Abstract
The extraction of glycyrrhizin from licorice root and stolon with ethanol/water solutions leaves a lignocellulosic residue, which could be potentially applied in biocomposites. This process proved difficult in principle, given the considerable hardness of this material as received, which impedes its use in polymer resins in large amounts. After ball milling, up to 10% of this fibrous residue, which shows very variable aspect ratio, was introduced into an epoxy matrix, to investigate its possible future application in sustainable polymers. Of the three composites investigated, containing 1, 5 and 10 wt% of licorice waste, respectively, by performing flexural testing, it was found that the introduction of an intermediate amount of filler proved the most suitable for possible development. Thermal characterization by thermogravimetry (TGA) did not indicate large variation of degradation properties due to the introduction of the filler. Despite the preliminary characteristics of this study, an acceptable resin-filler interface has been obtained for all filler contents. Issues to be solved in future study would be the possibility to include a larger amount of filler by better compatibilization and a more uniform distribution of the filler, considering their orientation, since most of it maintains an elongated geometry after ball milling.
Highlights
From the point of view of the present research, this demonstrates the persistence in the waste material, after extraction, of root exudates, such as organic acids, amino acids and phenolic compounds, which assist in the development of plant–fungal symbiosis by inducing spore germination [23]
The introduction of licorice waste in an epoxy resin proved feasible in lower amounts, not exceeding
The interface obtained between the matrix and the filler was of limited strength, no particular aspect ratio
Summary
The generation of lignocellulosic fibrous waste is abundant in the agro-food sector, from a large variety of botanical species: from this waste, the extraction of lignin has been attempted as an option to increase its profile of use, getting away from energy recovery to the production of new materials [1].A large number of possibilities are offered by the different methods of lignin extraction, while on the other hand, a simpler yet not always viable possibility is given by their integration into biopolymers, especially if their yield in lignin is not likely to be very high [2].In particular, the root and the stolon from licorice (Glycyrrhiza glabra) have a very long tradition of use in different regions in the world, including China, Turkey, Israel and some parts of southernEurope, such as in southern Italy [3]. The extraction of glycyrrhizin is often performed using an ethanol solution at high temperatures [10] Uses in both traditional and herbal medicine are related to the inhibitory effect to the action of Helicobacter pylori, working as a liver protector, due to flavonoids found in licorice root [11]. This potential was suggested for employing licorice extracts for the incorporation in active anti-oxidation food packaging films based on soy protein [12]. Thean idea wasratio to evaluate theThis possibility introduce a polymer matrix, in which particular a to offer thermosetting some reinforcement effect, amounts in apromising, random configuration traditional one, with theeven idea,ininsmall case the resultsand were to proceed, if[33].
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