Retardation lime

In 1990, appioximately 66,000 metric tons of alumina trihydiate [12252-70-9] AI2O2 3H20, the most widely used flame retardant, was used to inhibit the flammabihty of plastics processed at low temperatures. Alumina trihydrate is manufactured from either bauxite ore or recovered aluminum by either the Bayer or sinter processes (25). In the Bayer process, the bauxite ore is digested in a caustic solution, then filtered to remove siUcate, titanate, and iron impurities. The alumina trihydrate is recovered from the filtered solution by precipitation. In the sinter process the aluminum is leached from the ore using a solution of soda and lime from which pure alumina trihydrate is recovered (see Aluminum compounds). 

High alkalinities of limed juice serve several functions. Foremost is to retard sucrose hydrolysis, one of the oldest reactions in the Uterature of chemical kinetics (6). Sucrose hydrolysis proceeds much more slowly at a moderately high pH than at an even slightly acidic pH. 

If the Boltzmann superposition principle holds, the creep strain is directly proportional to the stress at any given time, f Similarly, the stress at any given lime is directly proportional to the strain in stress relaxation. That is. the creep compliance and the stress relaxation modulus arc independent of the stress and slrai . respectively. This is generally true for small stresses or strains, but the principle is not exact. If large loads are applied in creep experiments or large strains in stress relaxation, as can occur in practical structural applications, nonlinear effects come into play. One result is that the response (0 l,r relaxation times can also change, and so can ar... 

Hydrated or slaked lime Ca(OH)2 is an inorganic accelerator used in the curing of fluoroelastomers. In conventional sulphur cured polymers it counteracts the retardation of cure due to the presence of acidic substances in a rubber compound. Quicklime (CaO) dispersed in mineral oil or in wax/oil is used as a dessicant to reduce porosity in vulcanisates, particularly in fluid bed curing. 

The silica fume is said to decrease the formation of ettringite by reducing the concentration of calcium (Ca" +) and hydroxyl (OH ) ions involved in the formation of ettringite [146]. The expansion of lime-based admixtures is not affected by water-reducing admixtures to the same extent as observed for CSA-based admixtures. However, set retardation may result due to the increased amounts of calcium hydroxide produced in the presence of the WRA. 

During this phase the initial self-retarding calcium silicate hydrate layer appears to break down, allowing further hydration products from the C3S and C2S phases to be formed. These appear to be produced in three morphological forms, platelike, needles and crumpled foils. During this reaction considerable quantities of hexagonal prisms of precipitated lime are also formed. 

Studies of the kinetics of the C3S hydration in the absence and presence of accelerators show that the extent or degree of hydration of the silicate phase in the presence of calcium chloride is considerably increased, right up to at least 28 days, whether measured by the quantity of lime produced [6] (Fig. 5.8), X-ray analysis [15] (Fig. 5.9), or the amount of non-evaporable water [16] (Fig. 5.10). Figure 5.8 also shows that a small amount of TEA retards the hydration of the C S phase for a considerable time, and the trend... 

Sodium bisulfite-china clay proved to be an efficient initiator for homopolymerization and graft polymerization of methyl methacrylate onto cellulose. Grafting reactions using ceric ammonium sulfate, sodium bisulfite-soda lime glass or -china clay are inhibited or retarded on adding soda lignin to the grafting medium. 

It was found that for the charcoal based squib, the transfer time was almost double the initiation dme. This large transfer time obviously takes care of the variations in the excitation timings due to different factors in the manufacture of squibs. This ensures continuous flow of current thru all the squibs connected in series until, the time the most sensitive squib breaks the circuit. In the case of LMNR and LDNOC fuseheads the transfer time was found to be quite low and the total time of some of the fuseheads was less than or equal to the excitation times of some others in the same group. Such squibs when connected in series caused failures in r.eries firing. As a confirmation to this theory, a retardant was introduced in the LMNR fuse-heads to increase the transfer lime, and no misfires were noted... 

Fig. 6-2. Conversion lime plots for normal, retarded and inhibited free radical polymerizations.

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