Transparent Pullulan/Mica Nanocomposite Coatings with Outstanding Oxygen Barrier Properties

Abstract

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 (α), 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 ϕ ≈ 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 (≈12% and 23%, respectively) and PET coated with unloaded pullulan (≈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 ϕ ≈ 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.

Green Coating Polymers in Meat Preservation

“…Recent developments of implementation of pullulan include the creation of biopolymer nanocoating layer that is deposited directly in the form of liquid solution onto the surface of plastics, namely polyethylene terephthalate (PET). These nanocoatings create exceptional barriers against oxygen [83][84][85]. Among the few examples that used pullulan, we cite the recent study by Hassan et al [86] who developed and evaluated a pullulan-based active packaging film matrix incorporated with nisin, thymol, and lauric arginate with the aim of reducing foodborne disease strain growth in muscle foods.…”

Enzymatic Hydrolysis of Bacterial Cellulose for the Production of Nanocrystals for the Food Packaging Industry

“…Because of its unique physico-chemical properties, pullulan has been widely used for the generation of high-performance packaging materials, especially in the form of oxygen barrier coatings [19]. To improve the oxygen barrier performance of pullulan-based coatings, several inorganic and organic fillers have traditionally been used, such as microfibrillated cellulose [20,21], silica nanoparticles [22], graphene oxide [13,23], and mica [24]. In this work, we used, for the first time, BCNCs for the development of pullulan bionanocomposite coatings with high oxygen barrier properties.…”

Development of a Biopolymer-Based Anti-Fog Coating with Sealing Properties for Applications in the Food Packaging Sector

“…The data presented in Table 5 indicate no notable statistical differences in the haze values among the different formulations, except for the P75 and P100 formulations. Additionally, all measured values are below the 3% threshold, a value widely recognised for plastic materials in food packaging to ensure sufficient transparency for visual inspection of the contents [ 20 ]. The normalised haze values presented in Figure 4 correspond to an assumed coating thickness of 1 μm based on the premise that haze variation is directly proportional to thickness.…”