Abstract
In this work, a new eco-friendly method for the treatment of poly(3-hydroxybutyrate) (PHB) as a candidate for food packaging applications is proposed. Poly(3-hydroxybutyrate) was modified by bacterial cellulose nanofibers (BC) using a melt compounding technique and by plasma treatment or zinc oxide (ZnO) nanoparticle plasma coating for better properties and antibacterial activity. Plasma treatment preserved the thermal stability, crystallinity and melting behavior of PHB‒BC nanocomposites, regardless of the amount of BC nanofibers. However, a remarkable increase of stiffness and strength and an increase of the antibacterial activity were noted. After the plasma treatment, the storage modulus of PHB having 2 wt % BC increases by 19% at room temperature and by 43% at 100 °C. The tensile strength increases as well by 21%. In addition, plasma treatment also inhibits the growth of Staphylococcus aureus and Escherichia coli by 44% and 63%, respectively. The ZnO plasma coating led to important changes in the thermal and mechanical behavior of PHB‒BC nanocomposite as well as in the surface structure and morphology. Strong chemical bonding of the metal nanoparticles on PHB surface following ZnO plasma coating was highlighted by infrared spectroscopy. Moreover, the presence of a continuous layer of self-aggregated ZnO nanoparticles was demonstrated by scanning electron microscopy, ZnO plasma treatment completely inhibiting growth of Staphylococcus aureus. A plasma-treated PHB‒BC nanocomposite is proposed as a green solution for the food packaging industry.
Highlights
Synthetic polymers have been used in packaging for many decades and at least half of their consumption is by the food packaging industry [1,2]
In this work we propose a simple atmospheric pressure plasma treatment and coating process, which ensure the surface modification of PHB and
A rough proportion of 10% tributyl citrate (TBC) plasticizer was estimated in the commercial PHB granules [12]
Summary
Synthetic polymers have been used in packaging for many decades and at least half of their consumption is by the food packaging industry [1,2]. The large application of biopolymers in this sector has huge advantages in terms of a decreased dependence on fossil fuel reserves and limitation of the environmental problems associated with synthetic polymer pollution. Polyhydroxyalkanoates (PHAs), which are obtained by bacterial synthesis, are considered as very promising candidates for food packaging and biomedical applications [4,5,6]. Their hydrolytic degradation in the environment and in living systems leads to oligomeric byproducts that are further processed by biochemical pathways [5,7]
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