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Predecitive methods for determining the thermal decomposition properties of hazardous substances
(2017)
For substance classes like organic peroxides and self-reactive substances a model should be developed to predict thermal decomposition properties like the Self-Accelerating Decomposition Temperature (SADT). The applied Quantative Structur-Property Relationship (QSPR) model correlates the molecular structur with the properties of the substances, whereby a consolidated database is a precondition for a reliable model and finally for the prediction.
We present our results on the comparison of two methods for the SADT determination. Both methods, UN test H.1 and UN test H.4 are recommended by the international transport regulations from the UN. But during the last years the applicability of the UN test H.4 has been questioned for solid substances. Therefore, three organic peroxides and one self-reactive substance have been investigated in 5 kg and 20 kg packages as well as in the UN test H.4 in a 500 mL Dewar vessel. The SADT values determined with the different methods match. The UN test H.4 seems to be well suited for solid organic peroxides and self-reactive substances of at least 20 kg or 60 L.
We present our results on the comparsion of two methods for the SADT determination. Both methods, UN test H.1 and UN test H.4 are recommended by the international transport regulations from the UN. But during the last years the applicability of the UN test H.4 has been questioned for solid substances. Therefore, three organic peroxidesand one self-reactive substance have been investigated in 5 kg and 20 kg packages as well as in the UN test H.4 in a 500 mL dewar vessel. The SADT values determined with the different methods match. The UN test H.4 seems to be well suited also for solid substances at least for 20 kg or 60 L.
Predictive Methods for Determining the Thermal Decomposition Properties of Hazardous Substances
(2019)
Due to the fast development and availability of computers, predictive approaches are increasingly used in the evaluation process of hazardous substances complementary to experiments. Their use was recommended as alternative to experimental testing by the REACH regulation to complete the lack of knowledge on properties for existing substances that must be registered before 2018 (upon quantities). Among the proposed predictive approaches, Quantitative Structure Property Relationships (QSPR) are powerful methods to predict macroscopic properties from the only molecular structure of substances. In that context, the HAZPRED project (2015-2018, founded by the SAF€RA consortium) aims to develop theoretical models (e.g. QSPR) and small-scale tests to predict complex physico-chemical properties (e.g. thermal stability, explosivity) of hazardous substances to complete the lack of knowledge on these hazardous substances quickly or to understand their decomposition behaviour better. In particular, this contribution will present the work done in this project on the physical hazards of organic peroxides and self-reactive substances: gathering of existing experimental data, new experimental campaigns, review of existing models and proposition of new estimation methods.
IGUS is the International Group of Experts on the Explosion Risks of Unstable Substances. IGUS was established in 1962 with the objective to harmonize test methods used by different countries to identify and quantify the explosive properties of unstable materials. Over the years, IGUS has continued to offer scientists, who are advisers to their governments, and others, a forum to exchange data and information. The Energetic and Oxidizing Substances (EOS) working group as a sub-group of IGUS is dealing with test methods, Classification and safety aspects relating to organic peroxides, self-reactive substances and other energetic substances, fertilizers, ammonium nitrate and oxidizers.
The EOS working group holds an annual meeting alternating between Europe, the United States and Japan. The 2011 meeting took place from the 27th to the 29th of April 2011 at the Madison Hotel in Washington, D. C. The meeting was hosted by the Organic Peroxide Producers Safety Division (OPPSD) of the Society of Plastics Industry, Inc. (SPI). This was the fourth EOS meeting held in the USA since 1994. Of particular importance is the fact that 39 colleagues from authorities, universities, research institutes and industries attended the meeting. The delegates came from USA, Canada, China, France, The Netherlands, Norway, Sweden, Italy, Japan, United Kingdom and Germany. This confirms the breadth and scope of this forum and the value the participants associate with being able to contact other colleagues from around the world enabling the effective exchange of scientific results and discussion on the wide-ranging Problems concerning energetic and oxidizing materials.
Bronopol (2-Bromo-2-nitropropane-1,3-diol) is classified since many years as a substances related to self-reactive substances according to the international regulations on the transport of dangerous goods (UN 3241, Division 4.1, Packing Group III). Based on all new test results and according to the principles of the UN Recommendations, Bronopol is not an explosive according to UN TDG (Class 1) and GHS Chapter 2.1 and is also not a self-reactive substance (SADT > 75 °C). Listing of Bronopol under 2.4.2.4.2 (UN model regulations) appears not to be justified compared to Musk Xylene, Azodicarbonamide and Isosorbid-5-mononitrate.
Self-reactive substances are unstable chemical substances which can easily decompose and may lead to explosion in transport, storage, or process situations. For this reason, their thermal stability properties are required to assess possible process safety issues and for classification purpose. In this study, the first quantitative structure–property relationships (QSPR) dedicated to this class of compounds were developed to predict the heat of decomposition of possible self-reactive substances from their molecular structures. The database used to develop and validate the models was issued from a dedicated experimental campaign on 50 samples using differential scanning calorimetry in homogeneous experimental conditions. QSPR models were derived using the GA-MLR methods (using a genetic algorithm and multi-linear regressions) using molecular descriptors calculated by Dragon software based on two types of inputs: 3D molecular structures determined using the density functional theory (DFT), allowing access to three-dimensional descriptors, and from SMILES codes, favoring the access to simpler models, requiring no preliminary quantum chemical calculations. All models respected the OECD validation guidelines for regulatory ac
ceptability of QSPR models. They were tested by internal and external validation tests and their applicability domains were defined and analyzed.
Self-reactive substances are unstable chemical substances which can easily decompose and may lead to explosion. For this reason, their thermal stability properties are required within regulatory frameworks related to chemicals in order to assess their hazardous properties. Due to the fast development and availability of computers, predictive approaches like QSPR models are increasingly used in the evaluation process of hazardous substances complementary to experiments.
In that context, the HAZPRED project (2015-2018) aimed to develop QSPR models to predict physical hazards of substances to fill the lack of knowledge on these hazardous substances quickly.
An experimental campaign, based on 50 samples provided by Industrial producers, was carried out on potential self-reactive substances, for which no QSPR model already existed. Their heats of decomposition were characterized using differential scanning calorimetry in homogeneous experimental conditions.
QSPR models were derived using the GA-MLR method (using a genetic algorithm and multi-linear regressions) using molecular descriptors calculated by Dragon software based on both 3D molecular structures from density functional theory (DFT) optimizations, to access three-dimensional descriptors, and SMILES codes, favoring the access to simpler models, requiring no preliminary quantum chemical calculations. All models respected the OECD validation guidelines for regulatory acceptability of QSPR models. They were tested by internal and external validation tests and their applicability domains were defined and analyzed.
If improved models should be expected with larger database (and a better ratio between size and chemical diversity), these first models already represent a screening tool capable to access early reactive hazards.
Predictive Methods for Determining the Thermal Decomposition Properties of Hazardous Substances
(2019)
Due to the fast development and availability of computers, predictive approaches are increasingly used in the evaluation process of hazardous substances complementary to experiments. Their use was recommended as alternative to experimental testing by the REACH regulation to complete the lack of knowledge on properties for existing substances that must be registered before 2018 (upon quantities). Among the proposed predictive approaches, Quantitative Structure Property Relationships (QSPR) are powerful methods to predict macroscopic properties from the only molecular structure of substances.
In that context, the HAZPRED project (2015-2018, founded by the SAF€RA consortium) aims to develop theoretical models (e.g. QSPR) and small-scale tests to predict complex physico-chemical properties (e.g. thermal stability, explosivity) of hazardous substances to complete the lack of knowledge on these hazardous substances quickly or to understand their decomposition behaviour better.
In particular, this contribution will present the work done in this project on the physical hazards of organic peroxides and self-reactive substances: gathering of existing experimental data, new experimental campaigns, review of existing models and proposition of new estimation methods.