Lead exposure concentrate production, contaminant

Since a reaction product catalyses the reaction, the initial concentration of product also has a strong effect on the TMRad. In the case illustrated in (Figure 12.6), an initial conversion of 10% leads to a reduction of the TMRad by a factor of 2. This also has direct implications for process safety the thermal history of the substance, that is, its exposure to temperature for a certain time increases initial product concentration, leading to effects comparable to those illustrated in Figure 12.5. Hence it becomes obvious that substances showing an autocatalytic decomposition are very sensitive to external effects, such as contaminations and previous thermal treatments. This is important for industrial applications as well as during the experimental characterization of such decompositions the sample chosen must be representative of the industrial situation, or several samples must be analysed. 

These effects are less apparent to the manufacturer than to the end user of the polymer dispersion, but they must not be overlooked. Both the foul odours, particularly from hydrogen sulphide, and the actual presence of microbial spores can have a serious effect on man. Hydrogen sulphide levels in contaminated products have never been shown to reach toxic concentrations but even very small amounts can render a product unsaleable. In both of these examples there are strict guidelines on occupational exposure. In the case of microbial spores, overexposure can lead to respiratory disorders and asthmatic symptoms. 

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