Temperature dependence of the dielectric properties of metal-polymer composites based on zinc oxide nanoparticles stabilized in low-density polyethylene matrix

Concerns in food safety and the need for high-quality foods have increased the demand for extending the shelf life of packaged foods. Subsequently, promoting and investigating the development of antibacterial materials for food packaging has become inevitable. Zinc oxide nanoparticles have attracted attention lately owing to their multifunctional properties, especially antibacterial activity. For this study, antibacterial low-density polyethylene films were prepared by coating zinc oxide nanoparticles onto their surface. The low-density polyethylene film antibacterial activity was evaluated toward Gram-positive and Gram-negative bacteria. The scanning electron microscopy images showed that using anhydride-modified low-density polyethylene (LDPE-g-AM) resin permitted improved zinc oxide nanoparticle distribution on the low-density polyethylene film surface, reduced the agglomerate sizes, and reinforced the zinc oxide nanoparticle bonding to the low-density polyethylene film surface. We found that the coated low-density polyethylene films exhibited high antibacterial activity against both strains. The antibacterial tests also proved that the coated films retained their antibacterial efficiency toward Escherichia coli, even after eight months, with a reduction rate higher than 99.9%, whereas for Staphylococcus aureus the antibacterial properties for the linear low-density polyethylene (LLDPE) films decreased at eight months and improved for the LDPE-g-AM films. When the zinc oxide coated films were laminated with neat low-density polyethylene, only the LDPE-g-AM was still active against E. coli provided that the lamination thickness does not go beyond 8 µm. This research demonstrated that the coated low-density polyethylene films have excellent attributes when used as an active coating in the food packaging industry.

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Transparent ultraviolet-shielding composite films made from dispersing pristine zinc oxide nanoparticles in low-density polyethylene

Nanotechnology Reviews ◽

10.1515/ntrev-2020-0099 ◽

2020 ◽

Vol 9 (1) ◽

pp. 1368-1380

Author(s):

Lina Cui ◽

Canyi Huang ◽

Hong Xia ◽

Yiping Qiu ◽

Qing-Qing Ni

Keyword(s):

Zinc Oxide ◽

Zinc Oxide Nanoparticles ◽

Polymer Concentration ◽

Tensile Failure ◽

Casting Temperature ◽

Low Density Polyethylene ◽

Critical Conditions ◽

Dissolution Time ◽

Oxide Nanoparticles ◽

Low Density

Abstract This work proposes an approach to fabricate flexible transparent ultraviolet (UV)-shielding membrane by casting method, which uniformly disperses pristine zinc oxide nanoparticles (NPs) in low-density polyethylene (LDPE). The critical conditions for film fabrication, such as casting temperature, LDPE concentration in the solution, dissolution time, NP concentration, and post hot press cooling processes, are systematically studied. It is found that the casting temperature needs to be close to the melting temperature of LDPE, namely, 115°C, so that transparent film formation without cracks can be guaranteed. NP agglomerates are suppressed if the polymer concentration is controlled below 6%. For good dispersion of NPs, LDPE has to be swelled or unentangled enough in the solution (close to 200 h dissolution time), and then the NP agglomerates can be diminished due to the diffusion of the NPs into the polymer gel (322 h dissolution time). When the NPs are well-dispersed in the LDPE film, the film can completely shield UV light while allowing high transmissivity for the visible light. As the concentration of NPs in the film increases from 4 to 6%, the transmissivity of the film decreases, the tensile strength increases, and the tensile failure strain decreases.

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