Implication of microstructure on the mechanical behaviour of an aspirin–paracetamol eutectic mixture
The present work investigates the mechanical behaviour of an aspirin–paracetamol (ASP–PCM) eutectic mixture (EM). A EM of ASP–PCM was prepared using a solvent evaporation method. Differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) confirmed the eutectic formation with a composition of 53 : 47% w/w (ASP : PCM). The compaction behaviour of the EM and a physical mixture (PM) of ASP and PCM was compared using a fully instrumented rotary tablet press equipped with a Portable Press Analyzer™ (PPA). The obtained data were compared using compressibility, tabletability and compactibility profiles and Heckel analysis. The EM exhibited higher compressibility, tabletability and plastic deformation compared to the PM. Heckel analysis showed that the mean yield pressure, Py, was lower for the EM (46.9 MPa) than the PM (222.8 MPa), thus confirming the better plastic deformation of the EM. The better deformation behaviour of the EM was attributed to its layered microstructure. The sliding of adjacent layers over each other under an applied compaction pressure offered higher plastic deformation and thus provided a greater interparticulate bonding area in the EM compared to the PM. However, there was no significant difference in the compactibility profiles indicating a similar interparticulate bonding strength of the two powders. Thus, the EM showed better tabletability compared to the PM by virtue of its greater compressibility and plastic deformation.