Potential perspectives of CMC-PET/ZnO bilayer nanocomposite films for food packaging applications: physical, mechanical and antimicrobial properties

Green synthesis of non-isocyanate hydroxyurethane and its hybridization with carboxymethyl cellulose to produce films

Non-isocyanate polyurethanes (NIPUs) have attracted increasing attention as a sustainable alternative to conventional isocyanate-based polyurethanes. This study synthesized non-isocyanate hydroxyurethanes (NIHUs) through an addition reaction between propylene carbonate (PC) and 1,2-ethylenediamine (EDA). The resulting NIHU was then hybridized with carboxymethyl cellulose (CMC) to investigate its hybridization potential. Structural analysis through FTIR, NMR, and XRD confirmed the crystalline nature of NIHU, featuring urethane bonds and abundant hydroxyl groups. It was found that NIHU and CMC interacted by forming hydrogen bonds between hydroxyl groups of NIHU and carboxyl groups of CMC, resulting in a dense CMC/NIHU hybrid structure. NMR and XRD analyses revealed changes in the hybrids' chain mobility, the Young's modulus of the hybrid with 30 % NIHU content decreased from 1627 MPa to 502 MPa relative to CMC, and the elongation at break increased from 4.44 % to 17.2 %. Increasing the concentration of NIHU in CMC reduced the hydrophobicity, in terms of water contact angle, from 70° to 41.7°. The simplicity of the synthesis method for NIHU, coupled with the desirable structure, strength, and balanced flexibility of CMC/NIHU hybrids, is expected to facilitate the production of NIHU-rich hybrids and increase their application in packaging.

Development of basil seed mucilage (a heteropolysaccharide) - Polyvinyl alcohol biopolymers incorporating zinc oxide nanoparticles

The effect of zinc oxide nanoparticles (ZnONPs) on various properties of basil seed mucilage (a heteropolysaccharide)-polyvinyl alcohol (BSM-PVA) films was investigated. Increasing concentration of ZnONPs in BSM-PVA films reduced moisture content (from 24.73 to 17.09 %), water solubility (from 36.36 to 27.65 %), water vapor permeability (from 4.66 × 10-7 to 2.55 × 10-7 g·m/m2·Pa·h), oxygen permeability (from 2.96 to 2.13 cm3 μm/m2 d kPa), and elongation at break (from 40.34 to 29.44 %), and increased ultimate tensile strength (from 16.81 to 21.48 MPa). Color and light transmission were affected by ZnONPs concentrations. The lack of formation of new peaks, along with the displacement of peaks, indicated the formation of hydrogen bonds between ZnONPs and the film matrix. Dynamic mechanical-thermal analysis showed that storage modulus and glass transition temperature increased with the concentration of ZnONPs. Scanning electron microscopy images illustrated that the addition of ZnONPs improved film integrity. X-ray diffraction pattern showed that the crystal shape of nanoparticles was preserved in the film matrix. Films containing ZnONPs showed good antibacterial activity against Staphylococcus aureus (reductions ≥ 3 log CFU/cm2) and Escherichia coli (reductions ≥ 4 log CFU/cm2). Films containing ZnONPs also showed a suitable antifungal activity during the storage of wheat bread.

Antibacterial and Antifungal Properties of Electrospun Recycled PET Polymeric Fibers Functionalized with Zinc Oxide Nanoparticles

Currently, to reduce the environmental problems associated with plastic waste, methods are being sought to use this waste as raw materials in different applications, such as fibers. In addition, to improve these materials and provide different properties, nanoparticles (NPs) are incorporated. In the present work, polymeric fibers made of recycled polyethylene terephthalate (r-PET) from post-consumer water bottles, functionalized with 0%, 1.5%, 3% and 6% zinc oxide nanoparticles (ZnO-NPs) in function of r-PET weight, were elaborated to evaluate their antibacterial and antifungal characteristics. The ZnO-NPs were synthesized by the solvothermal method, obtaining particles with a mean diameter of 38.15 nm, while the fibers were obtained by electrospinning with a diameter range between 200-5000 nm. The functionalized fibers were carried out against Escherichia coli and Bacillus subtilis through the agar diffusion method, obtaining the highest inhibition halo at 6% w/w ZnO-NPs, being 26.5 mm and 34.25 mm, respectively. In addition, the same method was used to evaluate the antifungal activity of Penicillium s.p. and Fusarium graminearum, observing antifungal properties due to the presence of nanoparticles in the fibers.