In order to improve poly(lactic acid) (PLA) mechanical, thermal, and barrier properties, different layered silicate nanoclays are added. This work deals with the study of the effect of the type of nanoclays with different hydrophilicity on the preparation procedure and properties of PLA nanocomposites. Six kinds of clays have been loaded in PLA whose hydrophilicity varies in the following order of increased hydrophilicity: modified Dellite 67G (67G) < Cloisite 15A (C15A) < C20A < C93A < C30B < hydrophilic smectite clay (HPS). Resultant nanocomposites have been characterized both with respect to bulk and surface properties by mechanical, rheological, thermal analyses, X-ray diffraction study, Fourier transform infrared spectroscopy, gas permeability tests, contact angle measurements, scanning electron microscopy, and atomic force microscopy. Antimicrobial properties have been also tested. Evidenced was the dependence of most properties on the hydrophilicity/hydrophobicity of the clays. The nanocomposites containing the most hydrophilic clays such as Cloisite 93A, Cloisite 30B, and HPS show satisfactory antimicrobial activity against both Gram-positive and Gram-negative bacteria, excepting fungus Candida albicans.
Polylactic acid (PLA) films were coated by coaxial electrospinning with essential and vegetable oils (clove and argan oils) and encapsulated into chitosan, in order to combine the biodegradability and mechanical properties of PLA substrates with the antimicrobial and antioxidant properties of the chitosan–oil nanocoatings. It has been established that the morphology of the electrospun nanocoatings mainly depend on the average molecular weight (MW) of chitosan. Oil beads, encapsulated into the main chitosan nanofibers, were obtained using high-MW chitosan (Chit-H). Oil encapsulated in chitosan naoparticles resulted when low-MW chitosan (Chit-L) was used. The coating layer, with a thickness of 100 ± 20 nm, had greater roughness for the samples containing Chit-H compared with the samples containing Chit-L. The coated PLA films had higher antibacterial activity when the nanocoating contained clove oil rather than when argan oil was used, for both types of chitosan. Nanocoatings containing Chit-H had higher antibacterial activity compared with those containing Chit-L, for both types of oil tested, due to the larger surface area of the rougher nanoscaled morphology of the coating layer that contained Chit-L. The chitosan–clove oil combination had higher antioxidant activity compared to the simple chitosan nanocoating, which confirmed their synergistic activities. The low activity of systems containing argan oil was explained by big differences between their chemical composition and viscosity.
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