Gas-forming chemicals

Blowing agents Inert gas or gas-forming chemicals injected or mixed into a compound to react during processing Production of foams and expanded plastics replacement of chlorolluorocarbons (CFCs)... 

There are two types of gas-solid interaction (a) physical adsorption, which is due to van der Waals bonds and is reversible, (b) the chemisorption, where the gas forms chemical bonds with the solid surface and results in irreversible adsorption. 

A great many sealer applications are not visible in a modem automobile body. Low viscosity, rubbery sealers are used in virtually all metal-to-metal body joints prior to spot welding. Many of these materials contain gas-forming chemicals which decompose when heated to give a foamy seal which is able to seal out moisture, air, and dirt. They also reduce galvanic corrosion. 

Physically or chemically modifying the surface of PET fiber is another route to diversified products. Hydrophilicity, moisture absorption, moisture transport, soil release, color depth, tactile aesthetics, and comfort all can be affected by surface modification. Examples iaclude coatiag the surface with multiple hydroxyl groups (40), creatiag surface pores and cavities by adding a gas or gas-forming additive to the polymer melt (41), roughening the surface... 

Numerous organic reactions of sulfur monochloride are of practical and commercial importance. Of particular importance is the reaction of sulfur monochloride with olefins to yield various types of addition products (142). With ethylene, the severe vesicant bis(2-chloroethyl) sulfide [505-60-2] (mustard gas) forms with elemental sulfur and polysulfides (see Chemicals IN war). Propylene reacts similarly ... 

General description. Porosity refers to cavities formed within the weld metal during the solidification process. Such cavities may form due to decreased solubility of a gas as the molten weld metal cools or due to gas-producing chemical reactions within the weld metal itself. At times, cavities can form a continuous channel through the weld metal (worm holes, piping), resulting in leaks (Case History 15.3). 

The time required for atmospheric chemical processes to occur is dependent on chemical kinetics. Many of the air quality problems of major metropolitan areas can develop in just a few days. Most gas-phase chemical reactions in the atmosphere involve the collision of two or three molecules, with subsequent rearrangement of their chemical bonds to form molecules by combination of their atoms. Consider the simple case of a bimolecular reaction of the following type-. 

Fire Hazards - Flash Point (deg. F) 162 OC Flammable Limits in Air (%) 1.2 - 4.9 Fire Extinguishing Agents Foam, carbon dioxide, dry chemical, water fog Fire Extinguishing Agents Not To Be Used Water spray. Do not allow water to enter containers Special Hazards of Combustion Products Highly poisonous phosgene gas forms during fires Behavior in Fire At fire temperature the... 

Chemical Reactivity - Reactivity with Water When sodium cyanide dissolves in water, a mild reaction occurs and some poisonous hydrogen cyanide gas is liberated. The gas is not generally a concern unless it is generated in an enclosed space. If the water is acidic, then large amounts of the toxic gas forms... 

Chemical engineers could also work to devise processes to improve the flow characteristics of powders after they are formed. Such research would help control agglomeration of particles in subsequent processing steps as well as facilitate the production of compacted ceramic preforms. For example, gas-solid chemical reactions might be used to tailor the chemical composition of powders. As another example, better methods of componnding powders with binders might be achieved by processes that mix powders with suitable binders in a liquid and then spray dry the resulting suspension. 

For each of the following, note if a precipitate or a gas forms. The formation of water will not be obvious. When water forms, energy is usually given off. Therefore, if no product is immediately visible, insert a thermometer into the contents of the test tube to determine if heat is released. Use the increase in temperature as evidence for formation of water. If no evidence of a chemical reaction is evident, record No Reaction in the Evidence of Reaction column of Data Table 1. 

These models refer to reactions with the simplest nucleophile, H, both under neutral conditions and in the protonated form. Chemical reactivity can be strongly altered by catalytic effects acid/base catalysis is of particular importance. We regard the studies on ga phase acidities and on proton affinities discussed in the above sections to bear special significance for quantitative modelling of acid/base catalysis in the future. 

The state of matter within these regions needs to be determined before the balance of energy and chemistry can be understood. Extreme photon fluxes break all chemical bonds, prevent molecule formation and ionise atoms but as the density of species increases the UV and far-UV photons are absorbed and molecules begin to form. Chemical reactions are, however, slow in the gas phase due to the low temperature, and molecules condense out on the surface of dust particles, perhaps forming ice grains. Once on the surface, molecules continue to be photoprocessed by the starlight as well as by the continual bombardment of cosmic rays. 

Thermal gravitational analysis (TGA) Chemical testing technique that precisely measures weight loss (due to gas forming reactions) as a function of temperature and time. 

Transition metals are used extensively as reforming catalysts and the variation in the catalytic activity can be determined by the differences in the strength of the adsorbate-surface interaction with various metals. One of the fundamental properties of a metal surface is in fact its ability to bond or to interact vflth surrounding atoms and molecules. The bonding ability determines the state of the metal surface when exposed to a gas or liquid and it determines the ability of the surface to act as a catalyst. During catalysis, the surface forms chemical bonds to the reactants and it helps in this way the breaking of intramolecular bonds and the formation of new bonds. 

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