SELF-ACCELERATING DECOMPOSITION

INFRAREDTECHNOLOGYANDRAMANSPECTHOSCOPY-INFRAREDTECHNOLOGY] (Vol 14) SADT. See Self accelerating decomposition temperature. 

An 850 kg batch of a slightly doped form of azodicarbonamide exploded violently, with a TNT equivalence of 3.3 kg, 5 minutes after sampling at the end of drying. The probable initial temperature was 65°C, the lowest self accelerating decomposition temperature 90°C, and such decomposition is not explosive. Full explosibility tests, including detonability, had shown no hazard. Further study demonstrated that slightly contained azodicarboxamide, thermally initiated at the bottom of a column or conical vessel could explode even at the 5 kg scale. The above TNT equivalence corresponds to decomposition of 4% of the available charge. The cause of the presumptive hot spot is unknown. 

An attempt to chlorinate xylene with the dichlorohy dantoin caused a violent explosion [1], The haloimide undergoes immediate self accelerating decomposition in presence of solvents. Safe conditions (including lower temperatures and progressive addition of reagent to match its consumption) can be developed for its use [2],... 

When warmed slightly above its m.p., 10°C, the ester undergoes slow but self-accelerating decomposition, which may become dangerously violent under confinement. Bulk solutions of the peroxyester (45%) in benzene-cyclohexane stored at 5°C developed sufficient heat to decompose explosively after 1 day, and 50-90% solutions were found to be impact-sensitive [1]. The solid is normally stored and transported at below -18°C in loose-topped trays [2],... 

Though regarded as one of the more stable peroxides, it becomes shock-sensitive on heating, and self-accelerating decomposition sets in at 49° C [1]. One of the recently calculated values of 46 and 42°C for induction periods of 7 and 60 days, respectively, for critical ignition temperatures is closely similar to that (4577 days) previously recorded. Autocatalytic combustion of the polymerisation initiator is exhibited. Although not ordinarily shock sensitive, it responds to a detonator [2],... 

Self accelerating decomposition (Q = 0.43 kJ/g) occurs at 130°C in closed systems, such as are used for the Bucherer reaction. 

UN Recommendations on the Transport of Dangerous Goods, Part II, Test Methods for Determining the Self-Accelerating Decomposition Temperature (SADT) of Organic Peroxides and Other Thermally Unstable Substances," ST/SG/AC. 10/11/Rev. 1, United Nations, New York, NY (1990). 

Fisher, H. G. and D. D. Goetz, "Determination of Self-Accelerating Decomposition Temperatures for Self-Reactive Substances," /. Loss Prev. Process Ind., 6, No. 3,183-194 (1993). 

Critical steady-state temperature (CSST) the highest ambient temperature at which self-heating of a material as handled (in a package, container, tank, etc.) does not result in a runaway but remains in a stationary condition (see Self-Accelerating Decomposition Temperature). 

Self-Accelerating Decomposition Temperature (SADT) the lowest ambient temperature at which a runaway decomposition is observed within seven days the test is run with unstable substances, such as a peroxide, in its commercial shipping container, and the reported result applies only for the container used. 

The decomposition of some materials into smaller, more stable molecules can be initiated by mechanical shock alone, and they are known as shock-sensitive. Many commercially important chemicals are thermally sensitive and decompose with the addition of heat. For storage situations, the critical temperature at which the thermal energy is sufficient to start an uncontrolled reaction in a particular storage configuration for a specified time is known as the self-accelerating decomposition temperature (SADT), as described in NFPA 49. 

Selenourea inclusion compounds, 14 172 Selenous acid, 22 73t, 75t, 88-89 use in selenium analysis, 22 94 Self-accelerating decomposition... 

Certain compounds, when held at moderate ambient temperatures for an extended period of time, may undergo an exothermic reaction that accelerates with increase in temperature. If the heat liberated by this reaction is not lost to the environment, the bulk material increases in temperature, which leads to an increase in the rate of decomposition. Unchecked, the temperature grows exponentially to a point at which the decomposition cannot be stopped or slowed. The minimum temperature at which this exponential growth occurs in a material packed in its largest standard shipping container is defined as the self-accelerating decomposition temperature. Self-accelerating decomposition temperature is a measure of the... 

Self-accelerating decomposition temperature (SADT), screening methods, 56 Self-reactive materials chemical reactivity hazard, 1,2 screening methods, 54-58 Seveso, Italy incident, 4 Seveso II Directive, 5-6,27 Shelf life... 

Most of the isolated diacyl (including sulfonyl) peroxides are solids with relatively low decomposition temperatures, and are explosive, sensitive to shock, heat or friction. Several, particularly the lower members, will detonate on the slightest disturbance. Autocatalytic (self-accelerating) decomposition, which is promoted by tertiary amines, is involved [1]. Solvents suitable for preparation of safe solutions of diacetyl, dipropionyl, diisobutyryl and di-2-phenylpropionyl peroxides are disclosed [2], The class is reviewed, including hazards and safety measures [3], Cyclic diacyl peroxides are more stable, but scarcely to be trusted. Individually indexed compounds are ... 

See also ACCELERATING RATE CALORIMETRY, SELF-ACCELERATING DECOMPOSITION TEMPERATURE... 

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