Cynara cardunculus Biomass Recovery: An Eco-Sustainable, Nonedible Resource of Vegetable Oil for the Production of Poly(lactic acid) Bioplasticizers

Abstract

Cardoon seed oil (CO), derived from the nonedible Cynara cardunculus plant, growing in marginal and contaminated soils of Mediterranean regions, was successfully epoxidized (ECO) in a fed-batch modality. The cost-effective and environmentally friendly oils have been used as bioplasticizers of poly­(lactic acid) (PLA), to improve the overall properties and broaden its industrial applications as a biodegradable packaging material. Hence, physical blends and films of PLA, containing 3% by weight of CO and ECO, were prepared by melt extrusion and compression molding, and the effect of the both bioplasticizers on structural, thermal, and mechanical properties of the obtained films was investigated. Cardoon oils induced the decreasing of glass transition temperature due to PLA free volume enhancement. This effect was particularly marked in PLA–ECO film. Thermal stability of PLA was meaningfully improved upon addition of the oils, and the mechanical properties made evident the increase of PLA ductility, particularly enhanced in the PLA–ECO system, where the polymeric matrix and the oil showed stronger physical interaction and improved phase compatibility, as also revealed by spectroscopic and morphological analyses. Therefore, the plasticization action exerted by very low concentrations of epoxidized cardoon oil efficiently overcomes PLA drawbacks, thus encouraging the feasibility of its use as a bioplastic for packaging material.

Poly (Lactic Acid)/Thermoplastic Starch Films: Effect of Cardoon Seed Epoxidized Oil on Their Chemicophysical, Mechanical, and Barrier Properties

“…The environmental sustainability of the Cardoon is plenty reported in the current literature [33], considering its ability to grow in dry lands of Mediterranean lands and its potential application in green chemistry. Regarding the content of oil in the seeds, it was depicted to be close to soybean and a sunflower [32,34,35]. As matter of fact, Turco et al reported the epoxidation of cardoon seed oil, obtaining a product with quality properties similar to those of soybean.…”

“…Finalized to understand if during the thermoprocessing of the samples, extrusion, and compression molding, some reaction inducing the opening of epoxidized ring occurred, a comparison between PLA80_ECO and PLA80 spectra, was performed. Unfortunately, most of the vibration frequencies typical of epoxidized oil, in the fingerprint region of the spectrum, were not detectable since they were weak, broaded, and covered up by PLA main vibrational peaks (spectra not reported) [32]. Nevertheless, by means of a spectral subtraction between PLA80_ECO and PLA80 spectra reported in Figure 1c were weak, broaded, and covered up by PLA main vibrational peaks (spectra not reported) [32].…”

“…Moreover, in order to solve the food and no-food debate, a particular issue for developing countries, alternative vegetable sources of oil were explored. The Cynara cardunculus cardoon plant has been recently reported as interesting biomass, native to the Mediterranean basin, growing on arid lands, as biorefinery feedstock [32]. This crop can be adaptable enough to grow on contaminated lands and polluted soils, and it can therefore be considered as a sustainable no-edible resource: Its economic and environmental sustainability lies in notable profits due to lower cultivation costs and its potential to produce roots with high inulin content and seeds with high yield of oil extraction, about 25%−30%.…”

“…As matter of fact, Turco et al reported the epoxidation of cardoon seed oil, obtaining a product with quality properties similar to those of soybean. In particular, the epoxidized cardoon seed oil has been proposed for applications as a plasticizer of PLA, to overcome the bio-based polymer drawbacks and to improve the overall properties of biodegradable plastics for food packaging materials [32].…”

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“…), with a positive impact on the environment and farmers' income . Moreover, the cardoon biomass, which contains cellulose, hemicellulose, and lignin, can be used to produce energy (Raccuia and Melilli, 2007;Ierna et al, 2012;Ciancolini et al, 2013;Toscano et al, 2016;Ottaiano et al, 2017;Gominho et al, 2018;Petropoulos et al, 2019;Turco et al, 2019). Recent studies, on morphological and physiological characteristics and on seed germination process, showed intraspecific variability among different cardoon populations under salt and moisture stresses (Mauromicale and Ierna, 2004;Raccuia et al, 2004a;Benlloch-González et al, 2005;Pagnotta and Noorani, 2014;Toscano et al, 2016).…”