ZnO-Reinforced Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Bionanocomposites with Antimicrobial Function for Food Packaging

Abstract

Biodegradable nanocomposites were prepared by adding ZnO nanoparticles to bacterial polyester poly­(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) via solution casting technique. The morphology, thermal, mechanical, antibacterial, barrier, and migration properties of the nanocomposites were analyzed. The nanoparticles were uniformly dispersed within PHBV without the aid of coupling agents, and acted effectively as nucleating agents, raising the crystallization temperature and the level of crystallinity of the matrix while decreasing its crystallite size. A gradual rise in thermal stability was found with increasing ZnO loading, since the nanofillers hinder the diffusion of volatiles generated during the decomposition process. The nanocomposites displayed superior stiffness, strength, toughness, and glass transition temperature, whereas they displayed reduced water uptake and oxygen and water vapor permeability compared to the neat biopolymer, related to the strong matrix–nanofiller interfacial adhesion attained via hydrogen bonding interactions. At an optimal concentration of 4.0 wt % ZnO, the tensile strength and Young’s and storage moduli showed a maximum that coincided with the highest crystallinity and the best barrier properties. PHBV/ZnO films showed antibacterial activity against human pathogen bacteria, and the effect on Escherichia coli was stronger than on Staphylococcus aureus. The overall migration levels of the nanocomposites in both nonpolar and polar simulants dropped upon increasing nanoparticle content, and were well below the limits required by the current normative for food packaging materials. These sustainable nanomaterials with antimicrobial function are very promising to be used as containers for beverage and food products as well as for disposable applications like cutlery or overwrap films.

WS2 inorganic nanotubes reinforced poly(l-lactic acid)/hydroxyapatite hybrid composite biomaterials

“…Similar behaviour has been reported for other biopolyesterbased nanocomposites, 39,40 where the presence of inorganic nanoparticles increased the tortuosity of the transport path, efficiently reducing the water absorption. In fact, the ternary nanocomposites display the highest crystallinity values, and the crystalline regions are more resistant to water penetration hence retard degradation.…”

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) films for food packaging: Physical–chemical and structural stability under food contact conditions

“…The overall migration experiments show that the tested PHBV films is sufficiently inert and stable in contact with all simulants, either highly polar [water, acetic acid 3% (w/v) and ethanol 20% (v/v)] or apolar (iso‐octane and olive oil). These results are coherent with already published values for iso‐octane and ethanol 10% (v/v) . However, it is worth noting that a very high (nearly excessive) migration was noted in the case of ethanol 95% (v/v), with an overall migration value of 9.2 mg dm −2 .…”

“…Substances arising from physical–chemical material degradation as well as breakdown products and/or intentionally added additives such as antioxidants or plasticizers could migrate during the contact of the materials with the food. The inertness of PHBV‐based materials has already been evaluated through overall migration tests using liquid food simulants . However, knowledge is still missing on the dependency of the material inertness (evaluated through overall migration tests) with the structural and physical–chemical stability of biodegradable materials.…”

TiO2 nanoparticles/poly(butylene adipate‐co‐terephthalate) bionanocomposite films for packaging applications

“…To find effective application, the natural biopolymer has been blended with other synthetic polymers or nanomaterials. The incorporation of inorganic nanoparticles into the polymer matrix to enhance the properties of polymer materials was discussed …”