Mechanical energies associated with compaction of form I and form II paracetamol powder

Paracetamol solid state has three known polymorphic forms; monoclinic form (Form I), orthorhombic form (Form II) and Form III. In this work Form II was successfully produced in appreciable quantities by controlled crystallization of melted Form I. The moisture content of both forms stored for 3 weeks at 25 °C at different relative humidity conditions was investigated. It was found that neither form acquires any significant amount of moisture in any of the storage conditions. The results showed that Form II is stable for 3 weeks of storage at relative humidities of 23%, 43%, and 58%. Work of compression, work of decompression, plasticity index (ψ), and elastic energy/plastic energy (EE/PE) ratio associated with the compaction of both forms were determined at maximum applied compression forces of 35 kN, 27 kN, 18 kN, 11 kN, and 5 kN. It was found that both forms have high magnitude of elastic energy recovery during decompression. Moreover, it was found that for generating compacts of equal volumes of the two forms the plasticity index is larger for Form II and the EE/PE ratio is larger for Form I.

Figure optionsDownload as PowerPoint slideHighlights
► We produce paracetamol Form II and examine its physical stability.
► We compare energies associated with compaction of paracetamol Form I and Form II.
► Form II is stable for 3 weeks at relative humidity conditions of 23%, 43%, and 58%.
► For equal compact volumes, Form II is associated with larger plasticity index.
► For equal compact volumes, Form I is associated with larger EE/PE ratio.