Chemically Unstable Materials Decomposition and Polymerization

Decomposition and polymerization of materials which release energy are considered as hazardous they are treated following [28]. The groups of materials with propensity to decomposition at ambient temperature are 

Materials are called self-reactive, if they have a propensity to violent exothermic decomposition at temperatures above ambient or by contact with impurities. These are mostly materials with sensitive nitrogen-nitrogen groups in the molecule. 

Organic peroxides are materials which contain the bivalent peroxo-(O-O-) structural element and may be regarded as derivatives of hydrogen peroxides with one or both hydrogen atoms replaced by organic rests. They can already decompose exothermically at ambient temperature. The decomposition may be caused by heat, contact with impurities (e.g. acids and heavy metal compounds), friction or impact. 

Whilst materials decompose by breaking up into smaller entities, the uncontrolled polymerization leads to the formation of large molecules, the polymers, and to a temperature rise if the heat of reaction is not removed sufficiently. The rate of heat removal decreases the larger the molecules become during the progressing polymerization. Table 2.20 provides an overview of the quantities of heat released by the aforementioned reactions, which by the way can also act as sources of ignition. 

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