Calcium sulphate filler

All commercial materials are based on calcium hydroxide and liquid alkyl salicylates (Prosser, Grolfman Wilson, 1982) and are supplied as a two-paste pack. Zinc oxide is sometimes added to the calcium hydroxide, as are neutral fillers. A paste is formed from this powder by the addition of a plasticizer examples include A-ethyl toluenesulphonamide (o- orp-) and paraffin oil, with sometimes minor additions of polypropylene glycol. The other paste is based on an alkyl salicylate as the active constituent containing an inorganic filler such as titanium dioxide, calcium sulphate, calcium tungstate or barium sulphate. Alkyl salicylates used include methyl salicylate, isobutyl salicylate, and 1-methyl trimethylene disalicylate. An example of one commercial material, Dycal, is given in Table 9.7, but its composition has been subjected to change over the years. 

The resulting AN solution may be handled in various ways103. It can be stored as a solution, used in down-stream plants or sold as a solution it can be formed into solid AN by prilling or granulation, or it can be mixed with a solid filler. The most common filler is calcium carbonate in the form of ground limestone, dolomite or by-product calcium carbonate. This product is known as Calcium Ammonium Nitrate (CAN) and can be prilled or granulated. Granular products that contain AN and either ammonium or calcium sulphate are also manufactured. 

Oparex 15 calcined calcium sulphate (Yesos Ibericos) was evaluated as a filler in plasticised PVC cable insulation compounds in comparison with two grades of calcium carbonate. Improvements were observed in tensile, electrical and low temperature properties, flammability and heat ageing characteristics and chemical resistance for calcium sulphate filled compounds, while no significant differences in water absorption and hydrolysis were noted. Studies of rheological properties showed improved processability in mixing and extrusion trials. URALITA... 

Calcium sulphate pellets impregnated with tobramycin are now available in a ready prepared pack and can be used with deep, severely infected ulcers in combination with systemic antibiotic treatment. The Osteoset T (Wright Medical) is a prefabricated plaster of parts pellet impregnated with tobramycin and the Bone Void Filler is available as a mixing kit allowing fabrication of pellets of various sizes and strengths. Following application the pellets remain in place and are reabsorbed over a 2-3-month period. 

Fillers may be divided into particulate and fibrous types. Particulates include calcium carbonate, china clay, talc and barium sulphate. Fillers affect shrinkage on moulding and the dimensional stability of the finished plastic, increase tensile strength and hardness, enhance electrical insulation properties and reduce tackiness. They also impart opacity and colour (Figure 3.16). Carbon black is now the most widely used filler for polymers usually in the form of furnace carbon black, which has a particle diameter of 0.08 mm. Fibrous fillers reinforce polymers and greatly increase their tensile strengths. They include fibres of glass, textile and carbon. Plastics filled with fibrous fillers are known as composites. 

Fillers are inorganic particulates used in the polymeric matrix, both to reduce the final product cost and to improve material processing and certain properties of the pultruded part. Among the most currently used fillers are calcium carbonate, aluminium silicate (cauline), alumina trihydrate (ATH) and calcium sulphate. 

The fillers described previously form the bulk of materials used in rubber applications. The list is by no means exhaustive but those that are not covered are more specialised in use. Other fillers known to be used in rubber include calcium sulphate, cork, dolomites, feldspar, graphite, lead, lithopone, magnesium carbonate, molybdenum disulphide, rubber crumbs, textile fibres (flocks), wollastonite, wood flour, zinc oxide and many others. 

Flame retardants, fillers, granite effect fillers, calcium sulphate... 

Particulate fillers are divided into two types, inert fillers and reinforcing fillers. The term inert filler is something of a misnomer as many properties may be affected by incorporation of such a filler. For example, in a plasticised PVC compound the addition of an inert filler will reduce die swell on extrusion, increase modulus and hardness, may provide a white base for colouring, improve electrical insulation properties and reduce tackiness. Inert fillers will also usually substantially reduce the cost of the compound. Amongst the fillers used are calcium carbonates, china clay, talc, and barium sulphate. For normal uses such fillers should be quite insoluble in any liquids with which the polymer compound is liable to come into contact. 

For electrical insulation china clay is commonly employed whilst various calcium carbonates (whiting, ground limestone, precipitated calcium carbonate, and coated calcium carbonate) are used for general purpose work. Also occasionally employed are talc, light magnesium carbonate, barytes (barium sulphate) and the silicas and silicates. For flooring applications asbestos has been an important filler. The effect of fillers on some properties of plasticised PVC are shown in Figure 12.21 (a-d). 

Fillers. Fillers mentioned for epoxy systems (subsection 2.2.6.4) are used in polyurethanes too. Ground calcium carbonate (coated as well as uncoated) is commonly used. Barium sulphate, silica fumes, wood flour and milled glass fibres are also used. 

Fine powder fillers, usually barium sulphate (barytes) or calcium carbonate... 

The existence of a chemical reaction between filler and coupling agent depends not just on the nature of the coupling agent but also on the filler. Silanes react readily with glass beads, metal hydroxides, clay, silica, the silicates, wollastonite, mica and various oxides, but not with calcium carbonate, carbon black or barium sulphate. 

Fillers of mineral origin are used for a variety of purposes to affect physical, mechanical, electrical properties, and the appearance. Almost every crushed and ground rock may be compounded with UP resins. Hard carbonates such as calcium carbonate, nonreactive sulphates such as barium sulphate (baryte), and some metal oxides are used as fillers, and they result... 

Inorganic fillers, such as silica, silicates, barium sulphate and calcium carbonate, are used extensively in plastics and rubbers and to be effective these are usually incorporated at a level well in excess of 5%. This means that they can easily be quantified by TGA. Other inorganic compounds are also used in most products, and these include zinc oxide (a common co-agent used in the cure system of rubbers) and titanium dioxide (a popular weight pigment). In contrast to fillers, these additives are usually only added at levels below 5% but, given that the detection limit of TGA is around 0.5%, they can still be detected and a reasonably accurate quantification performed. 

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