(486a) Exploring the Physical Aging Behavior of Hpmcas Via Thermal Analysis
AIChE Annual Meeting
Wednesday, November 10, 2021 - 12:30pm to 12:54pm
In this study, we examine this hypothesis by analyzing the physical aging behavior of one of the most common polymer excipients in ASDs, hypromellose acetate succinate (HPMCAS), using conventional differential scanning calorimetry and fast scanning calorimetry. Through temperature scans across the glass transition temperature (Tg) and isothermal aging below the Tg, we compute the aging rate and observe the enthalpy recovery behavior on heating. Contrary to theoretical expectations, when it is aged well below Tg, HPMCAS exhibits a unique devitrification mechanism. In this mechanism, the enthalpy lost on physical aging is recovered notably before Tg, indicating a recovery process different from the alpha relaxation. More importantly, this process is not attributed to a secondary relaxation process as it is not discrete but rather continuous such that at longer aging times, the devitrification shifts towards the alpha relaxation process. This unique behavior suggests a relaxation mechanism that may directly influence the stability of drug molecules within the HPMCAS structure and impact ASD design, processing, and storage.