Modeling of the rheological properties of multinanolayer films in the presence of compatibilized interphase

Abstract

Rheological behavior of nanolayered films of polyethylene/polyamide 6 (PE/PA6) compatibilized in situ during the coextrusion process has been studied at a temperature between the melting temperatures of PE and PA6. Thanks to the high number of interfaces, a drastic increase in dynamic moduli has been measured when increasing the interphase volume fraction in the films, and a solid-like behavior for the interphase was identified. Different models are compared to capture the complex viscosity of nanolayered films as a function of angular frequency. A model considering interphase and bulk viscosities and a single fitting parameter, namely, the thickness over which the viscosity decreases linearly from the interphase to the bulk one, captures the complex viscosity of all samples. This thickness is comparable to the PE layer thickness up to values about 1 μm before a significant bulk region has to be added to capture the behavior for thicker layers. This suggests that the melt rheology is impacted by the presence of a nanometric interphase over very large (micronic) length scales.

Dewetting Dynamics of Sheared Thin Polymer Films: An Experimental Study

“…Because of the limited observation window of the microscope and the movements induced by shear, this study only deals with γ̇ < 2 s –1 . Such shear rates are nonetheless consistent with those typically achieved during multilayer coextrusion. , …”

“…Such shear rates are nonetheless consistent with those typically achieved during multilayer coextrusion. 28,44…”

Understanding the Rheology of Polymer–Polymer Interfaces Covered with Janus Nanoparticles: Polymer Blends versus Particle Sandwiched Multilayers

“…In light of the intimate structure–rheology relations, small amplitude oscillatory shear (SAOS) measurements of polymer blends have proven to be sensitive to changes in morphology and interfacial properties, because of which they are frequently being used to evaluate compatibilization in blends. − For instance, as compared to the neat components, blends with a droplet-in-matrix morphology are often characterized by an enhanced elasticity at low frequencies with a distinct shoulder in the storage modulus ( G ′) curve in linear viscoelasticity. − This G ′ shoulder is attributed to the shape relaxation of the dispersed phase, with a characteristic relaxation time denoted as τ F . Such shape relaxation is also measurable in blends with a co-continuous structure, whereby the enhanced elasticity at low frequencies is characterized by a power-law dependence of G ′ on frequency. , The addition of compatibilizers has been reported to alter the linear viscoelasticity of blends by shifting τ F toward a lower value (higher frequency) and introducing a more pronounced shape relaxation as a result of the reduction in droplet domain size and related increase of the interfacial area respectively. , More importantly, an additional interface-governed relaxation mechanism at a higher relaxation time (τ β ) than τ F was observed in the SAOS measurements of compatibilized blends. , Such interfacial viscoelasticity was mostly ascribed to the Marangoni stress of the interfacial compatibilizers and argued to be linked to the interfacial shear modulus identified from the generalized version of the Palierne emulsion model.…”

Extensional Viscosity of Immiscible Polymer Multi-Nanolayer Films: Signature of the Interphase

“…11,12 However, it was only recently that the complex viscosity of a compatibilized interface has been characterized over a large frequency range. 13,14 To do so, we took advantage of multi-nanolayer coextrusion that applies successive slicing and recombining a stratified polymer melt flow, giving rise to a material made of thousands of alternating nanometric layers. 15,16 By doing so, the effect of interfaces was drastically enhanced in the response of the materials under oscillatory shear.…”

“…The effect of the compatibilizer, such as the role of molecular weight or the amount of copolymer, has been quantified long ago on interfacial properties in the solid-state-like fracture toughness at the interface. , However, it was only recently that the complex viscosity of a compatibilized interface has been characterized over a large frequency range. , To do so, we took advantage of multi-nanolayer coextrusion that applies successive slicing and recombining a stratified polymer melt flow, giving rise to a material made of thousands of alternating nanometric layers. , By doing so, the effect of interfaces was drastically enhanced in the response of the materials under oscillatory shear. In noncompatibilized blends, a quantitative link has also been established between the fracture toughness and, this time, the interfacial nanometric thickness, which depends on the Flory–Huggins interaction parameter between the two polymers .…”