Solid particle targets

The job of a chemical munition is to create a toxic environment over as much of the target as is compatible with the toxicity of its charge. It must convert its bulk load either into an even distribution of liquid or solid particles, or into a cloud of vapour, or into both. It must, additionally, do this in a certain time. These are strict demands, and they are made more severe by the diversity of chemical agents now in stockpiles. Each agent has a combination of physical characteristics and toxic behaviour that is unique but, nevertheless, all munitions work on the same basic principle they cause the transfer of energy from a store, generally an explosive, to the chemical load. The simplest chemicals to disperse are the volatile, non-persistent ones such as phosgene the hardest ones... 

Of prime importance is the initial distribution of solids at the top of the heat-exchanging apparatus. Figure 48 shows the design of the bullet-head solids distributor. Solids fed from a nearly point source fall on a bullet-shaped target, from which they bounce off to land at some distance below on a fall-breaker baffle that either straightens the particles into essentially vertical paths or redistributes them by further deflection. The contour of the bullet head is calculated from the coefficient of restitution K between its material of construction and the solid particles concerned, and from the distance of solids feed point above it, h, and the distance to the fall-breaker baffle below, H. 

Dispersion of solid particles in a polymeric matrix is another target that can be reached successfully using a purposely tailored diblock copolymer. 

Trau, D. Renneberg, R. Caruso, R Lehmann, M. Capsules encapsulating solid particles of signal-generating organic substances and their use in in vitro bioassays for detection of target molecnles in a sample. PCT Int. Appl. WO 2002012888, 2002 Chem. Abstr. 2002,136, 163679. 

Another type of pesticide formulation is a suspoemulsion (47), in which one active ingredient is emulsified and another active ingredient is included in the continuous phase as a finely divided dispersion of solid particles. Although some work has also been done on microemulsion formulations of pesticides, they tend to be too expensive and have some stability problems with temperature changes and upon dilution. Their main advantage is the enhancement of efficacy by improved transport into the target organism. 

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