Ammonium Nitrate Coating with Nitrocellulose or the Inverse? A Study of the Coating Process and an Investigation of the Resulting Combustion Parameters

This research focused on studying the issue of coating ammonium nitrate (AN) with nitrocellulose (NC) and its microcrystalline form (MNC), using two esterification methods: traditional (HNO₃/H₂SO₄) and in situ synthesis (KNO₃/H₂SO₄). This study employed Raman and IR spectroscopy, SEM, as well as thermokinetic and mechanical analyses. The results showed that the addition of NC-KNO₃ significantly increased the pseudo-energy of activation (E_A ≈ 268 kJ/mol for pure NC), improving thermal stability. MNC modifications, however, yielded inconclusive results. Despite the confirmed presence of NC on the AN surface (Raman band at 1128 cm⁻¹), SEM analysis did not show formation of a core–shell structure—a reversed-layer formation was observed, where AN deposited onto NC instead of the expected coating. The addition of diesel oil reduced the sensitivity of the mixtures (e.g., ANNC-D showed 35 J for impact and 288 N for friction) due to improved homogeneity. The esterification method affected the mechanical properties of the material: NC synthesised from HNO₃ was less sensitive than that obtained from KNO₃. This paper highlights the key role of nitrocellulose in modifying the properties of energetic materials, but further research is needed to control the coating process and optimise the synthesis conditions.