Performance of polyethylene/ethylene-vinyl alcohol copolymer/polyethylene multilayer films using maleated polyethylene blends

Blends of linear low density polyethylene (LLDPE) and linear low density polyethylene grafted with maleic anhydride (LLDPE-gMA) were used to promote adhesion between LLDPE and ethylene-vinyl alcohol copolymer (EVOH) in a coextruded three layer flat film, trying to avoid the use of a tie layer. These particular films could be an option when the equipment for a five layer system is not available. The effect of the modified polymer on the surface of cast films was characterized through contact angle measurements. T-peel strength, and oxygen and water vapor transmission rate of the multilayer films were measured as a function of LLDPE-gMA content. Compressed films with 0%, 0.03%, and 0.08% of maleic anhydride (MA) were also analyzed by infrared spectroscopy (FTIR). The increased T-peel strength observed when using MA contents higher than 0.08% suggests a good interfacial adhesion between layers. This increase could be associated with specific interactions between the LLDPE-gMA and the EVOH, as the development of covalent bonds through the reaction of the anhydride with the EVOH hydroxyl groups across the interface. This was proved by the FTIR analysis that showed an increase in the ester band absorbance with an increase on the maleated polymer content and bonding time indicating that a chemical reaction occurred, at the interface. The observed changes on the oxygen and water vapor barrier properties of the films were not significant.     

Fusion bonding of maleated polyethylene blends to polyamide 6

Blends of linear low-density polyethylene (LLDPE) and linear low-density polyethylene–grafted maleic anhydride (LLDPE-gMA) were used to promote the adhesion to polyamide 6 (PA) in a three-layer coextruded film without using an additional adhesive or tie layer. The effect of bonding time and molecular weight (MW) of different maleated polyethylenes on the peel strength of the joints was analyzed. Direct evidence of a copolymer formed in-situ at the interfaces is also considered. The peel strength of fusion bonded layers of LLDPE/LLDPE-gMA blends with PA strongly depends on bonding time and molecular weight of the maleated polymer. Tensile properties of three-layer films, made up of PA as the central layer and LLDPE/LLDPE-gMA blends as the two external layers, are improved with increases in the maleic anhydride (MA) content in the blend. The in-situ formation of a copolymer between the MA in the blend and the terminal amine groups of the PA was confirmed by the Molau test, infrared (IR) spectroscopy, and thermal analysis (DSC).     

Multilayer films using polypropylene/polypropylene grafted with acrylic acid blends and polyamide 6

Blends of polypropylene (PP) with 0 to 100 wt% of polypropylene grafted with acrylic acid (AA-g-PP) were used to promote the adhesion to polyamide 6 (PA 6) in a three-layer coextruded film without using an additional adhesive or tie-layer. The effect of modified polymer content and its molecular weight on interfacial adhesion between PP and PA 6 was determined by T-peel strength measurements. The effect of melt temperature and bonding time on peel strength was determined. Oxygen and water vapor transmission rates of the films were measured. The peel strength of fusion bonded layers of PP/AA-g-PP blends with PA 6 strongly depends on bonding temperature and time, as well as on the molecular weight of the functionalized polymer. The peeled films surfaces were characterized using FTIR-ATR and scanning electron microscopy (SEM). Tensile properties of three-layer films, made up of PA 6 as the central layer and PP/AA-g-PP blends as the two external layers, are improved with increase in the acrylic acid (AA) content in the blend. The formation of an in situ copolymer between AA in the blend and the terminal amine groups of PA 6 was confirmed by the Moalu test.     

Polyethylene grafted maleic anhydride to improve wettability of liquid on polyethylene films

Blends of linear low density polyethylene (LLDPE) and LLDPE grafted maleic anhydride (LLDPE‐g‐MA) were prepared by melt mixing. The surface of cast films with different contents and types of maleated PE were characterized through contact angle and wetting tension measurements, as well as attenuated total reflection IR spectroscopy. The tensile properties and light transmission of extruded films, as well as the performance of these films compared with commercial “antifog” films, for greenhouses were determined. The carbonyl polar groups on the surface of LLDPE/LLDPE‐g‐MA blends increased, and the equilibrium contact angles of water and dimethylformamide decreased when the content of maleated PE increased. Films made with these blends showed a noticeable reduction in water drop formation as the MA content was increased and when using LLDPE‐g‐MA of lower molecular weight. The light transmission through these films under condensation was improved when using increased contents of MA, which promotes better wetting of the water on the surface. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1802–1808, 2001     

Dynamic rheological,morphology and mechanical properties of compatibilized LLDPE/EMA blends

Blends of linear low density polyethylene (LLDPE) and ethylene-co-methyl acrylate (EMA) having 60/40 composition was studied with and without compatibilizing agent. The compatibilizing agent used was maleic anhydride grafted linear low density polyethylene (LLDPE-g-MA). The LLDPE backbones of the compatibilizer are compatible with LLDPE blend component, whereas the maleic anhydride is affinated with carbonyl groups of EMA. The effectiveness of the compatibilizing agent was evaluated using different techniques like mechanical, thermal, scanning electron microscopy and rheological studies. Best compatibilization effect was found in the blend at a loading of 3 wt% of compatibilizer since at this level of compatibilizer complex viscosity, tensile strength, modulus, elongation at break, impact strength was found to be higher. The increase in the melt viscosity, storage modulus and thermal stability of the compatibilized blends indicated enhanced interactions between the discrete LLDPE and EMA phases induced by the functional compatibilizer.     

Development of blown film linear low-density polyethylene–clay nanocomposites: Part A: Manufacturing process and morphology

In this study, linear low-density polyethylene (LLDPE)/clay nanocomposites with different clay contents were prepared by melt intercalation using two different compatibilizers: maleic anhydride grafted styrene–ethylene–butylene–styrene and maleic anhydride grafted polyethylene (PE-g-MA). Melt intercalation was achieved by twin extrusion and nanocomposite films were produced by blown film extrusion. Effects of clay and compatibilizer fractions and type of compatibilizer on the structure, permeability, and the barrier properties of the nanocomposite films were investigated. PE-g-MA was shown to notably improve the dispersion of clay layers in the polyethylene matrix, and this was examined by atomic force microscopy and X-ray diffraction. The latter tests have also highlighted the importance of the screw configuration: the presence of mixing elements favors the dispersion and distribution of nanoclay. Moreover, differential scanning calorimetry results have shown no significant effect of the clay on the crystallinity of the composite while thermogravimetric analysis tests have demonstrated a decrease of onset and peak of decomposition temperatures. Finally, barrier properties toward water vapor transmission were measured. It was proven that not also clay, but the compatibilizer participated in decreasing the permeability of the film. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48589.     

LLDPE‐based mono‐ and multilayer blown films: Property enhancement through coextrusion

In this study we investigated the performance of multilayer coextruded linear low‐density polyethylene (LLDPE) blown films. Five‐layer films were compared with monolayer dry‐blended films, and the effects of layer composition and layout on the end‐use properties of the coextruded films were highlighted. Three different LLDPEs were used: a conventional Ziegler‐Natta LLDPE gas phase butene copolymer, an advanced Ziegler‐Natta LLDPE solution octene copolymer, and a single‐site LLDPE solution octene copolymer. Numerous five‐layer coextruded structures comprising the single‐site resin and the other two Ziegler‐Natta resins were produced. The coextruded structures composed of the LLDPE butene and the single‐site resin yielded improved end‐use properties relative to the monolayer‐blended films. This result was ascribed to the presence of interfacial transcrystalline layers. Also, blends of the single‐site LLDPE and the advanced Ziegler‐Natta LLDPE octene resins within selected layers of coextruded films showed slightly enhanced tear resistance. Finally, it was found that haze was significantly reduced when the outside layers were composed of the single‐site resin. POLYM. ENG. SCI., 45:1222–1230, 2005. © 2005 Society of Plastics Engineers     

Structure and oxygen‐barrier properties of (linear low‐density polyethylene/ethylene–vinyl alcohol copolymer)/linear low‐density polyethylene composite films prepared by microlayer coextrusion

Ethylene–vinyl alcohol copolymer (EVOH) and linear low‐density polyethylene (LLDPE) blends with 5% LLDPE grafted with 1% maleic anhydride (MAH; EVOH/LLDPE/LLDPE‐g‐MAH), created to increase the interfacial compatibility, were coextruded with pure LLDPE through the microlayer coextrusion technology. The phase morphology and gas‐barrier properties of the alternating‐layered (EVOH/LLDPE/LLDPE‐g‐MAH)/LLDPE composites were studied by scanning electron microscopy observation and oxygen permeation coefficient measurement. The experimental results show that the EVOH/LLDPE/LLDPE‐g‐MAH and LLDPE layers were parallel to each other, and the continuity of each layer was clearly evident. This structure greatly decreased the oxygen permeability coefficient compared to the pure LLDPE and the barrier percolation threshold because of the existence of the LLDPE/EVOH/LLDPE‐g‐MAH blend layers, and the LLDPE layers diluted the concentration of EVOH in the whole composites. In addition, the effects of the layer thickness ratio of the EVOH/LLDPE/LLDPE‐g‐MAH and LLDPE layers and the layer number on the barrier properties of the layered composites were investigated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42211.     

Adhesion and delamination failure mechanisms in alternating layered polyamide and polyethylene with compatibilizer

The effects of compatibilizer and the number of layers on the interfacial adhesion and delamination model of coextruded microlayer samples consisting of alternating layers of high‐density polyethylene (HDPE) and polyamide 6 (PA6) were studied with T‐peel test. When more maleic anhydride‐grafted HDPE was incorporated into HDPE layer, the interfacial delamination model changed from adhesive to cohesive failure in the case of bilayer samples. For high‐layer samples, the results of X‐ray photoelectron spectroscopy showed that the areal density of copolymers at the interfaces increased with increasing number of layers due to strong and durable shearing forces during microlayer coextrusion. Scanning electron microscopy observation revealed that the interfacial delamination model changed from single‐ to multiple‐interface delamination when the number of layers increased from 16 to 32. The crack propagation included a large number of layer–layer jumps. The peel strength of microlayer samples was found to be greatly influenced by the interfacial delamination mechanisms. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Conceptualizing Physical and Chemical Interactions in the Compatibilized HDPE/PA6 and HDPE/EVOH Pairs: Theoretical and Experimental Analyses

Physical/chemical interaction in blends of high-density polyethylene with polyamide 6 and polyethylene-co-vinyl alcohol compatibilized with maleic anhydride-grafted high-density polyethylene was discussed. The performance of maleic anhydride-grafted high-density polyethylene was assessed by domain size variation and interfacial adhesion examination. Analysis of impact strength elucidated physical interaction improvement by compatibilization (entanglements and hydrogen bonding), while chemical reactions between ?OH and ?NH (from polyethylene-co-vinyl alcohol and polyamide 6, respectively) and ?COOH functional groups resulting from ring-opening of maleic anhydride determined interfacial adhesion reinforcement, where interfacial adhesion parameter changed from 0.75 for noncompatibilized to 0.96 compatibilized high-density polyethylene/polyamide 6, but remained unchanged for high-density polyethylene/polyethylene-co-vinyl alcohol blends, from 0.98 to 1.02.     

The effect of polyamide end-group configuration on morphology and toughness of blends with maleated elastomers

The effect of polyamide end-group configuration on morphology generation and toughness of blends with maleated elastomers was investigated. Two difunctional polyamides, a copolymer containing 15% nylon 6,6 and an amine enriched nylon 6, were compared to monofunctional nylon 6 materials of equivalent molecular weight and melt viscosity. Difunctional polyamides have some chains with amine groups on both ends capable of reacting with the maleated rubber phase resulting in crosslinking-type effects. The elastomers used included styrene-butadiene-styrene block copolymers with a hydrogenated midblock, SEBS, and versions with X% grafted maleic anhydride, SEBS-g-MA-X%, and a maleated ethylene/propylene random copolymer, EPR-g-MA. Blends based on difunctional polyamides form large, complex rubber particles when compounded in a single-screw extruder; however, by compounding with an appropriate twin-screw extruder, the size and complexity of the particles can be reduced to levels similar to blends with the monofunctional nylon 6 controls. Measurement of the extent of reaction between the amine end groups and the grafted maleic anhydride revealed that a larger number of amine groups are consumed for the difunctional polyamides than for their monofunctional controls. The room-temperature Izod impact strength of blends with the difunctional polyamides is greater than are the corresponding blends with the controls; however, subambient toughness depends mainly on the inherent ductility of the polyamide matrix. © 1996 John Wiley & Sons, Inc.     

Blend compatibilizers based on silane‐ and maleic anhydride–modified polyolefins

Polypropylene (PP)/polyamide blends were compatibilized with PP modified with vinylsilane or maleic anhydride and ethylene–propylene random (EPR) copolymer modified with maleic anhydride. The thermal behavior, mechanical properties, and morphology of the blends were investigated. Thermal analysis showed that the polyamide crystallization temperatures shifted downward with all compatibilizers, whereas its melting behavior did not change. On the other hand, polypropylene crystallization temperatures shifted upward in all cases, except for blends containing EPR modified with maleic anhydride. Tensile strength and elongation at break increased for blends compatibilized with modified PP. Blends containing up to 7% of EPR modified with maleic anhydride did not show good yield stresses. The morphology of the blends showed a finer dispersion of the polyamide minor phase in the PP matrix. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2492–2498, 2003     

Polyethylene Grafted Polyether Pentaerythritol Mono-Maleate to Improve Wettability of Liquid on Polyethylene Films

Blends of linear low density polyethylene (LLDPE) and linear low density polyethylene grafted polyether pentaerythritol mono-maleate (LLDPE-g-PPMM) were prepared by melt mixing. The surface of LLDPE/LLDPE-g-PPMM films with different contents of LLDPE-g-PPMM was characterized through contact angle and FT-IR spectroscopy. The tensile properties and light transmission properties of extruded films, as well as the performance of these films compared with commercial anti-fog films, were determined. The carbonyl polar groups on the surface of LLDPE/LLDPE-g-PPMM films increased, and the contact angles of water and glycerol decreased when the content of LLDPE-g-PPMM increased. LLDPE/LLDPE-g-PPMM films showed a noticeable reduction in water drop formation as the LLDPE-g-PPMM content was increased. The transmittancy and haze of LLDPE/LLDPE-g-PPMM films were improved when using increased contents of PPMM, which promotes better wetting of the water on the surface.     

Permeability of oxygen and water vapor through polyethylene/polyamide films

Oxygen and water vapor permeability studies were carried out on binary polyethylene/polyamide immiscible blends incorporating three polyethylene resins (LDPE, LLDPE, and HDsPE), and three polyamide resins (PA-6, PA-6,6, and modified PA-6,6m). It was found that the incorporation of PA into PE reduces the oxygen permeability while water vapor permeability is increased. In the range of 0 to 30 weight percent of PA, the oxygen permeability of PE was reduced by a factor of 2.8 to 3.6. Maximum water vapor permeabilities increased: for HDPE by a factor of about 2.6 to 3.1 and for LDPE and LLDPE blends by about 1.6.     

Linear low‐density polyethylene/(soya powder) blends containing polyethylene‐g‐(maleic anhydride) as a compatibilizer

Blends were made from linear low‐density polyethylene (LLDPE) and various amounts of soya powder. The soya powder content was varied from 5 to 20 wt%. Polyethylene‐g‐(maleic anhydride) (PE‐g‐MA) was used as a compatibilizer. Tensile strength and elongation at break (EB) decreased with increasing soya powder content. However, Young's modulus increased with the incorporation of soya powder. The addition of PE‐g‐MA as a compatibilizer increased the tensile strength, EB, and modulus of the blends. The interfacial adhesion between soya powder and LLDPE was improved by the incorporation of PE‐g‐MA, as demonstrated by scanning electron microscopy. Increasing the content of soya powder reduced the crystallinity of the LLDPE phase. The addition of PE‐g‐MA had no significant effect on melting temperature, but the degree of crystallinity of the LLDPE was increased. The thermal stability of the blends was determined by using thermogravimetric analysis. Thermal stability decreased with increasing soya powder loading. However, the addition of PE‐g‐MA slightly increased the thermal stability of LLDPE/(soya powder) blends. J. VINYL ADDIT. TECHNOL., 2009. © 2009 Society of Plastics Engineers     

Degradation behavior of poly (caprolactone)–poly(ethylene glycol) block copolymer/low–density polyethylene blends

Blends of poly(carprolactone)-poly(ethylene glycol) block polymer (PCE) with low-density polyethylene (LDPE) were prepared by extrusion followed by compression molding into thin film specimens. The morphology, thermal properties, degradation, and mechanical behavior of the blends were investigated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), water immersion, static tensile testing, and dynamic mechanical analysis (DMA). The LDPE/PCE blends were immiscible for all chemical compositions. A LDPE/PCE (75/25 wt%) blend exhibited small reductions in weight and tensile strength after immersion in a buffer solution (pH = 5.0) at 50°C for extended periods of time. However, grafting maleic anhydride onto the LDPE/PCE blends improved the compatibility between the LDPE and PCE phases. Consequently, a 75/25 wt% blend of maleated LDPE/PCE exhibited significant losses in weight and tensile strength after immersion in the buffer solution. For comparison, blends of poly(caprolactone) (PCL) with LDPE were fabricated by similar techniques. The effect of compatibilizer on the degradation of LDPE/PCE and LDPE/PCL is discussed.     

Mechanical and shape‐memory properties of polyamide/maleated polyethylene/linear low‐density polyethylene blend

Novel polymer blends of polyamide and linear low‐density polyethylene with maleated polyethylene as compatibilizers were prepared in a modular intermeshing corotating twin‐screw extruder. Polymer blends with different contents of polyamide in polyethylene matrix were obtained. The mechanical properties were studied in terms of the tensile strength and elongation‐to‐break. The shape‐memory properties of the blended materials were characterized using three‐point bending test in a temperature‐controlled chamber. The results show that the incorporation of maleated polyethylene has a strong effect on the tensile properties and the morphology of the blends. The shape‐memory effect of blended materials is affected by polyamide weight fraction, and 60 wt % polyethylene, 20 wt % polyamide, and 20% maleated polyethylene have an acceptable performance. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Low molecular weight paraffin,as phase change material,in physical and micro-structural changes of novel LLDPE/LDPE/paraffin composite pellets and films

Latent heat storage system by phase change materials is an effective method to achieve high density energy storage. A novel composite pellet consisted of a blend of linear low density polyethylene and low density polyethylene (LLDPE/LDPE) with low molecular weight paraffin (a phase change material, at 25 and 50 wt%) has been developed and coated by calcium silicate to prevent paraffin leakage. Three-layer coextruded films containing the paraffin composites as the middle layer have been prepared from each group for application as plastic film cover to control undesirable temperature variations during the storage of agricultural crops. The Melt Flow Index and thermal properties of the pellets as well as the quantity of paraffin leakage were studied. Thermal/morphological and permeation properties of the coextruded films have been investigated. The results showed that the LLDPE/LDPE polymer matrix provided an appropriate structural morphology for low molecular weight paraffin (n < 18) entrapment with good miscibility and low paraffin leakage (< 5%). Based on differential scanning calorimetry (DSC) thermographs, this type of paraffin may promote the compatibility between linear and low-density polyethylene. A dispersion-type morphology was observed in the micrograph of LLDPE/LDPE film, where the sizes of the spherical micro-domains were reduced as evident in the microscopic images of the paraffin-containing composite films. At storage temperatures below the phase change temperature (T < 25 °C), the oxygen permeability was substantially decreased because of the combined effects of paraffin crystallites and calcium silicate.     

Synthesis and properties of polyamide/LLDPE composites with compatibilizer used as hot melt adhesive

In this work, a new polyamide (PA155) was synthesized from higher purity dimer acid, sebacic acid, ethylenediamine, and piperazine, and the ternary blends were prepared by blending PA155 with LLDPE in the presence of the compatibilizer, maleic anhydride grafted linear low-density polyethylene (LLDPE-g-MAH). The weight ratio of PA155 to LLDPE of the samples was kept constant at 80/20 and the amount of LLDPE-g-MAH was varied at 0, 3, 6, 9, and 12 wt% over the total weight of the blend respectively. The scanning electron microscope and mechanical properties tests showed that the compatibility and the mechanical properties were improved with the increase in LLDPE-g-MAH content, and the blend containing 9.0 wt% LLDPE-g-MAH exhibits an optimal miscibility behavior and mechanical properties. The hot melt adhesives which were prepared from the ternary blends were assessed by 180°peel tests of Al/adhesive/polypropylene stack. The peeling strength for the sample containing 9.0 wt% compatibilizer (82.5 N/2.5 cm) is much more than that of the samples without compatibilizer (<20 N/2.5 cm).     

Influence of interfacial agents on the physicochemical characteristics of binary polyethylene/polyamide 6 and ternary polyethylene/polypropylene/polyamide 6 blends

Binary low-density polythylene/polyamide 6 and ternary low-density polyethylene/polypropylene/polyamide 6 blends were prepared by melt mixing, without and with the addition of two different commercial products [poly(ethylere-co-buthylacrylate-co-maleic anhydride) and poly(ethylene-co-vinylacetate) grafted with maleic anhydride] used as interfacial modifiers. More precisely, the polypropylene was a propylene/ethylene random copolymer, containg 6% by weight of ethylene. The polyamide 6/interfacial agent and polyethylene/ interfacial agent systems were also considered. Differential scanning calorimetry, microscopic observations—together with chemical etchings—and mechanical tests supported the occurrence of strong interactions at the interface, especially when using the buthyl acrylate-based agent. The compatibilizing effect of the interfacial agents was also analyzed in the light of interfacial tension determinations. Eventually, low-density polyethylene modifications induced by compatibilization were studied carrying out WAXD analysis. © 1996 John Wiley & Sons, Inc.