Mechanical strength effects

Pyrotechnic mixtures may also contain additional components that are added to modify the bum rate, enhance the pyrotechnic effect, or serve as a binder to maintain the homogeneity of the blended mixture and provide mechanical strength when the composition is pressed or consoHdated into a tube or other container. These additional components may also function as oxidizers or fuels in the composition, and it can be anticipated that the heat output, bum rate, and ignition sensitivity may all be affected by the addition of another component to a pyrotechnic composition. An example of an additional component is the use of a catalyst, such as iron oxide, to enhance the decomposition rate of ammonium perchlorate. Diatomaceous earth or coarse sawdust may be used to slow up the bum rate of a composition, or magnesium carbonate (an acid neutralizer) may be added to help stabilize mixtures that contain an acid-sensitive component such as potassium chlorate. Binders include such materials as dextrin (partially hydrolyzed starch), various gums, and assorted polymers such as poly(vinyl alcohol), epoxies, and polyesters. Polybutadiene mbber binders are widely used as fuels and binders in the soHd propellant industry. The production of colored flames is enhanced by the presence of chlorine atoms in the pyrotechnic flame, so chlorine donors such as poly(vinyl chloride) or chlorinated mbber are often added to color-producing compositions, where they also serve as fuels. 

Concrete and fiberglass vaults are often used, although they can be subject to environmentally induced cracks. Soil and clay liners are not allowed. Flexible hner systems have been developed that may be a cost-effective and environmentally sound alternative. State-of-the-art liner technology has overcome many of the previous problems with seams, low mechanical strength, and chemical resistance. 

The venting capabihty EF and therefore the effective vent area of the explosion door is normally smaller than the capabihty of a plastic or aluminum foil rupture disk with the same area. Therefore, such devices need testing to determine the mechanical strength before actual use, and the venting capability or the pressure rise, respectively. 

Graphitic corrosion is a slow corrosion process, typically requiring many years to effect significant damage. Complete penetration of thick cross sections has, however, occurred in as little as 2 years in adverse environments. On the other hand, cast iron components can be found in use in Europe after 160 years of service. Although graphitic corrosion causes a substantial reduction in mechanical strength, it is well known that corroded cast iron, when sufficiently supported, may remain serviceable when internal pressure is low and shock loads are not applied. 

A composite separating agent has been produced by filling soft gels such as dextran and a agarose, which have poor mechanical strength but effectively... 

The conductivity of gelled electrolytes is determined primarily by the liquid and salt components. High liquid content, of the order of 40 percent, is required to attain conductivities comparable with those of the corresponding liquid electrolyte. At these liquid loading levels there is often insufficient mechanical strength, and although this effect may not be noticeable on 1-2 cm2 laboratory cells, it is certainly evident on scale-up [111]. Polymer blends such as PEO-MEEP are much more mechanically stable than MEEP itself and more conductive than PEO but there is little overall improvement of the room tern-... 

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