Low-density Polyethylene Layers Research Articles

Mechanical Analysis of Laminated Structures Consisting of Denim Fabric and Recycled HDPE / LDPE Bottle Caps

Industrialization and the increase in population in the world have led to a great increase in the amount of solid waste. Plastic and textile wastes have an important share among the solid wastes, which include many different waste groups. While the increase in disposable products increases the amount of plastic waste, the understanding of fast fashion is among the most important reasons for the increase in textile waste. In this study, cotton based woven textile wastes (2nd quality denim fabric) are laminated with plastic packaging wastes (high density polyethylene (HDPE) and low density polyethylene (LDPE) water bottle caps) in various sequences and thickness, areal density and fiber weight ratio values of these structures are examined. In addition, the impact properties of the produced laminated composite structures are analyzed via drop-weight impact testing machine. The results show that the increase in the number of fabric layers contributes positively to the energy absorption rate thus the samples including two layers of fabrics and one layer of either LDPE or HDPE plastic sheet have the highest maximum loads and absorbed energy values. In addition, it is also seen that HDPE lamination results in higher absorbed energy values compared to LDPE lamination.

Surface Modification of Polytetrafluoroethylene Hollow Fiber Membrane for Direct Contact Membrane Distillation through Low-Density Polyethylene Solution Coating.

Membrane distillation (MD) is an attractive technology for the separation of highly saline water used with a polytetrafluoroethylene (PTFE) hollow fiber (HF) membrane. A hydrophobic coating of low-density polyethylene (LDPE) coats the outer surface of the PTFE membrane to resolve membrane wetting as well as increase membrane permeability flux and salt rejection, a critical problem regarding the MD process. LDPE concentrations in coating solution have been studied and optimized. Consequently, the LDPE layer altered membrane morphology by forming a fine nanostructure on the membrane surface that created a hydrophobic layer, a high roughness of membrane, and a uniform LDPE network. The membrane coated with different concentrations of LDPE exhibited high water contact angles of 135.14 ± 0.24 and 138.08 ± 0.01° for membranes M-3 and M-4, respectively, compared to the pristine membrane. In addition, the liquid entry pressure values of LDPE-incorporated PTFE HF membranes (M-1 to M-5) were higher than that of the uncoated membrane (M-0) with a small decrease in the percentage of porosity. The M-3 and M-4 membranes demonstrated higher flux values of 4.12 and 3.3 L m–2 h–1 at 70 °C, respectively. On the other hand, the water permeation flux of 1.95 L m–2 h–1 for M-5 further decreased when LDPE concentration is increased.

Antioxidant Packaging as Additional Measure to Augment CO2-enriched Modified Atmosphere Packaging for Preserving Infant Formula Powder

Al-laminated packaging film incorporating ascorbic acid or tocopherol at inner food contact layer was tested in the potential to improve antioxidative preservation of powdered infant formula under CO2-enriched atmosphere. Product of 200 g was packaged with the packaging film containing 0.3% antioxidant in sealant layer of low density polyethylene and stored at 30oC for 286 days with periodic measurement of package atmosphere and product’s quality attributes. The CO2-flushed package resulted in shrinkage of tight contact between the product and the film not allowing gas sampling of package atmosphere after 140 days. Package of tocopherol-incorporated film allowed some ingress of oxygen after 112 days presumably due to its weakening of heat-seal area. The increased oxygen concentration in the tocopherol-added film package led to the concomitant increase of peroxide value, an index of lipid oxidation. On the other hand, packaging of ascorbic acid-added film pouch could suppress lipid oxidation marginally in consistent manner compared to control package without any antioxidant.

Enhanced thermal conductivity of multilayered sheets of polyethylene and boron nitride via promoting molecular diffusion between layers

In this work, we alternatively compressed a high density polyethylene/low molecular weight polyethylene (LMWPE)/hexagonal boron nitride (h-BN) composite layer and a low density polyethylene layer together to fabricate thermally conductive bulk products. Compared to our previous work (without the LMWPE component), introducing the short chain component, i.e., LMWPE, into the composite layers further enhanced the h-BN content to 18.3 vol. %, and, thus, more thermally conductive paths could be formed after annealing, resulting in higher thermal conduction performance. Also, the annealed multilayered cuboid in this work exhibited a high thermal conductivity of 1.96 (W/m K), 43% higher than that of our previous study (1.37 W/m K). In contrast with that of the samples with randomly distributed h-BN at the same loading, an approximately 145% enhancement was achieved. The results demonstrate that our method to fabricate the multilayered cuboids has a great opportunity for application in the thermal management field of electric devices.

Determination of Depth in Transmission Raman Spectroscopy in Turbid Media Using a Beam Enhancing Element

This study demonstrates experimentally a method to enable prediction of depth of a chemical species buried in a turbid medium by using transmission Raman spectroscopy alone. The method allows the prediction of the depth of a single, chemically distinct layer within a turbid matrix by performing two measurements, with and without a beam enhancing element, or "photon diode." The samples employed consisted of two different polymers, of total thickness 3.6 mm, whose optical properties are loosely relevant to pharmaceutical applications. A polymer layer of low-density polyethylene (LDPE) was placed at different positions within multiple layers of the polytetrafluoroethylene (PTFE) matrix and Raman spectra were recorded in each case. Both univariate and multivariate analyses were utilized to determine whether the depth of the LDPE layer could be predicted using the obtained data. The best-achieved RMSE of prediction was 4.2% of the total sample size (i.e., +/- 0.15 mm) with the multivariate approach.

Production and Evaluation of Type of Multi‐Layer Active Film for Packaging of Pasteurized Milk

AbstractObjectives: The main aim of this study was to evaluate the effect of antimicrobial films on the shelf life of pasteurized milk. Methods: A natural antimicrobial agent, cinnamaldehyde, was incorporated in 0.5%, 1.0%, 1.5% and 2% concentrations in the middle layer of low density polyethylene (LDPE) three layer films by an extrusion process. Thickness of the inner layer were adjusted to 30 µm, 45 µm, and 60 µm and 2% PEG were added to some of the inner layer formulations. Active pillow packaging (5 cm × 7 cm) with 16 different formulas were obtained from the fabricated three layered active films by thermo‐welding process and filled with pasteurized milk and stored at 4°C for 9 days. In order to see the effect of the active films on pasteurized milk quality, changes in total microbial counts monitored during the storage period. Results: During extrusion process, the mass loss of cinnamaldehyde were six times lowered when it was entrapped in the polymer matrix. All types of fabricated active films contributed to a reduction of total CFU growth rates in the pasteurized milk, when compared to plain (control) PE film, but the films coated with a thinner inner layer and films containing 2% PEG in the inner layers had a more pronounced effect than did the other films in inhibiting bacterial growth. Moreover, considering the five point hedonic scale sensory tests, film formulation number OM2I4 selected as the best one and its physical properties were compared to the control film.Practical ApplicationsConsidering the daily high usage of pasteurized milk in most countries and regarding the short shelf life and perishable properties of this food product, using of multi‐layer active films containing cinnamaldehyde (a natural antimicrobial) for packaging of pasteurized milk can extend its typical shelf life (4 days) to 6 days at 4°C of storage.

Study of the correlation between flexible food packaging peeling resistance and surface composition for aluminum-metallized BOPP films aged at 60°C

ABSTRACTThis study investigated the correlation between surface composition and peeling resistance in food packaging films by studying the heat aging of fabricated films over varying periods of time. The films consisted of a layer of aluminum (Al) metallized, biaxially oriented polypropylene (BOPP) bonded with a polyurethane (PU) adhesive onto another polymeric layer of low-density polyethylene (LDPE). The Al metallized films were prepared by physical vapor deposition (PVD) and aged at 60°C for either 5 or 15 days. The resulting aluminum surfaces were analyzed using X-ray photoelectron spectroscopy (XPS) and found to contain aluminum oxide (Al2O3) and trihydroxide (Al(OH)3). The XPS characterization also revealed a 29% increase in the Al(OH)3 layer thickness of the aged sample relative to a non-aged sample. Atomic force microscopy (AFM) was applied on investigations of possible morphology changes. The aluminum and PU adhesive surface energies were also determined using contact angles measurements and the aluminum surface energy was found to increase by as much as 11.7% compared to the non-aged sample, while the PU adhesive surface energy was at least 65% higher than that of the metallic substrate. The peeling resistance of the laminated aluminum was determined by average peel strength measurements and it was found that the variation in peel strength was related to changes in the Al2O3 layer thickness. The delaminated samples were analyzed using scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) and showed the cohesive failure of the aluminum film.

Study of Shear Dominant Delamination in Thin Brittle-High Ductile Interface

Thin laminates of Aluminum (Al) foil and Low Density Polyethylene (LDPE) film are essential constituents of food packages where these two substrates are bonded together with a thin layer of LDPE acting as adhesive. Noticeably, Al is a low ductile/quasi brittle material, whereas LDPE is highly ductile. The mechanism of delamination and strength of bond between the interfaces dictates the continuum and damage behavior of this composite. However, measuring the shear delamination properties is challenging as conventional test methods have limitations when the substrates are very thin and flexible. This study explains a tentative method that uses uniaxial tensile testing on the pre-cracked specimen of this composite to find energy dissipation due to shear delamination and successfully uses it in Finite Element Simulation in Abaqus. The delamination was observed in a narrow strip-like region close to fracture surfaces and measured with special visualization aid. A similar response was found in FEM simulation. Scanning Electron Microscopic (SEM) study of delaminated interface confirms the delamination to be shear in nature. In a cohesive zone modeling in Abaqus, the measured shear delamination energy was used as input parameter along with an arbitrary bi-linear cohesive law for validation of the experimental measurement.

Barrier, mechanical, and thermal properties of the three-layered co-extruded blown polyethylene/ethylene–vinyl alcohol/low density polyethylene film without tie layers

This article investigates three-layer co-extruded blown film comprised of low-density polyethylene (LDPE)/ethylene–vinyl alcohol (EVOH)/LDPE without adhesion layers. Various thicknesses of pure EVOH were sandwiched by outer LDPE layers blended with linear low-density polyethylene-grafted-maleic anhydride (LLDPE- g-MAH) as compatibilizer in concentrations from 0 wt% to 2.0 wt%. The study found that a mere 3-μ EVOH layer can achieve a 180 times improvement of oxygen barrier properties as compared to the control sample. When the EVOH loading is 10–15 wt% of the total film mass, the addition of LLDPE- g-MAH into the outer layers indicated a positive synergistic effect by enhancing barrier properties. In contrast, when the EVOH loadings are at 5 wt% and 7.5 wt%, the barrier properties of the film was reduced. Layer-to-layer interaction between the LDPE and EVOH was notably improved as demonstrated by a 26–42% increase of interlaminate peel strength in the presence of 0.5–2 wt% LLDPE- g-MAH in all samples. Congruently, the introduction of the LLDPE- g-MAH into the outer LDPE layers also resulted in an increased dart impact toughness and tensile strength for the film. The EVOH crystallinity showed a reduction after adding LLDPE- g-MAH, particularly apparent for the lower EVOH concentrations.

Effect of the compatibility on dielectric performance and breakdown strength of poly(vinylidene fluoride)/low‐density polyethylene blends

ABSTRACTImmiscible polymer blends with high dielectric constant (ε) and improved breakdown strength (Eb) performance were obtained by composing poly(vinylidene fluoride) (PVDF) with low‐density polyethylene (LDPE) or the LDPE grafted with maleic anhydride (LDPE‐g‐MAH) through melt‐blending way. The dielectric properties of these blends were emphasized for considering the compatibility effect on the energy storage application. Interface morphology, co‐continuity behavior, and grafted ratio were simultaneously investigated to detect the compatibility enhancement after introducing MAH. Results showed that the MAH positively improved the dielectric properties. Both the measured Eb of PVDF/LDPE and PVDF/LDPE‐g‐MAH blends showed a minimum value at vPVDF = 50 vol % because of the worst compatibility; meanwhile, higher Eb of PVDF/LDPE‐g‐MAH than that of PVDF/LDPE blend was observed owing to the better compatibility. For considering the effect interface morphology on the dielectric performance, layer‐structure films composing with pure PVDF and LDPE layers were further constructed and studied. It was revealed that the layered structure could be treated as a helpful way to improve ε and Eb for immiscible polymer blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42507.

Effect of Beta Low Irradiation Doses on the Micromechanical Properties of Surface Layer of LDPE

The experimental study deals with the effect of modification of the surface layer by irradiation cross-linking on the micromechanical properties of the low-density polyethylene (LDPE) tested using the instrumented nanohardness test. The surface layer of LDPE specimen made by injection technology was modified by irradiation cross-linking using beta irradiation, which significantly influences micromechanical properties of the surface layer. Compared to the heat and chemical-heat treatment of metal materials (e.g. hardening, nitridation, case hardening), cross-linking in polymers affects the surfaces in micro layers. These micromechanical changes of the surface layer are observed in the instrumented microhardness test. Our research confirms the comparable properties of surface layer of irradiated LDPE with highly efficient polymers. The subject of this research is the influence of irradiation dosage on the changes of micromechanical properties of surface layer of LDPE.

Fabrication and Properties of Antioxidant Polyethylene‐based Films Containing Marigold (Tagetes erecta) Extract and Application on Soybean Oil Stability

Four films were extruded in a pilot‐plant scale blown extrusion machine: a monolayer low‐density polyethylene (LDPE) film added with 2.90% of marigold (Tagetes erecta) extract, a two‐layer high‐density polyethylene/LDPE film added with 3.59% of the extract in the LDPE layer and the corresponding two control films without addition of the extract. More than 64% of astaxanthin contained in the extract was lost during the extrusion process. Spectroscopic, optical and mechanical properties of the films were affected by the addition of the marigold extract. The films showed to be light sensitive when exposed to commercial light at 25 °C; however, bags made of the films showed a positive effect on soybean oil stability when used as packaging. Copyright © 2012 John Wiley & Sons, Ltd.

Migration study of optical brighteners from polymer packing materials to jam squeeze and fruit drink by spectrofluorimetry and RP-HPLC methods.

Optical brighteners are commonly used to modify the appearance and to improve polymer properties of packaging. They are not chemically bound to polymers and able to migrate from packaging into the foods. These migrants are potentially harmful to human health. In concern with human safety an approach was made to analyze three optical brighteners such as diphenylbutadiene, Uvitex-OB, benzophenone in commercial fruit juice and jam. The migration level of these optical brighteners from low density poly ethylene packaging into fruit juice and jam was studied. Two optimized and validated analytical techniques such as spectrofluorimetry and high performance liquid chromatography with photo diode array detector used for migration study. Both methods have shown high correlation coefficients (>0.999), over a concentration range of 0.1-3.2μg/mL, 0.1-1μg/mL, 0.05-3.2μg/mL for diphenylbutadiene, Uvitex-OB and benzophenone respectively. The preliminary studies confirm that the low density poly ethylene layer taken for study contained of diphenylbutadiene and the other two were absent. The migration level of diphenylbutadiene was studied at room temperature and different elevated temperature from 30°C to 60°C for up to 3weeks. At room temperature no migration of diphenylbutadiene was observed where as at higher temperature migration could be observed. The maximum quantity of diphenylbutadiene migrated was found to be 0.0462mg/kg from tetrapak, and 0.0382mg/kg from jam squeeze after 3weeks treatment at 60°C. The migration of diphenylbutadiene was found to be less than allowable concentration during the study period.

Radiolysis products and sensory properties of electron-beam-irradiated high-barrier food-packaging films containing a buried layer of recycled low-density polyethylene

The aim was to study the effect of electron-beam irradiation on the production of radiolysis products and sensory changes in experimental high-barrier packaging films composed of polyamide (PA), ethylene-vinyl alcohol (EVOH) and low-density polyethylene (LDPE). Films contained a middle buried layer of recycled LDPE, while films containing 100% virgin LDPE as the middle buried layer were taken as controls. Irradiation doses ranged between zero and 60 kGy. Generally, a large number of radiolysis products were produced during electron-beam irradiation, even at the lower absorbed doses of 5 and 10 kGy (approved doses for food ‘cold pasteurization’). The quantity of radiolysis products increased with irradiation dose. There were no significant differences in radiolysis products identified between samples containing a recycled layer of LDPE and those containing virgin LDPE (all absorbed doses), indicating the ‘functional barrier’ properties of external virgin polymer layers. Sensory properties (mainly taste) of potable water were affected after contact with irradiated as low as 5 kGy packaging films. This effect increased with increasing irradiation dose.

Migration of α-tocopherol from an active multilayer film into whole milk powder

Antioxidant active packaging is a promising technology for whole milk powder (WMP) protection. In this study, the migration of α-tocopherol from a multilayer active packaging (made of high density polyethylene, ethylene vinyl alcohol and a layer of low density polyethylene containing the antioxidant) to WMP was studied. A model based on the Fick’s diffusion equation was used to calculate the diffusion coefficients (D) of α-tocopherol as 2.34 × 10−11, 3.06 × 10−11, and 3.14 × 10−11 cm2 s−1 at 20, 30 and 40 °C, respectively. The D at 20 °C was different from those at 30 and 40 °C (P < 0.05); but it was similar at 30 and 40 °C. This low influence of temperature on the migration of α-tocopherol from 20 to 40 °C assures the release at real storage and commercialization conditions in regions with warm/hot climate. The antioxidant delivering system delayed the lipid oxidation of WMP and it was more effective at 30 and 40 °C since the rate of oxidative reactions was higher at these temperatures than at 20 °C.

Release of antioxidants from co-extruded active packaging developed for whole milk powder

Control of oxidation is a basic criterion to maintain the quality of milk and dairy products. Multilayer co-extruded films are often used to limit the diffusion of oxygen from the environment into the package. In this study, multilayer co-extruded films made of high density polyethylene (added with titanium dioxide), ethylene vinyl alcohol and a layer of low density polyethylene containing the antioxidants butylated hydroxyanisole (1.5%), butylated hydroxytoluene (1.5%) and α-tocopherol (4%) were manufactured. The release of the antioxidants from the films to whole milk powder was determined during 30 days at 30 °C. Whole milk powder stability was measured by monitoring vitamin A, hexanal, pentanal and heptanal content. Butylated hydroxytoluene and butylated hydroxyanisole migrated quickly from the films to the milk powder, while α-tocopherol migrated gradually. Multilayer co-extruded films provided an adequate light-barrier for whole milk powder and the film added with α-tocopherol contributed to the protection of vitamin A degradation compared with the other films.

Ablation and water etching of plasma-treated polymers

Ablation and water etching of low-density polyethylene (LDPE), polytetrafluorethylene, polystyrene, and polyethyleneterephtalate (PET) modified by Ar plasma was studied. The amount of ablated and etched material was determined by gravimetry. The changes in polymer surface morphology were observed using atomic force microscopy, UV-Vis and FTIR spectroscopy. This was used for the determination of the chemical structure of modified polymers. Wettability of polymers modified in plasma and water etched was determined from contact angle measurement. It was found that under the plasma discharge the polymers are ablated and their surface morphology and roughness are changed dramatically. The plasma treatment leads to an increase in the concentration of conjugated double bonds. Dissolution of a thin surface layer of plasma-modified PET and LDPE during water etching was observed and preferential liberation of low-molecular weight segments was proved.

Determination of radiolysis products in gamma-irradiated multilayer barrier food packaging films containing a middle layer of recycled LDPE

Volatile and non-volatile radiolysis products and sensory changes of five-layer food packaging films have been determined after gamma irradiation (5–60 kGy). Barrier films were based on polyamide (PA) and low-density polyethylene (LDPE). Each film contained a middle buried layer of recycled LDPE or 100% virgin LDPE (control samples). Data showed that a large number of radiolysis products were produced such as hydrocarbons, alcohols, carbonyl compounds, carboxylic acid. These compounds were detected in the food simulant after contact with all films even at the lower absorbed doses of 5 and 10 kGy. The type and concentration of radiolysis products increased progressively with radiation dose, while no new compounds were detected as a result of the presence of recycled LDPE. In addition, irradiation dose appears to influence the sensory properties of table water in contact with films.

Release of Butylated Hydroxytoluene from an Active Film Packaging to Asadero Cheese and Its Effect on Oxidation and Odor Stability

Antioxidant active packaging consisting of coextruded films made of low density polyethylene (LDPE) added with 0, 8, and 14 mg/g of butylated hydroxytoluene (BHT) and polyamide 6/66 were fabricated. The release of BHT from the films to Asadero cheese was determined. Most of the BHT was diffused from the LDPE layer to the cheese during the first 20 d of storage at 5°C. Diffusion coefficient for the diffusion of BHT from the films 8 and 14 to the cheese was calculated as 6.24E-12 and 6.26E-12cm2/s, respectively. The release of BHT from the film added with 8 mg/g of the antioxidant in the LDPE layer complied with the legal limit established for food products. However, the film added with 14 mg/g of the antioxidant exceeded that limit. The film added with 8 mg/g of BHT maintained the same levels of oxidized odor from 20 to 100 d of storage.

Effect of Coextrusion On Pp/Ldpe Bicomponent Blown Films

The effect of coextrusion on the microstructure of polypropylene (PP) and low-density polyethylene (LDPE) bilayer films was investigated by the use of Raman spectroscopy. The onset crystallization-time difference for PP versus LDPE components is an important parameter that controls the orientation and morphology of the coextruded films. Although the overall molecular orientation of PP and LDPE was not significantly different in multilayer films, single-layer LDPE films displayed some row-nucleation of crystals that was not observed in the LDPE layer in coextruded films. Also, there was a slight decrease of crystalline a-axis orientation for coextruded LDPE layer relative to that obtained for single-layer LDPE films.