The rate of mechanical shear degradation of a 10% solution of Vistanex B‐100 polyisobutene (viscosity‐average molecular weight 1,740,000) in cetane has been studied at 60 and 80°C. at high rates of shear. The rate constants for the reaction at a given rate of shear energy application are found to decrease with temperature in this range. This result is interpreted as arising from a decreased efficiency at higher temperatures in the process of temporarily concentrating mechanical energy by means of intermolecular entanglements. The energy input requirements for degradation are found to increase with temperature.
Nitrogen compounds have been identified in the decomposition products from several commonly used foundry sand binders. These compounds include nitrogen oxides, hydrogen cyanide, ammonia, simple aromatic amines, and isocyanates. The concentrations of these compounds in foundry mold emissions do not appear to be directly related to the nitrogen content of the organic binders. Measurable concentrations were observed in some cases, indicating the necessity for periodic, monitoring in the foundry. Adequate ventilation will permit the use of these binders. The substitution of nitrogen-free binders suggests another possible control strategy.
The kinetics of the degradation of polyisobutene in cetane solutions produced by mechanical shearing action in a capillary has been studied as a function of rate of shear energy application and of concentration. The initial rate constant, k, for the degradation was determined as the initial rate of bond cleavage per unit concentration by weight. Log k was found to be a linear function of the reciprocal of the rate of shear energy application per unit volume, J. At all concentrations studied in the range 5–20 weight per cent, log k was the same function of 1/J, but such a plot for 3% solutions had a much greater negative slope. This indicates a decreased efficiency for the concentration of mechanical energy by the polymer molecules in less concentrated solutions.
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