Rheology studies of NTO–TNT based melt-cast dispersions and influence of particle–dispersant interactions

•Non-Newtonian behaviour with yield stress is observed in NTO/TNT melt-cast suspensions.•Yield stress of RDX/TNT is multiple times higher than spherical NTO/TNT.•The compositions are evaluated based on thixotropic index and activation energy for flow.•Molecular–orbital calculations are performed to calculate interaction energies.•The role of molecular forces and particle morphology on pourability are established.

3-Nitro-1,2,4-triazol-5-one (NTO) is a promising candidate of insensitive munitions and it is currently explored to achieve shock insensitive melt-cast formulations. Rheology of melt-cast formulations helps in implementing viscous behaviour to application. In the present study, NTO based melt-cast formulations are prepared using TNT as a dispersant and the flow behaviour of non-spherical and spherical NTO formulations are studied along with the bench-mark Composition B. All measurements are made at 81, 83, 86 and 90 °C and at shear rates varying from 8.5 to 59.5 s− 1. Flow behaviour of these formulations at process temperatures exhibit non-Newtonian behaviour with yield stress. Time and temperature dependency of these formulations are also studied and about two fold increase in thixotropic index is observed in RDX/TNT in comparison to spherical NTO/TNT (60:40). In order to get more insight on the flow properties, molecular–orbital calculations were performed at B3LYP 6-311G (d, p) level. The calculated interaction energies revealed that stronger attractive forces exist in NTO–NTO than RDX–RDX pairs and similarly in NTO–TNT than RDX–TNT. Correlation with particle morphology confirms domination of morphology over intra/intermolecular interactive forces in determining the yield value. This comparative study establishes the role of above interactive forces and morphology on pourability of melt-cast formulations and further reveals that the flow behaviour of NTO based formulations is superior to RDX/TNT formulations.

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