Hot-melt extrusion of low and high moisture Kollidon® SR with sorbitol: Nanoindentation microhardness, creep deformation and powdered extrudate compression

Kollidon® SR of low (KoL) or high (KoH) moisture content was hot-melt extruded with sorbitol (SOR). Microhardness of KoL/SOR and KoH/SOR extruded rods was determined by nanoindentation and deformation by creep analysis. Compression of powdered extrudates was studied by instrumented tablet press. Interactions were examined by vibration spectroscopy, thermal changes by differential scanning calorimetry, and rod morphology by atomic force microscopy. High moisture KoH/SOR with low SOR (0%, 2.5%) exhibited high microhardness and low deformability of extruded rods, and also high yield pressure of compacted extrudate powder estimated from Heckel and Adams models. These effects were remarkably reversed at the 5% and 10% SOR, indicating plasticization of polymer. Anti-plasticizing action was noticed at 2.5% SOR in the microhardness of extruded rods and in the tensile strength of extrudate powder tablets. The influence of SOR on the properties of KoL/SOR extrudates was less pronounced, signifying the involvement of moisture in the plasticization of the polymer during HME. There is a linear correlation between rod microhardness and extrudate powder yield pressure ( R 2 =0.792), and an excellent correlation with the tablet tensile strength ( R 2 =0.986) indicating the importance of intrinsic material structure on compression. The above findings emphasize the need for proper storage of polymeric excipients. • Pre-sorbed moisture in Kollidon® SR drives plasticization during hot-melt extrusion. • Low (2.5%) sorbitol shows anti-plasticizing, higher levels show plasticizing effect. • Microhardness correlates with yield pressure and tablet tensile strength. • Low pre-sorbed moisture and sorbitol addition yield tensile strengths >5 MPa.