Self-reactive Substances

Type A According to the results of tests in the UN Recommendations on the Transport of Dangerous Goods, Manual of Tests and Criteria, Part II and the application of the decision logic under Section 2.8.4.1. 

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Explosibility—detonation of pure substance not likely, deflagration cannot be excluded Thermal Stability/Runaway Potential—high energy compound, additional testing required Reactivity—self-reactive substance... 

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). 

Self-reactive substances (polymerizing, decomposing, rearranging)... 

If you are certain that NO self-reactive substances are present, then proceed to the next question (Question 12). If you are uncertain as to whether a material is self-reactive, a chemist or other expert should be consulted. Annex E to NFPA 704 (2001) gives a method for calculating an "instantaneous power density," defined as the product of the enthalpy... 

Self-reactive substances (aliphatic azocompounds, aromatic sulphohydrazides, N-nitroso compounds, diazonium salts), n.o.s. 3031, 3032... 

In the latter half of Chapter 3, standard testing methods are introduced which are applicable to the evaluation of self-reactive substances. As stated previously, methods already known and described in "Safety of Reactive Chemicals" 3 5 are briefly mentioned. Primarily methods developed after the publication of "Safety of Reactive Chemicals" are explained in this book, and all the methods 2 c adopted under the Japanese Fire Services Law are described. 

A reactive chemical is a substance which may cause fire or explosion by reacting with itself or with other substances. Reactive chemicals are divided into two categories self-reactive substances and reactive substances with other materials. 

Self-reactive substances are those which can initiate exothermic decomposition without reacting with oxygen in the air, causing rapid gas generation and deflagration leading to combustion or explosion. Self-reactive substances are occasionally called unstable substances because many of them experience thermal decomposition at a relatively low temperature. Recently the term "self-reactive substance" has been used as an official term both in Japan and abroad. 

Explosive substances (Self—reactive substances and products which contain self-reactive substances and may explode)... 

Two conditions can give rise to the spontaneous combustion of a fuel. One condition involves contact of the material with air. The other is the spontaneous ignition of an unstable self-reactive substance when it is kept at a sufficiently high temperature. Silane (SiH 4 ) and phosphine (PH 3 ) are the examples of the former case, and a mixed atmosphere of air and nickel carbonyl(Ni(CO) 4 ) or carbon disulfide (CS 2 ) are examples of the latter. 

The U.N. classification scheme defines flammable solids as solids, other than those classed as explosives, which under conditions encountered in transport are readily combustible, or may cause or contribute to fire through friction. The category includes self-reactive substances and wetted explosives. 

On the other hand, the Japanese Fire Services Law defines flammable solids as solids which tend to bum easily in the air, excluding self-reactive substances. 

Organic peroxides are thermally unstable substances which may undergo exothermic self-accelerating decomposition. The Japanese Fire Services Law has revised its classification to regulate organic peroxides as self-reactive substances. 

Although progress has been made in methods of evaluating hazards for self-reactive substances, further improvement is required on the international level. To insure safety, one needs to take the measures which are consider the best for each specific occasion. The flow chart shown in Fig.1.1 has been suggested by people involved with safety to evaluate whether new substances are hazardous reactive chemicals. 

A new method has recently been developed using DSC to predict whether a self reactive substance has the ability to propagate an explosion (See Chapter 3) 1 >. In this method, by plotting the log of QDSC against the log of (TDSC-25), the ability of a substance to propagate an explosion can be judged by seeing on which side of a certain line the plot falls (See Fig. 1.2.). 

The OECD—IGUS (Organization for Economic Cooperation and Development International Group of Experts on the Explosion Risks of Unstable Substances) has 4 working groups, three of which are related to self—reactive substances ... 

These were supposedly chosen as subjects of research because of their use in large quantities and because of the history of accidents involving them. In the following sections, accidents with self—reactive substances, including those listed above, will be described. 

Ammonium nitrate, both an oxidizer and a self—reactive substance, is still used in fertilizers and as a raw material for explosives. The following two are typical accidents involving ammonium nitrate. 

Organic peroxides belong to a group of relatively new self-reactive substances, which, having a broad application as polymerization initiators, have grown with advances in petrochemistry. 

Accidents of classical self-reactive substances have been described in previous sections, and those of newer ones are introduced below. 

The heat of decomposition and the extrapolated decomposition temperature of self—reactive substances are determined by DSC (or DTA), and fire and explosion hazards may be estimated from these parameters. 

When a boundary propagational—substance is a mixture of a self-reactive substance and an inert substance in a pure form, the SC-DSC measurement is made on the pure self—reactive substance, and the value obtained by multiplying the value of Qdsc by the ratio of the amount of the self-reactive substance to the boundary substance may also be used as the value of Qdsc for the boundary substance.Tosc is not changed by dilution. A5.2 Estimation of SADT... 

At Nanba laboratory, Professor Nanba was the predecessor of Professor Yoshida. A DSC apparatus was purchased with a Government subsidy for aiding scientific research in the early 1970 s. To determine the thermal decomposition characteristics of unstable substances, the literature was surveyed 1 in collaboration with S.Takeyama (Kinki University), then a student in the master s course of The University of Tokyo. As a result, DSC was found to be of very wide application. Moreover, a preliminary experiment showed that sealed cells were necessary for studying the decomposition reaction of self—reactive substances. For most self—reactive substances, evaporation or sublimation may occur before exothermic decomposition during DSC measurement made in an open cell at room temperature. This makes it impossible to measure an accurate heat of decomposition. 

A study of the kinetics of thermal decomposition reactions using pentaerythritol tetranitrate(PETN), a high explosive, as the model substance was first conducted by SC-DSC. In this study, information was obtained that was relative to the characteristics of the DSC technique. However, the question as to how the results of analyses of this type were useful for practical work arose, and studies in this area were stopped. Subsequently, studies have proceeded on the evaluation of hazards by collecting as much data on self-reactive substances as possible. 

In the beginning, the authors made SC-DSC measurements on combination explosives R>. The report on these measurements was translated into English at the U.S. Department of Energy. We have been consulted by several companies with respect to the evaluation of hazards of self—reactive substances. In these instances, we have inevitably referred to SC-DSC data. 

The pressure—proof capability of a sealed cell has limitations, and the pressure generated in a sealed cell depends on the amount of gas produced by the substance being tested. The amount of sample for typical self—reactive substances is thus confined to 1 to 3 mg. This is an advantage of the SC-DSC method in that safety is ensured and that a trace amount of sample suffices. In contrast, the difficulty of accurately weighing a sample and the occurrence of relative errors are problems. Moreover, no correct exothermic peaks may be obtained if the amount of sample is too small. 

As has been discussed, several requirements must be met to predict the explosiveness of self-reactive substances on the basis of the results of measurements by SC-DSC. First, a leak-free sealed cell must be used that is sufficient pressure-proof. Such cells are available from Nippon Kayaku Co. and Seiko Instruments Inc. Next, correct peak areas must be measured. Determination of correct exothermic peaks is one requisite for this purpose, and it is necessary to acquire some experience in this task. 

An SD-DSC test is highly useful for screening the danger of explosion of self-reactive substances. When the result of an SD-DSC test lies in the border zone between the explosive and nonexplosive regions, however, a more reliable standard propagational test should be conducted to determine which quality is accurate. 

Ease with which ignition or explosion occurs upon impact for relatively sensitive self-reactive substances. 

Three kinds of substances are ranked according to their ignitability flammable solids, mixtures of oxidizers and flammable substances, and self—reactive substances. 

The possibility of a deflagration-to-detonation transition (DDT) exists if a large quantity of a self-reactive substance is burned. Non—detonatable substance do not display this hazard. The possibility of detonation can be evaluated by the 50/60 steel tube test. We have performed a 50/60 steel tube test for mixtures of crystalline potassium perchlorate and HCH with large—sized sawdust. The result are shown in Table 3.19 and Fig.3.32. 

If an unstable substance or self-reactive substance in a tank or drum meets with a fire during storage or transportation, it begins to decompose with the heat conducted through the container. When the thermal decomposition is severe, an explosion or bursting may occur, causing damage. 

In Japan, the Fire Services Law(FSL) has recently been revised 1011 and a pressure vessel test has been newly stipulated as the test method for determining the pyrolytic severity of Dangerous Goods- Class 5 Self—Reactive Substances—set forth in the FPL 31 . In this section a description will be given of the procedure for pressure... 

Pressure vessel test (L) Classification test for FFL class 5 Dangerous Goods (Self—reactive substances)... 

For self—reactive substances typical dangerous reactions are detonation, deflagration... 

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