Diffusion Mechanism of Cinnamon Essential Oils Release from Calcium Alginate Based Controlled Release Films in Contact with Food Simulating Solvent

Calcium alginate based controlled release films with moderate mechanical properties were fabricated in this paper. The diffusion mechanism of these films contacting food simulating solvent (FSS) was explored in some detail. With the increase of glycerol content, the diffusion coefficient (D) values of cinnamon essential oils (CEOs) diffusing to ethanol first increased slowly (0.3–0.6 mL), then vigorously (0.6–0.9 mL), and then mildly (0.9–1.2 mL). The D values of the CEOs diffused to water are all in the order of magnitude of 10−10 cm2/s. The D values of CEOs diffused from films EG3 and EGC1 to aqueous ethanol altered enormously at a small moisture percentage (w = 0.3), then continuously varied vigorously, and at last altered mildly in the range of w = 0.3–1. All the results above indicate that, considering the FSS, the diffusion ability of molecules is jointly determined by the size and distribution of free volume in the system (polymer + diffusive substance + solvents), the intermolecular interaction, and the partition coefficient of the solvents. In addition, several pairs of D values, such as DEG and DGA, are very close to each other, indicating that different kinds of interactions between different groups may have the same effect on the diffusion ability of molecules. The correlation between D1 and D2 indicates that polymeric emulsifier chains also exist in the polymer-rich layer. All the findings and analysis could provide the theoretical basis and data support for further molecular dynamic simulation and could guide the design of controlled release food packaging for food protection.

Comparing the performance of electrospun and cast nanocomposite film of polyamide-6 reinforced with multi-wall carbon nanotubes

This study aims at fabrication and characterization of two different structures of electrically conductive polyamide 6/multi-wall carbon nanotube nanocomposite films at different multi-wall carbon nanotube concentrations including electrospun nanofibrous and cast films. Morphology, embedded multi-wall carbon nanotubes into nanofiber, thermal behavior, electrical conductivity and wettability of films were characterized. Scanning electron microscopy images depicted that the nanofiber diameter decreased with increased nanofillers. Enhancement of crystallinity, electrical and tensile properties, and simultaneously achieving a low percolation threshold confirmed good nanotube dispersion by employing a polymeric emulsifier, polyvinylpyrrolidone. The electrospun film crystalline content increased 18.5% and the cast ones increased 46.8% at 7 wt.% multi-wall carbon nanotubes loading. The electrospun and cast membrane electrical conductivity increased by 10 and 12 orders of magnitude. These results demonstrated higher values compared to previously reported data for polyamide 6/multi-wall carbon nanotube nanocomposites. The electrospun film Young’s modulus increased 93% and that of casted one increased 267%, due to the increased crystallinity after adding carbon nanotubes into the films.