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Effect of Natural Ageing on the Safety Parameters and Performance of TNT-based Melt Cast RDX/TNT Compositions

Sharma Tirupati Chander, Singh Arjun, Soni Pramod Kumar, Singh Vasundhara, Kishore Prateek

Central European Journal of Energetic Materials

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2023

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Vol. 20, no. 2

138--158

EN

2,4,6-Trinitrotoluene (TNT) based melt cast RDX/TNT compositions stockpiled for a period of time were exposed under natural environmental conditions, with humidity and temperature for storage in the range of 40-95% RH and 4-47 °C, respectively. The composition, chemical, thermal and mechanical properties of the RDX/TNT compositions before and after ageing were studied by high performance liquid chromatography, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and a universal test machine, respectively. In addition, the safety, mechanical sensitivities, detonation velocity and blast parameters were also investigated through vacuum stability tests (VST), a BAM fall hammer apparatus, a BAM friction tester and a piezoelectric accelerator, respectively. The results showed that after ageing, the colour of the composition had become dark but there was no variation in the RDX and TNT content by high performance liquid chromatography (HPLC). The VST results showed that the volume of evolved gas was almost the same and less than 2 mL/g, indicating chemical stability. The results obtained from different analytical techniques demonstrated that there was no significant variation in the chemical, thermal and mechanical properties for the aged samples as compared to the fresh composition. The change in mechanical sensitivity is related to the components and the ageing mode. The detonation velocity and detonation pressure were found to be similar to those of the freshly prepared composition and consistent with the data obtained from overall natural ageing. The results of blast studies revealed that there was either a similar or slight variation in the blast peak over pressure and impulse for RDX/TNT compositions at different locations before and after ageing under natural environmental conditions.

2

Effect of the Molecular Structure and Molecular Weight of Poly(Vinylidene Fluoride-Chlorotrifluoroethylene) Copolymers on the Characteristic Properties of TATB-based Composites

Singh Arjun, Sharma Tirupati Chander, Kumar Mahesh

Central European Journal of Energetic Materials

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2020

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Vol. 17, no. 3

428--450

EN

1,3,5-Triamino-2,4,6-trinitrobenzene (TATB) based composites with different molecular weights and molecular structures of poly(vinylidene fluoride-chlorotrifluoroethylene) (poly(VDF-CTFE) binder were studied to investigate their effect on the physical, thermal, mechanical and explosive properties. The poly(VDF-CTFE) with three different kinds of molecular weights (FKM1, FKM2 and FKM3 samples) and three different kinds of molar ratios of VDF and CTFE (FKM4, FKM5and FKM6) was chosen as the polymeric binder. The experimental results indicated that all of these kinds of TATB-based composites do not show any measurable changes in the particle density, detonation velocity and impact sensitivity. The thermal data revealed that weight loss occurs in two steps and, that the thermal stability deceases slightly with an increase in the molecular weight. On other hand, the weight loss occurred in a single step and the thermal stability increases slightly with an increase in the molar ratio of the CTFE to VDF monomer units. The adhesion properties between the two phases of TATB crystals and polymeric matrices rely on the properties of the interface, which is expressed in terms of the mechanical properties. The storage modulus decreases with increasing molecular weight. On other hand, an increase in the CTFE to VDF molar ratio in the poly(VDF-CTFE) binder remarkably improves the mechanical strength. FKM5-9505 shows a significant reduction in creep deformation and dramatically increases the elongation failure, compared to those of the FKM4-9505 sample. Finally, SEM observations clearly suggested that the coating of the polymer matrix onto the surface of the TATB crystals is clearly demonstrated.

3

Thermal Degradation Behaviour and Kinetics of aged TNT-based Melt Cast Composition B

Singh Arjun, Sharma Tirupati Chander, Singh Vasundhara, Mukherjee Niladri

Central European Journal of Energetic Materials

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2019

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Vol. 16, no. 3

360--379

EN

In the present paper, three kinds of aged and freshly prepared 2,4,6-trinitrotoluene (TNT) based Composition B stockpiled, for a period of 20 and 32 years, were investigated for the effect of natural ageing on their thermal degradation behaviour and kinetic parameters. The properties investigated indicated that there was no significant change in the thermal stability of the samples aged under natural environmental conditions. The kinetic parameters were studied by means of the Kissinger method using the peak temperature at maximum reaction rate from DSC data, and the isoconversional Kissinger-Akahira-Sunnose (KAS) and ASTM E689 methods from TGA data. The apparent activation energies calculated by the Kissinger method were 173.8 kJ·mol–1 for fresh, 170.4 kJ·mol–1 for 20 y old and 187.1 kJ·mol–1 for 32 y old Composition B, respectively. The values calculated by the KAS method were found to be in the range 77.2-235.8 kJ·mol–1 for fresh Composition B, 75.7-224.0 kJ·mol–1 for 20 y old and 70.4-196.0 kJ·mol–1 for 30 y old Composition B, respectively. The activation energies obtained from the KAS methods are in good agreement and consistent with the isoconversional ASTM E689 kinetic method. The thermodynamic parameters, such the Gibbs free energy of activation (ΔG#), activation enthalpy (ΔH#) and activation entropy (ΔS#) for the formation of activated complexes were also studied and are discussed.