Low-density Polyethylene Nanocomposite Films Research Articles

Impact of gamma irradiation on physico-chemical and electromagnetic interference shielding properties of Cu2O nanoparticles reinforced LDPE nanocomposite films

In the current work, cuprous oxide (Cu2O) nanoparticles coated with Tween 80 were successfully synthesized via the chemical reduction method. Nanocomposites composed of low-density polyethylene (LDPE) and different ratios of Cu2O nanoparticles were fabricated by the melt mixing process. 10% of ethyl vinyl acetate (EVA) as a compatibilizing agent was added to the molten LDPE matrix and the mixing process continued until homogenous nanocomposites were fabricated. To study the influence of ionizing radiation on the fabricated samples, the prepared species were exposed to 50 and 100 kGy of gamma rays. The synthesized Cu2O nanoparticles were investigated by transmission electron microscopy (TEM) and X-ray diffraction (XRD). XRD and TEM analysis illustrated the successful formation of spherical Cu2O nanoparticles with an average size of 16.8 nm. The as-prepared LDPE/Cu2O nanocomposites were characterized via different techniques such as mechanical, thermal, morphological, XRD, and FTIR. Electromagnetic interference shielding (EMI) of the different nanocomposite formulations was performed as a promising application for these materials in practical life. The electromagnetic shielding effectiveness (SE) of the produced samples was measured in the X-band of the radio frequency range from 8 to 12 GHz using the vector network analyzer (VNA) and a proper waveguide. All the samples were studied before and after gamma-ray irradiation under the same conditions of pressure and temperature. The shielding effectiveness increased significantly from 25 dB for unirradiated samples to 35 dB with samples irradiated with 100 kGy, which reflects 40% enhancement in the effectiveness of the shielding.

Low-density polyethylene based nanocomposite packaging films for the preservation of sugarcane juice.

Low density polyethylene (LDPE) based nanocomposite films made from different levels of nanoclay, compatibilizer and thickness were evaluated for the storage stability of sugarcane juice for 60days under ambient condition. During the storage period, important physico-chemical properties such as pH, total sugars, total soluble solids and overall acceptability were decreased with respect to increased level of nanoclay and compatibilizer as well as decreased thickness of film. Total plate count was nil till the storage period of 15days and then there was an increase in microbial population. Similarly, the overall color difference was also increased during the storage period. The better storage stability with respect to biochemical characteristics, overall acceptability and microbial load was recorded in the 100µm thick LDPE nano composite films developed from 93 percent LDPE, 2 percent nanoclay and 5 percent compatibilizer.

Mechanical properties of gamma irradiated TiO2NPs/MWCNTs/LDPE hybrid nanocomposites

This work investigates the impact of ϒ-irradiation on the mechanical properties of titanium oxide nanoparticles (TiO2NPs)/multi-walled carbon nanotubes (MWCNTs) hybrid low-density polyethylene (LDPE) nanocomposites. Hybrid LDPE nanocomposite films prepared using melt mixing technique were exposed to different doses of ϒ-radiation, ranging from 5 to 50 kGy. The tensile strength was diminished after TiO2NP or MWCNT addition, then increased with a further increase in the carbon nanotube (CNT) content. This behavior can be ascribed to stress transfer between the filler and the LDPE network. Besides, the tensile strength was enhanced after exposure to a dosage of 5 and 25 kGy of ϒ-radiation, then followed by a decline when exposed to 50 kGy, especially in the case of hybrid films due to the degradation and cross-linking of LDPE chains caused by ϒ-radiation. Because of the absorbance and antioxidant effects of CNTs, the CNT addition retarded the degradation of LDPE networks and decreased the catalytic activity of TiO2NPs to activate degradation upon radiation exposure. Therefore, the tensile strength was retained after exposure to a dose of 50 kGy of ϒ-radiation, especially in case of less TiO2NPs and more CNTs filled hybrid films. Furthermore, the % of the total elongation at break is decreased after incorporating MWCNTs. The % of the total elongation at break after exposure to a dosage of 25 kGy was reduced as a result of chain scissions and molecular weight decrease. Young’s modulus of the irradiated composites was lower than without irradiation. This effect was more significant for neat LDPE and TiO2NPs filled LDPE films, whereas MWCNTs had some stability effects on the nanocomposites.

Application of clay-TiO2 nanocomposite packaging films on pears (Prunus communis L. cv. Williams) under cold storage

Today, nanomaterials are presenting novel characteristics can be applied in developing new packaging with modified preferred properties. These are including the development of packaging with improved barrier characteristics which will extend the storage life of a product. In the present study, the effect of three types of developed low-density polyethylene nanocomposite films with two types of TiO2 (anatase and rutile) and clay (Closite 20A) nanoparticles were evaluated on the quality parameters of pear fruit (cv. ‘Williams’) during 48 days of storage at 4 °C. The Mechanical test revealed that the reinforcement in the presence of the nanocomposites was more than that with their conventional counterparts. The barrier properties against oxygen, carbon dioxide and water vapor of nanocomposite films were significantly decreased. The results showed that nanocomposite packaging film (NPFs) was a promising oxygen, carbon dioxide and water vapor barrier. Weight loss, firmness and the total solids content of pear in clay/TiO2-nanocomposite film decreased at the rates of 50%, 39% and 13%, respectively due to the modified atmosphere. Higher ascorbic acid content, lower ethylene production, reducing sugar content and PPO activity and higher POD of the packed fruits were observed in clay/TiO2-nanocomposite film. The single use of clay and TiO2 nanoparticles was not as effective as both of them in increasing durability of pear fruits. So, clay/TiO2-nanocomposite film can be considered as a practical approach to reduce the risk of pathogens, contamination and to improve the maintenance quality of pear fruit during the storage.

Cetylpyridinium bromide-modified montmorillonite as filler in low density polyethylene nanocomposite films

The development of clay polymer nanocomposites has been presented as an interesting alternative for design of new active food packaging materials. In this work, low density polyethylene (LDPE) nanocomposites with cetylpyridinium bromide (CPB) – modified montmorillonite (Mt) were developed. In a first stage, Mt. was modified with different CPB proportions based on cation exchange capacity (1:1 and 2:1), resulting in two different organoclays. These modified clays were hydrophobic and presented a good thermal stability that favored their capacity for extrusion to develop LDPE nanocomposites. Based on the incorporated organoclay, nanocomposite films showed important changes in morphology, and differences in mechanical properties, crystallinity, and gas permeability in comparison to polyethylene. All nanocomposites showed greater opacity than LDPE, however, their color changes did not exceed the visual perception limit. Finally, electrical conductivity (EC) measurements showed that CPB was able to migrate from the nanocomposite films to an aqueous food simulant. This behavior was dependent on the availably of free CPB in the matrix, its disposition in the organoclay and the organoclay distribution into the polymer matrix. These results highlight the migration of the surfactant from LDPE nanocomposites with Mt./CPB organoclays, making montmorillonite a potential surfactant carrier that increases compatibility and function in polymers allowing the generation of novel materials that could be used in the design of food packaging.

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.

Effect of isolation method on reinforcing capability of recycled cotton nanomaterials in thermoplastic polymers

Cellulose extracted from recycled pulverized cotton in nanocrystalline cellulose (CNC) and nanofibrillated cellulose (NFC) forms is investigated as a reinforcing agent in low-density polyethylene (LDPE) nanocomposites. The effect of extraction processing on the pulverized cotton is shown to influence the degree of crystallinity, morphology, and thermal stability of cellulose nanomaterials. Melt compounding of CNC with LDPE resulted in polymer nanocomposites with no discoloration at 170 °C. Significant differences observed in transparency, mechanical, and thermal properties of LDPE nanocomposite films, are demonstrated to be a result of the microstructure and the content of cellulose nanomaterials. Thermal analysis using thermogravimetric analyzer and differential scanning calorimeter showed higher thermal stability and degree of crystallinity of NFC/LDPE comparing to CNC/LDPE nanocomposite films. Tensile analysis exhibited a higher elastic modulus and tensile strength for the NFC material. 10 wt% of NFC reinforcing agent showed 32% improved strength and higher transparency over the one with CNC.

Antibacterial properties of LDPE nanocomposite films in packaging of UF cheese

The purpose of this study was to investigate antibacterial potential of low-density polyethylene (LDPE) packaging films incorporating silver (Ag), copper oxide (CuO) and zinc oxide (ZnO) nanoparticles in measuring of coliform amounts of ultra-filtrated (UF) cheese. The initial LDPE/nanoparticle composites were produced by melting extrusion followed by extruding the obtained composites through a die to achieve a film thickness of 45 ± 5 μm. The number of surviving coliform bacteria was decreased by 4.21 log cfu/g after 4 weeks of storage at 4 ± 0.5 °C, whilst pure LDPE films showed a reduction of only 1.04 log cfu/g. A composition of 0% Ag, 1% CuO, 0% ZnO gave an optimum point in combined design using Design Expert analysis. A suitable microbial model was suggested for retarding coliform bacteria growth in UF cheese. The difference between the optimum point of nanocomposite film and its repeat was not significant (p < 0.05) by one-way ANOVA analysis using SPSS software, while the difference was significant for pure film. Migration of metallic nanoparticles into a food stimulant was within the accepted safe level.

Barrier, Biodegradation, and mechanical properties of (Rice husk)/(Montmorillonite) hybrid filler-filled low-density polyethylene nanocomposite films

Rice husk (RH)/montmorillonite (MMT) hybrid filler-filled low-density polyethylene nanocomposite films were prepared by extrusion blown film. RH was used as a biodegradable filler in various concentrations (2, 5, and 7 parts per hundred composite), while the amount of MMT was held constant at 2 wt%. Delamination of MMT platelets and distribution of RH were investigated by X-ray diffraction and scanning electron microscopy. Diffractograms revealed the formation of intercalated structures, regardless of the RH content. Barrier properties revealed that MMT platelets have the potential to retard the diffusion of permeating molecules while, on the other hand, barrier efficiency of MMT is balanced by the subsequent incorporation of RH in RH/MMT hybrid filler-filled composite films. Despite an increase in permeability, the selectivity ratio (CO2/O2 permeability) increased with increasing RH contents in the hybrid filler-filled composite films showing the potential of these films in the development of modified atmosphere for fresh fruits and vegetables. The colonization of fungus and formation of holes as observed in micrographs of the test samples subjected to soil burial revealed that the biodegradation rate increased with the incorporation of RH in the hybrid composites. The composite films with higher contents of RH in hybrid filler are also more biodegradable than those having lower contents. Addition of RH contents in the hybrid filler increased the tensile modulus, while decreasing the tensile and tear strength. Addition of RH in the hybrid filler increased the melting and crystallization temperatures of the resulting nanocomposite films as well. J. VINYL ADDIT. TECHNOL., 23:162–171, 2017. © 2015 Society of Plastics Engineers

Effects of a combination of antimicrobial silver low density polyethylene nanocomposite films and modified atmosphere packaging on the shelf life of chicken breast fillets

Low-density polyethylene (LDPE) nanocomposite films containing different concentrations of silver (Ag) nanoparticles (NPs) (0.5 and 1% of polymer weight, w/w) were manufactured via extrusion and subsequently characterised. The microbiological quality of chicken breast fillets wrapped with Ag/LDPE nanocomposite films, followed by modified atmosphere packaging (using conventional laminates and employing a gas mix of 40% CO2:60% N2) were assessed. The tensile strength of Ag/LDPE nanocomposite films were significantly lower (p < 0.05) than control films (without Ag NPs), indicating that the presence of Ag NPs reduced the film strength. Independent of the concentration of Ag NPs used, Ag/LDPE nanocomposite films extended the shelf life of the chicken breast fillets and significantly (p < 0.05) enhanced oxidative stability compared to control films. The results indicated that LDPE nanocomposite films containing Ag NPs could potentially be used as antimicrobial packaging for food applications.

Montmorillonite reinforced polymer nanocomposite antibacterial film

In this work, montmorillonite (Mt) was first ion-exchanged with silver ions (Ag+Mt) then organically modified with cetyltrimethylammonium bromide, CTAB (Ag+OMt). Active carrier Mt-layers were then compounded into low density polyethylene (LDPE) polymer using a high shear force co-rotating twin screw extruder. The order of Ag ion and CTAB adsorption on to Mt was revised in order not to form AgBr nano particles of which existence was reported in previous studies. Antibacterial activity of the Ag+OMt–LDPE nanocomposite films was then investigated against powerful gram negative Escherichia coli (E. coli) bacteria. It seems there is strong synergetic effect between silver ions and OMt nanoparticles as evidenced by the bacterial inhibition properties of thin blow molded Ag+OMt–LDPE nanocomposite film samples using liquid surface bacterial testing at a much lower active component concentration than similar studies appeared in the literature.

Preparation and Application of LDPE/ZnO Nanocomposites for Extending Shelf Life of Fresh Strawberries.

Strawberries have a very short post-harvest life mostly due to their relatively high water content, intense metabolic activity and susceptibility to microbial rot. Antimicrobial low-density polyethylene nanocomposite films containing ZnO nanoparticles at different mass fractions were prepared by melt mixing and followed by compression moulding using a hot press machine. Fresh strawberries were packed in nanocomposite films and stored at 4 °C. Their microbial stability, ascorbic acid content and titratable acidity were evaluated after 0, 4, 8, 12 and 16 days of storage. Microbial growth rate was significantly reduced up to 16 days as a result of the use of nanocomposite packaging material containing ZnO nanoparticles. By increasing the ZnO nanoparticle mass fraction to 5%, the antimicrobial activity of the film increased. All packages containing the ZnO nanoparticles kept the microbial load of fresh strawberries below the level that affects shelf life (5 log CFU/g) up to 16 days. The lowest degradation of ascorbic acid content (6.55 mg per 100 g), and loss of acidity (0.68%) were observed in packages containing 3% of ZnO nanoparticles with 10% polyethylene-grafted maleic anhydride.

Improved mechanical and barrier properties of low-density polyethylene nanocomposite films by incorporating hydrophobic graphene oxide nanosheets

The successful conversion from hydrophilic GONSs to hydrophobic ODA–GONSs imparts LDPE nanocomposite films with enhanced mechanical and barrier performances for potential packaging materials.

Nanocomposite films with enhanced radiometric properties for greenhouse covering applications

Nanocomposite films for covering applications were developed. Mechanical, radiometric and ultraviolet stability properties of the films were characterized. Nanocomposites were obtained by incorporating nanoadditives to a thermoplastic polymer matrix by melt-mixing in a corotating twin screw extruder. Three common polymers in cover applications were used as matrix: low-density polyethylene, linear low-density polyethylene and ethylene–butyl acrylate. Three different nanoparticles were used as fillers (2 wt%): titanium dioxide (rutile), silicon oxide and zinc oxide. All nanocomposites were processed in a blown film extrusion line, producing 200 µm thick films. The mechanical properties of the nanocomposite films were found to be slightly different than those of the neat films, whereby the optical and radiothermal properties changed dramatically. Titania nanocomposite containing films had high ultraviolet shielding, however, significantly reduced transparency. Zinc oxide introduced high ultraviolet-shielding capability preserving transparency. High infrared efficiency has been found in silica nanocomposite films, exhibiting efficiency values greater than 79%, and an increment greater than 100% for linear low-density polyethylene and low-density polyethylene nanocomposite films. The extent of ultraviolet degradation of the films was determined by elongation at break tests. Zinc oxide/low-density polyethylene film underwent less degradation than neat low-density polyethylene film after photoaging. Thus, zinc oxide–filled polymer nanocomposite films are suitable for transparent ultraviolet-shielding applications and present low degradation rates. Silica incorporation highly improves polyethylene infrared efficiency, rendering a low-cost high-thermicity transparent film.