Abstract
In this study, ethylene vinyl alcohol (EVOH) nanocomposites elaborated by melt blending with four different fillers were investigated. Two graphene and two graphite fillers displaying various shapes were selected. The morphology, microstructure, thermal, mechanical, and barrier properties of the nanocomposite films prepared for 2 wt% fillers were analyzed with the aim to establish structure–function properties relationships. The nanocomposites properties significantly depended on the nature of the incorporated filler. The nanocomposite film prepared with the expanded graphite filler exhibited the highest Young modulus value (E = 1430 MPa) and the best barrier properties. Indeed, barrier properties, rarely studied at high water activities, evidenced a significant improvement with a decrease of the water vapor permeability by a factor 1.8 and of the oxygen permeabilities by a factor close to 2, for a critical water activity higher than 0.95. An increase of the thermal stability was also evidenced for this nanocomposite. It was shown that for all studied nanocomposites, the properties could be related to the dispersion state of the fillers and the simultaneous increase of the crystallinity of the matrix. A specific equation was proposed to take into account these both parameters to accurately predict the nanocomposite barrier properties.
Highlights
In the majority of the literature data related to ethylene vinyl alcohol (EVOH)/graphene systems, the elaboration of the nanocomposites was realized through a solution casting process, using dimethyl sulfoxide (DMSO) as a solvent
To analyze the nanocomposites morphology, transmission electron microscopy (TEM) analysis was performed at different magnifications and characteristic TEM images of the samples are shown in Figures 1 and 2
It is noteworthy that single-layer and few layer graphene sheets were clearly observed in EVOH/CT1 sample in addition to small stacks
Summary
In the majority of the literature data related to EVOH/graphene systems, the elaboration of the nanocomposites was realized through a solution casting process, using dimethyl sulfoxide (DMSO) as a solvent. This process displays the disadvantage of being complicated to scale up for industrial applications, as well as having a high environmental impact [21,22]. Only a few studies on the feasibility of EVOH/graphene-based nanocomposites preparation through a melt blending process have been undertaken [12,23,24] It appeared that the incorporated fillers were poorly dispersed, mainly because of a low compatibility with the EVOH matrix. It is noteworthy that the vast majority of the studies dedicated to barrier properties focused on measuring the materials performances at low hydration state
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