Large-scale fabrication of linear low density polyethylene/layered double hydroxides composite films with enhanced heat retention, thermal, mechanical, optical and water vapor barrier properties

Effects of biodegradable films on melon quality and substrate environment in solar greenhouse

With the increase in plastic pollution of farmland substrate, biodegradable mulch film research has become a hotspot. However, the degradation rate of biodegradable plastic film over the entire crop growth period is still unclear, as well as its impact on crop growth and product quality. Here, several properties of two kinds of composite biodegradable mulch films, PBAT/PLA-[S1] and PBAT/lignin-[S2], are studied with polyethylene-[PE] and uncovered substrate (CK) as controls. We tested the differences in morphological characterization, physical properties, and weight loss rate of the plastic films, as well as the effects of the different plastic films on melon yield and quality, substrate temperature and humidity, physical and chemical properties of the substrate, and substrate fungal species composition. Compared to PE, biodegradable plastic films S1 and S2 increased substrate temperature and the net photosynthetic rate of leaves. The results of substrate 18 s rDNA assay of CK, PE, S1, and S2 after 80 days of treatment and pre-treatment showed that a total of 12 fungal phylum, with 317 fungal genera were found, in which Ascomycota as the main phyla and Penicillium as the main genera. Compared with PE, the S2 treatment significantly increased the single fruit weight, central sugar content and soluble sugar of melon by 225.35 g, 1.26%, and 0.68%, respectively (p < 0.05). When buried for 240 d, the weight loss rate of S2 was significantly increased by 86.08% compared with PE (p < 0.05). From these results, we extrapolated that covering the substrate with the most biodegradable film, PBAT/lignin composite (10 μm), improved the yield and fruit quality of the melon in winter greenhouse production.

Morphology, Thermal Stability, and Flammability Properties of Polymer-Layered Double Hydroxide (LDH) Nanocomposites: A Review

The utilization of layered nanofillers in polymer matrix, as reinforcement, has attracted great interest in the 21st century. This can be attributed to the high aspect ratios of the nanofillers and the attendant substantial improvement in different properties (i.e., increased flammability resistance, improved modulus and impact strength, as well as improved barrier properties) of the resultant nanocomposite when compared to the neat polymer matrix. Amongst the well-known layered nanofillers, layered inorganic materials, in the form of LDHs, have been given the most attention. LDH nanofillers have been employed in different polymers due to their flexibility in chemical composition as well as an adjustable charge density, which permits numerous interactions with the host polymer matrices. One of the most important features of LDHs is their ability to act as flame-retardant materials because of their endothermic decomposition. This review paper gives detailed information on the: preparation methods, morphology, flammability, and barrier properties as well as thermal stability of LDH/polymer nanocomposites.

Micrometer-sized dihydrogenphosphate-intercalated layered double hydroxides: synthesis, selective infrared absorption properties, and applications as agricultural films

High-performance heat-retention agents for multifunctional green agricultural films are today largely suitable to increase the production yield as well as to save energy. Here, an adapted ammonia releasing hydrothermal method was used to produce a series of micrometer-sized carbonate-layered double hydroxide (CO₃-LDH) precursors of sizes ranging from 1.32 μm to 8.64 μm by simply adjusting the feeding Mg²⁺ concentration from 0.80 mol L^-1 to 0.20 mol L^-1. From these pristine LDH materials, μm-sized dihydrogenphosphate-intercalated LDHs (H₂PO₄-LDHs) were prepared by an anion-exchange method. The structure, the platelet size, and the associated selective IR absorption properties of the H₂PO₄-LDH and the derivative H₂PO₄-LDH/EVA composite as well as the related visible transmittance and the photostability of the H₂PO₄-LDH/EVA film were investigated. The results show that the selective IR absorption in the wavelength range of 7-14 μm enabling the heat retention of the H₂PO₄-LDHs and H₂PO₄-LDH/EVA composites depends on the corresponding number-averaged particle size of H₂PO₄-LDH in the range of 2.01 μm to 8.80 μm. Compared with EVA, the H₂PO₄-LDH/EVA composites demonstrate a significant improvement of selective IR absorption, while maintaining acceptable visible transmittance, and similar photostability. An optimized particle size of H₂PO₄-LDH of ca. 5.85 μm leads to 60% selective IR absorption and 64% selective IR absorption when dispersed in EVA, while the polymer free of filler exhibits less than 50% absorption in the 7-14 μm IR domain.

Scale-Up Fabrication of Biodegradable Poly(butylene adipate-co-terephthalate)/Organophilic-Clay Nanocomposite Films for Potential Packaging Applications

The development of biodegradable packing materials is a global priority due to the huge volumes of plastic refuse entering landfills and the environment. In this study, a series of biodegradable nanocomposite films based on poly(butylene adipate-co-terephthalate) (PBAT) and reinforced with an organophilic layered double hydroxide (OLDH) were scale-up fabricated. The OLDH nanosheets with a basal spacing of 4.07 nm were presynthesized on a large-scale by solvent-free high-energy ball milling. All of the PBAT/OLDH nanocomposite films (0.5-4 wt % OLDH) showed a uniform dispersion of OLDH nanosheets in the PBAT matrix. A PBAT/OLDH film containing 1 wt % OLDH (denoted herein as OLDH-1) demonstrated outstanding thermal, optical, mechanical, and water vapor barrier properties compared with a pure PBAT film (OLDH-0), including a 37% reduction in haze and a 41.9% increase in nominal tensile strain at break dramatically. Furthermore, the food packaging measurement revealed that the OLDH-1 film showed a better packaging effect than the pure PBAT film and commercial polyethylene packing materials. The feasibility of scale-up manufacture and the excellent processability, manufacturing scalability, mechanical performance, optical transparency, water vapor barrier properties, and food packaging performance of the PBAT/OLDH nanocomposite films encourage their future application as biodegradable packaging films.

Innovative Linear Low Density Polyethylene Nanocomposite Films Reinforced with Organophilic Layered Double Hydroxides: Fabrication, Morphology and Enhanced Multifunctional Properties

Herein, we reported the successful development of novel nanocomposite films based on linear low density polyethylene (LLDPE) with enhanced anti-drop, optical, mechanical, thermal and water vapor barrier properties by introducing organophilic layered double hydroxides (OLDHs) nanosheets. OLDHs loadings were varied from 0–6 wt.%. Structural analyses using the Fourier transform infrared spectrum (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) indicated that the OLDHs nanosheets were homogeneously dispersed with an ordered alignment in the LLDPE matrix. The LLDPE film containing 2 wt.% OLDHs (denoted as OLDHs-2) showed the optimal mechanical, thermal and water vapor barrier properties, whilst the anti-drop and optical performance of the films improved with increasing OLDHs content. The enhanced antidrop properties of the composite films relative to pristine LLDPE can be expected to effectively reduce agricultural losses to disease when the films are applied as agricultural films, whilst the superior light transmittance and water-retaining properties of the composite films will boost agricultural production. Results presented suggest that multifunctional LLDPE/OLDHs nanocomposites show great promise as low cost agricultural plastic films.