Browsing by Author "Trabattoni, Silvia"

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Citation - WoS: 24
Citation - Scopus: 23
Graphene Oxide Bionanocomposite Coatings With High Oxygen Barrier Properties
(Mdpi, 2016) Unalan, Ilke Uysal; Boyaci, Derya; Ghaani, Masoud; Trabattoni, Silvia; Farris, Stefano
In this work, we present the development of bionanocomposite coatings on poly(ethylene terephthalate) (PET) with outstanding oxygen barrier properties. Pullulan and graphene oxide (GO) were used as main polymer phase and nanobuilding block (NBB), respectively. The oxygen barrier performance was investigated at different filler volume fractions (phi) and as a function of different relative humidity (RH) values. Noticeably, the impermeable nature of GO was reflected under dry conditions, in which an oxygen transmission rate (OTR, mLm(-2)24 h(-1)) value below the detection limit of the instrument (0.01 mLm(-2)24 h(-1)) was recorded, even for phi as low as 0.0004. A dramatic increase of the OTR values occurred in humid conditions, such that the barrier performance was totally lost at 90% RH (the OTR of coated PET films was equal to the OTR of bare PET films). Modelling of the experimental OTR data by Cussler's model suggested that the spatial ordering of GO sheets within the main pullulan phase was perturbed because of RH fluctuations. In spite of the presence of the filler, all the formulations allowed the obtainment of final materials with haze values below 3%, the only exception being the formulation with the highest loading of GO (phi approximate to 0.03). The mechanisms underlying the experimental observations are discussed.
Citation - WoS: 19
Citation - Scopus: 20
Transparent Pullulan/Mica Nanocomposite Coatings With Outstanding Oxygen Barrier Properties
(Mdpi, 2017) Unalan, Ilke Uysal; Boyaci, Derya; Trabattoni, Silvia; Tavazzi, Silvia; Farris, Stefano
This study presents a new bionanocomposite coating on poly(ethylene terephthalate) (PET) made of pullulan and synthetic mica. Mica nanolayers have a very high aspect ratio (alpha), at levels much greater than that of conventional exfoliated clay layers (e.g., montmorillonite). A very small amount of mica (0.02 wt %, which is phi approximate to 0.00008) in pullulan coatings dramatically improved the oxygen barrier performance of the nanocomposite films under dry conditions, however, this performance was partly lost as the environmental relative humidity (RH) increased. This outcome was explained in terms of the perturbation of the spatial ordering of mica sheets within the main pullulan phase, because of RH fluctuations. This was confirmed by modelling of the experimental oxygen transmission rate (OTR) data according to Cussler's model. The presence of the synthetic nanobuilding block (NBB) led to a decrease in both static and kinetic coefficients of friction, compared with neat PET (approximate to 12% and 23%, respectively) and PET coated with unloaded pullulan (approximate to 26% reduction in both coefficients). In spite of the presence of the filler, all of the coating formulations did not significantly impair the overall optical properties of the final material, which exhibited haze values below 3% and transmittance above 85%. The only exception to this was represented by the formulation with the highest loading of mica (1.5 wt %, which is phi approximate to 0.01). These findings revealed, for the first time, the potential of the NBB mica to produce nanocomposite coatings in combination with biopolymers for the generation of new functional features, such as transparent high oxygen barrier materials.