Self-Accelerating Decomposition Temperature (SADT)
SADT is the lowest temperature at which a self-reactive substance or organic peroxide decomposes self-acceleratingly; IMDG derives control temperatures from it.
The self-accelerating decomposition temperature (SADT) is the lowest temperature at which self-accelerating decomposition can occur for a substance in the packaging used for transport. It is determined under Part II, section 28 of the UN Manual of Tests and Criteria , and it is the figure from which the IMDG Code derives the need for temperature control and the control and emergency temperatures.
Under IMDG Amendment 42-24 (resolution MSC.556(108)), a self-reactive substance of Division 4.1 requires temperature control where its SADT is 55 °C or less (2.4.2.3.4.1), and a substance whose SADT exceeds 75 °C for a 50 kg package is not self-reactive at all (2.4.2.3.1.1). Table 7.3.7.2.6 then sets the control and emergency temperatures as fixed offsets below the SADT, from 20 °C and 10 °C below for an SADT of 20 °C or less, to 10 °C and 5 °C below for an SADT over 35 °C. The polymerizing-substance equivalent is the self-accelerating polymerization temperature (SAPT).
The full article will cover the test methods, the derivation table for packagings, IBCs and portable tanks, the organic peroxide entries of Class 5.2 , and the shipboard monitoring that follows from the figure.