Anthocyanin Hybrid Nanopigments from Pomegranate Waste: Colour, Thermomechanical Stability and Environmental Impact of Polyester-Based Bionanocomposites

Abstract

In the present work, anthocyanin (ACN) hybrid nanopigments were synthetized by using a natural pomegranate dye (PD) and calcined hydrotalcite (HT) and montmorillonite (MMT) nanoclays. A wide colour gamut was obtained with MMT-based nanopigments ranging from reddish to bluish hues caused by structural transformations of ACNs at different pH values. However, a buffer effect was observed with HT obtaining samples a similar final colour regardless of the synthesis conditions. Nanopigments added with a biomordant extracted from pomegranate peels showed a different colour compared to the incorporation of a commercial mordant due to the intrinsic colouring properties of the pomegranate bioadditive. The developed nanopigments were incorporated at 7 wt% loading to produce novel polyester-based bionanocomposites which were characterized in terms of thermal, mechanical and colour properties. The encapsulation of PD into the nanoclays improved its thermal stability, in particular for MMT-based nanopigments. The pH changes observed during the nanofillers synthesis affected the final colour of the MMT-based nanocomposites, inducing a general increase in ∆E* and a decrease in gloss values. Slight improvements were obtained in terms of elastic modulus for MMT-based polymer samples confirming the applicability of the developed bionanocomposites as colouring and reinforcement materials. A very similar environmental profile was obtained for MMT and HT-based nanofillers showing MMT-based nanopigments a slightly better general behaviour. The results of the LCA study evidenced the suitability of the processes used in this work to the circular bioeconomy approach through sustainable food waste management and the production of bioplastics using waste substrates.

Using Laminar Nanoclays for Phycocyanin and Phycoerythrin Stabilization as New Natural Hybrid Pigments from Microalgae Extraction

“…The use of hybrids nanopigments from inorganic hosts such as laminar nanoclays and natural dyes extracted from agrowaste has been successful in advanced applications such as 3D-printing technologies. When hybrid nanopigments are exfoliated into a polymer matrix, the optical, thermal, and mechanical properties of that matrix improve, which provides original dye application possibilities [31].…”

Sustainable Bio-Based Polymers: Towards a Circular Bioeconomy

“…The valorization of biomass from different renewable resources (i.e., agriculture, food, forestry, fishery, etc.) by green processes to produce multifunctional polymers with potential industrial applications is a smart strategy to substitute non-biodegradable petroleum-based plastics [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. This allows a change of paradigm from a linear economy (“take, make, and dispose”) to a circular bioeconomy where typical plant and animal residues littered as wastes have a second chance and can be re-integrated into the productive cycle, thus reducing their environmental impact.…”

“…This allows a change of paradigm from a linear economy (“take, make, and dispose”) to a circular bioeconomy where typical plant and animal residues littered as wastes have a second chance and can be re-integrated into the productive cycle, thus reducing their environmental impact. In this context, the works published in this Special Issue have addressed such a topic from different perspectives, including bio-based alternatives to petroleum-based polymers [ 3 , 8 , 9 , 12 ], bioplastics for packaging [ 2 , 4 , 10 ] and other industrial uses [ 6 , 7 ], and sustainable food waste management and biorefinery [ 1 , 5 , 11 ].…”

“…In summary, ten papers about the fabrication, characterization, and potential uses of bio-based polymers and composites have been published in this Special Issue [ 1 , 2 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. It also contains two reviews about sustainable substitutes of phenol-formaldehyde resins [ 3 ] and synthetic and non-synthetic materials for packaging and textile uses [ 4 ].…”

“…Micó-Vicent et al prepared new anthocyanin hybrid nanopigments and fabricated new polyester-based biocomposites with them [ 1 ]. For this, they extracted anthocyanins from pomegranate wastes and incorporated them to calcined hydrotalcite (HT) and montmorillonite (MMT) nanoclays.…”