Abstract
The present study focuses on the preparation and characterization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films that were reinforced with cellulose microstructures to obtain new green composite materials for sustainable food packaging applications. The atomization of suspensions of microfibrillated cellulose (MFC) successfully allowed the formation of ultrathin cellulose structures of nearly 3 µm that were, thereafter, melt-mixed at 2.5, 5, and 10 wt % with PHBV and subsequently processed into films by thermo-compression. The most optimal results were attained for the intermediate MFC content of 5 wt %, however, the cellulose microstructures showed a low interfacial adhesion with the biopolyester matrix. Thus, two reactive compatibilizers were explored in order to improve the properties of the green composites, namely the multi-functional epoxy-based styrene-acrylic oligomer (ESAO) and the combination of triglycidyl isocyanurate (TGIC) with dicumyl peroxide (DCP). The chemical, optical, morphological, thermal, mechanical, and barrier properties against water and aroma vapors and oxygen were analyzed in order to determine the potential application of these green composite films in food packaging. The results showed that the incorporation of MFC yielded contact transparent films, whereas the reactive extrusion with TGIC and DCP led to green composites with enhanced thermal stability, mechanical strength and ductility, and barrier performance to aroma vapor and oxygen. In particular, this compatibilized green composite film was thermally stable up to ~280 °C, whereas it showed an elastic modulus (E) of above 3 GPa and a deformation at break (ɛb) of 1.4%. Moreover, compared with neat PHBV, its barrier performance to limonene vapor and oxygen was nearly improved by nine and two times, respectively.
Highlights
In recent years, there has been a growing interest in the development of sustainable alternative materials for food packaging due to the environmental impacts related to the high disposal of petrochemical polymers
As demonstrated in the present work, atomization allows us to obtain micrometric structures based on ultrathin cellulose fibers
It was evidenced that the direct incorporation of these cellulose microstructures into biopolyester matrices still present problems of chemical incompatibility, which is mainly reflected in a reduction of the mechanical and barrier performance
Summary
There has been a growing interest in the development of sustainable alternative materials for food packaging due to the environmental impacts related to the high disposal of petrochemical polymers. A possible solution, which is compatible with the recycling technologies, is the replacement of polymers that are derived from petroleum with biopolymers that are biodegradable [2]. These materials are macromolecules that are obtained from natural sources, are biodegradable, or show both features, which can be composted in industrial facilities and, in some cases, in domestic composting conditions and natural environments [3]. Among the currently available biopolymers, carbohydrates, such as starch [5], pectin [6], chitosan [7,8], and cellulose derivatives [9,10,11], or proteins, such as casein derivatives [12] and wheat gluten [13,14], have been widely explored as sustainable candidates in biodegradable food packaging applications
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