Silicate coatings

Inorganic salts/bases, slaked lime in, 15 65 Inorganic silicate coatings, 7 200 Inorganic surfaces, silylation of, 22 697-698, 701 Inorganic tellurium compounds, 24 417-422... 

A source for the NDMA was not found in this tannery. It was reported that they did use dimethylamine sulfate on an experimental basis and nitrosation of three of the bulk process water samples did result in the formation of 0.0015 to 0.0025 yg/ml of NDMA. We also collected three air samples using acid pH traps and after nitrosating the content, found twice the level of NDMA, thus indicating the presence of the NDMA precursor amine in the air. In a further experiment we sampled air over magnesium silicate coated with morpholine and found that from 3-20% of the 30 yg of morpholine had been converted to N-nitroso morpholine thus indicating an airborne nitrosating agent. 

BASF produces temperature-stable lead chromate pigments with a silicate coating obtained by hydrolysis of magnesium silicofluoride [3.140]... 

We will next deal with the hydrolysis reaction. Traditionally, most industrial processes used to make products containing the siloxane bond, such as silicones and silicates, involve the hydrolysis of chlorosilanes. This causes hydrochloric acid to be produced as a by-product. Hydrochloric acid is, however, an unacceptable by-product in products such as zinc-rich silicate coatings and glasses and glass ceramics made by the sol-gel process. The alternative is to use alkoxysilanes, which when hydrolyzed, have alcohols as a by-product. 

Until 1982, most alkoxysilanes had been produced from chlorosilanes and alcohols. Hydrochloric acid was therefore still a problem. In 1982, a process was developed in which TMOS could be made directly from elemental silicon and methanol [5]. In the production of silicate coatings, TMOS is first converted to TEOS by an alcoholysis reaction with ethanol. This prevents toxic methanol vapors from escaping from the curing coating. The TEOS is partially hydrolyzed with the rest of the hydrolysis occurring at the time of application. This is therefore a way to produce silicates without chlorine. (If a practical method for converting alkoxysilanes to alkylsilanes could be found, there would also be a nonchlorine method of production of silicones.)... 

The kinetics of the acid catalyzed hydrolysis of ethoxysilanes has been studied. Each of the silanes that were used had a phenyl or para-substituted phenyl group attached to the silicon atom. This permitted a study of the linear free energy relationships of this reaction. The reaction is of interest because of its role in silane coupling agent chemistry, in the preparation of zinc-rich silicate coatings, in the sol-gel process and in the preparation of silicones in general. 

A similar lamp was developed for solid elements in order to give intense light at wave lengths not included in the mercury spectrum. The situation is more difficult because the lamp cracks when the metal freezes. It is necessary then to use a new lamp for every experiment, but they are not expensive and they can be made to run for several hours. The most serious difficulty lies in the fact that these more basic metals attack the quartz at the very high temperatures forming a silicate coating which may be opaque to the ultraviolet light. The chemical combination of the metal with the silica is sufficient in a few hours to cause a considerable increase in the internal diameter. 

Singh, M.K. (2011a) XRD analysis of calcium silicate coating on titanium alloy. Indian J. Sci. Technol., 4, 1477 — 1480. 

Flow Indices for the same sand formulation, exposed to four test environments, are shown in Fig. 1. These test environments are characterized only by different relative humidity since the Flow Index for silicate coated sand is not significantly influenced by changes in temperature and anticipated CO levels in ambient air When the Flow Index of this formulation drops to 0 55, cores blown with 85psi air pressure have the minimum acceptable strength Sand with a higher Flow Index would produce more dense sand bodies and have higher strength ... 

A common method of producing foundry cores is to fluidize the coated sand and blow it into a core box using air pressure The strength of bound sand is determined in part by the bulk density of the sand body which in turn is determined by the air pressure used to blow the coated sand Core blowing tends to dry coated sand prior to forming into a sand body Consequently, water based silicate coated sand formulations must contain more moisture to allow for this production condition The amount of added water would depend on the relative humidity of the environment as well as production variables ... 

Figure L Work life of silicate-coated sand. Key (% relative humidity and 340 ppm COt) , 20% A, 60% O, 90%, loose cover over sand in 20% relative humidity environment and 97% sealed container.

The properties of sodium silicate, silicate coated sand, and of dehydrated silicate bound sand bodies have been examined in terms relevant to a foundry core process. The material and process variables of particular significance to manufacturing conditions are as follows ... 

Silicate coated sand has equipment in the casting plant. 

I. Silicate coated sand has a work life that depends... 

The expression water glass paints is understood to mean coating systems based on the binder water glass (potassium, sodium, or occasionally, lithium water glass). The general expression silicate coatings has been adopted for these systems and is therefore used throughout Section 2.15.1. 

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