LDPE composite films incorporating ceramic powder emitting far‐infrared radiation for advanced food‐packaging applications

A ceramic powder that emits far‐infrared radiation (FIR) was incorporated into low‐density polyethylene (LDPE) via melt‐compounding and subsequent melt‐extrusion processes. To investigate the feasibility of as‐prepared LDPE/FIR composite films for use in packaging applications, the composite films were characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, FIR emissivity and emissive power, antimicrobial activity assays, and storage tests. The physical properties and antimicrobial activities of the composite films were found to strongly correlate with the changes in the chemical and morphological structures that originate from different contents of FIR ceramic powder. A higher content of FIR ceramic powder in the LDPE/FIR composite film provided increased FIR emissivity and emission power of the composite and resulted in good antimicrobial activity. Storage tests also showed that incorporation of FIR ceramic powder into LDPE film was an effective method for maintaining the freshness of lettuce. Furthermore, the incorporation of FIR ceramic powder into LDPE films induced higher thermal stability and crystallinity and enhanced their barrier properties, which suggest these LDPE/FIR composite films are potential candidates for advanced packaging materials for the food and medical industries. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43102.     

In situ fibre‐reinforced composite films of poly(lactic acid)/low‐density polyethylene blends: effects of composition on morphology,transport and mechanical properties

This study aimed to investigate the effects of blend composition on packaging‐related properties of poly(lactic acid) (PLA) and low density polyethylene (LDPE) blown films. Blend films with PLA contents of 5–20 wt% were produced and compared. Scanning electron micrographs of cross‐sectional cryofractured surfaces of the blend films revealed that in situ fibre‐reinforced composites were obtained. Viscosity ratio of the polymer components of ca 1 confirmed that fibre formation was favourable for this blend system. PLA microdomains were dispersed throughout the film in forms of long fibres (length‐to‐diameter ratio > 100) and ribbons. The number of fibres and ribbons increased with an increase of PLA content. Critical content of PLA was found to be 20 wt% for effective improvement of both moduli and gas barrier properties. Incorporation of poly[ethylene‐co‐(methyl acrylate)] compatibilizer showed minimal effect on PLA structure. However, it did improve moduli and O₂ barrier properties when sufficient amount (1.5 pph) was used in 10 wt% PLA/LDPE. In short, flow behaviour, ratio of polymer components and degree of compatibility together played intricate roles in the morphology and hence mechanical and transport properties of PLA/LDPE immiscible blends. © 2017 Society of Chemical Industry     

Characterization and properties of LDPE film with gallic‐acid‐based oxygen scavenging system useful as a functional packaging material

We prepared and characterized active, oxygen‐scavenging, low density polyethylene (LDPE) films from a non‐metallic‐based oxygen scavenging system (OSS) containing 1, 3, 5, 10, and 20% of gallic acid (GA) and potassium chloride (PC). We compared the surface morphology and mechanical, permeability, and optical properties of the oxygen‐scavenging LDPE film with those of pure LDPE film. The surface morphology, gas barrier, and thermal properties indicate that the OSS was well incorporated into the LDPE film structure. The surface roughness of the film increased with the amount of oxygen scavenging material. The oxygen and water vapor permeability of the developed film also increased with the amount of oxygen scavenging material, though its elongation decreased. The oxygen scavenging capability of the prepared film was analyzed at different temperatures. The initial oxygen content (%) in the vial headspace, 20.90%, decreased to 16.6% at 4 °C, 14.6% at 23 °C, and 12.7% at 50 °C after 7 days of storage with the film containing 20% OSS. The film impregnated with 20% organic oxygen scavenging material showed an effective oxygen scavenging capacity of 0.709 mL/cm² at 23 °C. Relative humidity triggered the oxygen scavenging reaction. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44138.     

Synthesis of clay–TiO2 nanocomposite thin films with barrier and photocatalytic properties for food packaging application

In this study, low‐density polyethylene (LDPE) nanocomposite films with two types of nanoparticles, TiO₂ (3 wt %) and Closite 20A (3 and 5 wt %), were prepared using a melt blow extrusion as an industrial method and their properties such as mechanical properties, water vapor, oxygen and carbon dioxide gas barrier, and antimicrobial activity were tested. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) were also performed to determine the degree of dispersion and exfoliation of nanoparticles. Mechanical test indicated that the reinforcement in the presence of the nanocomposites was more than that with their conventional counterparts, and the highest stiffness was achieved in a sample containing 5 wt % clay and 3 wt % TiO₂. Exfoliation of silicate layers and a good dispersion of TiO₂ nanoparticles in LDPE were achieved as confirmed by XRD and TEM. The gas barrier properties were improved after formation of the nanocomposites especially by insertion of 5 wt % of clay nanoparticles as a filler in the LDPE matrix. The photocatalytic effect of the nanocomposite film was carried out by antimicrobial evaluation against Pseudomonas spp. and Rhodotorula mucilaginosa and by ethylene removal test using 8 W ultraviolet (UV) lamps with a constant relative intensity of 1 mW cm^?2. The greatest effects were recorded by combining UVA illumination and active film. It was also proven that the photocatalyst thin film with improved barrier properties prepared by extrusion could be used in horticultural product packaging applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41764.     

Zeolite A‐polypropylene and silver‐zeolite A‐polypropylene composite films for antibacterial and breathable applications

Polypropylene (PP) composite films were successfully prepared using melt blending by directly mixing PP pellets with zeolite A or silver‐zeolite A powder and then blowing. All the prepared films were characterized in terms of their physical, mechanical, optical, and gas permeability properties. The structure of each composite film was similar to that of the pure PP film. The crystallinity and glossy quality of the composite films were increased by the addition of silver, zeolite, and maleic anhydride grafted PP (PP‐g ‐MA). The composite PP film with zeolite A and PP‐g ‐MA exhibited a level of oxygen and carbon dioxide permeation (6438 and 15,087 cc m^?2 day^?1 atm^?1, respectively). Finally, all the films were evaluated for their antibacterial activity and fruit packaging applications. Silver‐zeolite A‐PP composite films exhibited a bactericidal activity of 79% against Staphylococcus aureus and 52% against Escherichia coli , while the zeolite A‐PP film could extend the shelf‐life of bananas for over a week. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45450.     

Analysis of low‐density polyethylene‐g‐poly(vinyl chloride) copolymers formed in poly(vinyl chloride)/low‐density polyethylene melt blends with gel permeation chromatography and solid‐state 13C‐NMR

Gel permeation chromatography (GPC) and solid‐state ¹³C‐NMR techniques were used to analyze the structural changes of poly(vinyl chloride) (PVC) in blends of a low‐density polyethylene (LDPE) and PVC during melt blending. The GPC results showed that the weight‐average molecular weight (M_w) of PVC increased with LDPE content up to 13.0 wt % and then decreased at a LDPE content of 16.7 wt %, whereas the number‐average molecular weight remained unchanged for all of LDPE contents used. The ¹³C‐NMR results suggest that the increase in M_w was associated with the formation of a LDPE‐g‐PVC structure, resulting from a PVC and LDPE macroradical cross‐recombination reaction during melt blending. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3167–3172, 2004     

The impact of microwave‐assisted thermal sterilization on the morphology,free volume,and gas barrier properties of multilayer polymeric films

Microwave‐assisted thermal sterilization (MATS) is an advanced thermal process that utilizes microwave (MW) energy for in‐package food sterilization. Benefits include much shorter processing times than conventional retort sterilization. This research explores how MATS affects the performance of high‐barrier multilayer polymeric films compared with conventional retort sterilization. The gas barrier, morphological, and free volume packaging properties of these films may influence the shelf‐life of shelf‐stable foods. In this study, we applied X‐ray diffraction (XRD) and positron annihilation lifetime spectroscopy in order to investigate film morphology and free volume characteristics, respectively. Results show that the conventional retort process affected gas barrier properties more than MATS processing did which could be explained by the morphological and free volume changes in the polymeric films. XRD revealed improved crystalline morphology of MW‐treated films in terms of overall crystallinity as compared with retort sterilization. On the other hand, higher free volume increase in MW‐treated films could be explained by the different heating mechanisms involved in MATS and retort sterilization. Overall, the oxygen transmission rate for both films remained below 2 cc/m²‐day after MATS and retort sterilization required for packaging applications for shelf‐stable foods. This work provides the basis for understanding the gas‐barrier changes of multilayer polymeric films after MATS application using Materials Science techniques. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40376.     

N2‐filled hollow glass beads as novel gas carriers for microcellular polyethylene

N₂‐filled hollow glass beads (HGB) were first used as novel gas carriers to prepare microcellular polymers by compression molding. Dicumyl peroxide was acted as crosslink agent to control the produced microcellular structure of low density polyethylene (LDPE)/HGB. The effect of temperature, pressure and the content of gel on the embryo‐foaming, and final‐foaming structure are investigated. Scanning electronic microscopy shows that the average cell size of microcellular LDPE ranges from 0.1 to 10 μm, and the foam density is about 10⁹–10¹¹ cells/cm³. A clear correlation is established between preserving desirable micromorphologies of microcellular LDPE in different processing stage and tuning processing factors. The pertinent foaming mechanism of microcellular materials foamed with HGB is proposed. Because of the good mechanical strength, low density, weak water‐absorption, and excellent heat insulate ability, microcellular LDPE has great potential application in energy building materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Ozone‐induced grafting of a sulfoammonium zwitterionic polymer onto low‐density polyethylene film for improving hemocompatibility

Ozone‐induced grafting was developed to improve the hemocompatibility of biomaterials based on low‐density polyethylene (LDPE). An LDPE film was activated with ozone and graft‐polymerized with N,N′‐dimethyl(methacryloylethyl)ammonium propane sulfonate (DMAPS). The existence of sulfobetaine structures on the grafted film was confirmed by X‐ray photoelectron spectroscopy and attenuated total reflection/Fourier transform infrared (ATR–FTIR). More DMAPS was grafted onto the LDPE film as the DMAPS concentration increased, as determined by ATR–FTIR. Static contact‐angle measurements indicated that the DMAPS‐grafted LDPE film had a significant increase in hydrophilicity. The blood compatibility of the grafted film was preliminarily evaluated with a platelet‐rich‐plasma (PRP) adhesion study. No platelet adhesion was observed on the grafted film incubated with PRP at 37°C for 180 min. This new sulfoammonium zwitterionic‐structure‐grafted biomaterial might have potential for biomedical applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3697–3703, 2006     

Surface modification of low‐density polyethylene films by UV‐induced graft copolymerization with a fluorescent monomer

Surface modification of argon plasma–pretreated low‐density polyethylene (LDPE) film via UV‐induced graft copolymerization with a fluorescent monomer, (pyrenyl)methyl methacrylate (Py)MMA, was carried out. The chemical composition and morphology of the (Py)MMA‐graft‐copolymerized LDPE [(Py)MMA‐g‐LDPE] surfaces were characterized, respectively, by X‐ray photoelectron spectroscopy (XPS) and by atomic force microscopy (AFM). The concentration of the surface‐grafted (Py)MMA polymer increased with Ar plasma pretreatment time and UV graft copolymerization time. The photophysical properties of the (Py)MMA‐g‐LDPE surfaces were measured by fluorescence spectroscopy. After graft copolymerization with the fluorescent monomer, the surface of the LDPE film was found to have incorporated new and unique functionalities. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1526–1534, 2001     

Effect of pro‐oxidants on biodegradation of polyethylene (LDPE) by indigenous fungal isolate,Aspergillus oryzae

Proxidant additives represent a promising solution to the problem of the environment contamination with polyethylene film litter. Pro‐oxidants accelerate photo‐ and thermo‐oxidation and consequent polymer chain cleavage rendering the product apparently more susceptible to biodegradation. In the present study, fungal strain, Aspergillus oryzae isolated from HDPE film (buried in soil for 3 months) utilized abiotically treated polyethylene (LDPE) as a sole carbon source and degraded it. Treatment with pro‐oxidant, manganese stearate followed by UV irradiation and incubation with A. oryzae resulted in maximum decrease in percentage of elongation and tensile strength by 62 and 51%, respectively, compared with other pro‐oxidant treated LDPE films which showed 45% (titanium stearate), 40% (iron stearate), and 39% (cobalt stearate) decrease in tensile strength. Fourier transform infrared (FTIR) analysis of proxidant treated LDPE films revealed generation of more number of carbonyl and carboxylic groups (1630–1840 cm⁻¹ and 1220–1340 cm⁻¹) compared with UV treated film. When these films were incubated with A. oryzae for 3 months complete degradation of carbonyl and carboxylic groups was achieved. Scanning electron microscopy of untreated and treated LDPE films also revealed that polymer has undergone degradation after abiotic and biotic treatments. This concludes proxidant treatment before UV irradiation accelerated photo‐oxidation of LDPE, caused functional groups to be generated in the polyethylene film and this resulted in biodegradation due to the consumption of carbonyl and carboxylic groups by A. oryzae which was evident by reduction in carbonyl peaks. Among the pro‐oxidants, manganese stearate treatment caused maximum degradation of polyethylene. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Thermally stable low‐density polyethylene/polyhydroxybutyrate pairs: Synergy between organomodified nanoclay and LDPE‐g‐MAH

Nanocomposites of low‐density polyethylene/polyhydroxybutyrate (LDPE/PHB) containing organomodified montmorillonite (OMMT) and/or LDPE grafted maleic anhydride (LDPE‐g‐MAH) were prepared with a wide range of composition ratios using a vertical co‐rotating twin‐screw microCompounder. To infer the effect of OMMT and LDPE‐g‐MAH on the thermal stability of prepared nanocomposites, all samples were characterized by thermogravimetric analysis while changing clay and compatibilizer contents. Accordingly, two commonly used kinetic models (Coats–Redfern and Horowitz–Metzger) were employed to correlate the thermal stability of the samples with kinetic parameters, including activation energy and pre‐exponential factor. Furthermore, morphological features of LDPE/PHB in the presence or absence of OMMT and LDPE‐g‐MAH were studied using scanning electron microscopy, transmission electron microscopy, and wide‐angle X‐ray diffraction analysis. It was found that for a specific OMMT composition ratio (1 wt %), the thermal stability is enhanced due to an exfoliated structure. However, for samples containing more organoclay (>=3 wt %), the thermal stability was reduced showing the competition between the barrier effect of organoclay platelets and the catalyzing effect of ammonium salts. Moreover, when using LDPE‐g‐MAH as compatibilizer, it acted as a good coupling agent in all compositions in LDPE major phase systems in contrast to PHB major phase samples. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45922.     

Reactive extrusion for the synthesis of nylon 12 and maleated low‐density polyethylene blends via the anionic ring‐opening polymerization of lauryllactam

Nylon 12 was successfully synthesized in a twin‐screw extruder via the anionic ring‐opening polymerization of lauryllactam (LL). Maleated low‐density polyethylene (LDPE–MAH) was added to improve the mechanical properties of nylon 12. The in situ blends of nylon 12 and LDPE–MAH were characterized by mechanical testing and scanning electron microscopy. With increasing LDPE–MAH content, the tensile strength and flexural strength decreased, whereas the blend had improved impact strength and achieved supertoughness when the content of LDPE–MAH was 30 wt %. In the in situ formed low‐density polyethylene‐g‐PA12 copolymer, the domain of the LDPE–MAH phase was finely dispersed in the nylon 12 matrix. The good interface between the two phases demonstrated that LDPE–MAH could be used as a macromolecular activator to induce the polymerization of LL. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Soil burial test for poly(ethylene‐co‐vinyl alcohol)‐graft‐polycaprolactone

The ring‐opening polymerization of ε‐caprolactone was carried out with poly(ethylene‐co‐vinyl alcohol) as a macroinitiator to synthesize poly(ethylene‐co‐vinyl alcohol)‐graft‐polycaprolactone (EVOH‐g‐PCL). A simple low‐density polyethylene (LDPE)/polycaprolactone (PCL) (64/36) blend lost 5.3 wt % of its original weight after 90 days of a soil burial test. However, the elongation at break of the LDPE/PCL blend remained almost invariable even after the solid burial test because the tensile properties depended mostly on the LDPE phase on account of the poor interaction between the continuous LDPE matrix and the dispersed PCL phase. For EVOH‐g‐PCL, the elongation at break decreased drastically as a result of the soil burial test, and the reduction of the elongation at break was more pronounced for EVOH‐g‐PCL with a higher PCL concentration, even though the weight loss of EVOH‐g‐PCL after the soil burial test was as low as 1.2–1.3% and was nearly independent of the PCL concentration. Few holes were observed in EVOH‐g‐PCL when the PCL concentration was less than 26 wt % after an accelerated hydrolysis experiment at 60°C for 7 days in a 0.1M KOH solution. In contrast, the hydrolysis formed small holes in EVOH‐g‐PCL with a PCL concentration of 36 wt %. The LDPE/PCL blend was much better percolated, as a result of the hydrolysis, than EVOH‐g‐PCL with the same PCL concentration; the soil burial test showed the same results. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1064–1071, 2005     

Compatibilizer in waste tire powder and low‐density polyethylene blends and the blends modified asphalt

With the increasing ratio of waste tire powder (WTP) to low‐density polyethylene (LDPE), the hardness and tensile strength of the WTP/LDPE blends decreased while the elongation at break increased. Five kinds of compatibilizers, such as maleic anhydride‐grafted polyethylene (PE‐g‐MA), maleic anhydride‐grafted ethylene‐octene copolymer (POE‐g‐MA), maleic anhydride‐grafted linear LDPE, maleic anhydride‐grafted ethylene vinyl‐acetate copolymer, and maleic anhydride‐grafted styrene‐ethylene‐butylene‐styrene, were incorporated to prepare WTP/LDPE blends, respectively. PE‐g‐MA and POE‐g‐MA reinforced the tensile stress and toughness of the blends. The toughness value of POE‐g‐MA incorporating blends was the highest, reached to 2032.3 MJ/m³, while that of the control was only 1402.9 MJ/m³. Therefore, POE‐g‐MA was selected as asphalt modifier. The toughness value reached to the highest level when the content of POE‐g‐MA was about 8%. Besides that the softening point of the modified asphalt would be higher than 60°C, whereas the content of WTP/LDPE blend was more than 5%, and the blends were mixed by stirring under the shearing speed of 3000 rpm for 20 min. Especially, when the blend content was 8.5%, the softening point arrived at 82°C, contributing to asphalt strength and elastic properties in a wide range of temperature. In addition, the swelling property of POE‐g‐MA/WTP/LDPE blend was better than that of the other compalibitizers, which indicated that POE‐g‐MA /WTP/LDPE blend was much compatible with asphalt. Also, the excellent compatibility would result in the good mechanical and processing properties of the modified asphalt. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Silver‐nanoparticle‐loaded chitosan lactate films with fair antibacterial properties

Food quality and safety are major concerns in the food industry. Antimicrobial packaging can be considered an emerging technology that could have a significant impact on life and food safety. Antimicrobial agents in food packaging can control the microbial population and target specific microorganisms to provide greater safety and higher quality products. In this work, a lactic acid grafted chitosan film was synthesized. Silver nanoparticles were loaded into the chitosan lactate (CL) film by equilibration in a silver nitrate solution, which was followed by citrate reduction. The presence of silver nanoparticles was confirmed with transmission electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, and thermogravimetric analysis of the film. The silver‐nanoparticle‐loaded CL film was investigated for its antimicrobial properties against Escherichia coli. This newly developed material showed strong antibacterial properties and thus has potential for use as an antibacterial food‐packaging material. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Barrier properties of a thermotropic liquid‐crystalline polymer

A developmental thermotropic liquid‐crystalline polymer (TLCP) made by Eastman (trade name LN001) was used for barrier property studies. This material is a highly aromatic TLCP with a T_m of 332°C. A permeability study was carried out to determine the chemical resistance of the TLCP. The permeability of methanol and toluene through a membrane of the TLCP was studied using a two‐part cell and a gas chromatograph to monitor the flux. The membranes of the TLCP and LDPE (as control) were made by compression molding. Both solvents had higher permeability through LDPE than TLCP and that of toluene was higher than that of methanol. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2457–2463, 2003     

Mechanical and thermal properties of LDPE‐cellulose acetate phthalate blends—Effect of maleic anhydride‐grafted LDPE compatibilizer

Biodegradable blends of LDPE and cellulose acetate phthalate have been prepared. Maleic anhydride‐grafted LDPE has been added as a compatibilizer to this blend. The elastic modulus and tensile strength has been considerably improved by adding LDPE‐g‐maleic anhydride compatibilizer. Scanning electron microscope micrographs reflected the observed results for the increase in mechanical properties of the blend. Further blend morphology exhibited a deformed matrix for the compatibilized blends. Thermogravimetric analysis studies showed two‐stage degradation for the blends. Differential scanning calorimetry thermograms showed a loss of crystallinity for the LDPE phase. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Aluminium‐filled low‐density polyethylene—structural,morphological, and mechanical properties

Low‐density polyethylene (LDPE) was filled with aluminium (Al) powder having concentrations of 1, 4, and 6% w/w. The samples in the form of disc containing the above concentration of Al powder were obtained using hot press molder. The structural properties have been investigated using density measurement and WAXD techniques. The morphology of pure LDPE and Al‐filled LDPE samples has been studied from scanning electron micrographs. The modulus of elasticity of the samples has been determined using Instron tensile tester. Results indicate that the crystallinity of LDPE component increases with the concentration of aluminium filler. Morphological changes also have been observed. The Young's modulus (Y) generally increases and becomes maximum for 4% Al‐filled LDPE sample. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Application of polymer gel electrolyte with graphite powder in quasi‐solid‐state dye‐sensitized solar cells

A polymer gel electrolyte with ionic conductivity of 5.11 mS cm⁻¹ was prepared by using poly (acrylonitrile‐co‐styrene) as polymer matrix, acetonitrile and tetrahydrofuran as binary organic mixture solvent, NaI + I₂ as electrolyte, graphite powder and 1‐methylimidazole as additives. The components ratio of the polymer gel electrolyte was optimized, and the influence of the components and temperature on the ionic conductivity of the polymer gel electrolyte and photoelectronic properties of dye sensitized solar cell were investigated. On the basis of the polymer gel electrolyte with the optimized conditions, a quasi‐solid‐state dye‐sensitized solar cell was fabricated and its light‐ to‐electricity energy conversion efficiency of 3.25% was achieved under irradiation of 100 mW cm⁻². POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers