Complex thermokinetic characterization of polydioxanone for medical applications: Conditions for material processing

How the Presence of Crystalline Phase Affects Structural Relaxation in Molecular Liquids: The Case of Amorphous Indomethacin

“…Note that the decrease in the non-linearity parameter x indicates a larger dependence of the relaxation motions on the actual material's structure (as opposed to the dependence on T alone). When comparing these findings to the literature data (introduced in Section 1), the broadened distribution of the relaxation times appears to be quite a common feature [42][43][44]47], also confirmed by our results. The non-monotonic evolution of x with increasing crystalline content was, to the authors' knowledge, not reported in the literature; the initial steep increase in x can be considered conformant with [47].…”

“…When comparing these findings to the literature data (introduced in Section 1), the broadened distribution of the relaxation times appears to be quite a common feature [42][43][44]47], also confirmed by our results. The non-monotonic evolution of x with increasing crystalline content was, to the authors' knowledge, not reported in the literature; the initial steep increase in x can be considered conformant with [47]. Both TNM parameters were determined with the ~± 0.02 errors.…”

“…Note that the preparation of IMC powders with 1 > χ c > 0.5, where the glass transition phenomenon would manifest clearly enough, was found to be extremely difficult, hence the low amount of data in the corresponding χ c range. As was already stated in the introductory part, various ∆h*-χ c trends exist in different materials [42,47,48]. Regarding the interpretation of the data shown in Figure 6C, the constancy of ∆h* in the low-χ c range implies that similar explanations cannot be used for the evolution of T g and ∆h*.…”

“…On the other hand, well below T g , only local movements occur in both the mobile and rigid amorphous phases, and the effect of imposed crystallinity is minor. The effect of crystallinity on the structural relaxation of poly(p-dioxanone) was studied in [47]. With the increasing amount of crystalline content, ∆h* and A remained unchanged, β suddenly and largely decreased (0.50 → 0.15) only at a very high degree of crystallinity, and x continually increased from 0.45 to 0.80.…”

Simulation and non-linear optimization of kinetic models for solid-state processes

“…One of the highest precisions and reproducibilities of the thermo-analytical measurements are obtained for the polymeric materials. In [66], a complete thermo-kinetic characterization of the amorphous poly(p-dioxanone) was introduced with the following results: errors of the determination of the activation energies of structural relaxation, different types of crystallization, and depolymerization were 1.7%, 0.7/0.9/2.3%, and 2.9%, respectively; crystallization enthalpies were reproducible to ∼0.3%; variability of the kinetic exponents was interpreted with 0.05 precision (in absolute values) in mind. In case of the low-molecular glass indomethacin (amorphous anti-inflammatory drug) [48], the errors in determined activation energies were 2.0% for structural relaxation, 2%-6% for the crystallization of different powders, and 3.5% for thermal decomposition; the errors of crystallization enthalpies varied between 3% and 10%; the kinetic exponents of the corresponding models varied with 0.03-0.07 errors (in absolute scale) and their larger changes were already interpreted as temperature-dependent trend in kinetic behavior.…”