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Sheep wool waste has become a problem affecting the environment, as today the wool of most species has no commercial application and is considered a waste product. Sheep’s wool is mainly composed of keratin which, due to its protein nature and multiple functional groups, has attracted great interest in applications such as support materials in tissue engineering, bioactive materials, and targeted drug delivery. Support materials can be fabricated by 3D printing by syringe extrusion. However, keratin is not suitable for this technique as it does not present proper rheological characteristics. Alginate, a biopolymer derived from brown seaweed, offers a wide range of viscosities at room temperature and offers good performance in 3D printing. Thus, keratin and alginate-based mixtures, due to their properties and ecoefficiency, are interesting candidates to prepare 3D-printed scaffolds. The aim of this work was to develop fully biobased printable inks containing keratin, alginate, salvia extracts, and cellulose nanofibers. In a first stage, keratose, an oxidized form of keratin, was obtained from sheep wool by a clean extraction methodology, and the miscibility and viscosity of keratose-alginate mixtures were assessed. In a second stage, biobased inks were prepared parting from miscible keratose-alginate mixtures. Flow analysis, spectromechanical analysis, and recovery tests were carried out to analyze the effect of the ink formulation over rheological parameters and printability. Mesh and cylinder geometries were 3D printed and their mechanical properties, as well as shape fidelity and self-standing ability, were assessed.

The chemical structure of lycopene has been associated with significant health benefits as an antioxidant, resulting in promising applications as a food additive. However, lycopene is susceptible to chemical changes, such as isomerization and decomposition, when exposed to light and high temperatures. Therefore, lycopene stability during its isolation, food processing, and storage has sparked interest. Isolation includes the extraction of lycopene from vegetable cells by various means and its preservation to protect the biocompound from decomposition. This review explores opportunities to improve lycopene extraction and preservation through the nanotechnology value chain, a framework introduced in 2004. The nanotools explored to extract lycopene are techniques already used in the food industry, such as high-pressure homogenization and microfluidization, which allow the use of food-grade solvents, such as edible oils. Lycopene in oil can be protected by a Pickering emulsion or nanoemulsion, developed with the same nanotools used in lycopene extraction.

Bamboo is a material with good tensile and flexural resistance. As a construction material with structural capacity, using bamboo implies considerable environmental advantages in relation to other typical materials such as steel or concrete. For its correct implementation, it is necessary to define its mechanical properties and durability. Bamboo is susceptible to degradation due to the lack of natural toxins and thin walls, which means that shallow decomposition processes can imply appreciable reductions in its mechanical capacity. The main degrading agents considered in this study were beetles, termites, and xylophagous fungi. The aim of this study was to analyze the durability of three different species: DS, PA, and AA. Durability and mechanical tests results after 6 months of exposure to biotic and abiotic agents were compared with their original properties and chemical composition. In this study, durability was analyzed in two ways. Firstly, the loss of mass due to fungal infection was investigated. The results obtained were based on the standard EN 113 using the fungus CP. Secondly, bending and compressive strength was evaluated after a durability test according to the standard EN 335:2013 for the CU3.1 use class after a 6 month period in the city of Donostia/San Sebastian, Spain. The DS and AA varieties were rated as very durable CD1, while the PA variety is durable CD2, thus proving to be an attractive material for construction. Financial support from the Basque Country Government in the frame of Grupos Consolidados (IT-1690-22).

Polyurethanes are gaining increasing interest for their use as structural components subjected to cyclic loads, such as leaf springs. Thermoset polyurethane (PUR) based technology offers some advantages, such as fatigue resistance, low viscosity, and fast curing. However, current PUR formulations present two major drawbacks: their petrochemical origin and high reactivity. The aim of this work was to develop a novel biobased PUR (BIO-PUR) with the required mechanical properties and processability for manufacturing structural composites by resin transfer moulding (RTM). For this purpose, a high functionality and high hydroxyl index castor-oil-based polyol was used combined with a biobased glycerol (BIO-Gly) to increase the crosslinking density and improve the final properties of the BIO-PUR. The viscosity and reactivity of the different systems were studied by means of rheology tests and differential scanning calorimetry (DSC). Thermal and mechanical properties were studied by dynamic mechanical analysis (DMA) and flexural tests. Furthermore, the RTM process of a representative part was simulated and validated through the manufacturing and testing of plates. The properties of the BIO-PUR resin systems were strongly influenced by the addition of biobased glycerol and its effect on the crosslinking density. The combination of a high functionality and hydroxyl index biobased polyol with the biobased glycerol resulted in a high-performance BIO-PUR with the required reactivity and final properties for structural applications. This research was funded by the Basque Government through the ELKARTEK 2021 (Project NEOMAT KK-2021/00059) and in the frame of Grupos Consolidados (IT-1690-22) and by the University of the Basque Country (UPV/EHU) in the frame of GIU18/216 Research Group.

This article belongs to the Special Issue Advanced Polymer Nanocomposites II. To prepare nonwoven mats constituted by submicrometric fibers of thermally responsive biopolyurethanes (TPU) modified with multiwalled carbon nanotubes (MWCNT), solution blow spinning (SBS) was used. The TPU was the product of synthesis using poly(butylene sebacate)diol, PBSD, ethyl ester L-lysine diisocyanate (LDI), and 1,3-propanediol (PD) (PBSe:LDI:PD) as reactants. TPU was modified by adding different amounts of MWCNT (0, 0.5, 1, 2, and 3 wt.%). The effect of the presence and amount of MWCNT on the morphology and structure of the materials was studied using field-emission scanning electron microscopy (FESEM) and Fourier-transform infrared spectroscopy (FTIR), respectively, while their influence on the thermal and electric behaviors was studied using differential scanning calorimetry (DSC) and capacitance measurements, respectively. The addition of MWCNT by SBS induced morphological changes in the fibrous materials, affecting the relative amount and size of submicrometric fibers and, therefore, the porosity. As the MWCNT content increased, the diameter of the fibers increased and their relative amount with respect to all morphological microfeatures increased, leading to a more compact microstructure with lower porosity. The highly porous fibrous morphology of TPU-based materials achieved by SBS allowed turning a hydrophilic material to a highly hydrophobic one. Percolation of MWCNT was attained between 2 and 3 wt.%, affecting not only the electric properties of the materials but also their thermal behavior. This research was funded by the Fondos de Investigación de Fco. Javier González Benito, política de reinversión de costes generales, Universidad Carlos III de Madrid [2012/00130/004], the Acción Estratégica en Acción Estratégica en Materiales nanocompuestos multifuncionales, Universidad Carlos III de Madrid [2011/00287/003], and the Project PID2020-112713RB-C22-C21 supported by AEI [Ministerio de Ciencia e Innovación of Spain], the University of the Basque Country (UPV/EHU) and (GIU18/216 Research Group).

Bacterial cellulose (BC) is a polymer with interesting conformation and properties. BC can be obtained in different shapes and is easily modified by chemical and physical means, so its applications in the production of new materials and nanocomposites for different purposes have been in the focus of many research projects. However, one of the major challenges to address in bacterium-derived polymer technology is to find suitable carbon sources as substrates that are cheap and do not compete with food production for achieving large scale industrial applications. Agricultural wastes are defined as the residues from the growing and processing of raw agricultural products such as crops, fruits, vegetables and dairy products. Their composition can vary depending on the type of agricultural activity and harvesting conditions, but these residues are suitable for the production of BC. The aim of this review is to give insight into the production of BC using agro-wastes and an overview of the most interesting and novel applications of this biopolymer in different areas i.e. environmental applications, optoelectronic and conductive devices, food ingredients and packaging, biomedicine, and 3D printing technology.

The main aim of this work is to study the importance of the coupling agent on tensile and thermomechanical performance of annealed composites based on poly (lactic acid)/poly (methyl methacrylate) ...

Cellulose nanocrystals (CNC) have been studied as rheological modulator in order to improve the printing performance of a novel polycaprolactone-polyethylene glycol (PCL-PEG) waterborne polyurethane urea (WBPUU) based ink for direct ink writing 3D-printing technology. The cellulose nanocrystals are chemically bonded to the WBPU, since they were added during the synthesis of a WBPUU, in order to tune the rheological properties of the ink and thus, improve the printing performances. The WBPUU-CNC inks have been extensively characterized from the rheological viewpoint and have been subsequently used to print different pieces. To determine the capacity of the CNC to improve the printing performance of this type of inks, we establish the relationship between the rheological properties of the inks and their printing viability by an optimal window of compositions of the inks. Additionally, we have measured the mechanical and thermomechanical properties of printed WBPUU-CNC pieces to evaluate the effective reinforcement of in situ incorporated CNC in the WBPUU-CNC inks. The results showed that the addition of CNC accentuates the shear-thinning behaviour, presenting lower tan δ, especially at the lowest CNC contents compared with the matrix, which resulted in inks with excellent printable properties. Moreover, the shape fidelity is increased by the solid-like behavior due to the filler effect of CNC and confirmed by SEM images. Finally, a large increase in Young’s modulus and thermal and thermomechanical stability were observed on the printed pieces that contained only 0.5 wt% CNC compared to the matrix, suggesting the formation of effective interactions between CNC and WBPUU, as corroborated by FTIR, that lead to a greater reinforcement.

Bio-based cyclic carbonates are of significant research interest as monomers for non-isocyanate polyurethane (NIPU) synthesis. This research describes the synthesis of a series of five-membered bis(cyclic carbonate)s using bio-based polyether polyols (PO3G) with different molecular weights (250, 650 and 1000 g mol−1) and carbon dioxide as green feedstocks. The utilization of CO2 as a source of carbon in the chemical reaction is in agreement with the sustainable chemical industry. Furthermore, in order to support the green and sustainable polymer chemistry approach, the syntheses were attempted under solvent-free conditions. The implemented synthetic methods are focused on the design of processes and final products that minimize negative environmental impact. Detailed chemical structure analysis of synthesized products was performed using a combination of spectroscopy techniques (ATR-FTIR as well as 1D and 2D NMR techniques), mass spectrometry (MALDI-TOF MS) and chromatography analysis (SEC). The formation of the main product with two terminal cyclic carbonates was confirmed and the formed side products were also identified, characterized and quantified. Finally, as a proof of concept, the synthesized bis(cyclic carbonate)s were successfully used for the preparation of NIPU thermosets. Chemical and mechanical properties of the produced materials suggest their high potential for future applications, e.g. as sound absorbing materials.

[EN] Starch-based tablets with tailored releases were prepared by 3D printing using a hydrophobic drug. The importance of the origin of the excipient in the inks and tablets was analyzed. Besides, the effect of the geometry of the tablet on the drug release profile was also evaluated. The rheological properties of the inks was influenced by the botanic origin of the starch. Consequently, tablets presented different microporous structure and particular compression and swelling behaviors. Normal maize starch showed a non-well-defined porous morphology, not being able to form a stable structure whereas, waxy maize and potato starches exhibited a well-defined porous structure and were both able to maintain their integrity after long time immersion. Finally, tablets combining different starches and geometries were printed tailoring the drug release from 10 min to 6 h and designing two-steps profiles. The applicability of the developed 3D printed drug release systems in personalized therapies was demonstrated. Financial support from the University of the Basque Country (UPV/EHU) (GIU18/216 Research Group), from the Basque Government in the frame of Elkartek KK-2020/00053 and PIBA2020-1-0041 and from Spanish Ministry of Science and Innovation and Spanish State Research Agency (MCIN/AEI/10.13039/501100011033) in the frame of PID2019-105090RB-I00 project, are gratefully acknowledged. Moreover, we are grateful to the Macrobehavior-Mesostructure-Nanotechnology SGIker unit of the UPV/EHU. K. González thanks the University of the Basque Country for the grant “Contratación de doctores recientes hasta su integración en programas de formación postdoctoral en la UPV/EHU «DOKBERRI» 2020-I” (DOCREC20/07).

Bacterial cellulose (BC)/graphene oxide (GO) sphere-like hydrogels have been biosynthesized by in situ route in dynamic cultivation. The GO concentration during BC biosynthesis (0.01 and 0.05 mg mL−1) was the determining factor for the conformation of the final hydrogels: encapsulation (BC/GO 0.01) or distribution through all the body of the spheres (BC/GO 0.05). The as-prepared sphere hydrogels were characterized in terms of physico-chemical properties, thermal stability, microstructure, and swelling capacity in different media. In addition, a chemical treatment with ascorbic acid was performed in order to obtain reduced graphene oxide (rGO) into the spheres (BC/rGO). After the chemical treatment, electrostatic force microscopy (EFM) revealed electrical interactions due to the presence of rGO inside the spheres and resistivity values in the range of semiconductive materials were obtained (106 Ω·cm), making BC/rGO spheres promising for the development of electro-stimulated systems. The in vitro release study of ibuprofen (IB), showed that the reduction process led to an increase of 73 and 92% of drug release with respect to BC/GO 0.05 and BC/GO 0.01 spheres, respectively. Moreover, the encapsulation conformation showed more homogeneous porous structure and thus, a cumulative drug release of 63% was reached after 6 h.

Improving the efficiency of enzymes towards decomposing substrates has been one of the central goals in the biotechnology industry. However, the modification of enzymes for upgrading natural materials to high-value performant materials is largely unexplored. Here, we demonstrate that the ancestral form of a Cel5A bacterial endoglucanase, unlike its modern descendant from Bacillus subtilis, was able to generate cellulose nanocrystals (EnCNC) chemically pure, maintaining native cellulose structure and displaying higher thermal stability and crystallinity than standard CNC obtained by acidic treatment. We demonstrate that EnCNC alone is a suitable matrix to grow cells in 2D and 3D cultures. Importantly, EnCNC accepts well graphene derivatives to fabricate conductive hybrids inks forming a stable flat surface where cells also attach and proliferate. Our results demonstrate that EnCNC has physicochemical properties unattainable with standard CNC, making it a unique material ideal as a matrix for the design of biocompatible advanced materials for tissue engineering and other applications. Enzymes are effective at upgrading natural materials to high-performance biomaterials. Here, an ancestral endoglucanase is used to obtain highly crystalline cellulose nanocrystals, which can act as a matrix for cell growth and be combined with graphene for conducting inks.

The interest on poly(lactic acid) (PLA)/poly(methyl methacrylate) (PMMA) blends has increased during the last years due to their promising properties. The novelty of the current work focuses on the preparation and characterization of biocomposites based on PLA/PMMA matrix and NaOH-treated sisal fibers. The effect of the addition of treated sisal fibers on the physico-mechanical properties of high polylactide content composites was studied. For this purpose, PLA/PMMA blend (80/20 wt%) was prepared by melt-blending and reinforced with different fiber contents. Although composites showed interesting specific tensile properties, the estimated heat deflection temperature (HDT), that is, the maximum temperature at which a polymer system can be used as a rigid material, barely increased 4°C respect to unreinforced system. After the annealing process, the HDT of the unreinforced polymer blend increased around 25°C, whereas the composites showed an increase of at least 38°C. Nonetheless, the specific tensile strength of composite decreased approximately 48% because the adhesion between fiber and polymer matrix was damaged and cracks were formed during annealing process.

Cocoa shell (CS) is a by-product of the chocolate industry with limited economic benefit and a high environmental impact. In this study, a new material for the food industry that consists of nanocellulose fibers with CS fat was successfully isolated (yield of approximately 7.12%). The material was characterized with attenuated total reflection–Fourier transform infrared spectroscopy (ATR–FTIR), solid-state 13C nuclear magnetic resonance (13C NMR), X-ray diffraction (XRD), fluorescence and atomic force microscopy (AFM). The XRD, 13C NMR, and ATR–FTIR results suggest that the structure of the cellulosic CS fibers can be interpreted as cellulose Iβ. The crystallinity index (CrI) of an isolated sample was investigated by different methods with ATR–FTIR, 13C NMR, and XRD. According to the results, 13C NMR and XRD are the most adequate methods for quantifying the CrI of cellulosic samples in the presence of fat. In addition, the XRD results indicate that approximately 65 to 70% of the sample was crystalline. According to the fluorescence microscopy results, the cellulosic sample formed a suspension with fat, and the AFM results show that the cellulosic part of the sample had nanometric diameters between 30–80 nm with high aspect ratios. Consequently, a suspension of nanocellulose, hemicellulose, and fat was isolated from CS by chemical and mechanical treatments. The new material can be called a “suspension of holocellulose nanofibers and fat” owing to its composition and fiber diameters. The high aspect ratio of the nanocellulose fibers in the suspension resulted in an entangled network that stabilized the CS fat.

Starch-based nanocomposite hydrogels were successfully prepared by the Diels-Alder click cross-linking reaction between furan-functionalized starch derivative and a water-soluble tetrafunctional maleimide compound, adding cellulose nanocrystals (CNC) as nanoreinforcement. The effect of increasing the CNC content on rheological and swelling properties as well as on the morphology of the hydrogels was analyzed. Besides, in order to evaluate the applicability of the as-prepared hydrogels as delivery systems, drug release measurements and in vitro cytotoxicity assays were also performed. It was found that the prepared nanocomposite hydrogels presented higher stiffness as the CNC content increased. The incorporation of the nanocrystals modified the internal porous microstructure of the hydrogels, affecting consequently both the swelling capacity and the drug-delivery kinetics. Moreover, the prepared nanocomposite hydrogels showed non-toxic behavior, demonstrating their potential applicability in the biomedical field, especially as sustained drug delivery systems.

Polyurethane based materials show great potential for many applications, and their reinforcement with different kinds of nano-entities can improve their properties or supply them with new ones, widening their fields of applications to new opportunities. In this work, nanocomposites composed of a biobased waterborne polyurethane and carbonaceous reinforcements were prepared and characterized. Parting from graphite, graphene, and graphene oxide were obtained through a mechanical and a chemical route, respectively, and graphene oxide was reduced into graphene through a thermal process. Successful exfoliation, oxidation, and reduction processes were proven when characterizing graphene, graphene oxide, and reduced graphene oxide. Nancomposites reinforced with graphene and graphene oxide showed improved mechanical and thermomechanical properties, whereas they did not show electrical conductivity. Coatings of the systems with graphene and reduced graphene oxide were studied, to grant electrical properties to the composites. Electrical conductor materials were obtained after coating the systems, as shown by Electrostatic Force Microscopy and electrical conductivity measurements.

This study investigated the performance of polyurethane adhesives prepared with various combinations of wheat starch that had been modified by isophorone diisocyanate (MS), two polyol types (1,3-propanediol (PD) and glycerol (Gly)), native wheat starch (NS), and 4,4′-diphenylmethane diisocyanate (pMDI) at a NCO:OH weight ratio of 1:1. Two more adhesives were also synthesized with NS, PD, or Gly and pMDI blends and served as controls. The thermal behavior of the adhesives before and after the curing process, as well as their rheological performance and lap shear strength, were analyzed. Differential scanning calorimetry (DSC) showed a reduction in curing temperature and heat by adding MS. The thermal stability of the cured adhesives was slightly increased by MS addition. The viscosity of the adhesives that contained MS substantially increased at a linear ascendant ramp of shear, while the controls exhibited relatively low viscosity during the whole shear rate spectrum from 0.1 to 100 s−1. The tensile shear strength of wood veneers was also significantly increased by the incorporation of MS under both dry and wet measuring conditions. The maximum dry shear strength was obtained for the adhesive with Gly polyol and a higher content of MS and was comparable to the control adhesive with pMDI This research was funded by Lantmännen Forskningsstiftelse (Grant No. 2017H011) and Formas, Swedish Research Council for Sustainable Development (Grant No. 2018-00637).

In this work, shape-customized scaffolds based on waterborne polyurethane-urea (WBPUU) were prepared via the combination of direct ink writing 3D-printing and freeze-drying techniques. To improve the printing performance of the ink and guarantee a good shape fidelity of the scaffold, cellulose nanocrystals (CNC) were added during the synthesis of the WBPUU and some of the printed constructs were immersed in CaCl2 prior to the freeze-drying process to promote ionic crosslinking between calcium ions and the polyurethane. The results showed that apart from allowing the ink to be successfully printed, obtaining scaffolds with good shape fidelity, the addition of the CNC resulted in a greater homogeneity of the porous structure as well as an increase of the swelling capacity of the scaffolds. Additionally, the CNC has a reinforcement effect in the printed systems, presenting a higher compression modulus as the CNC content increases. In the case of samples crosslinked by calcium ions, a rigid shell was observed by scanning electron microscopy, which resulted in stiffer scaffolds that presented a lower water absorption capacity as well as an enhancement of the thermal stability. These results showed the potential of this type of post-printing process to tune the mechanical properties of the scaffold, thus widening the potential of this type of material. The financial support of the Basque Government within the framework of Grupos Consolidados (IT-1690-22) and the Spanish Ministry of Science and Innovation (MINCIN)—State Investigation Agency (AEI) (PID2019-105090RB-I00/AEI/10.13039/501100011033) is acknowledged.

In order to continue the development of inks valid for cold extrusion 3D printing, waterborne, polyurethane–urea (WBPUU) based inks with cellulose nanofibers (CNF), as a rheological modulator, were prepared by two incorporation methods, ex situ and in situ, in which the CNF were added after and during the synthesis process, respectively. Moreover, in order to improve the affinity of the reinforcement with the matrix, modified CNF was also employed. In the ex situ preparation, interactions between CNFs and water prevail over interactions between CNFs and WBPUU nanoparticles, resulting in strong gel-like structures. On the other hand, in situ addition allows the proximity of WBPUU particles and CNF, favoring interactions between both components and allowing the formation of chemical bonds. The fewer amount of CNF/water interactions present in the in situ formulations translates into weaker gel-like structures, with poorer rheological behavior for inks for 3D printing. Stronger gel-like behavior translated into 3D-printed parts with higher precision. However, the direct interactions present between the cellulose and the polyurethane–urea molecules in the in situ preparations, and more so in materials reinforced with carboxylated CNF, result in stronger mechanical properties of the final 3D parts. Financial support from the Basque Government (Grupos Consolidados (IT-1690-22), Elkartek (KK19-00048)) is acknowledged.

Curcumin and chloramphenicol are drugs with different solubility properties in physiological conditions due to their hydrophobic and hydrophilic structure, respectively. In this work, sodium alginate-cellulose nanofibers (SA-CNF) based inks loaded with curcumin and/or chloramphenicol have been developed for syringe extrusion 3D printing technology. Printability and shape fidelity of the drug-loaded inks were analyzed through rheological characterization. Suitable drug-loaded inks were 3D printed showing shape fidelity, and samples were either freeze-dried or crosslinked with Ca2+ and air-dried to achieve functional pharmaceutical forms with different morphological characteristics. In vitro drug delivery tests were carried out from the resulted forms and it was observed that the release performed faster in freeze-dried than in Ca2+ crosslinked/air-dried ones for all cases, resulting in two different methods for controlling drug delivery over time. The differences in aqueous solubility of the drugs, the different CNF content of the inks and the surface area of the samples also played an important role during drug delivery, involving strategies to control the release over an extended duration.

Thiol modified chitosan (CsSH) was covalently cross–linked with a water–soluble bismaleimide (BMI) to obtain chitosan–based hydrogels by thiol–Michael addition reaction at physiological conditions. By modifying the composition of the as–prepared hydrogels, final properties could be modulated. Thus, the rheological and swelling behaviour were controlled by altering the amount of cross–linking agent in the networks. An increase in the cross–linker ratio leaded to an increase in the hydrogel storage modulus and decrease in swelling ratio due to provided rigidity to the structure and a higher cross–linked degree. Furthermore, 3D porous structures were observed to be sensitive to pH stimulus and showed interesting degradation kinetics under specific enzymes, suggesting the formation of these novel materials to be worthy of biomedical applications.

Amphiphilic poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-b-PPO-b-PEO) and poly(propylene oxide-b-ethylene oxide-b-propylene oxide) (PPO-b-PEO-b-PPO) triblock copolymer based waterbo...

This work reports on the development of fully bacterial cellulose-derived stiff nanopapers by the infiltration of bacterial cellulose nanocrystals (BCNCs) into bacterial cellulose (BC) membranes. The incorporation of the nanocrystals into BC membranes led to a more dense and compacted structure with smoother surface, improving both, the oxygen barrier properties due to the tortuous path created by the BCNCs, and the mechanical performance. This simple and practical method provides a new approach to make stiff nanopapers fully derived from BC with potential applications in eco-friendly packaging.

Water-activated shape memory bacterial cellulose/polyurethane nanocomposites were prepared by the immersion of bacterial cellulose (BC) wet membranes into waterborne polyurethane (WBPU) dispersions for different times. The high affinity between the hydrophilic BC and water stable polyurethane led to the coating and embedding of the BC membrane into the WBPU, facts that were confirmed by FTIR, SEM and mechanical testing of the nanocomposites. The mechanical performance of the nanocomposites resulted enhanced with respect to the neat WBPU, confirming the reinforcing effect of the BC membrane. An improvement of the shape fixity ability and faster recovery process with the presence of BC was observed. In 3 min, the nanocomposite with highest BC content recovered the 92.8 ± 6.3% of the original shape, while the neat WBPU only recovered the 33.4 ± 9.6%. The obtained results indicated that 5 min of impregnation time was enough to obtain nanocomposites with improved mechanical performance and fast shape recovery for potential biomedical applications. The present work provides an approach for developing environmentally friendly and biocompatible BC/polyurethane based materials with enhanced mechanical and shape memory properties.

Poly(propylene oxide)–poly(ethylene oxide)–poly(propylene oxide) (PPO–PEO–PPO) based bismaleimide (BMI) was employed as cross–linking agent for the synthesis of pH–sensitive clicked hydrogels by Diels–Alder (DA) reaction with furan–grafted chitosan in aqueous solution. The effect of the surrounding pH over the microstructure and the swelling ability of the hydrogels was evaluated depending on the initial composition. The results suggested that the hydrogels maintained the characteristic responsive properties of the original biopolymer even after the cross–linking reaction. The different macromolecular networks remarkably affected the final properties, especially when referring to pH–swelling sensitiveness and hydrogel porosity. In addition, the swelling parameters revealed that the hydrogels presented large liquid absorption capacity, showing excellent recovery properties and responsiveness at different pHs. The promising features of the ensuing hydrogels made them suitable as targeted pH–sensitive drug delivery systems.

The degradation of two poly(ethylene terephtalate) (PET) samples from urban and marine wastes (PET-u and PET-m, respectively) has been studied by comparing their properties with those of virgin PET (PET-v) and post condensed PET for bottle fabrication (PET-ssp). FTIR spectroscopy, DSC analysis, WCA and MFI results have confirmed that all PET residues were degraded. Therefore, the chemical recycling has been evaluated in order to valorize PET-m and PET-u wastes, analyzing the effect of degradation on the process. Glycolysis of degraded and non-degraded PET samples has been carried out in a pressure reactor at 220C for 30 min. For all the cases almost pure BHET monomer has been obtained: 96.5 and 96.7 % for PET-m and PET-u respectively, values 2 and 13 % higher than those obtained for PET-ssp and PET-v. Obtained results indicate that the initial degradation of PET wastes increases the BHET monomer content in the glycolyzed sample. Financial support from the University of the Basque Country in the frame of GIU18/216 and from the Provincial Council of Gipuzkoa (ItsasMikro project) are gratefully acknowledged. Authors thank the Circular Economy University-Company Classroom (Faculty of Engineering Gipuzkoa, UPV/EHU, Provincial Council of Gipuzkoa) . More-over, we are grateful to the Macrobehaviour-Mesostructure-Nanotechnology SGIker unit of UPV/EHU. Eider Mendiburu Valor thanks Basque Government for PhD grant (PRE_2018_1_0014) .

Hernia injuries are the main condition where mesh implants are needed to provide a suitable reinforcement of the damaged tissue. Mesh implants made of polypropylene (PP) are widely used for this application, however complications related to lack of flexibility, elasticity, and mesh infection have been reported. The development of mesh implants from safer materials adaptable to patient necessities can suppose an alternative for conventional PP meshes. In this work, personalized mesh implants made of alginate and waterborne-polyurethane (A-WBPU) are developed using 3D printing technology. For that purpose, five waterborne polyurethane ink formulations with different amounts of alginate are developed and rheologically characterized. All ink formulations are 3D printed showing good printability, manufacturing surgical mesh implants with suitable morphological characteristics customizable to patient injury through computer-aided design (CAD) mesh model adaptation. A calcium chloride (CaCl

In this work, polycaprolactone–polyethylene glycol (PCL–PEG) based waterborne polyurethane–urea (WBPUU) inks have been developed for an extrusion-based 3D printing technology. The WBPUU, synthesized from an optimized ratio of hydrophobic polycaprolactone diol and hydrophilic polyethylene glycol (0.2:0.8) in the soft segment, is able to form a physical gel at low solid contents. WBPUU inks with different solid contents have been synthesized. The rheology of the prepared systems was studied and the WBPUUs were subsequently used in the printing of different pieces to demonstrate the relationship between their rheological properties and their printing viability, establishing an optimal window of compositions for the developed WBPUU based inks. The results showed that the increase in solid content results in more structured inks, presenting a higher storage modulus as well as lower tan δ values, allowing for the improvement of the ink’s shape fidelity. However, an increase in solid content also leads to an increase in the yield point and viscosity, leading to printability limitations. From among all printable systems, the WBPUU with a solid content of 32 wt% is proposed to be the more suitable ink for a successful printing performance, presenting both adequate printability and good shape fidelity, which leads to the realization of a recognizable and accurate 3D construct and an understanding of its relationship with rheological parameters. Financial support from the University of the Basque Country (UPV/EHU) (GIU18-216), Spanish Ministry of Economy and Competitiveness (MINECO) (MAT2016-76294R and PID2019-105090RB-I00) and the Basque Government (KK-2019/00048) are gratefully acknowledged. Julen Vadillo wishes to acknowledge both the University of Pau and Pays de l’Adour and the UPV/EHU for his PhD grant.

International audience; This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY; 3D printing has exponentially grown in popularity due to the personalization of each printed part it offers, making it extremely beneficial for the very demanding biomedical industry. This technique has been extensively developed and optimized and the advances that now reside in the development of new materials suitable for 3D printing, which may open the door to new applications. Fused deposition modeling (FDM) is the most commonly used 3D printing technique. However, filaments suitable for FDM must meet certain criteria for a successful printing process and thus the optimization of their properties in often necessary. The aim of this work was to prepare a flexible and printable polyurethane filament parting from a biocompatible waterborne polyurethane, which shows potential for biomedical applications. In order to improve filament properties and printability, cellulose nanofibers and graphene were employed to prepare polyurethane based nanocomposites. Prepared nanocomposite filaments showed altered properties which directly impacted their printability. Graphene containing nanocomposites presented sound enough thermal and mechanical properties for a good printing process. Moreover, these filaments were employed in FDM to obtained 3D printed parts, which showed good shape fidelity. Properties exhibited by polyurethane and graphene filaments show potential to be used in biomedical applications.

[EN]Soil contamination, sustainable management of water resources and controlled release of agrochemicals are the main challenges of modern agriculture. In this work, the synthesis of sphere-like bacterial cellulose (BC) using agitated culture conditions and Komagateibacter medellinensis bacterial strain ID13488 was optimized and characterized from grape pomace (GP). First, a comparative study was carried out between agitated and static cultures using different nitrogen sources and applying alternative GP treatments. Agitation of the cultures resulted in higher BC production yield compared to static culture conditions. Additionally, Water holding capacity (WHC) assays evidenced the superabsorbent nature of the BC biopolymer, being positively influenced by the spherical shape as it was observed an increase of 60% in contrast to the results obtained for the BC membranes under static culture conditions. Moreover, it was found that sphere-like BCs were capable of retaining urea up to 375% of their dry weight, rapidly releasing the fertilizer in the presence of water. According to our findings, sphere-like BCs represent suitable systems with great potential for actual agricultural hazards and grape pomace valorisation. Financial support from the University of the Basque Country (UPV/EHU) (GIU18/216 Research Group), from the Basque Government in the frame of Elkartek KK-2020/00053 and PIBA2020-1-0041 and from Spanish Ministry of Science, Innovation and Universities and European Union (MICINN/EU/FEDER) in the frame of MAT2016-76294-R and PID2019-105090RB-I00 projects, are gratefully acknowledged. The authors also thank the technical support and personnel provided by the Servicio de Lipidómica y Metabolomica of the SGIKER (UPV/EHU,MICINN, GV/E.G., ESF) and the Phytotron Service of UPV/EHU. Moreover, are grateful to the Macrobehavior-Mesostructure-Nanotechnology SGIker unit of the UPV/EHU. Díaz-Ramírez J wishes to acknowledge the Department of Agriculture, Fisheries and Food policy of the Basque Government for the PhD grant (00020-PIT2019-22).

This study reports the fabrication and performance of sustainable polyurethane (PU) films based on wheat starch (native NS, modified MS), bio-polyols (1,3-propanediol PD, glycerol Gly), and polymeric diphenylmethane diisocyanate (pMDI). NS was successfully modified with isophorone diisocyanate, confirmed by Fourier transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance (13C NMR). Various PU films were prepared using NS, PD or Gly, MS and pMDI. For comparison, reference films were also synthesized without MS. PU films were analyzed from the viewpoint of their chemical, thermomechanical and flexural properties, and microstructural morphology. FTIR spectra demonstrated the total consumption of NCO groups, while the scanning electron microscopy micrographs of the films revealed that MS addition promoted the interactions between the compounds, enhancing in consequence their mechanical and thermomechanical performance. The study supported the suitability of functionalized carbohydrates to substitute petrochemical compounds in the synthesis of more environmentally-friendly PUs. The authors acknowledge the financial support of Lantm¨annen Forskningsstiftelse (Grant No. 2017H011), University of the Basque Country (UPV/EHU) (GIU18/216 Research Group) and Basque Government (PIBA2020-1-0041). Authors are also grateful to the SGIker units of the UPV/EHU. Dr Hosseinpourpia also wishes to thank the support of Formas, Swedish Research Council for Sustainable Development (Future research leaders, Grant No. 2018-00637). info:eu-repo/semantics/publishedVersion

Although marine debris has been accumulating for many decades, only during the last three the accumulation of millions of waste tons at seas and oceans has generated interest and concern of scientists and governments. While marine debris may present different origins and nature, polymers lead in abundance. Annually, 1.15–2.41 million tons of plastic arrive to the ocean from rivers. Wastes are distributed at different marine compartments according to their density, with a huge impact in both marine fauna and water pollution. It becomes necessary, consequently, besides avoiding further waste dumping, to collect and manage the waste, not only marine one, but also the land waste. Both terrestrial and marine plastic waste can constitute resources or raw materials for different applications such as fuel, energy and of materials production. Research on suitable management and recycling/valorization are required to move towards a circular economy for generating more sustainable societies. In the present chapter, the main studies carried out about the recyclability of the main polymers present in marine waste are presented and analyzed, together with the main limitations and opportunities related with this recycling process.

The depolymerization process of PET by glycolysis into BHET monomer is optimized in terms of reaction temperature and time, by carrying out the process under pressure to be faster for reducing the energy required. Almost pure BHET has been obtained by working in a pressure reactor at 3 bar both at 220 and 180 °C after short reaction times, while for longer ones a mixture of oligomers and dimers is obtained. Depending on the potential application required, the obtention of different reaction products is controlled by adjusting reaction temperature and time. The use of a pressure reactor allows work at lower temperatures and shorter reaction times, obtaining almost pure BHET. To the best of our knowledge, except for microwave-assisted procedures, it is the first time in which pure BHET is obtained after such short reaction times, at lower temperatures than those usually employed.

Hybrid biobased polyurethane flexible foam composites containing a residue from surf industry (polyurethane powder) as filler and graphite or graphene residue were synthe-sized. It was observed that the addition of the powder at low contents did not modify the final properties considerably, since the cell structure was not compromised. Moreover, the powder increased the capacity of the foams to retain the carbonaceous fillers. The compressive properties of the hybrid foams were not altered with the addition of the graphite and graphene. Finally, hybrid composites showed selective absorption capacity since the presence of the carbonaceous fillers provided the foams oil absorption capacity without modifying the hydrophobic nature of the matrix foams. (C) 2021 The Author(s). Published by Elsevier B.V. Authors thank the University of the Basque Country (UPV/EHU) (GIU18/216 Research Group), the Basque Government (PIBA19-0044 project) and the Provincial Country of Gipuzkoa (DG 19/28 Support Program for the Guipuzcoan Science, Technology and Innovation Network 2019) for the financial support. We also acknowledge the "Macrobehavior-Mesostructure-Nanotechnology " SGIker unit from the UPV/EHU, for their technical support and Olatu S.A. (Gipuzkoa) for providing the PUP. T.C-C. thanks the Provincial Country of Gipuzkoa (2017-BE01-000002-01) and the UPV/EHU (ESPDOC19/41).