This work reports the effects of free volume on curcumin release in various polymer-based composite films. Curcumin-reinforced biocomposite films were fabricated with natural biopolymers (carrageenan and chitosan) and bioplastics (poly(lactide) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT)) via the solvent casting method. The curcumin release test was performed using an aqueous medium, and it was found that it was released the fastest in the carrageenan film, followed by the chitosan, PLA, and PBAT films, presumably owing to the dissimilarity of the polymer matrix. The free volume of the polymer films was determined using positron annihilation lifetime spectroscopy (PALS) to understand the release phenomena of curcumin. The free volume fraction was varied and reliant on the type of polymer, with the highest in the PBAT-based film followed by the PLA-, chitosan-, and carrageenan-based films. The free volume method helps analyze the release of bioactive compounds in a polymer matrix and may help to achieve a better understanding of the release of bioactive compounds.

In this study, the nanostructural vacancy behavior of bovine derived hydroxyapatite (BHA) doped with powder zirconmullite (ZM) contents of 5, 7.5, 10 and 12.5 wt.% were presented at sintering temperatures of 1000, 1100, 1200 and 1300°C. ZM‐doped BHA (ZM‐BHA) was characterized by X‐ray diffraction and positron annihilation lifetime spectroscopy (PALS). Density and hardness behavior were measured with respect to increasing sintering temperature. PALS results indicate that the longest lifetime component τ3 of ortho‐positronium (o‐Ps) localized at open spaces is attributed to the vacancy site and almost constant with the ZM contents and the sintering temperatures to have a mean value of 0.680 ns (corresponding to the radius of 0.997 nm). This average value is ascribed to the OH group defects along the main crystalline line. On the other hand, the o‐Ps intensity attributed to the number of vacancy sites increases almost linearly with ZM additives and sintering temperatures. The intensity is also related to the density and hardness of ZM‐BHA in terms of ZM contents.