydrate Al203 3H20, hydrated silica or calcium carbonate, a peroxide curing agent and... 

As an example, a foam prepared from III, alumina trihydrate as a filler, benzoyl peroxide as a curing agent, and azobis formamide as a blowing agent, leads to a material with an oxygen index of 48, a long-term stability to at least 150 °C, and a smoke density about one fifth that of a commercial foam [284]. 

Attempts have been made to improve the mechanical properties of these cements by adding reinforcing fillers (Lawrence Smith, 1973 Brown Combe, 1973 Barton et al, 1975). Lawrence Smith (1973) examined alumina, stainless steel fibre, zinc silicate and zinc phosphate. The most effective filler was found to be alumina powder. When added to zinc oxide powder in a 3 2 ratio, compressive strength was increased by 80 % and tensile strength by 100 % (cements were mixed at a powder/liquid ratio of 2 1). Because of the dilution of the zinc oxide, setting time (at 37 °C) was increased by about 100%. As far as is known, this invention has not been exploited commercially. 

The use of reinforcing fillers was examined by Seed Wilson (1980). An alumina-fibre cement had a flexural strength of 44 MPa, while one reinforced by carbon fibre had a flexural strength of 53 MPa. Metal reinforcement has also been examined. Seed Wilson (1980) found that a cement reinforced with silver-tin alloy had a flexural strength of 40 MPa. 

Control shrinkage after moulding. Any filler will decrease shrinkage most commonly used are silica, clay, calcium carbonate, alumina, talc, powdered metals and lithium aluminium silicate. 

Some elucidation of the mechanism of elastomer reinforcement is being obtained by precipitating chemically-generated fillers into network structures rather than blending badly agglomerated filler particles into elastomers prior to their cross-linking. This has been done for a variety of fillers, for example, silica by hydrolysis of organosilicates, titania from titanates, alumina from aluminates, etc. [85-87], A typical, and important, reaction is the acid- or base-catalyzed hydrolysis of tetraethylorthosilicate ... 

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