Linear Low-density Polyethylene Films Research Articles

Thermomechanical and transport properties of LLDPE films impregnated with clove essential oil by high-pressure CO2

Clove essential oil (CEO) was impregnated in linear low-density polyethylene (LLDPE) films by high-pressure CO2 technique. Impregnations were performed at 150 bar, 25 and 32 °C for 2 h followed by depressurization at 10, 50 and 100 bar min−1. The influence of operational parameters was observed on impregnation, optical, topographic, morphological, thermomechanical and transport properties of films. Higher amounts of CEO were impregnated when reducing depressurization rate and increasing temperature, with a maximum of 26.83 mg CEO/g LLDPE. Diffusion mechanism governed CEO migration from LLDPE in 10% and 95% (v/v) ethanolic solutions. The effective diffusion coefficient of CEO in LLDPE ranged from 5.4 × 10−13 to 1.0 × 10−12 m2 s−1. Operational parameters can be adjusted to enhance CEO incorporation, presenting negligible effect over CEO diffusivity in LLDPE. The results suggest the potential for developing active food packaging materials by green processes, also aggregating value to compounds from natural sources.

Different structure transitions and tensile property of LLDPE film deformed at slow and very fast speeds

In the present work, the uniaxial deformation of 1-hexene based Linear Low Density Polyethylene (LLDPE) cast film at slow to very fast stretching speed (initial strain rate 10−3 to 8.3 s−1) was investigated, together with a high speed video camera for capturing craze morphologies. The structural evolution of the deformed film at different speeds was also studied with Small Angle X-ray Scattering. Very different tensile behavior is observed when the film is stretched at very fast speed. Voids are detected by SAXS for slow MD and TD stretching processes; but no visible crazes are observed. However, visible crazes appear starting at a small satrain of 0.3 during fast MD stretching, due to the film being more rigid when stretched at the fast speed. The crazes appear with the length direction being perpendicular to the stretching direction and propagate quickly in the length direction. The crazes appear almost everywhere in the film during the fast MD stretching, while only occur in the central region during the fast TD stretching due to the preferred crystal orientation in MD direction where crazes can propagate more easily and faster. The structure transition at lamellar level is much faster during the fast stretching process, due to the formation of the visible crazes. The leaning is helpful for better understanding puncture, dart and tear tests of PE films, where the films undergo the fast deformation.

Compression molded LLDPE films loaded with bimetallic (Ag-Cu) nanoparticles and cinnamon essential oil for chicken meat packaging applications

This study describes the development of bioactive linear low-density polyethylene (LLDPE) films, blended with cinnamon essential oil (CEO), and selected concentrations of silver-copper (Ag-Cu) nanoparticles (NPs), and processed by compression molding. Influence of Ag-Cu NPs and CEO on thermo-rheological, structural, barrier, morphological and antimicrobial properties of LLDPE composite films were investigated. Ag-Cu NPs reinforcement effectively improved the mechanical and barrier properties of the films, whereas, CEO improved the flexibility of the composite films by lowering the complex viscosity and the melting temperature. The composite films exhibited excellent anti-UV properties, and appearance of new peaks corresponding to the aromatic domain with N-H bending vibration was confirmed by FTIR spectroscopy. Films loaded with Ag-Cu NPs and 50% CEO showed maximum antimicrobial activity against Listeria monocytogenes, Salmonella Typhimurium and Campylobacter jejuni. Chicken samples contaminated with S. Typhimurium and C. jejuni; packed in the composite films containing 4% (w/w) Ag-Cu and 50% CEO (w/w), and stored at refrigerated temperature for 21 days showed a complete inhibition.

Whey protein-coated high oxygen barrier multilayer films using surface pretreated PET substrate

Whey protein isolate (WPI)-coated multilayer films were developed using polyethylene terephthalate (PET) film as a substrate. To improve the interfacial compatibility between PET film and water-based WPI coating solution, various surface pretreatments (corona discharge, plasma, and primer coating) were applied to PET. Water contact angles of the plasma-treated PET were significantly decreased by 12.8% related to the untreated PET, suggesting an increment of hydrophilic functional groups. Oxygen transmission rates of surface-pretreated multilayer films with WPI coating layer [PET/WPI/nylon/linear low-density polyethylene (LLDPE)] were significantly lower, about 43–234 times, than the multilayer films without WPI film layer. In addition, tensile strength of the plasma-pretreated PET/WPI/nylon/LLDPE films was 13.4 and 21.8% higher, elongation at break was 29.7 and 2.6% higher than the corona discharge- and primer-pretreated films, respectively. Taken together, WPI films are promising candidates for replacing synthetic oxygen-barrier materials. Specifically, plasma-pretreated PET/WPI/nylon/LLDPE films have a high potential as high oxygen-barrier packaging materials.

Influence of Food with High Moisture Content on Oxygen Barrier Property of Polyvinyl Alcohol (PVA)/Vermiculite Nanocomposite Coated Multilayer Packaging Film.

We believe this manuscript would be of interest to the wide group of researchers, organizations, and companies in the field of developing nanoclay-based gas barrier packaging for foods with high moisture content. Hence, we wish to diffuse our knowledge to the scientific community.

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.

The Effect of Potassium/Sodium Lactate (Pl/Sl), Sodium Erythorbate (Nae), and Sodium Bicarbonate (Sb) on Quality of Aerobically Stored Beef Trimmings

ObjectivesThe objective of the study was to investigate various concentrations of solutions that can be applied to aerobically stored beef trimmings as a processing aid to prevent further deterioration of color, lipid, odor and/or microbial growth.Materials and MethodsBeef trimmings (∼15 kg) were fabricated from beef forequarters and aerobically stored (5°C) for 6 d in a plastic container covered with linear low-density polyethylene film (LLDPE; Oxygen Transmission Rate: 5,000 cc/m2 per 24 h at 25°C and 0% R.H.) to simulate the collection, storage, transportation and receipt of a combo of beef trimmings. A total of 12 treatments (4 solutions × 3 concentration levels) consisting of PL and SL at 0.1, 0.2 and 0.5 M; NaE at 1, 2, and 100 mM; and SB solutions at 0.1, 0.2 and 1.5 M; and a control (water). Concentrations of the solutions were based on previous research. After aerobic storage the beef trimmings (∼20% fat) were coarse ground (12 mm) and 9 mL of each treatment and control solution was applied to ∼454-g samples. The treated samples were reground (3 mm) placed into Petri dishes and overwrapped with LLDPE film. The patties (2 per treatment/control (13) × 2 storage d; N = 52 per replication) were stored under simulated retail conditions: 5°C under cool white fluorescent light (200 to 300 lux) and analyzed at 0 and 5 d of storage to assess the effectiveness of each treatment solution in preventing further quality deterioration. Objective color (L*, a*, b*; metmyoglobin concentration, MMB), 2-thiobarbituric acid (TBA) determinations, GC–MS identification of volatile compounds for off-odor assessment and aerobic plate counts (APC) were conducted. The results of 2 replications were analyzed using one-way ANOVA and Tukey HSD with a significance level of P < 0.05.ResultsNo differences were observed for treated and control patties for color, lipid oxidation or microbial analyses on storage d 0. Additionally, no differences were observed between treatments and the control for any volatile off odor compounds (ketones, aldehydes and acids) at 0 and 5 d of storage (P > 0.05). Samples treated with varying concentration of PL did not significantly impact any quality factors evaluated (P > 0.05). Analyses of SL, SB and NaE treated patties at 5 d of retail storage exhibited differences in color, lipid oxidation and microbial growth (P < 0.05). Pattie samples treated with SB (1.5 M) exhibited the highest a* value (13.63) and lowest MMB content (33.92%) compared to other treatments (P < 0.05). Samples treated with NaE (100 mM) had the lowest TBA value (0.79) compared to other treatments and control. Samples treated with SL (0.4 M) exhibited the lowest AM and AP counts (8.4 and 7.4 log10 CFU/g, respectively) compared to other treatments and control.ConclusionIn conclusion, samples treated with the SB (1.5 M), NaE (100 mM), and SL (0.4 M), had the greatest effect on improving color stability, reducing lipid oxidation, and controlling microbial spoilage, respectively at 5 d of retail storage. Results of this study suggest that a solution could be developed as a processing aid using a combination of SB, NaE, and SL to prevent further deterioration of beef trimmings prior to use in the manufacturing of ground beef products.

고온기 결구상추의 포장재와 포장방법 적용에 따른 선도 비교

Effects of different packaging methods for maintaining the shelf life and postharvest quality of iceberg lettuce (Lactuca sativa L.) were studied after harvesting in summer season. Lettuce heads were packaged in plastic crate with or without different films such as (A) Individual lettuce head sealed packaging with linear low density polyethylene (LLDPE) film; (B) Packaging lettuce head in plastic crate and wrapped with LLDPE film; (C): Individual lettuce head sealed packaging with perforated high density polyethylene (HDPE) film; (D) Packaging lettuce head in plastic crate and wrapped with perforated HDPE; and (E) Packaging lettuce head in plastic crate without any film (control), and stored at 2°C for 35 days. Several quality parameters such as fresh weight loss, SPAD (soil & plant analyzer development) meter value, respiration rate, moisture content and appearance of lettuce were investigated. The lettuce wrapped with individually- sealed LLDPE film showed the lowest weight loss and the highest SPAD value rendering the best appearance index among the treataments throughout the three-week storage period at 2oC. Extending the freshness of iceberg lettuce during low temperature storage will definitely increase the salability potential in the domestic market even during summer season.

Simple and economical CALB/polyethylene/aluminum biocatalyst for fatty acid esterification

Candida antarctica lipase B was immobilized for the first time (at the author's knowledge) onto linear low density polyethylene (LLDPE) films. Polymer films were previously bonded to a commercial aluminum sheet using a simple support preparation method. Biocatalyst performance was evaluated in penthyl oleate synthesis at room temperature. Two different catalyst geometries were tested and compared: one aluminum‐polyethylene 50 mm × 50 mm foil (50CAT) or near 5 mm × 5 mm aluminum‐polyethylene foils (5CAT). The obtained results demonstrate that the biocatalyst obtained with 50 mm × 50 mm aluminum‐polyethylene foil or 50CAT is reusable in up to 7 cycles, easy to separate from reaction products, and economical in comparison with commercial Novozym 435. Novel and economical CALB/LLDPE/Al biocatalyst is an attractive alternative for possible applications in a continuous monolithic reactor and future industrial scaling up.

Nonlinear thermomechanical response and constitutive modeling of viscoelastic polyethylene membranes

Thin films of linear low-density polyethylene show a significant time-dependent behavior, strongly reliant on temperature and strain rate effects. A constitutive nonlinear thermo-viscoelastic relation is developed to characterize the response of thin membranes up to yielding, in a wide range of temperatures, strain rates, and mechanical loading conditions. The presented plane stress orthotropic formulation involves the free volume theory of viscoelasticity and the time-temperature superposition principle, necessary to describe non-linearities and non-isothermal conditions. Uniaxial tension tests at constant strain rate and long-duration biaxial inflation experiments have been employed in the calibration of the material parameters. The model has been implemented in the Abaqus finite element code by means of a user-defined subroutine based on a recursive integration algorithm. The accuracy of the constitutive relation has been validated against experimental data of full field diaphragm inflation tests and uniaxial tension, relaxation and cyclic experiments, covering sub-ambient temperatures and strain rate ranges observed during the operation of stratospheric balloons.

Effects of incorporation of additives in the mechanical properties of films of linear low-density polyethylene

In this investigation the effect of the incorporation of additives in the mechanical properties of LLDPE films, made to be used as greenhouse covers, was analyzed. All films were fabricated by the method of extrusion blow. Two types of formulations are raised in order to determine the influence of the concentration of one additive and identify the existence of some synergy by combining active ingredients in the formulations. Modulus of elasticity, yield stress and tear resistance of the films were evaluated. The results indicate that variation in the concentration of an additive in the mixture does not generate significant changes in the physical-mechanical properties of the films. However, the incorporation of the UV light absorber and Smartlight fotoselector in formulations favors their mechanical properties. Compared with the reference film, an increase higher than 200% in modulus of elasticity and yield stress of the films was determined.

The effect of comonomer concentration and distribution on the photo-oxidative degradation of linear low density polyethylene films

The photo-oxidative degradation of two complementary linear low density polyethylene (LLDPE) films has been studied: a Ziegler-Natta catalysed 1-octene copolymer (ZN-LLDPE) and a 1-octene copolymer produced by a single site constrained catalyst (m-LLDPE). The degradation processes were followed using a range of characterisation techniques including tensile testing, GPC, MAS-NMR, FTIR, WAXS and SAXS. The chemical species formed on degradation were similar for both polymers. Both also showed an increase in crystallinity and modulus with UV ageing time and a decrease in the long spacing of the lamella. However, the m-LLDPE showed a significantly shorter time to embrittlement than the ZN-LLDPE, which correlated in both polymers with the disappearance of the second yield point. The major observed difference in crystalline structure was a significantly higher interfacial thickness between the crystalline lamellae and the amorphous regions for the ZN-LLDPE, which decreased rapidly on UV ageing. This difference in behaviour was attributed to the nature of the branching in the ZN-LLDPE, which was presumed to sit in blocks along the chain and thus to reside in the interfacial regions. Cleavage of the tertiary carbons in these interfacial regions was less damaging to the mechanical properties than for the m-LLDPE, where chain scission broke more of the tie molecules, thus limiting the ability of the polymer to draw. . This work advances our understanding of polymer microstructural evolution during degradation and the implications of initial polymerisation route and molecular structure on the degradation mechanisms.

Rheological, structural, ultraviolet protection and oxygen barrier properties of linear low- density polyethylene films reinforced with zinc oxide (ZnO) nanoparticles

Abstract Linear low-density polyethylene (LLDPE) and zinc oxide (0–10%, w/w) nanocomposite (NC) films were produced through melt-mixing extrusion process. Both LLDPE and LLDPE/ZnO NC exhibited predominating liquid-like property in the lower frequency range, however, a distinct gel point was detected at higher frequency. At 10% loading of ZnO to LLDPE followed the time-temperature-superposition (TTS) principle adequately in the selected temperature range (140–170 °C). Tensile strength (TS) of the NC increased whereas the elongation at break (EAB) decreased with increasing loading concentration of ZnO. NC films showed lower transparency, b*-values (yellowness), and ΔE*-values (total color difference) than the control LLDPE film. Incorporation of ZnO improved the ultraviolet (UV) barrier properties whereas the oxygen transmission rate decreased significantly from about 11,000 to 8000 cm 3 /(m 2 24 h). X-ray diffraction (XRD) analysis confirmed the crystalline structure of the NC films, and an improvement in thermal stability was detected through thermogravimetric analysis. Scanning electron microscopy (SEM) exhibited well dispersion of nanoparticles in the NC matrix with a coarse film surface. Thus, LLDPE/ZnO nanocomposite films could be used as a food packaging material to prevent oxygen and UV induced lipid oxidation in food materials.

High pressure carbon dioxide for impregnation of clove essential oil in LLDPE films

Abstract High-pressure carbon dioxide (CO2) impregnation is a promising technology in the development of active packaging films. Clove essential oil (CEO), a multicomponent active agent naturally rich in eugenol, was incorporated in linear low density polyethylene (LLDPE) films by using high pressure CO2 impregnation. The parameters of temperature (25, 35 and 45 °C), pressure (150 and 250 bar) and CEO:CO2 mass ratio (2 and 10%) were screened using a variable-volume view cell for 4 h to determine the best impregnation conditions. Kinetic assays of CEO impregnation were also performed. The highest amount of CEO (40.2 mg g− 1 of LLDPE) impregnated was obtained at 10% CEO:CO2 mass ratio, 45 °C and 150 bar. The impregnation at 2 h showed advantage in reducing processing time. A preferential eugenol impregnation was observed due to thermodynamic interactions and mass transfer phenomena. Thermal and mechanical properties of LLDPE films remained stable after high pressure processing. Industrial relevance The development of innovative technologies for active packaging systems has attracted the interest of food, pharmaceutical, and chemical industries. The consumer's demand for products with low healthy risk makes the CEO an advantageous active agent for packaging development purposes, besides possessing strong antimicrobial and antioxidant activities. The employment of high pressure CO2 allowed a homogeneous CEO impregnation in LLDPE films without damaging mechanical and thermal properties of the polymer matrix, which is important for industrial applications. The CEO-impregnated LLDPE films have potential use in antimicrobial and antioxidant packaging systems.

Novel antifog modification for controlled migration and prolonged wetting of LLDPE thin films

This paper focuses on the development of a novel modification method of commonly used antifog (AF) additives such as glycerol monooleate (GMO) and sorbitan monooleate (SMO). In this method, the AF organic molecules were grafted to vinyl silane, methacryl-oxypropyl-trimethoxy-silane (MEMO), to form MEMO grafted GMO (MEMO-g-GMO) and MEMO grafted SMO (MEMO-g-SMO). A thorough study of linear low density polyethylene (LLDPE) containing the modified AF (LLDPE/MEMO-g-AF) was performed, including investigation of the additives' migration from the LLDPE matrix.Thermal gravimetric analysis (TGA) and Fourier transform IR (FTIR) measurements showed a successful grafting of GMO and SMO to MEMO. Thermal analysis showed that 1 part per hundred parts resin (phr) MEMO-g-GMO has no effect on the thermal decomposition of LLDPE. According to hot fog test results, it was found that only LLDPE films containing 1phr MEMO-g-GMO exhibited excellent antifog performance, while LLDPE films containing 1phr MEMO-g-SMO exhibited poor antifog performance. It was found that LLDPE/MEMO-g-GMO system is characterized by a slower AF migration rate and a lower diffusion coefficient, compared to the reference system, LLDPE/GMO; these results are well correlated with the hot fog test results. Morphological studies revealed a fine dispersion of the MEMO-g-GMO in the polymer.

Extraction of Process-Structure Evolution Linkages from X-ray Scattering Measurements Using Dimensionality Reduction and Time Series Analysis.

The rapid development of robust, reliable, and reduced-order process-structure evolution linkages that take into account hierarchical structure are essential to expedite the development and manufacturing of new materials. Towards this end, this paper lays a theoretical framework that injects the established time series analysis into the recently developed materials knowledge systems (MKS) framework. This new framework is first presented and then demonstrated on an ensemble dataset obtained using small-angle X-ray scattering on semi-crystalline linear low density polyethylene films from a synchrotron X-ray scattering experiment.

Effect of the blow-up ratio on morphology and engineering properties of three-layered linear low-density polyethylene blown films

A series of linear low-density polyethylene films were produced using a three-layer co-extrusion machine. How the blow-up ratio and resin characteristics affected the final film morphology and engineering properties were studied. The crystalline morphology and orientation during the blown film process of the low-density polyethylene film were investigated using small-angle X-ray scattering, transmission electron microscopy and scanning electron microscopy. Increasing the blow-up ratio increased the transverse direction molecular orientation and decreased the machine direction orientation. The resulting low-density polyethylene morphology was a regular lamellar stacking parallel to the machine direction. The film morphology strongly influenced the mechanical properties. Increasing the blow-up ratio from 1.7 to 2.8 decreased the machine direction tensile strength by 14% and increased the transverse direction tensile strength up to 27% for both the low-density polyethylene/1-butene and low-density polyethylene/1-octene co-monomers, while the machine direction tear strength increased up to 36% and the transverse direction decreased by 16%. Moreover, the first and second heating characteristics from differential scanning calorimeter showed the inherent crystallinity change with increasing blow-up ratio for both the low-density polyethylene/1-octene and the low-density polyethylene/1-butene copolymer. The crystalline orientation changes induced with increasing blow-up ratio affected the film water vapor and oxygen permeability.

Improvement of Water Vapor Permeability of LLDPE/EVA Film with Zeolite A as Filler

In this work, water vapor permeability of linear low density polyethylene (LLDPE)/ethylene vinyl acetate copolymer (EVA) film is improved by incorporation of zeolite A as filler (0-25%wt) for prolonging shelf-life of fresh produces. All films were characterized by SEM, DSC, tensile testing, contact angle measurement and tested for water vapor permeability (WVP). The shelf-life of Bird’s eye chili in the film samples was also tested at 10°C for 21 days. It was found that zeolite A particles were virtually dispersed in EVA phase. Accordingly, crystallinity and tensile properties of LLDPE/EVA/Zeolite A films is independent to zeolite loading. Despite, when zeolite loading was increased, the dispersion became low. The film’s wetting behavior was enhanced by increasing zeolite content in the LLDPE/EVA/Zeolite A films. The observed increase in the film’s polarity significantly enhances the WVP. Therefore, less water condensed can be found inside the package made with LL80E20Ze25 film, as compared to LLDPE or LLDPE/EVA film. The LL80E20Ze25 also possesses comparable tensile properties to the commercial LLDPE film and hence can used as packaging for extending the shelf-life of fresh produces.

Water vapor permeability, morphological properties, and optical properties of variably hydrolyzed poly(vinyl alcohol)/linear low-density polyethylene composite films

Poly(vinyl alcohol) (PVA)/ linear low-density polyethylene (LLDPE) composite films were prepared using PVAs of various molecular weights and degrees of hydrolysis. The crystallinity, water permeability, mechanical properties, and optical properties of the composite films were analyzed based on the absorption properties of the different PVAs. The formation of the composite film became increasingly difficult with increase in the molecular weight and the degree of hydrolysis of PVA, because the resulting crystallinity increased the intramolecular hydrogen bonding of the hydroxyl groups on the main chains of PVA. The 4-98/LLDPE composite film absorbed water gradually and continuously for a long time, and its water vapor absorption rate was similar to that of the 4-88/LLDPE film but lower than that of the PVA 205/LLDPE film. The mechanical properties of the 4-98/LLDPE film were slightly better than those of the 4-88/LLDPE film but inferior to those of the PVA 205/LLDPE film.

Improved Morphology and Properties of Nanocomposites, Linear Low Density Polyethylene, Ethylene-Co-Vinyl Acetate and Nano Clay Particles by Electron Beam

Surface modification of linear low-density-polyethylene (LLDPE), ethylene-co-vinyl acetate (EVA), and clay nanoparticles composite films was promoted by potassium permanganate solutions in HCl acidic medium using eight conditions by variation times and temperature, also concentrated oxidation solution of LLDPE and EVA blend films shows a very good clarity and tensile properties, this property can be improved by adding the clay nanoparticles as a filler in the composite. The influence of electron beams (EB) irradiation and amount of clay nanoparticles loading on the overall properties of linear low-density polyethylene (LLDPE) /ethylene-co-vinyl acetate blends was investigated. Samples were subjected to the EB irradiation with the dose values of 75 and 150kGy, afterwards mechanical and thermal properties of the LLDPE/EVA blends with and without clay nanoparticles at different irradiation dosages were utilized in order to analyze the characteristics of the final composite. These enhanced properties are due to the homogenize dispersion of Clay nanoparticles in LLDPE matrix. Moreover, in order to verify these characteristics and compare composite samples with and without Clay nanoparticles (Cloisites 30B), some tests such as DSC, TGA, PSA, SEM and Optical Micrographs (OM) were taken from the samples.