Linear Low-density Polyethylene Films Research Articles

Pigmentation and Degradative Activity of TiO2 on Polyethylene Films Using Masterbatches Fabricated Using Variable-Frequency Ultrasound-Assisted Melt-Extrusion.

Ultrasound-assisted melt-extrusion method (USME) is a high-quality process used to produce polymeric compounds with an adequate homogeneous dispersion. This study evaluates white-color films of linear low-density polyethylene (LLDPE) prepared using TiO2 masterbatch obtained by ultrasound-assisted melt-extrusion at variable frequencies (USME-VF). LLDPE with three different melt-flow indices (2, 20 and 50 g/10 min) were used as the polymer matrix. The films were obtained from the dilution of masterbatches of LLDPE (melt-flow index = 2) at a concentration of 7 wt% TiO2. The morphology, pigmentation, TiO2 reactivity, and the mechanical stability of the films were assessed. The masterbatch compounds were evaluated by melt-flow index (MFI) and scanning electron microscopy (SEM). The contrast ratio, yellowness index and mechanical properties of films were also measured. The properties of whiteness and elongation at break improved in the films prepared using masterbatches with higher dispersion. Though the reactivity of the TiO2 particles increased during accelerated aging, it did not affect the elongation to rupture. The yellowness index was moderately affected in films that included TiO2 particles processed using USME-VF.

Long-lasting intrinsic polyethylene antifogging films generated by incorporating SiO2 nanoparticles into covalently grafted antifog agents

Antifogging films are used in an increasing number of applications in greenhouse cultivation because fog formation affects transmission. Here, we summarize a way to improve the antifogging duration of linear low-density polyethylene (LLDPE) films by controlling the migration of the antifog agent. We prepared SiO2-grafted glycerin monostearate (SiO2-g-GMS) by covalently grafting surface modified SiO2 nanoparticles and glycerin acrylic acid monostearate (GMS-AA). Then, SiO2-g-GMS was added in LLDPE, and antifogging films were prepared for study of their properties. The reaction with modified SiO2 and GMS-AA was demonstrated by Fourier transform infrared spectroscopy, thermogravimetric analysis and grafting degree (GD). The GD of SiO2-g-GMS was approximately 54.95%. Accelerating dripping experiments and contact angle measurements illustrated that GMS-AA-grafted modified SiO2 exhibited delayed migration of the antifog agent, prolonging the antifogging duration by approximately 3 days. We determined that 3 wt% SiO2-g-GMS was a suitable proportion, considering economy and the desired properties. The SEM images indicate that dispersion of SiO2-g-GMS in the film was extensive, and the particle size was 160 ± 40 nm. In addition, the study also showed how modified SiO2 grafted with GMS-AA does not affect the processes and usability of antifogging films.

Fast atmospheric plasma treatment of LLDPE film for preparing formaldehyde emission-free plywood

Atmospheric plasma was utilized to modify linear low-density polyethylene (LLDPE) film. On that basis, formaldehyde emission (FE)-free plywood was prepared using plasma-treated LLDPE film as the adhesive. Obtained results suggested that atmospheric plasma treatment leads to grafting of multiple oxygen-containing groups, thus evidently elevating the surficial polarity of LLDPE. Enhanced interaction between polar groups contributed to improve interfacial compatibility and interfacial adhesion between LLDPE and poplar veneer. Prepared by plasma treatment on both LLDPE and veneer, LLDPE/poplar plywood exhibited fine shear strength (around 0.87 MPa) and dynamic mechanical properties. Furthermore, the mechanical properties of plasma-treated LLDPE/poplar plywood were similar to those prepared by coupling agent treatment. It is believed that plasma treatment is a promising way to overcome the inherent hydrophobic surface of LLDPE and therefore improve the interfacial adhesion between LLDPE and wood. LLDPE/poplar plywood can be effectively manufactured using plasma treatment with reduced chemical consumption and total cost. The FE of prepared LLDPE/poplar plywood was remarkably low, indicating its suitability for indoor applications.

Modified high-density polyethylene films: preparation, composition and their physical properties

To prepare high-density polyethylene (HDPE) films with excellent mechanical properties and lower haze, HDPE was modified by using linear low-density polyethylene (LLDPE) and polypropylene (PP), and their characterizations were performed by melt index, light transmittance/haze, dart impact and elongation at break, infrared (IR) spectra, scanning electron microscopy image and IR image analyses. The results showed that the modifying effect of the 10% PP/30% LLDPE/60% HDPE composition was the best; the haze was reduced 6% and the translucency, dart impact strength, elongation at break and tensile strength were increased 1, 27.3, 29.4 and 1.0%, respectively. The blend of 10% PP/30% LLDPE/60% HDPE had good compatibility, and PP, LLDPE and HDPE were only the physical entanglement, and no chemical reaction, the modified HDPE films can partly replace polyvinyl chloride and LLDPE films.

Nano-titanium dioxide/basic magnesium hypochlorite-containing linear low-density polyethylene composite film on food packaging application

The aim of this research was to probe the potential application of nano-titanium dioxide (TiO2)/basic magnesium hypochlorite (BMH)-containing linear low-density polyethylene (LLDPE) composite film in grape fresh-keeping. Mechanical properties, transparency, barrier performance and antibacterial activity of the nano-composite membrane were measured, and results showed that the antibacterial zone diameter of TiO2/BMH on pathogen-Aspergillus niger was 31.4 mm, with mixing ratio of BMH/TiO2 to 2:1. It was clearly shown that the synthesized nano-composite films decreased mechanical properties and transparency of the membrane, and also had a significant impact on sensory score, mass loss rate, decay rate, ascorbic acid (Vc) content and titratable acid content compared with LLDPE films. Moreover, the results revealed that the LLDPE antibacterial film can be effectively used for storing grapes, preserving the flavor of grapes and had an obviously effect in prolonging grapes’ shelf life.

Electrothermal Actuators with Ultrafast Response Speed and Large Deformation

The ability to fabricate electrothermal actuators (ETAs) simultaneously featuring ultrafast response speed (within 0.1 s), large deformation (bending for at least 360°), high figure‐of‐merit (FoM, larger than 0.1%), and low driving voltage (smaller than 1 V) in a single device is extremely important and challenging for their applications in artificial muscles, switches, and microsensors for robotics and biomimetic devices. Herein, an ETA composed of a silver nanowire (AgNW) layer and an ultrathin linear low‐density polyethylene (LLDPE) film with all the aforementioned features is designed. Due to the high conductivity of the AgNW layer and the great difference between the coefficients of thermal expansion of AgNW layer and LLDPE film as well as the huge change in the heat transfer coefficient between flat and rolled ETA, the obtained ETA exhibits an ultrafast response speed of 0.08 s for a bending angle of 360° with a FoM of 0.46% at a low driving voltage of 1 V, over one order of magnitude larger than those of reported ETAs. As a proof‐of‐concept application, the as‐prepared ETAs can be used as intelligent mechanical devices with excellent performance.

Performance of Straw/Linear Low Density Polyethylene Composite Prepared with Film-Roll Hot Pressing.

Thermoplastic composites are usually prepared with the extrusion method, and straw reinforcement material must be processed to fiber or powder. In this study, film-roll hot pressing was developed to reinforce linear low density polyethylene (LLDPE) with long continuous straw stems. The long straw stems were wrapped with LLDPE film and then hot pressed and cooled to prepare straw/LLDPE composite. Extruded straw fiber/LLDPE composite was prepared as a control. The mechanical properties of these LLDPE-based composites were evaluated. The hot pressed straw/LLDPE composite provided higher tensile strength, tensile modulus, flexural strength, flexural modulus, and impact strength than the traditional extruded straw/LLDPE composite, by 335%, 107%, 68%, 57%, and 181%, respectively, reaching 35.1 MPa, 2.65 GPa, 3.8 MPa, 2.15 GPa, and 25.1 KJ/m2. The density of the hot pressed straw/LLDPE composite (0.83 g/cm3) was lower than that of the extruded straw/LLDPE composite (1.31 g/cm3), and the former had a higher ratio of strength-to-weight. Scanning electron microscopy indicated that the orientation of the straws in the composite was better with the new method. Differential scanning calorimetry tests revealed that in hot pressed straw/LLDPE composite, straw fibers have a greater resistance to the melting of LLDPE than extruded composite. Rotary rheometer tests showed that the storage modulus of the hot pressed straw/LLDPE was less affected by frequency than that of the extruded composite, and the better elastic characteristics were pronounced at 150 °C. The hot pressed straw/LLDPE composite absorbed more water than the extruded composite and showed a potential ability to regulate the surrounding relative humidity. Our results showed that straw from renewable sources can be used to produce composites with good performance.

Mechanical properties and crystallinity of linear low density polyethylene based biocomposite film

Cassava starch filled linear low-density polyethylene (LLDPE) films are made in order to make plastics which environmentally friendly. The use of compatibilizer ethylene - acrylic ester - maleic anhydride polymerized is needed to obtain a compatible mixture of starch which is hydrophilic and LLDPE which is hydrophobic. In this study LLDPE films obtained were tested for tensile strength and elongation before and after accelerated aging and density. Melt flow index (MFI) of the film was also measured to determine the rheological properties. Crystallinity has been done by an X-Ray diffraction. The results showed that the addition of thermoplastic starch tended to reduce the tensile strength, elongation, and MFI values but increase the density of LLDPE films. The aging process at a temperature of 70°C ± 2°C for 168 hours ± 2 hours tends to increase the tensile strength but decrease the extension of the break.

Thermoplastic starch and green tea blends with LLDPE films for active packaging of meat and oil-based products

Abstract Thermoplastic starch (TPS) is an alternative biomaterial that can be used to produce bioplastics to replace petroleum-based food packaging. Active films were developed from acetylated cassava TPS and green tea using the blown extrusion process. Green tea (GT) and TPS from native starch (NS) and acetylated starch (AS) with different degrees of substitution (DS) were extruded with linear low-density polyethylene (LLDPE) at LLDPE/TPS-GT ratios of 70/30 and 60/40 prior to blown-film extrusion. Results indicated that a higher DS of AS enhanced melt flow index which altered processability and subsequently impacted film microstructures and physical and barrier properties. NS showed highest dispersed particles in film matrices with a lower reduction of mechanical and barrier properties. AS showed reduced surface hydrophobicity with increased water vapor permeability and film solubility due to pore formation. Increased DS of AS films showed enhanced radical scavenging activity (DPPH and FRAP) with improved phenolic release. GT release from the starch matrix effectively limited microbial growth, reduced metmyoglobin forming brown pigment, and stabilized the red color of bacon. Lipid oxidation of packaged soybean oil was effectively reduced by up to 38% depending on the TPS ratio which was attributed to hydrophobicity of the film matrices. Developed TPS-GT films showed high efficacy as active eco-friendlier food packaging, with enhanced stability of meat and oil-based food products.

Large-area and transparent antifogging polymeric coatings via highly efficient and facile layer-by-layer assembly

Abstract Fogging can completely obscure the optical transparency of transparent surfaces, which results in inconvenience and even possible harm. The present work addresses this issue by developing large-area functional polymeric coatings on linear low-density polyethylene films by a rapid and effective layer-by-layer assembly involving orthoboric acid (H3BO3) and poly(vinyl alcohol) (PVA). The resulting coatings are highly transparent and demonstrate an antifogging property due to high wettability. The rapid fabrication of polymeric coatings is facilitated by the mechanism of H3BO3 chelation with the numerous hydroxyl groups of PVA. The polymeric coatings attain a thickness of 22.24 ± 0.66 μm within just 4 deposition cycles. The resultant H3BO3/PVA coatings present a transmittance of >80% at 700 nm and an antifogging property with a contact angle

Potential of Incorporation of Antimicrobial Plant Phenolics Into Polyolefin-Based Food Contact Materials to Produce Active Packaging by Melt-Blending: Proof of Concept With Isobutyl-4-Hydroxybenzoate.

There is an increasing interest for active food packaging incorporated with natural antimicrobial agents rather than synthetic preservatives. However, most of plastics for direct contact with food are made of polyolefins, usually processed by extrusion, injection, or blow-molding methods while most of natural antimicrobial molecules are thermolabile compounds (e.g., essential oils). Therefore, addition of plant phenolics (with low volatility) to different polyolefins might be promising to design active controlled release packaging processed by usual plastic compounding and used for direct contact with food products. Therefore, up to 2% (wt/wt) of isobutyl-4-hydroxybenzoate (IBHB) was mixed with 3 polyolefins: EVA poly(ethylene-co-vinyl acetate), LLDPE (Linear Low Density Polyethylene), and PP (PolyPropylene) by melt-blending from 75 to 170°C and then pelletized in order to prepare heat-pressed films. IBHB was chosen as an antibacterial phenolic active model molecule against Staphylococcus aureus to challenge the entire processing. Antibacterial activity of films against S. aureus (procedure adapted from ISO 22196 standard) were 4, 6, and 1 decimal reductions in 24 h for EVA, LLDPE, and PP films, respectively, demonstrating the preservation of the antibacterial activity after melt processing. For food contact materials, the efficacy of antimicrobial packaging depends on the release of the antimicrobial molecules. Therefore, the three types of films were placed at 23°C in 95% (v/v) ethanol and the release rates of IBHB were monitored: 101 ± 1%, 32 ± 7%, and 72 ± 9% at apparent equilibrium for EVA, LLDPE, and PP films, respectively. The apparent diffusion coefficients of IBHB in EVA and PP films were 2.8 ± 0.3 × 10−12 and 4.0 ± 1.0 × 10−16 m2s−1. For LLDPE films, IBHB crystals were observed on the surface of films by SEM (Scanning Electron Microscopy): this blooming effect was due the partial incompatibility of IBHB in LLDPE and its fast diffusion out of the polymer matrix onto the film surface. In conclusion, none of these three materials was suitable for a relevant controlled release packaging targeting the preservation of fresh food, but a combination of two of them is promising by the design of a multilayer packaging: the release could result from permeation through an inner PE layer combined with an EVA one acting as a reservoir.

Different Dependence of Tear Strength on Film Orientation of LLDPE Made with Different Co-Monomer.

Crystal orientations, tear strength and shrinkage of Linear Low-Density PolyEthylene (LLDPE) films made with different processes (compressed, cast and blown) were investigated. The films were made with three different LLDPE resins, respectively, which have similar density and molecular weight but are made with different comonomers (1-butene, 1-hexene and 1-octene), in order to investigate if tear strength in Machine Direction (MD) of the LLDPE films made with different comonomer has similar dependence on crystal orientation. Our study indicates that the films made of 1-hexene and 1-octene based LLDPE resins have significantly higher intrinsic tear strength and less decrease in MD tear strength for a given film orientation. That is, for a given orientation in MD, the MD tear drops dramatically for films made with butene-based resin but much less decrease for the films made with hexene and octene-based resins. The shrinkage property at high temperature shows a good correlation with crystal orientation and the fraction of the crystals melted at this temperature.

Effect of Pallet Size Modified Atmosphere Packaging Using Polyamide Film and Linear Low Density Polyethylene Film on the Shelf Life of Strawberries

Effect of Pallet Size Modified Atmosphere Packaging Using Polyamide Film and Linear Low Density Polyethylene Film on the Shelf Life of Strawberries

Effect of media on degradability, physico-mechanical and optical properties of synthesized polyolefinic and PLA film in comparison with casted potato/corn starch biofilm

The present work focuses the degradation rate of compression moulded Low Density Polyethylene (LDPE), High Molecular Weight High Density Polyethylene (HMHDPE), Linear Low Density Polyethylene (LLDPE) and PLA (Poly lactic acid) films in comparison with solvent casted starch (corn and potato) films under different media. The control film (0 week) and degraded films were subjected to various physical and thermal test (density, crystallinity, tensile, melt flow index, Young’s modulus, elongation) and biodegradation quantification (mass loss, swelling index, haze, transmittance, gloss). The microstructure revealed that potato starch film containing lower amylose content (21%) and 2 ml (32 wt% of starch dry basis) glycerol (plasticizer) produced transparent, uniform, thin (117 μm) films with higher tensile (3.16 MPa) and good surface gloss at 45° (17.4%) whereas corn starch films (water solubility - 40.26%) has a higher biodegradability rate in all the media (94.23% in vegetable waste and 99.99% in 0.1 N HCl) can act as a better biofiller. The highest degradation was observed in soil in which LDPE showed the maximum weight loss (0.974%) and drop in tensile load at break (30.176 N to 14.93 N) and HMHDPE showed the minimum value of 0.868% and 44.67 N to 40.24 N respectively in one year.

On the Kinetics of Degradation Reaction Determined Post Accelerated Weathering of Polyolefin Plastic Waste Blends.

Polyolefin (PO) polymers constitute the majority of consumer plastic commodities. The reliance on such materials make it near imposable to avoid touching one in any given day. Therefore, the accumulation of plastic solid waste (PSW) in developed and developing societies alike requires immediate attention to manage and valorize this type of waste. In this work, PSW originating from real life sources and virgin linear low-density polyethylene (LLDPE) films were compounded in a mechanical recycling effort. The recycled blends constituted up to 100% (by weight) of the waste material. Accelerated weathering (aging) was conducted on the blends, reaching threshold limit of exposure to study the major changes occurring on the recycled blends. Thermogravimetry and differential scanning calorimetry (DSC) were used to determine their characteristics and applicability for future recycling using thermo-chemical treatment (TCT) methods. Analytical solution methods following the international committee of thermal analysis and calorimetry (ICTAC) were followed in conducting the measurements and kinetic calculations alike. A novel analytical mathematical solution model is also introduced to determine both the pre-exponential factor (Ao) and apparent activation energy (Ea) of the degradation reaction. The model proved to be a more accurate analysis tool, and the work in whole enabled the determination of future plans for using such waste components as a feedstock to thermal units.

Insecticide-releasing LLDPE films as greenhouse cover materials

The use of chemical pesticides is limited by several public health concerns regarding their toxicity levels and indiscriminate use. Nevertheless, they are still vital components of agricultural industry since no other competitive equivalents to chemical pesticides still exist in terms of efficiency. This study describes the preparation and biological assessment of an insecticide releasing plastic film for agricultural covering purposes. The formulation was prepared by incorporation of deltamethrin loaded, nano-sized halloysite nanotubes into polymeric films. Thermal, morphological, and mechanical properties of films were characterized by Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and Universal Testing Machine UTM. Sustained release profiles of the films were evaluated by Thermogravimetric Analysis (TGA). Results reveal that deltamethrin was successfully loaded into halloysite nanotubes and nanotube incorporation enhances the elastic modulus of linear-low density polyethylene (LLDPE) films. In addition, films exhibit sustained release function of the active agent for 60 days. Bioassays of the nanocomposite films with varying deltamethrin doses tested on grasshoppers showed that the LD50 values of the films are 1.85x10-5 g/cm2. Insecticidal activities of films were tested in greenhouse on Medicago Sativa plants contaminated with thrips and aphid. Nanocomposites are observed to repel mature aphids and kill young aphids and thrips.

Long- and short-term antibacterial properties of low-density polyethylene-based films coated with zinc oxide nanoparticles for potential use in food packaging

Concerns in food safety and the need for high-quality foods have increased the demand for extending the shelf life of packaged foods. Subsequently, promoting and investigating the development of antibacterial materials for food packaging has become inevitable. Zinc oxide nanoparticles have attracted attention lately owing to their multifunctional properties, especially antibacterial activity. For this study, antibacterial low-density polyethylene films were prepared by coating zinc oxide nanoparticles onto their surface. The low-density polyethylene film antibacterial activity was evaluated toward Gram-positive and Gram-negative bacteria. The scanning electron microscopy images showed that using anhydride-modified low-density polyethylene (LDPE-g-AM) resin permitted improved zinc oxide nanoparticle distribution on the low-density polyethylene film surface, reduced the agglomerate sizes, and reinforced the zinc oxide nanoparticle bonding to the low-density polyethylene film surface. We found that the coated low-density polyethylene films exhibited high antibacterial activity against both strains. The antibacterial tests also proved that the coated films retained their antibacterial efficiency toward Escherichia coli, even after eight months, with a reduction rate higher than 99.9%, whereas for Staphylococcus aureus the antibacterial properties for the linear low-density polyethylene (LLDPE) films decreased at eight months and improved for the LDPE-g-AM films. When the zinc oxide coated films were laminated with neat low-density polyethylene, only the LDPE-g-AM was still active against E. coli provided that the lamination thickness does not go beyond 8 µm. This research demonstrated that the coated low-density polyethylene films have excellent attributes when used as an active coating in the food packaging industry.

Smart Packaging in the Sustainability Challenge: Eumelanin as a UV-Absorption Enhancer of Polymers

The black-brown biopigment eumelanin screens the harmful ultraviolet (UV) radiation in the human skin. In industry, the absorption of plastics in the UV range is improved by the inclusion of additives. Our work reports an evaluation of the biopigment eumelanin as a nature-inspired additive for polymers to improve their UV-absorption. Eumelanin, being non-toxic and produced by natural sources, represents an interesting candidate for sustainable plastic additives. We fabricated eumelanin-including films of commercial linear low-density polyethylene (LLDPE), a plastic ubiquitous in packaging applications. The films were obtained by melt-compounding and compression molding. The melanin free acid treatment (MFA) was used to enhance the biopigment dispersion in the films. We observed that amounts of eumelanin as low as 0.8% wt. bring about an increase of the UV absorption up to one order of magnitude in the UVA range. We also assessed the effect of eumelanin on the film stability under prolonged UV irradiation: the biopigment proved to work both as UV-absorption enhancer but also as a photo-prooxidant, as inferred by thermogravimetric analysis (TGA) and infrared (IR) spectroscopy.

Relationship between the passivation of TiO2particles and LLDPE photodegradation: a comparison between bulk and surface impacts

ABSTRACTThe effect of the concentration of alumina (Al2O3) and silica (SiO2) used to passivate titanium dioxide (TiO2) particles on the photodegradation of plastic films containing these particles was investigated. The films were made of linear low‐density polyethylene (LLDPE) containing four different types of passivated TiO2particles. The UV degradation of the films was evaluated for the surface and the bulk by measuring the physical and chemical changes as a function of time. The surface chemical and physical degradation effects were measured by ATR‐FTIR and AFM, respectively. A statistical Gaussian adjustment was proposed to correlate the AFM depth profiles of the eroded surfaces of the films after the photodegradation process. The bulk physical effect was evidenced by the loss of mechanical properties in the films. The results showed that the higher the concentrations of Al2O3are, the better the inhibition of the photodegradation of the LLDPE films. In this study, it was confirmed that the observed UV degradation effect correlated at both the surface and bulk levels. The results showed not only the reduction of the photodegradative effect as the passivation of the TiO2particles increased but also the possibility of using these particles as UV stabilizers of LLDPE films. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2019,136, 47026.

Deterioration of irradiation/high-temperature pretreated, linear low-density polyethylene (LLDPE) by Bacillus amyloliquefaciens

A Bacillus amyloliquefaciens strain was isolated from composted plastics and identified using microbial identification system BIOLOG and 16S rDNA sequences. The capability to attack virgin and ɣ-irradiation/high temperature-pretreated LLDPE films was investigated for comparison to evaluate the effect of pretreatment. A biodeteriorating effect characterized by low weight reductions of 1.1 ± 0.3 to 3.2 ± 1.3% was observed with the pretreated LLDPE within 40–60 days. The precision of the gravimetric method was sometimes negatively affected by the fragmentation of plastic films during the biological treatment or by traces of microbial biofilm firmly adhering to the plastic material. FTIR spectra before and after 60-day treatment indicated a decrease of carbonyl band and flattening of the 1300-1100 cm−1 zone due to bacterial action. GPC showed an increase of Mn and Mw of 2300–3700 and 32 200–35 500 g mol−1, respectively, and a decrease of polydispersity index suggesting presence of low molar weight LLDPE oligomers in pretreated LLDPE. The analysis of crystallinity and melting enthalpy detected the removal of oligomers during biodeterioration. ESI-MS analysis of the medium after 60-day biotreatment of pretreated LLDPE showed a presence of 3-hydroxybutyrate oligomers linked to the disappearance of low molar weight LLDPE oligomers that was not observed with virgin LLDPE. Coincidence of the removal of LLDPE oligomers and the appearance of 3-hydroxybutyrate oligomers suggested metabolization of low molecular LLDPE fractions present in the pretreated LLDPE by B. amyloliquefaciens. The experiments with virgin LLDPE demonstrated a positive effect of the pretreatment.