Low-density Polyethylene/ethylene Vinyl Acetate Research Articles

Organopalygorskite and Molybdenum Sulfide Combinations to Produce Mechanical and Processing Enhanced Flame‐Retardant PE/EVA Blend Composites with Low Magnesium Hydroxide Loading

The effect of organopalygorskite (OPGS), molybdenum sulfide (MoS2), and magnesium hydroxide (MH) combinations on fire retardant and flammability characteristics of low‐density polyethylene/ethylene vinyl acetate (LDPE/EVA) blends was investigated using the limited oxygen index (LOI), horizontal burning test (UL‐94), and cone calorimeter measurements. The combination of OPGS with exfoliated MoS2 nanosheets is employed to reduce the conventional hydroxide content and enhance the PE/EVA blend flame‐retardant properties with a notable improvement in mechanical and processing characteristics. The flame‐retardant properties of the composites were compared with a reference PE/EVA sample with 55 wt% of MH, which is commonly used for wire coating. The effect of each additive and the use of a maleated polyethylene (PEgMA) as a compatibilizing agent on PE/EVA flame‐retardant properties were analyzed. The results of the LOI and UL‐94 tests confirmed that the addition of OPGS combined with MoS2 substantially increases the LOI value (26%) and reduces the burning rate (66%) and the pHRR (83%) compared with neat polymer blend and passes V‐0 rating during UL‐94 vertical test, which were very similar to the values obtained for the reference sample with higher MH content. In addition, the results indicate that the addition of these additives simultaneously increases the tensile modulus with mechanical properties even higher than the reference sample. Most important, the results indicated that these additive combination allows to reduce the total MH filler content to achieve the flame‐retardant requirements and with enhanced mechanical properties and with higher melt flow rates and lower viscosities facilitating the processing of the polymer composites at lower pressure in the processing extruder. Therefore, this additives combination provides a favorable way to obtain efficient flame‐retardant materials with halogen‐free, low smoke, and easy processing characteristics. J. VINYL ADDIT. TECHNOL., 26:434–442, 2020. © 2020 Society of Plastics Engineers

The synthesis of organically modified layered double hydroxide and its effect on the structure and physical properties of low-density polyethylene/ethylene–vinyl acetate blends

Organically modified layered double hydroxide (OM-LDH) was synthesized via anion exchange reaction and potassium monolauryl phosphate (MAPK) was used as an intercalator. The OM-LDH nanofillers were embedded into low-density polyethylene/ethylene–vinyl acetate (LDPE/EVA) via melt blending process which provided LDPE/EVA/OM-LDH nanocomposites. The structure and properties of the fabricated samples were characterized through Fourier transform infrared spectroscopy, X-ray diffraction techniques, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and tensile testing. The results showed that the organic anion was intercalated into the interlayer region of LDH and enlarged the interlayer distance. The TGA results of the nanocomposites showed significantly improved thermal stability at a higher temperature when containing 6 wt% OM-LDH due to the good dispersion of OM-LDH in the matrix. The DSC data indicated that the degree of crystallinity was increased obviously due to the incorporation of OM-LDH in the matrix. The formation of organic side chains on the OM-LDH surface also contributed to an improvement in the interfacial adhesion, resulting in enhanced tensile strength and elongation at break compared with LDH.

Influence of keratin and DNA coating on fire retardant magnesium hydroxide dispersion and flammability characteristics of PE/EVA blends

For the first time the combination of keratin fibers (KF), obtained from poultry feathers, with deoxyribose nucleic acid (DNA) are employed in low-density polyethylene-ethylene vinyl acetate (LDPE/EVA) blends in order to reduce the conventional hydroxide content and enhance the blend flame retardant properties. The combined effect of each filler and the use of maleated polyethylene (PEgMA) as compatibilizer on PE/EVA flame retardant properties was analyzed. DNA by its chemical structure can be considered as an intumescing agent and when it is combined with keratin the char formation is promoted and the flame retardant properties are enhanced. DNA was distributed in specific layers forming a segregated film which resulted in better PE/EVA blend flame retardant properties compared with either DNA deposited simply by compression molding on the material surface or with melt compounding in the bulk. The flame retardant behavior was compared with a reference PE/EVA sample with 55 wt% of Magnesium Hydroxide currently used for wire coatings in the wire and cable industry. The additives combination with DNA deposited as a segregated structure significantly increases the LOI up to 24.5% and reduces the heat release rate by 82% during cone calorimetry tests with very similar flame behavior as the reference sample with 55 wt% magnesium hydroxide loadings. The mechanical properties indicated that DNA has a marked increase in elongation as well as a marked reduction in torque and viscosity indicating that the combination of these additives can improve the mechanical performance, as well as facilitate the melt processing. Most important, the results indicated that the combination of these additives makes it possible to reduce the total Magnesium hydroxide filler content from 55 to 20 wt% to achieve the flame retardant requirements and with enhanced mechanical performance. Thus, this additives combination and this coating methodology provides a promising way to meet the growing demand and stringent requirements for high performance materials with high flame retardant standards using high efficient and green fire retardant coatings.

Effects of Allium sativum essence oil as antimicrobial agent for food packaging plastic film

Abstract This research is focused on the development of antimicrobial (AM) plastic packaging by using blown film extrusion machine. Plastic films incorporated with 0, 2, 4, 6 and 8% Allium sativum essence oil (AEO) (% w/w) were tested for AM activities against beef related bacteria namely Listeria monocytogenes , Escherichia coli and Brochothrix thermosphacta . Mechanical properties, thermal properties and microstructure of films were investigated to justify the effects of AEO on the film physicomechanical functionality. The retraction zone in agar disk diffusion result shows that low-density-polyethylene/ethylene-vinyl-acetate (LDPE/EVA) co-polymer film with 8% AEO significantly reduce the concentration of bacteria with inhibition strength of L. monocytogenes > B. thermosphacta > E. coli . For challenge test, the AM films sufficiently reduced the growth rate of L. monocytogenes on cooked beef at 4 °C. High amount of AEO only slightly weakens the mechanical properties whereby film crystallinity increases significantly when small amount of AEO incorporated. Industrial relevance The current innovation is applied for the meat industry where a prolong storage of meat is required. A. sativum extract is a natural essential oil which will not cause health risk when in contact with food when applied in the packaging.

Effects of calcium stearate and metal hydroxide additions on the irradiated LDPE/EVA compound properties

Abstract The effects of the addition different fillers, such as calcium stearate (CS), aluminum trihydrate (ATH), and magnesium hydroxide (MH), on the properties of low-density polyethylene/ethylene vinyl acetate (LDPE/EVA) compounds were studied. It was determined that the adhesion forces among MH and LDPE/EVA compounds were stronger than those among analogue compounds containing ATH in each irradiated sample. The gel content (GC) values of irradiated compounds containing ATH were higher than those of the analogue MH compounds, and CS addition enhanced the GC values of all compounds in each irradiated sample. The density values of compounds with MH content were higher than those of analogue compounds containing ATH in each irradiated sample. It was shown that all pristine compounds whose density was compared with irradiated samples had maximum values. Addition of CS and enhancing irradiation to polymer compounds reduced the density values. Compounds with high CS contents and were highly irradiated showed high tensile strength (TS) values. The TS values of compounds containing ATH were lower than those of analogue compounds containing MH in each irradiated sample. ATH or MH addition to polymer matrices reduced the elongation at break (EB) values in each irradiated sample. The EB values of compounds containing ATH were higher than those of compounds containing MH in each irradiation range. CS addition improved polymer chain flexibility and enhanced the compounds’ EB values with irradiation.

Investigation of enhancing effect of nano-montmorillonite on fire-retardant added low-density polyethylene–ethylene vinyl acetate hybrid system

In this study, nano-montmorillonite (NMMT) was incorporated in alumina trihydrate (ATH) added low-density polyethylene–ethylene vinyl acetate (LDPE-EVA) for enhancing the mechanical and electrical properties of the hybrid blends. The Young’s modulus of 50 phr ATH added LDPE-EVA (LE) blends has improved significantly, when the NMMT loading level increased from 5 to 15 phr. This is because the intercalation of NMMT particles reduces the cavities while enhancing the interfacial adhesion between the particle surface and LE matrix as observed via morphology analysis. The good interfacial adhesion could effectively transfer the stress from polymer matrix to filler’s particles during straining and improved the mechanical properties. On the other hand, the volume resistivity of 5 phr added LE blends was gradually decreased as the loading level of ATH has increased from 50 to 150 phr. The surface and volume resistivity of LE blends exhibited that high polarity of ATH and NMMT molecules could increase the mobility of charges in passages through polymer matrix and surface. Thus, the incorporation of ATH and NMMT could reduce the electrical resistance of LE blends. In addition, the increasing of ATH loading level also improved fire resistivity of LE blends as indicated by the promising limiting oxygen index. This is because the endothermic reaction of ATH during combustion process could reduce the temperature of polymer blends while releasing water vapour and the formation of alumina char. Furthermore, the increasing of NMMT loading level in ATH-added LE blends was found to slightly increase the fire retardancy. This is due to the addition of NMMT that could promote the dripping characteristics and charring effect during combustion and subsequently improve the fire retardancy of ATH added LE blends.

Preparation of radiation crosslinked foams from low‐density polyethylene/ethylene‐vinyl acetate (LDPE/EVA) copolymer blend with a supercritical carbon dioxide approach

AbstractLow‐density polyethylene/ethylene‐vinyl acetate copolymer (LDPE/EVA) blend foams were prepared by a combination of radiation and supercritical carbon dioxide (ScCO2) approach. The radiation effects on LDPE/EVA foams in different ratios were investigated in detail. For the LDPE/EVA blend in a w/w ratio of 70/30, the cell size decreased and the cell density increased with an increase of absorbed dose. The optimal dose and EVA content for the foaming of LDPE/EVA blend in ScCO2 was found to be 50 kGy and 30%, respectively. It was also found that the radiation crosslinked LDPE/EVA blends had a wider foaming temperature range than uncrosslinked samples. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation of Mg(OH)2-Melamine Core-Shell Particle and Its Flame Retardant Property

Magnesium hydroxide-melamine core-shell particles were prepared through the coating of melamine monomer on the surface of magnesium hydroxide in the presence of phosphoric acid. The melamine monomer was dissolved in hot water but recrystallized on the surface of magnesium hydroxide by quenching to room temperature in the presence of phosphoric acid. The core-shell particle was applied to low-density polyethylene/ ethylene vinyl acetate (LDPE/EVA) resin by melt-compounding at <TEX>$180^{\circ}C$</TEX> as flame retardant. The effect of magnesium hydroxide and melamine content has been studied on the flame retardancy of the core-shell particles in LDPE/EVA resin according to the preparation process and purity of magnesium hydroxide. Magnesium hydroxide prepared with sodium hydroxide rather than with ammonia solution revealed higher flame retardancy in core-shell particles with LDPE/EVA resin. At 50 wt% loading of flame retardant, core-shell particles revealed higher flame retardancy compared to that of the exclusive magnesium hydroxide in LDPE/EVA composite, and it was possible to satisfy the V0 grade in the UL-94 vertical test. The synergistic flame retardant effect of magnesium hydroxide and melamine core-shell particles was explained as being due to the endothermic decomposition of magnesium hydroxide and melamine, which was followed by the evolution of water from the magnesium hydroxide and porous char formation due to reactive nitrogen compounds, and carbon dioxide generated from melamine.

Sorption and diffusion of aromatic solvents through linear low density polyethylene–ethylene vinyl acetate blend membranes

An investigation has been made for understanding the transport behaviour of organic solvents through linear low-density polyethylene (LLDPE)/ethylene vinyl acetate (EVA) blend membranes with special reference to the effects of blend ratio, concentration of cross-linking agent, penetrant size and temperature. Attempts have been made to relate the transport parameter with the morphology of the blend. The various transport parameters such as diffusion coefficient (D), permeation coefficient (P) and sorption coefficients (S) were evaluated at different diffusion conditions. The results were compared with theoretical predictions and found that the diffusion process follows anomolous type behaviour. The blends show dispersed/matrix and co-continuous phase morphologies depending on the composition. Dynamic vulcanization leads to fine and uniform distribution of the dispersed domains with a stable morphology. Among the blends E70 sample shows the maximum solvent uptake and E30 the minimum. The solvent uptake of blend varies with concentration of cross-linking agent. Molecular size of the solvent is a decisive factor in the solvent uptake. The rate of sorption and maximum solvent uptake increase with increase of temperature. Irrespective of the solvents used, the maximum solvent uptake increases with increase of temperature. The observed sorptivity, diffusivity and permeability are associated with cross-link densities of different samples. The D, S and P values increase with increase of EVA content in the blend.

Effects of high‐energy electron beam on low‐density polyethylene materials containing EVA

AbstractA series of low‐density polyethylene (LDPE) blends with different amounts of ethylene–vinyl–acetate (EVA) was prepared and irradiated with 10 MeV electron beam in the range of 0–250 kGy at room temperature in air. EVA was used as a compatibilizer and softener in four different amounts: 5, 10, 20, and 30 wt %, based on polyethylene (PE). The crosslinking of the samples was studied on the basis of gel‐content measurements as well as some thermal and mechanical properties of the specimens. The results indicated that the LDPE and LDPE–EVA blends could be crosslinked by a high‐energy electron beam, of which their thermal and mechanical properties changed effectively, however, because of EVA content of the polymer; the blends were more sensitive to lower doses of radiation. These studies were carried out to obtain a suitable compound for heat‐shrinkable tubes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1049–1052, 2004

Shrinkage effect on polyethylene based blends

An experimental study of the shrinkage effect in low density-high density polyethylene blends, high density-high density polyethylene blends and low density polyethylene-ethylene vinyl acetate copolymer blends is presented. Viscosity measurements are also included. The strain recovery is analysed as the addition of the interfacial tension effect and the elastic recoverable strain. The results are compared with those obtained for other polyolefin blends observing that in the case of compatible systems as low density-high density polyethylene and high density-high density polyethylene blends the strain recovery and the viscosity follow approximately the additive rule. In the case of more incompatible systems like polyethylene-ethylene vinyl acetate copolymer, polyethylene-polypropylene and others very large recoveries were observed. The formation of minifibres of the dispersed phase during the preparation of the samples is suggested as responsible for the obtained results.