Thermo-mechanical properties of high density polyethylene with zinc oxide as a filler

Enterobacter cloacae-mediated polymer biodegradation: in-silico analysis predicts broad spectrum degradation potential by Alkane monooxygenase

Plastic pollution poses a significant environmental challenge. In this study, the strain Enterobacter cloacae O5-E, a bacterium displaying polyethylene-degrading capabilities was isolated. Over a span of 30 days, analytical techniques including x-ray diffractometry, scanning electron microscopy, optical profilometry, hardness testing and mass spectrometric analysis were employed to examine alterations in the polymer. Results revealed an 11.48% reduction in crystallinity, a 50% decrease in hardness, and a substantial 25-fold increase in surface roughness resulting from the pits and cracks introduced in the polymer by the isolate. Additionally, the presence of degradational by-products revealed via gas chromatography ascertains the steady progression of degradation. Further, recognizing the pivotal role of alkane monooxygenase in plastic degradation, the study expanded to detect this enzyme in the isolate molecularly. Molecular docking studies were conducted to assess the enzyme's affinity with various polymers, demonstrating notable binding capability with most polymers, especially with polyurethane (- 5.47 kcal/mol). These findings highlight the biodegradation potential of Enterobacter cloacae O5-E and the crucial involvement of alkane monooxygenase in the initial steps of the degradation process, offering a promising avenue to address the global plastic pollution crisis.

Antimicrobial Packaging for Plum Tomatoes Based on ZnO Modified Low-Density Polyethylene

Food safety and quality are major concerns in the food industry. Despite numerous studies, polyethylene remains one of the most used materials for packaging due to industry reluctance to invest in new technologies and equipment. Therefore, modifications to the current materials are easier to implement than adopting whole new solutions. Antibacterial activity can be induced in low-density polyethylene films only by adding antimicrobial agents. ZnO nanoparticles are well known for their strong antimicrobial activity, coupled with low toxicity and UV shielding capability. These characteristics recommend ZnO for the food industry. By incorporating such safe and dependable antimicrobial agents in the polyethylene matrix, we have obtained composite films able to inhibit microorganisms' growth that can be used as packaging materials. Here we report the obtaining of highly homogenous composite films with up to 5% ZnO by a melt mixing process at 150 °C for 10 min. The composite films present good transparency in the visible domain, permitting consumers to visualize the food, but have good UV barrier properties. The composite films exhibit good antimicrobial and antibiofilm activity from the lowest ZnO composition (1%), against both Gram-positive and Gram-negative bacterial strains. The homogenous dispersion of ZnO nanoparticles into the polyethylene matrix was assessed by Fourier transform infrared microscopy and scanning electron microscopy. The optimal mechanical barrier properties were obtained for composition with 3% ZnO. The thermal analysis indicates that the addition of ZnO nanoparticles has increased thermal stability by more than 100 °C. The UV-Vis spectra indicate a low transmittance in the UV domain, lower than 5%, making the films suitable for blocking photo-oxidation processes. The obtained films proved to be efficient packaging films, successfully preserving plum (Rome) tomatoes for up to 14 days.

Innovative HDPE Composites Enriched with UV Stabilizer and Diatomaceous Earth/Zinc Oxide for Enhanced Seafood Packaging and Antimicrobial Properties

The fisheries industry encounters distinct packaging challenges, including the need to protect perishable seafood from rapid spoilage caused by UV radiation while allowing for reuse. This study tackles these issues by introducing advanced high-density polyethylene (HDPE) composites enhanced with a UV stabilizer and inorganic fillers, such as diatomaceous earth/zinc oxide (DZ). Our investigation explores the transformative effects of weathering on these pioneering composites, evaluating shifts in mechanical, physical, thermal properties, and sub-zero temperature stability. Incorporating a UV stabilizer alongside DZ within the HDPE matrix significantly enhances mechanical performance and weathering resilience. These enhancements extend the longevity of seafood packaging while preserving product quality. Moreover, our findings reveal a substantial breakthrough in antimicrobial properties. The inclusion of DZ, with or without a UV stabilizer, results in an impressive up to 99% enhancement in antibacterial activity against both Gram-positive and Gram-negative bacteria. This discovery not only bolsters the protective attributes of HDPE packaging but also presents a compelling case for the development of active packaging materials derived from DE/ZnO composites. This study bridges the gap between packaging and seafood quality, introducing advanced polymeric packaging technology for seafood products. It highlights the mutually beneficial link between packaging improvements and ensuring seafood quality, meeting industry needs while promoting sustainability.

Effect of Strain Rate on Nano-Scale Mechanical Behavior of A-Plane (112¯0) ZnO Single Crystal by Nanoindentation

In this study, nanoindentation tests at three different strain rates within 100 nm indentation depth were conducted on an a-plane (112¯0) ZnO single crystal to investigate the effect of strain rate on its nano-scale mechanical behavior. The load-indentation-depth curves, pop-in events, hardness and Young's moduli of an a-plane (112¯0) ZnO single crystal at different strain rates were investigated at the nano-scale level. The results indicated that, with the indentation depth increasing, the load increased gradually at each maximum indentation depth, h_ma, during the loading process. A distinct pop-in event occurred on each loading curve except that corresponding to the h_max of 10 nm. The applied load at the same indentation depth increased with the increasing strain rate during the nanoindentation of the a-plane (112¯0) ZnO single crystal. The higher strain rate deferred the pop-in event to a higher load and deeper indentation depth, and made the pop-in extension width larger. The hardness showed reverse indentation size effect (ISE) before the pop-in, and exhibited normal ISE after the pop-in. Both the hardness and the Young's modulus of the a-plane (112¯0) ZnO single crystal increased with the increasing strain rate, exhibiting the positive strain-rate sensitivity.

Active Packaging Material Based on Immobilized Diatomaceous Earth/Zinc Oxide/High-Density Polyethylene Composite for Sea Food and Products

One of the key factors of supporting the rapidly expanding seafood product industry in terms of quality control is the utilization of active packaging materials. Microorganisms are primarily responsible for the perishability and rapid disintegration of seafood. The incorporation of an inorganic compound, such as silica-based diatomaceous earth (DE), and a metal oxide, such as zinc oxide (ZnO), is proposed to develop active packaging materials with excellent antibacterial activity, minimized fishy odor, and brittleness at subzero temperatures. The mechanical, morphological, and physicochemical properties of these materials were investigated. The results show that the addition of DE/ZnO improved the antibacterial activity of high-density polyethylene (HDPE) samples by up to approximately 95% against both gram-positive and -negative bacteria. Additionally, it enhanced the Izod strength and stability at subzero temperatures of the samples. The odor evaporation test revealed that trimethylamine can be minimized in proportion to increasing DE/ZnO composite concentration. As a result, the development of active packaging materials from DE/ZnO composites is an emerging polymeric packaging technology for seafood products, wherein packaging and seafood quality are linked.