Browsing by Author "Weaver, M."

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    Compatibility assessment of thermoplastic formulations
    (2016-07-01) McAteer, D.; Weaver, M.; Blair, L. H.; Flood, N.; Gaulter, S. E.
    Prior to the large-scale preparation of any new chemical formulation an assessment of the potential reactivity between the components must be carried out. This practice, which is common to many fields including pharmaceutical science, is particularly essential in the case of energetic formulations whose chemical incompatibility may result in an unexpected and potentially explosive decomposition. The common method used to investigate incompatibility is to heat 1:1 (w/w) formulations and evaluate the variation in their thermal stability with respect to the neat, pristine explosive. The techniques used are: differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), vacuum stability and heat flow calorimetry. As trends in energetics move towards safer formulations the components are more commonly selected for their high thermal stability and low sensitivity to initiation. However, recently prepared thermoplastic formulations which incorporate a thermally stable explosive, 2,2’,4,4’,6,6’-hexanitrostilbene (HNS II), and a selection of high-melting-point thermoplastics produced anomalous results during their compatibility assessment leading to the suggestion that historical tests originally devised for less thermally stable materials, such as N,N’,N’’-trinitro-1,3,5-triazacyclohexane (RDX), may not be directly transferable to the newer generations of insensitive explosive formulations.
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    A review of the mallet impact test for small scale explosive formulations
    (2016-07-01) Weaver, M.; Blair, L. H.; Flood, N.; Stennett, C.
    Development of new explosive formulations begins with the generation of only a few milligrams of material which is investigated using a number of small scale tests such as DSC, TGA, response to flame, mallet impact (mallet friction either glancing or direct blow) to determine whether the formulation is safe to scale up to 10 g. The latter of these tests, mallet impact, can be particularly subjective as the result is directly influenced by the operator carrying out the assessment. Not only can there be a change from one operator to another but there can also be a change in the force applied during each strike potentially leading to inconsistent results. This study highlights this encountered variation and assesses the load applied by a variety of operators with varying levels of explosive experience. This paper also proposes the use of a small scale laboratory based impact test which would provide improved confidence in the assessment of impact sensitiveness of explosive formulations and assist in justifying whether a formulation can be taken to the next scale. A small scale version of the BAM impact test (EMTAP Test 43) has been devised that allows the comparison of the sensitiveness of small scale formulations relative to RDX (8.7 J, EMTAP Test 43B) whilst also ensuring a reproducible result.