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The main objective of this work was to study the release of cinnamaldehyde (CIN) from electrospun poly lactic acid (e-PLA) mats obtained through two techniques: (i) direct incorporation of active compound during the electrospinning process (e-PLA-CIN); and (ii) supercritical carbon dioxide (scCO2) impregnation of CIN within electrospun PLA mats (e-PLA/CINimp). The development and characterization of both of these active electrospun mats were investigated with the main purpose of modifying the release kinetic of this active compound. Morphological, structural, and thermal properties of these materials were also studied, and control mats e-PLA and e-PLACO2 were developed in order to understand the effect of electrospinning and scCO2 impregnation, respectively, on PLA properties. Both strategies of incorporation of this active compound into PLA matrix resulted in different morphologies that influenced chemical and physical properties of these composites and in different release kinetics of CIN. The electrospinning and scCO2 impregnation processes and the presence of CIN altered PLA thermal and structural properties when compared to an extruded PLA material. The incorporation of CIN through scCO2 impregnation resulted in higher release rate and lower diffusion coefficients when compared to active electrospun mats with CIN incorporated during the electrospinning process.

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Abstract:In this work, electrospun fibers of polyvinyl alcohol (PV) and starch (ST) were obtained to improve dispersion of cellulose nanocrystals (CNC) within a poly(lactic acid) (PLA) matrix with the aim of enhancing mechanical and barrier properties. The development and characterization of electrospun fibers with and without CNC, followed by their incorporation in PLA at three concentrations (0.5%, 1% and 3% with respect to CNC) were investigated. Morphological, structural, thermal, mechanical and barrier properties of these nanocomposites were studied. The purpose of this study was not only to compare the properties of PLA nanocomposites with CNC embedded into electrospun fibers and nanocomposites with freeze-dried CNC, but also to study the effect of electrospinning process and the incorporation of CNC on the PV and starch properties. SEM micrographs confirmed the homogenous dispersion of fibers through PLA matrix. X-ray analysis revealed that the electrospinning process decreased the crystallinity of PV and starch. The presence of CNC enhanced the thermal stability of electrospun fibers. Electrospun fibers showed an interesting nucleating effect since crystallinity of PLA was strongly increased. Nanocomposites with electrospun fibers containing CNC presented slightly higher flexibility and ductility without decreasing barrier properties.