Development and evaluation of a new screening workflow for the determination of the self-accelerating decomposition temperature of solids

Abstract

According to the UN (United Nations) recommendations for the transport of dangerous goods self reactive substances need to be identified and classified with a suitable temperature for transportation, the so-called self-accelerating decomposition temperature (SADT). Several test methods (H.1-H.4) are suggested by the UN for the determination of the SADT1. The suggested tests are inappropriate for many practical situations as they require a large amount of test substance, a significant experimental effort and the tests are hazardous with regard to laboratory safety2. Thus, the quantity of performed tests should be reduced to an absolute minimum. This is achievable if these tests could be limited to critical substances that are expected to have an SADT value below the 75 °C threshold for a 50 kg package, as defined by the UN. Hence, the development of a screening workflow, which is able to identify such critical substances is required.

Such screening methods already exist, but they are often based on a single calorimetric principle and were not validated consequently. Here we present a new screening workflow to determine the SADT, by combining accelerating rate calorimetry (ARC) and differential scanning calorimetry (DSC). The experimental data were evaluated using nth-order kinetic combined with the Semenov model. The results of this screening workflow are validated for twelve solid compounds with data obtained from the H.2-adiabatic storage tests. The H.2-adiabatic storage tests were performed by an iso-certified reference laboratory. All of the twelve evaluated solid compounds were accurately categorized above or below the 75 °C threshold value. Furthermore, the new screening workflow identifies and flags substances with potentially autocatalytic decomposition kinetics. To our knowledge, we offer the first free, validated, standalone ready-to-use screening workflow for the categorization of solid compounds according to the 75 °C SADT threshold value. The workflow is implemented in MATLAB with an open source code. This enables further validation and development of this workflow towards a best practice method for the categorization of substances according to the 75 °C SADT threshold value.