INTRODUCTION

The rising demand for biodegradable materials has driven the development of biopolymers such as PBAT/TPS blends, making it essential to assess their stability and performance in different environments. Physical treatments such as non-thermal plasma (NTP) may generate reactive oxygen species (ROS) and induce accelerated surface and bulk modifications. This work aims to evaluate the consequences induced by NTP dielectric barrier discharge (DBD) on commercial films of PBAT-TPS.

METHODS

Commercial PBAT/TPS films were exposed to non-thermal plasma generated by means of dielectric barrier discharge (NTP-DBD) by an Eltech Engineers Lab Corona Treater (Dahisar, Mumbai). The system operates in air atmosphere using a generator with a nominal power of up to 500 W, a frequency of 30 kHz, and an output current of 1.9 A. Films of 100 µm thickness were exposed to irradiation power from 10 to 60 min. Analytical characterisation included colorimetry, FTIR, SEM and DSC to analyse both the bulk and surface modifications.

RESULTS AND DISCUSSION

Abiotic degradation induced by NTP-DBD provoked significant variations observed in colorimetry results, particularly an increase in yellowing with treatment duration. Chemical structure analyses revealed a progressive reduction in the absorbance bands at 1268 cm⁻¹ and 1709 cm⁻¹, corresponding to C–O and C=O stretching vibrations of ester groups in PBAT, indicating ester bond degradation. A decrease in the melting endotherm associated with butylene terephthalate (BT) segments, along with a shift in the melting transition to butylene adipate (BA) phase, was observed with increasing exposure time. Finally, surface electron micrographs demonstrated surface etching after 30 and 60 min of plasma treatment, attributed to the interaction between ROS and the polymer surface.

CONCLUSION

NTP-DBD was demonstrated to promote relevant abiotic degradation of PBAT-TPS-based commercial films, with notable modifications not only at the macroscopic level but also at the molecular scale.

ACKNOWLEDGEMENTS

The authors acknowledge funding from the Agència Valenciana de la Innovació (AVI) through the INNEST/2022/295 project.

The accumulation of discarded fishing nets in coastal zones significantly contributes to marine pollution, with polyamide 6 (PA6) being the predominant polymer in these residues ¹. Chemical recycling through depolymerization offers a promising strategy to transform this waste into high-value building blocks, particularly ε-caprolactam, supporting circular economy initiatives while reducing ocean contamination.

Neoteric solvents have the potential to act as catalytic cosolvents for other purposes ². In this study, deep eutectic solvents (DESs) were evaluated as green media for depolymerizing PA6 recovered from fishing nets. The tested DESs included choline chloride (ChCl)/urea, ChCl/glycerol, ChCl/monoethanolamine (MEA), and ChCl/diethanolamine (DEA) under mild conditions (160–180°C). The catalytic effects of 4-(dimethylamino)pyridine (DMAP), solvolysis time, and the reaction system were investigated to determine their effectiveness in promoting depolymerization. After solvolysis, the crude reaction mixture was filtered to assess conversion, and attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy was used to monitor the depolymerization process by identifying the functional groups associated with PA6 chain cleavage.

Although several DESs facilitated polymer dissolution, those containing MEA and DEA exhibited significantly higher depolymerization efficiencies. This enhanced performance was attributed to their dual function, acting not only as solvents but also as nucleophilic agents capable of attacking amide bonds, thereby promoting solvolysis reactions under the tested conditions. The findings of this screening enable the selection of MEA- and DEA-ChCl-based DESs as the most promising candidates for subsequent optimization through experimental design. This approach will contribute to advancing chemical recycling pathways for fishing net waste by enabling the recovery of high-value building blocks for future production of new polyamides and advanced materials, thus supporting environmental sustainability while generating added value within the polymer recycling chain.

Citric acid is a widely distributed bio-based monomer, and its polyfunctionality makes its derivatives a potential choice as cross-linkers for thermosets. The utilization of bio-based precursors to prepare polymers is very beneficial for environmental protection and sustainable development. However, thermosets usually lack reprocessability and recyclability due to their permanent chemical cross-linking. To achieve sustainable recycling, the design and modification of citric acid as a precursor for vitrimers is a promising strategy. In this work, we synthesized a new cross-linker that incorporated acetoacetate groups onto citric acid and performed the synthesis and evaluation of citric-acid-based vitrimers. A series of bio-based vitrimers with different dynamic bond contents was prepared by adjusting the ratio of the reactants, and their properties were characterized. The process adopted melt polymerization without additional catalyst, which was green and environmentally friendly and avoided the problem of catalyst escape or decomposition during reprocessing. The incorporation of the amide segment enhanced the mechanical properties and the thermal stability, whereas vinyl urethane bonds provided reprocessability, degradability, and self-healing capabilities. At the same time, it was physically and chemically recycled and showed excellent stability in terms of its chemical structure and physical properties. Chemical recycling through acid-catalyzed degradation also provides a route for monomer recovery.

To reduce dependence on fossil resources and limit the use of harmful isocyanates, researchers are increasingly developing polyurethanes (PUs) using renewable building blocks like bio-based polyols and diisocyanates. In this work, new PUs were produced using poly(ethylene glycol) (PEG), isosorbide (ISO), and pentamethylene diisocyanate (PDI) to create more sustainable materials. Various compositions were prepared with ISO levels ranging from 0 % to 70 % in a vacuum reactor fitted with a condenser and magnetic stirring. The resulting polymers were analyzed using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TG). The DSC data showed exothermic peaks in the 100–200 °C range, revealing active crosslinking reactions. Increasing ISO content made the curing reaction faster, with the T_0.01 shifting from 95 °C at 50 % ISO to 91 °C at 70 % ISO, and the maximum rate constant (Cmax) rising slightly as well (0.2750 to 0.2964 min^-1, respectively). FTIR confirmed the chemical bonding between hydroxyl (OH) groups in ISO/PEG and isocyanate (NCO) groups in PDI, showing full NCO conversion at the 2267 cm⁻¹ band. Formulations with higher ISO content (>50 %) exhibited an excess of hydroxyl groups, increasing the system’s reactivity through both covalent and hydrogen bonding, which promoted more extensive crosslinking. For samples with 70 % ISO, the NCO groups were completely reacted at 126 °C, while the 50% ISO variant reached near-total (99 %) curing at 192 °C. TG results indicated that higher ISO levels caused earlier weight loss due to degradation, starting around 146–151 °C for 50 and 70 % ISO, respectively. The curing and thermal degradation processes were modeled with Friedman, Kissinger–Akahira–Sunose, and Ozawa–Flynn–Wall methods, confirming that moderate ISO content (i.e., 30 – 50 %) enhances both curing speed, degradation activation energy and thermal stability.

Polylactic acid (PLA) is a biodegradable polyester derived from renewable resources and is increasingly used as a sustainable alternative to conventional plastics. However, due to limitations in mechanical recycling, chemical recycling methods are needed to promote a circular plastic economy. One promising approach is the ethanolysis of PLA to produce ethyl lactate (EtLa), a valuable green solvent used across several industries.

Previous studies have explored the use of deep eutectic solvents (DES) as sustainable catalysts for PLA depolymerisation. However, limited work has been done on the influence of catalyst composition and reaction kinetics. In this study, the ethanolysis of PLA using a DES composed of choline chloride (ChCl) and zinc acetate (ZnAc) in a 1:1 molar ratio was investigated, with a focus on the effect of ZnAc form (anhydrous vs. dihydrate) on catalytic performance.

Reactions were carried out using PLA in powder and film forms (3g) with ethanol (50 mL, ≥99.5%) and ChCl/ZnAc DES (1:1) under continuous stirring. A range of temperatures (80 °C to 180 °C) and reaction times (up to 8 hours) were tested using a 100 mL glass reactor with oil bath heating at atmospheric pressure. After reaction, mixtures were filtered under vacuum, and the yield of EtLa was quantified by using gas chromatography. PLA conversion and EtLa yield were systematically evaluated as functions of morphology, temperature, and reaction time.

The highest EtLa yield of 92% was achieved after 8 hours at 140 °C using PLA film, with complete conversion observed. In comparison, PLA powder yielded lower conversion under the same conditions, indicating that film morphology enhances degradation efficiency. Compared to existing studies, the method enabled higher EtLa yields at lower temperatures and shorter times, demonstrating improved efficiency. A temperature-dependent kinetic model was developed to describe the ethanolysis process and predict optimal conditions based on reaction parameters.

Polyethylene terephthalate (PET) is a common plastic found in everyday items such as clothing and beverage bottles. Unfortunately, PET contributes to plastic pollution due to its limited recyclability through mechanical means. Valuable chemicals can be recovered from waste PET through chemical recycling, which involves reacting PET with suitable chemicals. One notable reaction is between PET and 2-ethyl-1-hexanol (2-EH), resulting in the production of dioctyl terephthalate (DOTP). This compound has gained attention as a green plasticiser in the plastics industry.

Researchers have previously studied the use of deep eutectic solvents (DESs) as sustainable catalysts for the formation of DOTP from PET. However, the kinetics of this reaction have not been thoroughly documented. In this work, the temperature-dependent kinetics of the reaction between PET and 2-EH, catalysed by choline chloride (ChCl)-Zn acetate (ZnAc) DES, to produce DOTP are presented.

The reactions involved PET in powder form (5 g), as well as 2-EH (17 g, 99%), ChCl (≥99%) and anhydrous ZnAc (99.9%). The experiments took place in a 100 mL glass reactor with continuous stirring at atmospheric pressure, and heating was provided by an oil bath. Reaction temperatures ranged from 150 °C to 190 °C. The yield of DOTP was determined by gas chromatography, while PET conversion was determined gravimetrically. The kinetic model developed from this study can predict the maximum yield observed at specific temperatures, aligning with findings from this and previous research.

Poly(β-hydroxyurethane) (PHU) derived from five-membered cyclic carbonates and amines, is a promising alternative to conventional polyurethanes. However, common PHUs relying on hydroxyl/carbamate exchange exhibit poor reprocessing efficiency and non-degradability. This study addresses these limitations by developing high-performance, reprocessable, and degradable PHUs from renewable feedstocks, advancing sustainable chemistry. Therefore, novel cross-linked PHU networks with vinylogous urethane bonds were prepared. Thereinto, a five-membered dicyclic carbonate was synthesized via the reaction of diglycerol with dimethyl carbonate, and diglycerol tetraacetoacetate was prepared and used as a crosslinker. They reacted with 1,6-diaminohexane to synthesize a series of biobased crosslinked PHUs (PDGVU6s). The obtained PDGVU6s with dual dynamic covalent bonds exhibited relatively low activation energy (27.66 kJ/mol) and significant reprocessing efficiency (~100%, 30 min at 150 °C). Notably, the introduction of vinylogous urethane bonds not only enabled efficient material recycling but also enhanced mechanical properties, achieving tensile strength up to 53.4 MPa. In addition, the presence of dynamic β-hydroxyurethane and vinylogous urethane bonds realized network rearrangement without additional catalysts. Therefore, the obtained PDGVU6s possessed rapid shape memory behavior and self-healing properties (2 h at 70 °C). And the obtained PDGVU6s demonstrated degradation in acidic solutions while achieving a balance between highlyefficient self-healing and excellent mechanical properties. This study presents an efficient method for synthesizing PDGVU6s from renewable resources, which enriches synthetic diversity and holds a promise for further exploration in sustainable chemistry.

Chitosan (CS) is a biocompatible and biodegradable polysaccharide with high potential for functional material development, especially in the design of active films for biomedical or packaging applications. However, its limited solubility and moderate bioactivity restrict the applicability. In this study, a novel CS derivative was synthesized via N-acylation using 1-methylimidazole (MeIm), aiming to enhance the intrinsic antimicrobial and antioxidant properties of this native polymer. An acidic group was added into MeIm (MeImB) and then, the functionalization with the polymer was performed under aqueous conditions employing an EDC/NHS coupling, targeting the primary amino groups of CS to introduce the imidazole ring moieties covalently. Structural characterization of the modified polymer (CS-MeImB) was performed by solid state NMR and elemental analysis, confirming successful functionalization

The resulting derivative (CS-MeImB) was processed into thin CS based films by solvent casting in acidic aqueous media, and using glycerol as plasticizer. In addition, a chitin nanowhiskers (Nw) were prepared and added to reinforce these films. The characterization of these Nw and the resulting films was performed by thermogravimetric analysis (TGA) and X-ray diffraction analysis (DRX), confirming successful integration, while mechanical tests showed good flexibility and improved stability.

The incorporation of the MeIm group significantly enhanced the bioactivity of the films. Antimicrobial assays demonstrated strong inhibition against both Gram-positive (Staphylococcus aureus, Enterococcus faecalis) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. Moreover, antioxidant activity evaluated via DPPH assay revealed a notable radical scavenging ability, which was markedly higher than that of native chitosan, reaching complete inhibition at lower concentrations.

These results suggest that the integration of 1-methylimidazole into the CS matrix is a promising strategy to create multifunctional biopolymer films with improved production for sustainable applications in food packaging requiring antimicrobial and antioxidant activity.