The global production of thermosets has been increasing in recent years causing rapid consumption of fossil-based feedstocks and contributing to the plastic waste accumulation in the environment, especially because they cannot be easily reprocessed or recycled at the end of their lifetime. These drawbacks can only be overcome with the development of environmentally friendly, recyclable thermosets from renewable resources. For this reason, we present a facile way to produce a biobased reprocessable thermoset, a vitrimer, by thiol-acrylate coupling between epoxidized soybean oil acrylate and a diboronic ester dithiol dynamic cross-linker. The synthesis of the cross-linker and all the processes for the production of the vitrimer has been done following green chemistry principles. The developed vitrimer material can be reprocessed multiple times like a thermoplastic, without compromising its mechanical properties. Moreover, it can be conveniently recycled by reversible hydrolysis in 90% ethanol and subsequent solvent evaporation, regenerating the original vitrimer. An important advantage of the developed material, especially regarding its applications, is that it is able to self-repair mechanical abrasion-related defects, like scratches and cuts, at room temperature, thanks to the low glass transition temperature and rapid boronic ester exchange, which enables it to demonstrate great potential as a self-healing coating. In case of an accidental release into the environment, it is able to biodegrade, solving the problem of waste accumulation.

Molecular dynamics (MD) simulations and extended x-ray absorption fine structure (EXAFS) investigations of the structure of lead-silicate glasses, xPbO(1 − x)SiO2, have been undertaken to elucidate the problem of partially contradicting experimental findings reported in the literature about basic structural units and their interconnection. The MD simulations were performed in a wide range of compositions, x = 0.1–0.9. The atoms were assumed to interact by a two-body Born–Mayer–Huggins interaction potential. The EXAFS measurements were performed for x = 0.3, 0.5 and 0.7, and also for pure crystalline (red) PbO at the L3-edge of Pb. The absorption spectra were analysed within the GNXAS approach.Our EXAFS and MD results are in good agreement, and support some previous suggestions that: (1) the PbO4 groups are the dominant structural units in lead-silicate glasses for any concentration and (2) at lower PbO concentrations the co-existence of the PbO4 and PbO3 groups is possible.The medium-range ordering in the simulated glasses has also been investigated in detail. The connectivity of the SiO4 tetrahedra network breaks at about x = 0.45, whereas the Pb structural units form a continuous (mainly edge-sharing) network even at relatively low PbO concentrations (x > 0.2). The cation–anion ring statistics is also discussed.

Bio-based and biodegradable packaging combined with chemical sensors and indicators has attracted great attention as they can provide protection combined with information on the actual freshness of foodstuffs. In this study, we present an effective, biodegradable, mostly bio-sourced material ideal for sustainable packaging that can also be used as a smart indicator of ammonia (NH 3 ) vapor and food spoilage. The developed material comprises a blend of poly(lactic acid) (PLA) and poly(propylene carbonate) (PPC) loaded with curcumin (CCM), which is fabricated via the scalable techniques of melt extrusion and compression molding. Due to the structural similarity of PLA and PPC, they exhibited good compatibility and formed hydrogen bonds within their blends, as proven by Fourier transform infrared (FTIR) and X-ray diffraction (XRD). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis confirmed that the blends were thermally stable at the used processing temperature (180 °C) with minimal crystallinity. The rheological and mechanical properties of the PLA/PPC blends were easily tuned by changing the ratio of the biopolymers. Supplementing the PLA/PCC samples with CCM resulted in efficient absorption of UV radiation, yet the transparency of the films was preserved (T 700 ∼ 68−84%). The investigation of CCM extract in ethanol with the DPPH • assay demonstrated that the samples could also provide effective antioxidant action, due to the tunable release of the CCM. Analyses for water vapor and oxygen permeability showed that the PPC improved the barrier properties of the PLA/PPC blends, while the presence of CCM did not hinder barrier performance. The capacity for real-time detection of NH 3 vapor was quantified using the CIELab color space analysis. A change in color of the sample from a yellowish shade to red was observed by the naked eye. Finally, a film of PLA/PPC/CCM was successfully applied as a sticker indicator to monitor the spoilage of shrimps over time, demonstrating an evident color change from yellow to light orange, particularly for the PPC-containing blend. The developed system, therefore, has the potential to serve as a cost-effective, easy-to-use, nondestructive, smart indicator for food packaging, as well as a means for NH 3 gas monitoring in industrial and environmental applications.

A completely green approach was adopted for the production of biocomposites of polylactic acid (PLA) and cellulosic fibers (CF) via functionalization of CF with an aqueous solution of poly­(ethylene oxide) (PEO) followed by extrusion with PLA and injection molding. The treatment with PEO improved the interfacial interaction among the components as well as the CF dispersion and free flow upon extrusion, allowing loading up to 30 wt % of CF. Moreover, the synergistic effect of PEO and CF greatly enhanced the physical–chemical properties of the biocomposites. Their storage modulus was higher with respect to pure PLA in the rubbery region. The stiffness and mechanical strength were found to be higher than those of PLA/PEO and remained comparable to pure PLA, whereas the elongation at break was 73–143% higher owing to the effective plasticizing and reinforcing effect exerted by PEO and CF respectively. Addition of PEO and CF had a great influence on the thermal properties, particularly on the glass transition and cold crystallization temperatures. Overall, the appealing properties of the proposed biocomposites combined with the sustainability of the developed process render them ideal for several technological applications within the plastic industry including food and cosmetic packaging, disposable items, and toys.

No abstract