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Foaming agents are widely used in the processing of polymer materials. The p-toluenesulfonyl hydrazide (TSH), as a foaming agent, generates foams that are fine and uniform. However, the extensive heat produced during the thermal decomposition of foaming agents greatly increases the risk throughout the process. Accidents involving TSH have caused severe economic losses of 300,000 RMB in China. In this study, a differential scanning calorimetry, adiabatic accelerating calorimeter, thermogravimetric-infrared spectrometer, and Gaussian molecular simulation software were adopted to explore the pyrolysis characteristics and decomposition mechanism of TSH and TSH containing impurities (water, urea). Experimental results indicated that the apparent activation energy of pure TSH was 173.39 kJ mol−1. The potential for explosion is high when TSH decomposed, as it releases heat and gaseous products. The addition of water or urea reduces the hazard level of TSH, but urea promotes the decomposition of TSH. The time it takes for a reaction to reach its maximum rate under adiabatic conditions (TMRad) to reach 24 h (TD24) and 8 h (TD8) was 46.8 and 56 °C, respectively. Comparing the experimental results with molecular simulations, the products of thermal decomposition of TSH include nitrogen, water, aryl disulphides, and sulphide sulphonates. [ABSTRACT FROM AUTHOR]

Methylene diphenyl diisocyanate (MDI) serves as a primary component of polyurethane in various applications, including household appliances, architectural structures, automobiles, and adhesives. A recent MDI plant explosion in China highlighted the importance of studying MDI's thermal stability and parameters to prevent accidental thermal decomposition. In this study, an extensive array of analytical techniques, including differential scanning calorimetry, thermogravimetric analysis, and adiabatic accelerating calorimeter, was employed to determine the thermokinetic constants of MDI, providing a solid foundation for further in-depth investigations. The findings revealed that MDI containing water reacts at substantially lower temperatures, while pure MDI can release heat and gases in an adiabatic environment, posing a considerable explosion risk. The kinetic constant of MDI was calculated using the Flynn–Wall–Ozawa method, yielding apparent activation energy values ranging from 51.78 to 96.70 kJ mol−1 across a conversion degree range of 0.05–0.70. The Coats–Redfern model pinpointed the kinetic reaction mechanism as a two-stage chemical process based on the apparent activation energy. Molecular optimization, following the energy minimisation principle, was conducted using Gaussian 09 software, which led to the identification of the optimal pathway for generating carbodiimide and carbon dioxide. This investigation offers valuable insights for the effective management of MDI during production, transportation, and storage, contributing to improve loss prevention practices in the industry. [ABSTRACT FROM AUTHOR]