Physical Properties and Biodegradability Evaluation of Vulcanized Epoxidized Natural Rubber/Thermoplastic Potato Starch Blends.

The sustainable material-thermoplastic potato starch (TPS)-was blended with modified natural rubber-epoxidized natural rubber (ENR). The poor mechanical properties of the ENR/TPS blends limited the application. Sulfur vulcanization is a common and economical method to improve the mechanical properties in the rubber industry. To fully understand the relationship between vulcanization systems and ENR/TPS blends and the sustainability of the developed material, the effects of a vulcanization accelerator (N-cyclohexylbenzothiazole-2-sulphenamide (CBS), 2-mercaptobenzothiazole (MBT), N-tert-butylbenzothiazole-2-sulphenamide (TBBS)) and a system type (conventional vulcanization (CV), semi-efficient vulcanization (SEV) and efficient vulcanization (EV)) on curing characteristics, mechanical and thermal properties, water absorption and biodegradability were systematically evaluated. The results indicate that vulcanization significantly improves the mechanical properties of ENR/TPS blends. The performance optimization of the CBS-CV vulcanization system is the best for improving the mechanical properties and reducing the water absorption. The CBS-CV curing system makes ENR/TPS less biodegradable (12-56% of mass loss) than other accelerators and systems. TBBS-CV makes the material more biodegradable (18-66% of mass loss). The low rubber content enables the rapid biodegradation of the vulcanized blend. This has implications for research on sustainable materials. The material can be applied for eco-friendly packaging and agricultural films, etc. The investigation on performance by using common accelerators and systems provides ideas for industries and research.

Investigation of tadalafil molecular arrangement in solid dispersions using inverse gas chromatography and Raman mapping.

The aim of this study was to investigate the molecular structures of tadalafil solid dispersions prepared by different techniques and further to relate them to surface free energy information indicating the final amorphousness of the product. Thus, we tried to complement the existing knowledge of solid dispersion formation. Poorly water-soluble tadalafil was combined with different polymers, i.e. Kollidon® 12 PF, Kollidon® VA 64 and Soluplus®, to form model systems. To assess the extent of drug-polymer miscibility, we studied model solid dispersion surface energy using inverse gas chromatography and phase micro-structure using confocal Raman microscopy. The selection of the preparation method was found to play a crucial role in the molecular arrangement of the incorporated drug and the polymer in resulting solid dispersion. Our results showed that a lower surface free energy indicated the formation of a more homogeneous solid dispersion. Conversely, a higher surface free energy corresponded to the heterogeneous systems containing tadalafil amorphous clusters that were captured by Raman mapping. Thus, we successfully introduced a novel evaluation approach of the drug molecular arrangement in solid dispersions that is especially useful for examining the miscibility of the components when the conventional characterizing techniques are inconclusive or yield variable results.

Investigation of Dissolution Mechanism and Release Kinetics of Poorly Water-Soluble Tadalafil from Amorphous Solid Dispersions Prepared by Various Methods.

The aims of this study were to investigate how the release of tadalafil is influenced by two grades of polyvinylpyrrolidone (Kollidon® 12 PF and Kollidon® VA 64) and various methods of preparing solid dispersions (solvent evaporation, spray drying and hot-melt extrusion). Tadalafil is poorly water-soluble and its high melting point makes it very sensitive to the solid dispersion preparation method. Therefore, the objectives were to make a comparative evaluation among different solid dispersions and to assess the effect of the physicochemical nature of solid dispersions on the drug release profile with respect to the erosion-diffusion mechanism. The solid dispersions were evaluated for dissolution profiles, XRD, SEM, FT-IR, DSC, and solubility or stability studies. It was found that tadalafil release was influenced by polymer molecular weight. Therefore, solid dispersions containing Kollidon® 12 PF showed a faster dissolution rate compared to Kollidon® VA 64. Tadalafil was released from solid dispersions containing Kollidon® 12 PF because of the combination of erosion and diffusion mechanisms. The diffusion mechanisms were predominant in the initial phase of the experiment and the slow erosion was dissolution-controlling at the second stage of the dissolution. On the contrary, the tadalafil release rate from solid dispersions containing Kollidon® VA 64 was controlled solely by the erosion mechanism.