Development of blown film linear low‐density polyethylene‐clay nanocomposites: Part B: Mechanical and rheological characterization

Abstract

In a previous article nanocomposite films made from linear low-density polyethylene (LLDPE) as matrix and org-MMT clay as reinforcement were produced. Morphology, thermal stability, and barrier properties were already investigated. The actual work constitutes a complement of the aforementioned article where many mechanical aspects will be assessed: Unlike maleic anhydride grafted styrene-ethylene-butylene-styrene (SEBS-g-MA) as compatibilizer, using maleic anhydride grafted polyethylene (PE-g-MA) has shown remarkable improvement of most of the properties and this for an optimum clay content ranging between 2 and 4%: the tensile strength has increased by 45%, the stiffness in transverse direction (TD) by 48%, the dart impact has improved by 20%, the tear resistance in machine direction (MD) has increased by 33% and the creep resistance by 20%. Other properties were found to improve with the clay content. In addition, the evolution of the storage and loss moduli as well as the complex viscosity with the frequency were recorded; the drop by 76% of the crossover frequency for 6% weight of clay has shown that the solid-like behavior of the composite is pronounced with the increment of clay content. Melt flow index was found to vary inversely with clay amount; this indicates an increase in and hence a good dispersion of the clay within the polyethylene matrix.

Robust Tear-Resistant Blown Nanocomposite Films for Barrier Packaging: Role of Clay Platelet Thickness in Tear Mechanics and Barrier Performances

“…At low BUR, the molecules are predominantly oriented along the MD in the thin film prepared by a blown film extruder. In TD, tear force ( T F ) is higher than the magnitude of the force in CD because clay lamella stacks get preferentially oriented in the parallel direction to CD, leading to an enhanced extent of obstruction to the propagation of the tear. − Trouser tearing force in TD has further been observed to steadily increase from ∼4.6 N for neat LLDPE to ∼10.44 N for LLC5 Tensile strength remained nearly unaffected (marginal affected), indicating a matrix-dominated uniaxial tensile response. Elongation (%) to break decreased upon the incorporation of nanoclay by ∼10–25% due to clay tactoids resisting plastic (bulk) deformation of the physically entangled LLDPE network by partially immobilizing a fraction of polymer chain segments Strain energy density decreased in variable extents in various composites, with the extent of reduction remaining in the range of ∼10–20%. …”

“…The polyethylene/clay nanocomposites lead to a structurally intercalated matrix in the presence of a compatibilizer . Therefore intercalated layered silicate enhanced various properties, including water and gas barrier resistance, by creating a longer tortuous path. , Said et al have reported that clay improved properties in the transverse direction (TD), as clay lamella stack aligns in the cross direction (CD) for the films made by blown film extrusion. , …”

“…The radius of gyration of polymers ( R g ) gives a sense of the size of the polymer coil in nanocomposites, which were investigated using small-angle X-ray scattering (SAXS) in the Guinier region . Incorporating organically modified clay leads to better polymer–clay interaction, where the clay, being in the rigid phase, may impart its functionality as a stress transfer agent and hence ultimately increasing the mechanical properties . Tearing of polymer films remains most decisive mechanical property for packaging films in all testing protocols; for this, the trouser tear test is typically performed in the transverse and cross-direction for better indication of tear strength of the nanocomposite films and for ensuring tear-resistance isotropy arising from the film-blowing process.…”

Physico‐mechanical, rheological and gas barrier properties of organoclay and inorganic phyllosilicate reinforced thermoplastic films

“…To improve this property, the introduction of nanofiller such as nanoclay plays an important role. [18][19][20] Montmorillonite (MMT) has been widely used in the synthesis of polyethylene nanocomposites. MMT clays have an alumino-silicate structure where an octahedral layer is sandwiched between two tetrahedral layers and Na + or Ca + ions are occupied in the interlayer.…”

“…Virgin polyethylene films have poor oxygen permeability properties although high density polyethylene (HDPE) possesses good water vapor permeability. To improve this property, the introduction of nanofiller such as nanoclay plays an important role 18–20 . Montmorillonite (MMT) has been widely used in the synthesis of polyethylene nanocomposites.…”