Thermokinetic characterization of amorphous carbamazepine was performed utilizing non-isothermal differential scanning calorimetry (DSC) and thermogravimetry (TGA). Structural relaxation of the amorphous matrix was described in terms of the Tool-Narayanaswamy-Moynihan model with the following parameters: Δh* ≈ 200-300 kJ·mol-1, β = 0.57, x = 0.44. The crystallization of the amorphous phase was modeled using complex Šesták-Berggren kinetics, which incorporates temperature-dependent activation energy and degree of autocatalysis. The activation energy of the crystal growth was determined to be >320 kJ·mol-1 at the glass transition temperature (Tg). Owing to such a high value, the amorphous carbamazepine is stable at Tg, allowing for extensive processing of the amorphous phase (e.g., self-healing of the quench-induced mechanical defects or internal stress). A discussion was conducted regarding the converse relation between the activation energies of relaxation and crystal growth, which is possibly responsible for the absence of sub-Tg crystal growth modes. The high-temperature thermal decomposition of carbamazepine proceeds via multistep kinetics, identically in both an inert and an oxidizing atmosphere. A complex reaction mechanism, consisting of a series of consecutive and competing reactions, was proposed to explain the second decomposition step, which exhibited a temporary mass increase. Whereas a negligible degree of carbamazepine degradation was predicted for the temperature characteristic of the pharmaceutical hot-melt extrusion (~150 °C), the degradation risk during the pharmaceutical 3D printing was calculated to be considerably higher (1-2% mass loss at temperatures 190-200 °C).

• Keywords
• carbamazepine, crystal growth, structural relaxation, thermal decomposition,
• MeSH
• Calorimetry, Differential Scanning MeSH
• Carbamazepine * chemistry   MeSH
• Kinetics MeSH
• Crystallization MeSH
• Temperature MeSH
• Thermogravimetry MeSH
• Transition Temperature MeSH
• Hot Temperature MeSH
• Phase Transition * MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Carbamazepine * MeSH