Silica diatomaceous earth

Antiblock additives are often incorporated into packaging films to prevent them sticking together. Their effectiveness relates directly to the roughness they impart on a film surface while minimising loss in optical properties. They are often used in association with slip additives such as erucamide. Common antiblock additives include crystalline silica, diatomaceous earth and talc (magnesium silicate). 

Eillers used in epoxy resins are normally inert, finely divided powders. Common fillers include calcium carbonate, clay (bentonite), talc, silica, diatomaceous earth, and asbestos. Workers exposed to excessive amounts of some of these dusts may experience lung damage. ... 

Sample preparation Condition an Extrashot-Silica (diatomaceous earth) SPE cartridge (Kusano Scientific) with 200 p,L EtOH and 200 p-L dichloromethane, force out the remaining solvent with 500 pL air. Add 5 pL serum to the surface of the cartridge and pass 130 pL dichloromethtme gently through the cartridge into the 100 pL sample loop. 

SYNONYMS amorphous silica, diatomaceous earth, diatomaceous silica, diatomite, infusorial earth. 

Silica, amorphous (diatomaceous earth, precipitated and gel silica) Possesses little or no potential to oause silicosis. Most sources of amorphous silica contain quartz (see orystalline silica, below). If greater than 1% quartz is present, the quartz hazard must be addressed. When strongly heated (calcined) with limestone, diatomaceous earth becomes crystalline and can cause silicosis. Amorphous silica has been associated with lung fibrosis, but the role of crystalline silica contamination remains controversial. 10 mg/m (precipitated silica, diatomaceous earth, silica gel) 3 mg/m (respirable dusH 2 mg/m (silica fume) 3000 mg/m White to gray powders. Odorless with a negligible vapor pressure. The TLV for dusts is 10 mg/m if no asbestos and less than 1% quartz ate present. 

Diatomaceous earth (diatomite) is composed of fossilized silica-based shells of diatoms, single-celled marine organisms. Like synthetic silica, it is used mainly at low percentages for its anti-blocking properties in clear PE films (see Chapter 12). However, also like synthetic silica, diatomaceous earth absorbs water, which limits its shelf life [7-20],... 

Synonyms Amorphous silica Diatomaceous earth, natural Diatomaceous silica Diatomite Infusorial earth Kieselguhr... 

The choice of antiblocking additive depends on the polymer, the desired film quality, and whether there is a pigment. Several inorganic substances are used, including synthetic amorphous precipitated silica, diatomaceous earths, nepheline syenite, calcined clay, coated calcium carbonate, magnesium carbonate, magnesium sulphate, mica, talc and various zeolites. Calcium carbonate particles are approximately spherical, but silica ones are irregular mica forms sheets and talc is plate-like. 

Figures 13.7 and 13.8 show the efficiency of various antiblocking agents. S5mthetic silica (Figure 13.8) is the most efficient antiblocking agent, followed by natural silica (diatomaceous earth in Figure 13.7), and talc (Figure 13.8). Even...

Non-black fillers may also be employed, but it is important to use neutral or medium high pH grades such as silane-treated calcined clay, synthetic sodium aluminum silicate, platy talc, neutral pH silicas, diatomaceous earth, hydrated aluminum silicate, calcium meta silicate, precipitated calcium carbonate, and so on. An indication of non-black filler requirements for one point of hardness increase is shown in Table 5.10. 

The most widely used particulate support is diatomaceous earth, which is composed of the silica skeletons of diatoms. These particles are quite porous, with surface areas of 0.5-7.5 m /g, which provides ample contact between the mobile phase and stationary phase. When hydrolyzed, the surface of a diatomaceous earth contains silanol groups (-SiOH), providing active sites that absorb solute molecules in gas-solid chromatography. 

MicrocrystaUine Silicas. Various microcrystalline (cryptocrystalline) materials such as flint, chert, and diatomaceous earth are found ia nature (see Diatomite). These may arise from amorphous silica, often of biogenic origin, which undergoes compaction and microcrysta11i2ation over geologic time. 

Filter aids should have low bulk density to minimize settling and aid good distribution on a filter-medium surface that may not be horizontal. They should also be porous and capable of forming a porous cake to minimize flow resistance, and they must be chemically inert to the filtrate. These characteristics are all found in the two most popular commercial filter aids diatomaceous silica (also called diatomite, or diatomaceous earth), which is an almost pure silica prepared from deposits of diatom skeletons and expanded perhte, particles of puffed lava that are principally aluminum alkali siheate. Cellulosic fibers (ground wood pulp) are sometimes used when siliceous materials cannot be used but are much more compressible. The use of other less effective aids (e.g., carbon and gypsum) may be justified in special cases. Sometimes a combination or carbon and diatomaceous silica permits adsorption in addition to filter-aid performance. Various other materials, such as salt, fine sand, starch, and precipitated calcium carbonate, are employed in specific industries where they represent either waste material or inexpensive alternatives to conventional filter aids. 

A crystalline form of free silica, extremely hard and inert chemically very resistant to heat. Quartz in refractory bricks and amorphous silica in diatomaceous earth are altered to cristobalite when exposed to high temperatures (calcined). Cristobalite is extensively used in precision casting by the hot wax process, dental laboratory work, and certain speciality ceramics. 

A soft, gritty amorphous silica composed of minute siliceous skeletons of small aquatic plants. Used in filtration and decoloration of liquids, insulation, filler in dynamite, wax, textiles, plastics, paint, and rubber. Calcined and flux-calcined diatomaceous earth contains appreciable amounts of cristobalite, and dust levels should be the same as for cristobalite. 

Diammonium peroxydisulphate as SoOg Diatomaceous earth, see Silica, 1 ... 

Diatomaceous earth, widely-known and long-used as a filteraid in process and waste filtrations, has a high microcrystalline silica content. As well as being a respiratory hazard in the workplace, the silica is being scrutinized in some jurisdictions as a potentially hazardous dust in landfills in which spent filter cakes are deposited. 

Diatomaceous earth A fine, siliceous (made of silica) "earth" composed mainly of the skeletal remains of diatoms (single cell microscopic algae with rigid internal structure consisting mainly of silica). Tests prove that DE leaches unacceptable amounts of silicate into the water for fish health. If used as a filter substance, a silicone removing resin should be employed afterwards. 

Amorphous free silica (Noncrystalline) Diatomaceous earth... 

Diatomaceous earth A soft, gritty amorphous silica composed of minute siliceous skeletons of small aquatic... 

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