I've been working on acyclic, cyclic, and oligomers of organic peroxides for the last three years. Although all literature reports do mention that these are potentially explosive, there aren't many references in which the authors determined explosive potential. On several occasions I myself found these compounds to behave explosively. We have done calorimetry experiments, TGA, DTA, and DSC for thermal stability. However, I was wondering if the decomposition of such compounds liberating large amounts of energy and heat could be accurately measured and used in some way to benefit us.
You can measure the enthalpy of thermal decomposition and activation energy of the reaction by DSC.
Dear colleague,
Relevant test methods to determine explosive properties of organic peroxides you fin in the UN Recommendations on the Transport od Dangerous Goods, Manual of Tests and Criteria (http://www.unece.org/trans/danger/publi/manual/manual_e.html). If you look also to my list of papers at Reseachgate you will find additional information.
Regards, Klaus Wehrstedt
Using Differential Scanning Calorimetry will give activation energy, quantity of heat librated and thermal kinetic model.
Regards
With a Calorimetric Bomb you will measure it for sure, as well as with a DSC.
DSC/TGA is a great suggestion. It will not tell you directly about the tendency to explode but it will give you an estimate of the potential energy. In addition, an often overlooked use of DSC/TGA is to help you estimate a working temperature range that will hopefully allow you to avoid a self-accelerating decomposition in a reaction flask.
Small quantities (e.g., 10-20 mg) of solid peroxides can be tested for shock sensitivity simply with a hammer and a concrete surface. Use eye protection, etc. This is a low-tech version of a falling weight test used to rate sensitivity of explosives. However, this test will usually not reveal the latent danger of liquids or low-melting solids (for example, most ozonides). Also, be extremely careful about "digging" for crystals out of a larger stock. For the acetone peroxides and similar molecules, this act alone could detonate the entire stock.
Finally, before make something, calculate the "active oxygen" content, the mass of the extra or "peroxidic" oxygen divided by the molecular weight of the entire compound. For example, H2O2 has active oxygen content of 16/34 or nearly 50%. Low active oxygen content does not guarantee safety (more below) but can help predict danger, particularly within a class. For example, Me-OOH has an active oxygen content of 33% and spontaneously detonates. Hexyl hydroperoxide has 13% active oxygen and is moderately safe in small amounts. An eighteen carbon hydroperoxide has an active oxygen content of app. 5%; you probably couldn’t trigger an explosion even if you tried.
Below is the chart we use in my lab in assessing "first approach" to new peroxides.
Active Oxygen
15% Assume the worst unless you have direct knowledge of the safety of the molecule. Carry out all procedures as if the material could detonate without warning. (t-Butyl hydroperoxide is an example of a molecule that is somewhat of an exception to the last. It has a high A.O. rating and can be dnagerous, but doesn't tend to have problems under most conditions.
Overall, enjoy peroxide chemistry but be very careful. The O-O bond is weak and most O-element bonds are strong, so decompositions are usually associated with large amounts of energy. Solutions of peroxides are nearly always safer than neat liquids and almost always safer than dry solids, which are often very shock sensitive.
Below I put the link for TNT explosive power which contains useful information as the reference list.
http://en.wikipedia.org/wiki/TNT_equivalent
My answer is more general, but it can be applied to your product.
An explosion / detonation of a chemical compound occurs when you have three components
oxidiser, fuel and an initiation means
Initiation means(stimulus) for explosive materials are the following ones
■ Friction
■ Impact
■ Static
■ Heat
The above stimulus are known as FISH.
DSC, etc provide heat stimulus.
For friction, there are special instruments where the sample is placed on top of a sand paper and then the sample undergoes friction by a swinging sand paper.
For impact test, a weight is dropped on the sample at different height and the 50% of sample initiation is the parameter measured
Static - I do not remember how this test is done
The above test use mg size samples. The test are quite useful for primary explosives (lead azide, mercury fulminate, etc)quite sensitive), for most of high explosives (PETN, TNT, RDX, etc). However for secondary explosives (which show non ideal detonation), the test are different. Impact is done in tubes of different diameter and the velocity of detonation is measured.
My suggestion is that you measure the impact and friction sensitivity of your samples. I know of two accidents where students scratched the bottom of a flask, trying to remove the synthesized compound and the compound exploded. DSC / TGA will not help to determine the impact friction sensitivity. For impact you can do a rough test using a hammer (like Patrick Dassault recommended) but do it in steel - steel surface, as steel is able to deliver energy (the stimulus) in a very short time. Concrete and plastic take longer time to deliver the stimulus and will produce false results (no detonation / explosion).
Always work with small amount of product for the tests and when the tests give you the assurance that with that small amount nothing happens, you can scale up (a bit larger amount could be used). A pass on any of the test does not means that with large amount will pass too. They may fail.
I hope this help
Miguel
Hello,
For me the best choice is the bomb calorimeter. It has the advantage to be more robust than the DSC or TGA measurments.
Good luck and be carefull !
Dear Colleague, Sorry, in our crime scene investigation (CSI) and forensic analysis we had no experience with peroxides misuse, until now. So, I can only generally propose use set of the methods and techniques described in Chapter 3.3.2 Sensitivity of Explosives to Heat, Impact, Friction, Spark and Shock in "High Energy Materials: Propellants, Explosives and Pyrotechnics" writen by J.P. Agrawal (2010).
In a brief research carrier I’ve realized that taming the oxidation potential of these acyclic aliphatic peroxides and their oligomers is rather difficult especially w.r.t to explosion. I’ve observed explosion several times while working on one of the schemes. I’ve done DSC and TG-DTA, which as Patrick Sir (from University of nebraska) rightly said does not tell anything about the tendency to explode.
Thank you all for the suggestions.
Stay safe while enjoying the oxidation potential and doing peroxide chemistry.
The American Society for testing and Materials (ASTM) has numerous test protocols for explosion potential and hazards. I suggest you read their protocols to better understand what is considered standard practice. Below is one example. They also have standards specific to peroxides. Their web site is www.astm.org and their search feature is quite efficient.
ASTM E1231-10 Standard Practice for Calculation of Hazard Potential Figures-of-Merit for Thermally Unstable Materials
Active Standard(Latest Version)
1.1 This practice covers the calculation of hazard potential figures-of-merit for exothermic reactions, including: (1) Time-to-thermal-runaway, (2) Time-to-maximum-rate, (3) Critical half thickness, (4) Critical temperature, (5) Adiabatic decomposition temperature rise, (6) Explosion potential, (7) Shock sensitivity, (8) Instantaneous power density, and (9) NFPA instability ...
The SDT is not a good idea. The thermocouple is just only below the pan and the pan typically is open. So we will loose a lot of information. The DSC is used to measure the runaway reactions but it has to be done in very high pressure pans. The calorimetric bomb is a good idea but you will only measure the total heat. You can not follow the reaction. The best way is the thermal activity monitor (TAM). It is a standar in the industry of the laundry products for example. All the big producers have this instrument. It is a semiadiabatic calorimeter that can follow the heat of reaction and after you can do kinetic analysis and a lot of staff.
A considerable number of electrostatic test devices work in the Fixed Gap regime, whose advantage is inter alia its electro-mechanic simplicity, versatility and easy operation. A similar design is used also in the Small Scale test Device of the type of University and OZM. Standard testing of electrostatic sensitivity of secondary explosives requires a fast increase of liberated output, (dP/dt = 100 MW/micsec). The discharge into the circuit is short and oscillating. Standard sensitivity tests of readily inflammable loose materials that react with atmosferic oxygen, pyrotechnic materials and primary explosives are usually caried out at included resistor 1 k - 10 MOhm.
You may wish to consider the tendency of most organic peroxides to be unstable and slowly self-decompose in time, therefore changing its energy content.
The following paper may be found of some help: D.C. Noller, S.J. Mazurowski, G.F. Linden, F.J.G. De Leeuw, O.L. Mageli, "A relative hazard classification of organic peroxides", Ind. Eng. Chem., 56(12) 1964, 18-27; DOI: 10.1021/ie50660a005; with corr.: ibidem, 57(6) 1965, 17; DOI: 10.1021/ie50666a600
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