The use of biomass waste for polymer production is a key component of the global plastic sustainability strategy. Bark contains low molecular weight polyphenolic and carbohydrate compounds rich in hydroxyl groups, making it a potential macromonomer source for plastics. The global annual volume of bark waste is estimated at 300–400 million m³, making it a cheap and highly available raw material.

This study focused on the waste-free processing of pine (Pinus sylvestris) bark into rigid polyurethane (PUR) foam. Extractives, obtained in a yield of 25%, enriched with low molecular weight carbohydrates, were separated via pressurized water extraction at 150 °C. Increasing the extraction temperature above 150 °C significantly reduced both the extractives yield and their hydroxyl content due to carbohydrate dehydration. Extractives were converted into liquid polyols through "green" oxypropylation with propylene carbonate (PC), varying PC/OH ratios. The residual bark was introduced into PUR foam formulation as a filler.

The resulting polyols exhibited viscosities ranging from 8.6 to 210 Pa·s, and hydroxyl values between 580 - 660 mg KOH/g were used to synthesize PUR foams with PMDI at an NCO/OH ratio of 1.1.

In the PUR foam formulations, commercial polyols (Lupranol 3300 and Lupranol 3422) were partially or fully replaced by the bark extractives-based polyols. Key material properties —apparent density, deformation, morphological, and thermal characteristics—were evaluated and compared to foams based on commercial polyols.

Polyol synthesized at a PC/OH ratio of 3 was the most promising for PUR foam production, yielding materials with properties equal to or better than those of foams based on commercial polyols. However by incorporating the residual bark after extraction as a filler led to a slight reduction in mechanical performance.

Acknowledgements:

This research is supported by the project: Innovation in Forest Management and Value Chain for Latvia's Growth: New Forest Services, Products and Technologies (Forest4LV) – Project Nr. VPP-ZM-VRIIILA-2024/2-0002.

The European Commission promotes the increase of recycled plastic in short-term applications as its strategy to introduce plastic products into a circular economy model. However, the mechanical recycling process could reduce the thermal stability and mechanical properties of plastics. In this regard, six (TGA) and tensile tests were performed and case materials assessed included two (PET), two (PP), and two (PE) in their virgin and recycled forms.

The samples were sorted, cleaned, shredded into flakes, and then extruded. So, according to the manufacturer, the samples were processed with the same conditions used for the virgin counterparts. However, additives such as plasticizers and fillers were added in order to increase the thermomechanical properties of the materials, among others.

The TGA curves obtained were similar no matter the origin of the plastic, although a residue of 5% was found in some recyclates—in all except for PET.

Relative to the mechanical properties, the elongation, Young modulus, and ultimate tensile strength for the three polymers PET, PP, and PE were analyzed. In the case of PET, the recyclates showed greater ultimate tensile strength and elongation than the virgin plastics, showing, however, the same young modulus. For the other polymers, the virgin PP material showed better properties by 10% to 15% in all the parameters. Regarding PE, the recyclate had a greater elongation by 5%, and the other properties of the virgin PP were about 35% above the recyclates.

The studies showed a good overall performance of the recycled material thermally and mechanically, which makes the recycled polymers a good replacement for the virgin polymers.

Only a small fraction of the plastics produced is being recycled, with the vast majority landfilled or released into the environment. Mechanical recycling is currently used to recycle plastic; however, this method is efficient only for homogeneous and non-contaminated feedstock, as well as easily identifiable objects such as bottles made of PET or HDPE. Polyolefins in the plastic waste stream can be processed via pyrolysis, the most common process in chemical recycling. Pyrolysis, however, decomposes the polymers, resulting in undesirable greenhouse gas (GHG) emissions. Furthermore, pyrolysis is not viewed as constituting recycling when its product, pyrolysis oil, is not converted into new polymers.

Plastics recycling research in our group involved the examination of physical, solvent-based processes that do not break down the polymer chains. This constitutes true recycling, as the recovered polymer is the same as the starting material. Such molecular recycling processes leave the polymer chains intact, thus maintaining their embodied energy and emitting relatively little GHG.

This presentation addresses the mechanism of semicrystalline polyolefin dissolution as revealed through joint in situ infrared spectroscopy experiments and diffusion kinetics modeling. It also highlights the application of polyolefin recovery to switchable hydrophilicity solvents (SHSs), which can cycle between a form that dissolves the target polymer and a form that does not, hence facilitating closed-loop solvent cycling.

The insights obtained from these studies facilitate the design of solvent systems and processing conditions for the molecular recycling of polyolefins via dissolution–precipitation. Dissolution–precipitation is an energy-efficient and environment-friendly recycling process that can recover specific polymer types from mixtures, blends, or multilayer films and purify them from additives without negatively affecting the properties of the original polymers.

Only a small fraction of plastics produced are being recycled, with the great majority landfilled or released into the environment. Mechanical recycling, currently used to recycle plastic, cannot handle films, which constitute about 40% of all plastic packaging. Polyolefin-rich films are suitable feedstock for pyrolysis; however, pyrolysis breaks down the polymer chains to produce hydrocarbons that are typically used as fuel, which is not true recycling.

Research in our group advances solvent-based molecular recycling, whereby polymers are selectively dissolved and precipitated to achieve separation and recovery. Because the polymer chains do not break and retain all their embodied energy, this is a promising, low-energy, low-greenhouse gas (GHG) plastic recycling methodology.

This project addresses the recycling of multilayer films, which comprise multiple layers of polymer combined into a single film to meet consumer specifications such as preserving food and medicine, acting as an oxygen or moisture barrier, and keeping products sterile. This presentation highlights the solvent-assisted delamination process that we have developed, which recovers the major component, polyethylene, in its solid form, from multilayer films, hence greatly reducing solvent amounts and the corresponding energy needs and GHG emissions compared to dissolution–precipitation recycling. Delamination recycling presents an energy-efficient and environmentally friendly approach to recover value from the approximately 17 million metric tons of multilayer plastic films that are produced every year globally.

Segmental bone defects represent a significant clinical challenge in orthopedic medicine, often resulting from trauma, infection, or tumor resection. Traditional treatments frequently fail to achieve adequate bone regeneration in large defects. This study evaluated the regenerative potential of a novel composite biomaterial combining Wollastonite, β-tricalcium phosphate (β-TCP), and polyethylene glycol dimethacrylate (PEGDMA) for treating segmental bone defects. The composite hydrogel was synthesized using 80% Wollastonite, 20% β-TCP, and PEGDMA polymeric matrix through foam replication and UV-curing techniques. Twelve New Zealand rabbits underwent surgical creation of 5 mm radius segmental defects. Animals were randomly assigned to implant group (GI, n=6) receiving the composite biomaterial or control group (CG, n=6) with standard plate fixation only. Both groups received identical stabilization with locked plates and screws. Comprehensive evaluation included clinical monitoring, radiographic imaging, computed tomography, and histopathological analysis over 120 days. The composite demonstrated excellent biocompatibility with no adverse reactions observed. Radiographic analysis revealed significant differences in biological activity scores between groups (GI: 3.0±0 vs CG: 1.6±0.51, p<0.05 at 120 days). Tomographic evaluation showed superior tissue neoformation (2.8±0.4 vs 2.0±0.63, p<0.05) and mineralization (2.6±0.51 vs 1.5±0.54, p<0.05) in the implant group. Histomorphometric analysis demonstrated dramatically enhanced tissue proliferation in treated animals (4798.33±151.32 μm vs 2408.33±148.51 μm, p<0.01 at 120 days). Complete bone consolidation was achieved in the implant group at 120 days, while control group showed persistent defects. The Wollastonite-β-TCP-PEGDMA composite hydrogel effectively promotes bone regeneration in segmental defects, demonstrating superior osteoinductive and osteoconductive properties compared to natural healing. This innovative biomaterial represents a promising therapeutic approach for challenging bone reconstruction scenarios.

Pharmaceutical formulations based on polymeric micro/nanoparticles offer multiple advantages for drug delivery applications. They can significantly reduce treatment costs and toxicity risks while enabling patient-specific therapies. Moreover, micro/nanoformulations enhance therapeutic efficacy, prevent the premature degradation of active agents, and improve interaction with the biological environment. Among the various particle fabrication techniques in existence, electrospraying stands out due to its precise control over particle size, morphology, and surface characteristics.

In this study, we selected two biopolymers for nanoparticle production: chitosan (extracted in our laboratory from industrial crustacean waste in Mar del Plata) and soy protein isolate (SPI), which is obtained from the byproducts of soybean oil extraction. To modulate the swelling behavior and degradation profile of the resulting particles, the polymers were cross-linked using oxidized sucrose, following a green chemistry approach aimed at minimizing environmental impact.

Electrospraying conditions were optimized to generate nanoparticles from a chitosan/SPI blend dissolved in 10 mol/L acetic acid. The polymeric solution was infused at a constant rate of 0.2 mL/h, while varying the needle-to-collector distance (10, 13, 15, and 17 cm) and the applied voltage (10–17 kV). SEM analysis has been conducted, and data processing is currently ongoing to identify the optimal parameters. Once optimized, these particles are loaded with ivermectin to evaluate drug loading capacity, encapsulation efficiency, and release kinetics.

Epoxy resins are extensively utilised across diverse applications owing to their superior chemical resistance, thermal stability, and mechanical properties. Traditionally, these resins are cured using amine or anhydride hardeners; however, increasing attention is being directed towards alternative, more sustainable curing agents, notably carboxylic acids. These acids offer environmental advantages and enable simpler processing without the need for catalysts; however, their curing efficiency is highly dependent on their chemical structure. This study examines the curing of epoxy resin using three distinct carboxylic acids—salicylic acid (a monoacid), citric acid (a triacid), and maleic acid (a diacid featuring conjugated double bonds)—in the absence of catalysts. The objective was to assess their effectiveness in facilitating epoxy ring-opening and network formation. Formulations were prepared by combining each acid with the epoxy resin in stoichiometric proportions, followed by thermal treatment. Curing progression was monitored using Fourier-transform infrared spectroscopy (FTIR), while differential scanning calorimetry (DSC) was employed to evaluate thermal behaviour and degree of cure. Furthermore, gel content analysis quantified the insoluble fraction of the cured samples, serving as a direct indicator of crosslink density. The results revealed that both salicylic and citric acids effectively promoted epoxy ring-opening, leading to the formation of crosslinked networks. Citric acid exhibited superior performance, attributed to its three carboxylic groups, resulting in higher gel content and enhanced crosslink density. In contrast, maleic acid failed to promote curing under the applied conditions, likely due to its conjugated double bonds diminishing the nucleophilicity of its carboxylic groups or causing steric hindrance in reactions with epoxy moieties. These findings highlight the critical influence of acid structure on curing efficiency, positioning multifunctional acids such as citric acid as promising sustainable alternatives for catalyst-free epoxy resin curing.

Flexible multilayer films are indispensable in food packaging, but their complex composition makes recycling significantly more difficult. To support a circular packaging economy, this study investigates mono-material multilayer films based entirely on polyethylene (PE), incorporating both virgin and recycled feedstocks.

Several three-layer films were fabricated via film blowing extrusion using ultra-low-density polyethylene (ULDPE), post-consumer recycled low-density polyethylene (rLDPE), and their blends. A comprehensive set of characterizations was conducted, including differential scanning calorimetry, thermogravimetric analysis, and melt flow index to assess thermal and molecular properties, as well as mechanical testing (tensile, tear, and dart drop impact). Proxy-based migration experiments were conducted to determine contamination risks relevant to food-contact applications.

Molecular analyses revealed opposing degradation mechanisms: chain scission in ULDPE and crosslinking in rLDPE. The rLDPE showed higher crystallinity, contributing to mechanical robustness when combined with ULDPE. Mechanical tests indicated that increasing rLDPE content reduces ductility and impact strength, though moderate levels preserve acceptable performance. Migration testing confirmed no detectable proxy contaminant transfer through virgin outer layers down to 10 μm thickness, even in films with 75% recycled content.

Controlled blending of rLDPE and ULDPE enables the design of recyclable, mono-material multilayer films with tailored mechanical and barrier properties. The findings suggest that high recycled content can be safely used in packaging, provided design-for-recycling principles are applied. This work highlights a viable strategy for integrating post-consumer waste into high-performance flexible packaging.

Interpenetrating polymer networks (IPNs) of poly(methyl methacrylate) (PMMA)/poly(urethane) PU exhibit good mechanical strength and weather resistance. PMMA/PU IPNs have been studied due to their balanced combination of stiffness, flexibility, and chemical resistance. Grafting crystalline nanocellulose (CNC) onto PMMA to obtain particles that enhance compatibility, improve tensile strength, and impart degradability has not been studied when dispersing it into PMMA/PU IPNs. For this reason, IPNs were obtained through sequential polymerization using 50/50 (PMMA₅₀/PU₅₀) and 80/20 (PMMA₈₀PU₂₀) ratios and different wt% of CNC_x grafting (x = 5, 10, 20, 30 wt%) onto PMMA to obtain PMMA_xCNC_y particles, which were dispersed during the synthesis in 0.1 and 0.5 wt%. This study presents the results of their characterization through mechanical testing performed before and after accelerated weathering to evaluate the effects of the accelerated weathering (ACW) test in a QUV following ASTM G154 for 672 h. Mechanical, thermo-mechanical, and structural analyses were performed through a tensile test, dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA) to determine the final properties after ACW. The sample that was reinforced in stress and Young's modulus is when 0.1 wt.% PMMA₇₀CNC₃₀ particles are added into 50/50 PMMA/PU. The sample closest to the stress of the pure sample was PMMA₅₀PU₅₀/PMMA₇₀CNC₃₀ (0.1 wt%), exhibiting minimal damage in stress and strain after ACW. For PMMA₈₀PU₂₀ systems, reinforcement was made for the following samples: PMMA₈₀PU₂₀/PMMA₉₅CNC₅ (0.1 wt%), PMMA₈₀PU₂₀/PMMA₉₅CNC₅ (0.5 wt%), PMMA₈₀PU₂₀/PMMA₉₀CNC₁₀ (0.1 wt%), and PMMA₈₀PU₂₀/PMMA₇₀CNC₃₀ (0.1 wt%). PMMA₈₀PU₂₀/PMMA₇₀CNC₃₀ (0.1 wt.%) was the most durable material in the 80/20 sample after ACW. Thermo-mechanical analysis indicates an increase in stiffness, changing the glass transition in dependence on the type of particle added, and the structural analysis indicates minimal damage.

Plastic mulch films are widely used in agriculture to improve moisture retention, weed suppression, and enhance yields. However, conventional films, typically made of polyethylene (PE), pose significant end-of-life challenges due to their low commercial value, contamination with soil and residues, and high transportation costs. They often leave persistent fragments in the field that contribute to microplastic pollution and soil degradation.

Although some biodegradable mulch films are commercially available, most are based on PBAT, PLA, or their blends. While compostable under industrial conditions, their degradation in soil or agro-composting environments is often too slow. Furthermore, some studies have highlighted potential ecotoxic effects from PBAT degradation intermediates. Meanwhile, active mulches described in the literature commonly rely on pesticidal or biocidal agents, raising environmental and regulatory concerns.

The ACTIBIOMULCH project proposes an alternative: multilayer mulch films based on polyhydroxyalkanoates (PHAs), fully biodegradable in soil, incorporating natural compounds that activate plant defense mechanisms and enhance resilience to biotic stress without direct toxicity. A biodegradation-promoting additive is also included to modulate the disintegration rate under different conditions.

This work focuses on the polymer technology side. The structural layer was produced by extrusion of PHA-based blends, and the active layer was applied by electrospinning using biodegradable matrices with functional compounds. Structure and morphology were analyzed by SEM, and thermal and mechanical properties were assessed using DSC, TGA, and tensile testing. Biodegradability was evaluated under industrial composting, soil burial (ISO 14855, ISO 17556, ISO 20200), and greenhouse conditions. In addition, a comprehensive ecotoxicological evaluation was carried out, with no adverse effects observed.

Preliminary results show that the films offer suitable mechanical properties, efficient biodegradation, and good environmental compatibility. In tomato trials, they improved pathogen resistance and increased the proportion of top-quality fruits. These findings support their potential as sustainable alternatives to conventional mulches, in line with circular economy principles.