JNIOSH

Abstract of SD-89

National Institute of Occupational Safety and Health, Japan

DSC Data for Reactive Chemical Substances (2)

SD-89
Takayuki ANDO, Yasuhiro FUJIMOTO and Shigeru MORISAKI

: In recent years, the hazard evaluation of chemical substances has become important in chemical industries because chemical accidents such as explosion or fire have occasionally occured in batch process industries in Japan. These accidents are mostly attributable to thermal hazards such as runaway reaction or thermal decomposition of unstable chemicals in the processes of reaction, distillation or drying.
    The chemical industries in Japan have a tendency to produce more keenly fine-chemicals including Pharmaceuticals and functional resins. The production of these chemicals is usually carried out by a varied and small quantity type process to enhance the value of the chemicals in which many kinds of chemicals may be used without a full investigation of chemical hazard characteristics. Therefore, the potential hazards of chemicals including raw materials, intermediates, and finished goods may be increased in connection with the increase of unreliability for the installations and operations.
    In this report, 358 chemicals in which functional groups such as nitro or azo group are contained in the molecules were allowed to decompose mostly in inert gas atmospheres using differential scanning calorimetry (DSC : Du Pont 910 pressure DSC). In most cases, samples weighing about l-2mg were sealed in an aluminum cell with a pin-hole on the lid, and enviroments were pressurized with argon gas up to around 34kg/cm2G. Heat rate was 10 °C/min.
    The data obtained are exothermic onset-temperature, decomposition heat, maximum exothermic accelaration and so on. As is well known, the exothermic onset-temperature are influenced by heat rate which gives lower decomposition temperature with lower heat rate. Moreover, adiabatic effect which decrease the decomposition temperature must also be considered when a large amount of sample is treated. On the other hand, the decomposition heat by DSC is also affected by sample weight or sample phase. In particular, volatile sample tends to evaporate during heating even in the pin-hole cell under pressure gas atmosphere, and consequently the decomposition heats measured from DSC curves have a tendency to show lower values. Therefore, these factors must be taken into consideration when one apply these data to a practical state.

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