Abstract of Special Research Report (SRR-83)

National Institute of Occupational Safety and Health, Japan

Special Research on Thermal Stability of Reactive Materials

Special Research on Thermal Stability of Reactive Materials

Shigeru MORISAKI, Kogaku KOMAMIYA and Michio NAITO

: In recent years, some explosions or fires occurred in fine-chemistry factories in Japan, killing some workers and causing extensive damage to plant and buildings on the site. The causes of those accidents are mostly attributable to runaway reactions or thermal explosions of reactants. The investigations of thermal hazard potential, therefore, of chemical plant or reactive materials are seemed to be essential for the prevention of these explosions or fires.
    For the study of the thermal risks of chemical processes, there are basically three aspects to be considered, they are :
  (1) Physical and chemical properties of the reaction.
  (2) Characteristics of the plant.
  (3) Way in which the process is carried out.
In this research, the chemical or physical properties of the reactants such as thermodynamics and kinetics were investigated with a differential scanning calorimeter (DSC) and an accelerating rate calorimeter (ARC).
    Thermal analysis has widely been used as screening test of the reactive materials whose thermal risks are not well known. In this analysis, very small amounts of reactants are allowed to decompose or react under a certain heating rate. Therefore, we must take into consideration the influences of heating rate or sample weight on the thermal data for the evaluation of thermal risks.
    On the other hand, the experiment under adiabatic condition may give more critical data than thermal analysis. For example, decomposition or reaction temperature in adiabatic condition will generally be low as compared with those under non-adiabatic experiment. In ARC experiment, the thermal data such as self-heat rate, adiabatic maximum temperature, and time to maximum reaction rate are able to obtain with the pressure data such as maximum pressure and pressure rate at the same time. Therefore, adiabatic data such as ARC data may be very useful for the evaluation of chemical hazards of plant or reactive materials.
    In this report, the thermal decompositions of about thirty reactive materials were carried out using ARC and DSC to see their thermal stabilities. These figures are shown in the appendix with the fifty case histories of explosions by reactive materials. Moreover, the theoretical considerations on these calorimetries are given in the text to be able to estimate the thermal hazards of these materials.

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