According to Plastics Europe, only 18.7% of the 58.8 Mt of plastic produced in Europe in 2022 was made from recycled materials.[1] Furthermore, just 26.9% of the 32.3 Mt of plastic waste generated was successfully recycled.[1] To increase these percentages, advancements in recycling technologies and the development of virgin plastic materials and products designed for recyclability are essential.

This study explored the potential for mechanically recycling post-industrial waste (PIW) high-impact polyamide 6,6 (HI-PA 6,6) in natural and red colors. It examined different suppliers of virgin HI-PA 6,6 (S1 and S2) and various red-colored masterbatches (MB1 and MB2), either alone or in combination. To assess the recyclability of these materials, comparisons were made between samples processed once and those processed ten times for each composition, by analyzing their color, thermal, and rheological properties.

Overall, color darkening and a combination of chain scission and crosslinking phenomena, typical of the thermo-oxidative degradation of PA 6,6,[2] were observed in all compositions. However, both color changes and molecular chain variations were more pronounced in the presence of red-colored masterbatches and were affected differently depending on the specific pairing of supplier and masterbatch. This demonstrates that the composition of the masterbatch, as well as its pairing with a specific supplier, is crucial in designing recyclable plastic.

Inkjet printing enables the production of higher-resolution objects compared to other layer-by-layer additive manufacturing techniques, thanks to the exceptionally small droplets generated during the process 1. However, designing recyclable materials for inkjet printing remains a significant challenge. The polymeric resins must meet low-viscosity requirements while ensuring that deposited droplets solidify rapidly, to prevent inaccurate placement or material flow. This study presents a proof of concept utilizing reversible Diels-Alder chemistry for inkjet printing, achieving a balance between recyclability and material strength. The formulation consists of multi-armed furan monomers and an aliphatic bismaleimide, BMI–689. The kinetics of the Diels-Alder reaction between furan and maleimide groups were analyzed using variable-temperature attenuated total reflectance infrared (ATR-FTIR) spectroscopy, complemented by nuclear magnetic resonance (NMR) spectroscopy 2. This approach combined with rheological studies, provides insights into gelation behavior and reaction conversion under various conditions and formulations during the printing process. We highlight the range of material stiffness and elasticity and the tunability of the mechanical properties, being supported by tensile tests. The overall robustness of printed objects can be further improved by introducing a post-curing step where double Diels-Alder reactions are introduced 3. Overall, this work presents an alternative to the conventional inkjet formulations (irreversible acrylate cross-linking) and offers a promising avenue for developing recyclable inkjet-printed materials with other dissociative reversible reactions as well.

In this study, we synthesized amine-functionalized graphene oxide (AGO) and incorporated it into poly(vinylidene fluoride-trifluoro ethylene) (PVDF-TrFE) to develop high-performance piezoelectric nanocomposites. The incorporation of AGO at an optimized concentration of 0.1 wt% led to significant enhancements in piezoelectric, ferroelectric, and dielectric properties of the polymer matrix. Structural analysis using Wide-Angle X-ray Scattering (WAXS), Small-Angle X-ray Scattering (SAXS), and calorimetry revealed that these improvements are primarily attributed to an increased fraction of the polar β-crystalline phase with a TTTT conformation, as well as an enlargement of lamellar structures within the polymer matrix. Building on these findings, we further optimized the formulation to develop inkjet-printable inks by tuning fluid dynamic parameters such as Reynolds and Weber numbers. The resulting inks were successfully printed to fabricate flexible piezoelectric sensors and energy harvesters. These devices demonstrate excellent energy conversion capabilities, paving the way for the development of next-generation self-powered electronics and wearable sensing technologies. Our work highlights the potential of AGO-modified PVDF-TrFE composites for scalable, printed energy harvesting and sensing applications.

This study presents novel vitrimeric, biobased scaffolds for hard tissue applications, using acrylated soybean oil (AESO) as biobased matrix, reinforced with Tellurium-doped bioactive glass (BG-Te) and silanized BG-Te (BG-Te-Sil). These materials were specifically designed to optimize mechanical strength and antibacterial properties, improving previous research [1].
The scaffolds were fabricated using a DLP 3D printing method, enabling the creation of complex, hollow structures with excellent resolution. Biological evaluation demonstrated that the scaffolds effectively supported the attachment and proliferation of human bone marrow-derived mesenchymal stem cells (hBMSCs). Immersion in simulated body fluid (SBF) for 28 days showed the possibility of hydroxyapatite (HaP) formation on the scaffold surface. Antibacterial testing revealed that BG-Te reduced Staphylococcus aureus adhesion by 87%, while BG-Te-Sil achieved a 54% reduction compared to the pristine control, confirming the antibacterial efficacy of Tellurium.
Mechanical tests and FESEM images showed improved mechanical behaviour in composite containing silanised BG-Te, attributed to its better incorporation within the matrix.
The reprocessability of the vitrimeric material was validated through stress relaxation experiments, confirming the activation of transesterification reactions within the polymer matrix in the presence of a transesterification catalyst.
This work highlights the synergy between the vitrimeric polymer matrix and bioactive glass, showing their combined potential to produce biocompatible, biobased, and antibacterial scaffolds for hard tissue applications. These findings highlight the promise of these innovative materials and advanced manufacturing techniques in dealing with challenges within tissue engineering and regenerative medicine. [2]

Microplastic (MP) poses a serious risk to the environment and human health. As a result, MP has been included in the REACH and other EU regulations, pushing stakeholders to take action in MP monitoring. While detection methods exist, a major challenge is the lack of suitable reference materials for standardization and validation. Current production methods such as cryogenic grinding and sieve fractionation have limitations, including poor size control and rely on mass-based measurements rather than particle count. Synthetic alternatives face similar issues and are restricted to a few polymer types. These challenges underline the need for improved reference materials.
We present a cost-effective, scalable method using microextrusion as an additive manufacturing process. This approach enables precise control over particle number, size, and shape, and works with all thermoplastics. It enables direct comparison of mass- and number-based analyses. Up to 1,000 particles can be produced within one hour, with automation and inline process control planned to enhance efficiency and reduce waste. So far, we have reproducibly produced particles ranging from 224 to 1400 µm from PLA, PCL, PMMA, PP, LDPE, and PA6, with some as small as 150 µm and with a standard deviation of the particle sizes of less than 10% for the majority of particle fractions. These particles have already been used in environmental studies, including vegetation plots, and soil column experiment to model microplastic transport behavior. Further research aims to reduce the minimum size below 100 µm and expand the polymer range.

Phosphorus-containing polymers have applications as fire retardant additives and biomimicking macromolecules.(1,2) Herein, a series of polymers are synthesized by thiol-ene polymerization using a novel, high-phosphorus-content diacrylate monomer (PNDA) and various aliphatic and aromatic dithiols and amines. Depending on the chemical structure of the dithiol, low-molecular-weight polymers with relatively low or high glass transition temperatures are obtained. Molecular weight can be increased by copolymerizing the dithiols with PNDA in the presence of other more reactive diacrylates or by polymerizing PNDA with amines.(1) Furthermore, polyhydroxyurethanes were synthesized by derivatizing unsaturated phosphates and subsequently to cyclic carbonates, which were then reacted with diamines. We also explore the polymers thermal stability and their application as a fire-retardant additive for epoxy resins.(1)

Shaping biomaterials in 3D using additive manufacturing opens up new opportunities in tissue engineering for biomedical research and personalized medicine. In particular, two-photon 3D laser printing offers precise processing of biomaterials with submicron, i.e. subcellular, resolution making it suitable for the fabrication of single-cell scaffolds. Current research efforts include the development of new biomaterial inks which mimic natural extracellular matrices as well as the exploration of new applications of two-photon laser printing, such as in-vivo printing within organisms.
To mimic extracellular matrices, we have developed a new collagen-based ink which is stable for several weeks at room temperature and can be 3D printed into complex free-standing collagen microstructures using a commercial setup at 780 nm. The 3D printed collagen hydrogel was examined for its internal fibrillar nanostructure by electron microscopy, and its biocompatibility was confirmed by cell viability studies. Moreover, reversible unfolding and folding of the collagen trihelix upon heating and cooling of the printed collagen resulted in shrinkage of the microstructures. The temperature response was studied experimentally and theoretically.
In addition to designing new biomaterial inks for microprinting, we explored for the first time two-photon 3D laser printing of microstructures in vivo to study developmental processes. For this purpose, a suitable biocompatible ink was first injected into fruit fly or medaka fish embryos and subsequently printed into various 3D shapes. The studied polydimethylsiloxane-based biomaterial did not elicit any significant immune response and developmental damage in medaka fish making it a suitable candidate for future microimplant fabrication.

Additive manufacturing, particularly vat photopolymerization, has emerged as a promising method for fabricating intricate, high-resolution structures with minimal waste. However, concerns regarding the sustainability of vat photopolymerization resins emphasize the need for incorporating biomaterials into these techniques. Lignin, the second most abundant biopolymer and a large-scale industrial byproduct, presents a sustainable alternative to petrochemical-based resins for vat photopolymerization. Despite its potential, lignin’s strong UV absorption, which disrupts photoinitiator activation, has restricted its use in high-resolution vat photopolymerization processes. This study addresses these challenges by developing resins with high lignin content up to 40 wt.% for digital light processing (DLP). Organosolv lignin is acetylated and subjected to an optimized, low-energy UV decolorization process, reducing UV absorption by 71 %. The decolorized lignin is incorporated into bio-based tetrahydrofurfuryl acrylate, enabling high-resolution additive manufacturing with a resolution of 250 µm. The resulting resins exhibit significant mechanical improvements, with stiffness and strength increasing by factors of 15 and 2.3, respectively, demonstrating lignin’s reinforcing effect. This work highlights the potential of high lignin-content resins for sustainable vat photopolymerization additive manufacturing. It provides a pathway to repurpose lignin waste into high-resolution, high-performance, and environmentally friendly materials, promoting the sustainability of additive manufacturing technologies.

Itaconic acid has rapidly emerged as a naturally occurring building block for (meth)acrylate-free photocurable formulations used in vat photopolymerization (VP) [1,2]. Thanks to its dual carboxylic functionality, itaconic acid can form photocurable esters and polyesters such as PET, which can be chemically recycled through depolymerisation and re-polymerisation. This enables a closed-loop system that allows rPET to be depolymerised into its monomers, which can then be re-polymerised into new PET [3]. This study introduces a solvent-free, one-pot, two-step method for synthetizing photocurable polymers from waste PET bottles, using minimal catalysts and producing ethylene glycol as the only by-product. Two polymers were synthesized: PBIT (using butanediol) and PDHIT (utilizing a butanediol/hexanediol mixture). These were compared to analogous polymers produced with adipic acid instead of terephthalic acid. Formulations incorporated up to 75 wt. % of synthetized polymers, achieving 22 wt.% of rPET in printed materials. Mechanical analysis revealed that terephthalic acid enhances mechanical properties compared to adipic acid, while longer diols increase flexibility achieving the best performance, with Young's modulus of 1.4 GPa and tensile strength of 54 MPa, the highest reported for itaconic acid-based resins. This study highlights how waste PET can be transformed into high-performance, itaconic acid-based photocurable resins, offering a sustainable, high-value solution for plastic waste recycling.

Dual modification of starch has since been demonstrated to circumvent many of the limitations of native and single modified starch, resulting into materials with improved functionality(1,2). Herein, we report the dual modification of corn starch via succinylation and acetylation. The initial modification was carried out with octenyl succinic anhydride using previously optimised conditions while reaction parameters for the acetylation were optimized using central composite design, a statistical experimental design (3,4). The succinylation resulted into starch octenyl succinate with degree of substitution (DS) of succinate groups of 0.026 while the subsequent statistically optimised acetylation resulted into dual modified starches with DS of acetyl groups between 0.35 and 2.05. The quadratic model generated from the optimization reactions predicted 188 min, 112°C, 4.25 acetic anhydride/starch mass ratio and 1.24 NaOH/starch molar ratio as the optimal conditions for high degree of substitution of acetyl groups ~2.3. The model was also found to be significant based on its F-value (26.72), adequate precision ratio (17.95), as well as the R2 (0.9664), adjusted R2 (0.9302), and predicted R2 (0.8014) values. Finally, the obtained modified starches were characterised using NMR, FTIR, SEM, TGA, DSC, and melt flow analyses(5). These findings provide some insights into the modification of starch using a statistical approach, as well as the functional properties of the modified biopolymers for prospective thermoplastics applications.
Acknowledgement: This project has received funding from the Research Council of Lithuania (LMTLT), agreement No S-PD-24-33.

Conventional plastics play a crucial role in our daily life due to a set of versatile properties, including lightweight, high durability, flexibility and low production costs. However, the massive production of polymers, reaching 413.8 Mt in 2023,[1] combined with their fossil-origin and low recycling rates, is causing severe environmental and public health issues. Therefore, finding sustainable solutions is essential. This includes using alternative bio-based polymers and implementing interventions at both the manufacturing stage and end-of-life phase, with a strong emphasis on reuse and recycling.
The project “OLIpush - Redesign for greater circularity and a smaller environmental footprint” focuses on finding more sustainable polymers to use in flush toilet system components. As part of the project, a comprehensive survey of commercially available bio-based polymers able to replace the fossil-based acrylonitrile-butadiene-styrene (ABS) was conducted. An in-depth evaluation of the physical and mechanical properties of these alternative polymers was carried out to ensure they meet the necessary properties requirements for toilet flush production.
Another key strategy involved studying the end-of-life materials from toilet flushes systems, namely poly(propylene) and poly(oxymethylene) waste. Their structural and thermal properties was analysed to assess their potential re-incorporation into the production process, supporting a more circular and sustainable approach.

Acknowledgements
Study developed under Project “Agenda ILLIANCE” [C644919832-00000035|Project nº 22], financed by PRR—Plano de Recuperação e Resiliência under Next Generation EU from European Union. Also CICECO-Aveiro University, UIDB/50011/2020 (DOI 10.54499/UIDB/50011/2020), UIDP/50011/2020 (DOI 10.54499/UIDP/50011/2020), LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020), financed by national funds through FCT/MCTES (PIDDAC). PSSL acknowledges “Agenda ILLIANCE” for research contract.

Enhancing carbon dioxide (CO₂) detection remains a critical challenge due to limitations in selectivity, sensitivity, and stability of conventional sensors, particularly at ambient conditions1-3. This study addresses these issues through the development of p-type heterojunction nanocomposites based on electrodeposited polypyrrole (PPy) doped with n-dodecylbenzene sulphonate (DBSA) and functionalized reduced graphene oxide (rGO-aryl-COOH). Utilizing a one-step chronoamperometric process, two nanocomposites—PPy/rGO and PPy/rGO-aryl-COOH—were synthesized on flexible indium tin oxide (ITO)/polyethylene terephthalate (PET) substrates. Functionalization of rGO with aryl 4-carboxybenzene diazonium salts mitigated graphene aggregation and enhanced charge transfer, as confirmed by structural analyses (FTIR, XRD, Raman, SEM). The PPy/rGO-aryl-COOH nanocomposite exhibited superior crystalline ordering and homogeneity compared to non-functionalized PPy/rGO. CO₂ sensing evaluations demonstrated a sensitivity of 0.93%/ppm and excellent reproducibility at room temperature, attributed to the synergistic effects of carboxylated graphene and PPy’s redox-active matrix. The electrochemical synthesis enabled precise control over nanomaterial dispersion, addressing challenges in traditional methods4. This work pioneers a one-step fabrication route for hybrid conductive polymer/graphene sensors, offering a scalable and energy-efficient solution for real-time environmental monitoring. The results highlight the potential of functionalized nanocomposites in advancing CO₂ detection technologies, aligning with global initiatives to reduce carbon emissions.

Current industry approach for CO₂ capture is based on mature absorption technologies such as liquid amine scrubbers or cryogenic installations, technologies that are widely used and are well tested. These approaches have high energy demands, sometimes lack selectivity and require conditioning. Newer technologies based on MOFs and amine-functionalized adsorbents promise better efficiency and elimination of problems of current industry go-to technologies, yet are not ideal. A mitigation of aforementioned problems propose amine containing polymeric adsorbents. Poly(hydroxyurethane)s and polyacrylates containing amine groups have been synthesized and coated onto typical carriers such as silica fume and cellulose. CO₂ adsorption capabilities in varying humidity environments, amine efficiency, specific surface area and thermal stability have been examined, and adsorbent preparation process have been optimised for best performing carrier/adsorbing layer mass ratio. Results demonstrated superior adsorbent thermal stability for polymeric adsorbent and satisfactory adsorption capacity over conventional amine coating. Also the results have shown that thinner adsorption layers show faster adsorption-desorption rate without substantial capacity decrease. Outcome of the research is that amine-functionalized adsorbents could someday replace current industrial operations as more robust and more energy efficient solutions.

The increasing motorisation rate worldwide is responsible for the huge demand of tyres that, after their life, become waste and should be properly managed. Due to the presence on the market of low cost of tyres and due to the complexity related to recycling, worldwide around 41% of the total amount of end-of-life tyres is discarded into landfills or stockpiles without any recovery of the material or energy. Europe entirely relies on imports of natural rubber, whose greatest part is used in tyres, where it constitutes up to 40 % by mass. For these reasons it is crucial to (i) find recycling strategies for waste tyres, (ii) reduce the consumption of raw materials. Moreover, since Europe is leading the transition to a green economy, it is also important to assess the environmental benefits arising from possible strategies such as rubber reclaiming and tyre retreading. In this work the environmental impact of retreaded tyres was studied and compared with that of new tyres. Moreover, the reclaiming process of ground tyre rubber was investigated and the possible environmental benefits arising from the partial substitution of virgin rubber with reclaimed one were quantified. The results showed that the retreading process of tyres leads to a decrease of around 40 % of their environmental impact thanks to the lower use of raw materials. The use of reclaimed rubber leads to a reduced use of raw materials and to a further environmental benefit on the total environmental impact of tyres.

Lignin, a complex aromatic biopolymer and a key structural component of plant cell walls, offers significant potential for high-value applications, such as antioxidants for packaging and food preservation.[1] The physicochemical properties of lignin, i.e. molecular weight (Mw) and the content of functional groups, are profoundly influenced by the extraction method and the biomass source.[2] This study utilizes a design of experiments (DOE) approach to optimize the organosolv process conditions for lignin extraction from grape pomace, pruning, and reed.
The experimental factors, including temperature, process time, and ethanol concentration, were systematically varied to study their effects on Mw and total phenolic content (TPC). The findings indicate that the ethanol concentration exerts a substantial influence on the Mw of both p-hydroxyphenyl, guaiacyl and syringyl (HGS) and GS lignin-containing biomass. Temperature exhibited a non-linear effect, where higher Mw lignins were increasingly isolated at lower temperatures, while higher temperatures promoted recondensation. Conversely, TPC showed the opposite trend, with a local maximum observed at approx. 170 °C. Higher ethanol concentrations (90 v/v %) and lower temperatures (150 °C) resulted in lignin fractions with higher Mw and reduced TPC.
The correlation between Mw and TPC, along with their opposing trends, indicates that extraction conditions directly influence lignin's antioxidant potential. Prediction and optimization plots suggest that lignin properties can be tailored for specific applications, by adjusting ethanol concentration and temperature. The study underscores the crucial role of precise process parameter control in enabling biomass-specific lignin extraction, thereby paving the way for environmentally friendly advanced material applications.

The global plastic industry relies on fossil-based materials, presenting significant environmental challenges. Poly(limonene carbonate) (PLimC), a sustainable alternative, is made from two renewable monomers: limonene oxide, derived from non-food sources, and CO₂, positioning it as a promising material for applications requiring flame retardants (FRs) to meet fire safety standards.

Thermal properties were initially assessed to better understand the thermal stability and fire behavior of PLimC. This analysis builds on PLimC's unique structural characteristics: its carbonate group resembling polycarbonate (PC) and its aliphatic limonene-derived segment resembling polyolefins (PO). The initial results revealed similarities to both PO and PC, prompting the evaluation of various commercially available flame retardants (FRs) at standard market concentrations.

Four halogen-free FR systems were chosen for evaluation (Figure 1.a), with the conclusion that ATH proved to be the most effective FR, decreasing the heat release rate (Figure 1.b) and the total heat evolved. With these results, we understood that the FRs commonly used with polyolefins (at concentrations standard in the industry) exhibit similar behavior in terms of flammability and flame retardancy when applied to PLimC.

Figure 1. a) Composition of the systems used. b) Cone calorimeter results.

While ATH has proven to be an effective FR, we aim to investigate bio-based alternatives. Phytic acid salts [2] and lignin [3] have shown excellent FR performance in PO, and we believe these compounds could achieve similar success in our system. Their integration could bring us closer to achieving a fully sustainable material that aligns with current environmental goals.

As the quest for innovative and sustainable materials continues to shape the field of polymer science, furfural and hydroxymethylfurfural derivatives have emerged as critical renewable building blocks.[1,2] In this context, 3,4-di(furan-2-yl)cyclobutane-1,2-dicarboxylic acid (CBDA) stands out as a highly promising rigid-structure biobased monomer that is easily derived from furfural.[3,4] Thus, this study sought to further develop CBDA-based polymers by synthesizing this platform molecule and exploring its polymerization with various linear aliphatic diols of different chain lengths. CBDA was efficiently obtained from furfural-derived 3-(2-furyl)acrylic acid through a green, UV-mediated solid-state dimerization reaction,[3] followed by solvent-free melt polymerization via a two-step method.[5] The success of the polymerization was confirmed via ATR-FTIR, ¹H NMR, and ¹³C ssNMR spectroscopy. The resulting polymers achieved average molecular weights (Mn) of up to 11,225 g/mol. Thermal characterization via TGA revealed a Td10% ranging from 261 to 282 °C, with 50% weight retention observed up to 386 °C. Additionally, the DSC results demonstrated a tunable glass transition temperature (Tg) that varied from 6 to 52 °C on the basis of the diol chain length. These findings highlight the versatility of CBDA-based polymers, advancing the development of sustainable biobased materials.

In this work polyurethane (PU) and phenolic foam (PF) panels were mechanically grinded into two different particle sizes and incorporated at various concentrations within an expanded polyurethane matrix utilized for thermal insulation, to reduce the use of virgin material and promote a circular re-utilization of recycled materials. The effectiveness of this approach was evaluated through a comprehensive microstructural and thermo-mechanical characterization of the resulting panels. As observed by scanning electron microscopy (SEM), the formulations containing both PU and PF recyclates showed a rather homogeneous cell structure. The presence of recycled material slightly increased the geometrical and apparent density compared to the neat PU foams, thus leading to a strong reduction of the closed porosity. This aspect was also reflected in a slight increase in the thermal conductivity, which reached maximum values of 0.030 W/m∙K in foams with 7.5%wt of recycled PF particles. The introduction of the recyclates slightly improved the thermal stability of the PU foams, as observed from thermogravimetric analyses (TGA), but led to a general decline in flexural and compression properties. Cone calorimetry tests demonstrated that the inclusion of 5% wt of PF particles resulted in a reduction of the peak heat release rate (pkHRR) of 28% compared to neat PU foam, enhancing fire safety of the insulating panels. This research demonstrated that the introduction of recycled PU and PF, obtained from mechanical reprocessing of insulating panels into PU foams could lead to the development of more eco-sustainable materials with good thermal insulation power and increased fire resistance.