Homogeneity degree, mixing

In both explosives and propellants the materials are relatively non-porous. The binders and plasticizers used effectively fill the pore spaces. Pyrotechnics are porous and the heat transfer related to the hot gas permeation into the reactant material mixture becomes important. In many pyrotechnics no binders or plasticizers are used. The explosives and propellants have burning (or detonation) rates that depend on density, temperature, and pressure. However, the burning rates of pyrotechnics are, in addition, affected by porosity, particle sizes, purity, homogeneity (degree of mixing), and stoichiometry (fuel or oxidizer ratio). 

Equations 6.2 and 6.3 can be used to calculate mixing indices defined by Equation 6.1. Another suggestion for the characterization of degree of homogeneity in mixing of powders has been reviewed by Boss (1986), with the degree of mixing M3 defined as... 

Several types of information can be obtained by multinuclear solid state NMR, such as stmctural homogeneity, degree of condensation of the inorganic species, presence of mixed X-O-Y linkages in case of mixed oxide compositions, phase separation and polymerization of the organic functional groups. 

Uniformity of Mixture The proper type of mixer shoiJd be chosen to assure the desired degree of batch homogeneity. This cannot be compromised for other conveniences. Information is given under Types of Solids-Mixing Machines about the special abilities of various lands of machines to blend different types of materials. 

The eoneept of a bateh reaetor assumes that the reaetion is instantaneously eharged (i.e., filled) and perfeetly homogenized in the reaetor. Also, its temperature is immediately adjusted to that of the heat transfer medium. Therefore, the ehemieal reaetion takes plaee at the temperature of the heat transfer medium under perfeet mixing. The proeess is stopped as soon as the degree of eonversion is aehieved. 

Mixing of fluids is necessary in many chemical processes. It may include mixing of liquid vith liquid, gas with liquid, or solids with liquid. Agitation of these fluid masses does not necessarily imply any significant amount of actual intimate and homogeneous distribution of the fluids or particles, and for this reason mixing requires a definition of degree and/or purpose to properly define the desired state of the system. 

With all mixers, however, it is necessary to establish that an acceptable degree of homogeneity has been reached. Quantitative methodologies for establishing an index of mixing or efficiency of mixing are reported in the literature [94]. 

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