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Polymeric materials, such as polyvinyl alcohol (PVA) and ethylene–PVA copolymers (EVOH) are widely used in the food sector as packaging materials because of their excellent properties. TiO2 nanoparticles (NPs) show photocatalytic activity; when added to the aforementioned polymers, on the one hand, they are expected to provide bactericidal capacity, whereas on the other hand, they could favor nanocomposite degradation. These types of nanoparticles can be derivatized with cyclodextrin macromolecules (CDs), which can act as food preservative carriers, increasing the packaging food protective properties. In this work, films containing β-Cyclodextrin (βCD)-grafted TiO2 nanoparticles and PVA or EVOH were prepared. Regarding the photocatalytic activity of the nanoparticles and the possible environmental protection, accelerated aging tests for PVA, EVOH, and their composites with cyclodextrin-grafted TiO2 nanoparticle (NP) films were performed by two methods, namely, stability chamber experiments at different conditions of temperature and relative humidity and UV light irradiation at different intensities. After analyzing the systems color changes (CIELAB) and Fourier transform infrared spectroscopy (FTIR) spectra, it was observed that the film degradation became more evident when increasing the temperature (25-80 °C) and relative humidity percentage (28–80%). There was no significant influence of the presence of CDs during the degradation process. When irradiating the films with UV light, the largest color variation was observed in the nanocomposite films, as expected. Moreover, the color change was more relevant with increasing NP percentages (1-5%) due to the high photocatalytic activity of TiO2. In addition, films were characterized by FTIR spectroscopy and variation in the signal intensities was observed, suggesting the increase of the material degradation in the presence of TiO2 NPs.

No abstract

Molybdenum disulfide (MoS 2 ) nanoparticles, obtained from liquid phase exfoliation in the presence of chitosan, were melt mixed with a linear low-density polyethylene (LLDPE) matrix to produce novel antimicrobial active packaging materials. The LLDPE/MoS 2 composites presented exfoliated nanoparticles forming aggregates that are well dispersed in the polymer matrix. These 2Dlayered MoS 2 nanoparticles at concentrations of 0.5, 1.0, and 3.0 wt% rendered several functionalities to the LLDPE, as for example an antimicrobial behavior against Salmonella typhi and Listeria monocytogenes bacteria that can be explained not only by the photoactivity of the filler but also by changes in the composite surface. For instance, the composites presented a reduction in the water contact angle (i.e., an increased hydrophilicity) and relevant changes in the surface topography (i.e., reduced roughness) as compared with pure LLDPE. Regarding the barrier properties, while MoS 2 dramatically increased the water vapor permeation (WVP) of the polymer matrix, until 15 times for composite with 3.0 wt% of filler, the oxygen permeation decreased around 25%. All these novel functionalities in the nanocomposites were obtained without significantly affecting the tensile mechanical properties of the pure LLDPE matrix. These results show that MoS 2 is a promising filler for the development of antibacterial active packaging films with behaviors as similar as other 2Dlayered fillers such as graphene derivatives.

Currently, there is a global concern about the environmental problems related to plastic wastes. Cellulose acetate (CA) and polylactic acid (PLA) are the most frequently used biopolymers in the food packaging industry. In this work, TiO2 nanoparticles and β-cyclodextrin (βCD) have been incorporated into nanocomposite films made of PLA and CA and then evaluated under biodegradation assays in wastewater to assess the effects of both additives on the biodegradability of films. TiO2 nanoparticles clearly enhanced the biodegradability of CA and PLA; PLA-TiO2 nanocomposites disappeared after 60 days, whereas plain PLA remained present after 100 days. The presence of the additives provided an exponential growth to BOD profiles. FTIR spectra showed a much faster deacetylation of CA for the nanocomposites than for the bare CA, and XRD diffractograms showed that PLA nanocomposites became more amorphous than bare PLA. The thermal resistance of CA and PLA nanocomposites substantially decreased, while plain matrices remained fairly stable up to 60 days. SEM micrographs of CA and PLA nanocomposites presented voids and larger surface erosion than the plain matrices. βCD modification of TiO2 nanoparticles seems to have a protective effect on the biodegradation of the polymers with respect to the unmodified TiO2.