Browsing by Keyword "Polymers and Plastics"
Now showing 1 - 20 of 84
Results Per Page
Sort Options
Item Additive Manufactured Scaffolds for Bone Tissue Engineering: Physical Characterization of Thermoplastic Composites with Functional Fillers: Physical Characterization of Thermoplastic Composites with Functional Fillers(2021-08-13) Sinha, Ravi; Sanchez, Alberto; Camara-Torres, Maria; Uriszar-Aldaca, Iñigo Calderon; Calore, Andrea Roberto; Harings, Jules; Gambardella, Ambra; Ciccarelli, Lucia; Vanzanella, Veronica; Sisani, Michele; Scatto, Marco; Wendelbo, Rune; Perez, Sergio; Villanueva, Sara; Matanza, Amaia; Patelli, Alessandro; Grizzuti, Nino; Mota, Carlos; Moroni, Lorenzo; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓN; Tecnalia Research & InnovationThermoplastic polymer–filler composites are excellent materials for bone tissue engineering (TE) scaffolds, combining the functionality of fillers with suitable load-bearing ability, biodegradability, and additive manufacturing (AM) compatibility of the polymer. Two key determinants of their utility are their rheological behavior in the molten state, determining AM processability and their mechanical load-bearing properties. We report here the characterization of both these physical properties for four bone TE relevant composite formulations with poly(ethylene oxide terephthalate)/poly(butylene terephthalate (PEOT/PBT) as a base polymer, which is often used to fabricate TE scaffolds. The fillers used were reduced graphene oxide (rGO), hydroxyapatite (HA), gentamicin intercalated in zirconium phosphate (ZrP-GTM) and ciprofloxacin intercalated in MgAl layered double hydroxide (MgAl-CFX). The rheological assessment showed that generally the viscous behavior dominated the elastic behavior (G″ > G′) for the studied composites, at empirically determined extrusion temperatures. Coupled rheological–thermal characterization of ZrP-GTM and HA composites showed that the fillers increased the solidification temperatures of the polymer melts during cooling. Both these findings have implications for the required extrusion temperatures and bonding between layers. Mechanical tests showed that the fillers generally not only made the polymer stiffer but more brittle in proportion to the filler fractions. Furthermore, the elastic moduli of scaffolds did not directly correlate with the corresponding bulk material properties, implying composite-specific AM processing effects on the mechanical properties. Finally, we show computational models to predict multimaterial scaffold elastic moduli using measured single material scaffold and bulk moduli. The reported characterizations are essential for assessing the AM processability and ultimately the suitability of the manufactured scaffolds for the envisioned bone regeneration application.Item Applicability of a Material Constitutive Model Based on a Transversely Isotropic Behaviour for the Prediction of the Mechanical Performance of Multi Jet Fusion Printed Polyamide 12 Parts(2024-01) Perez-Barcenilla, Sergio; Cearsolo, Xabier; Aramburu, Amaia; Castano-Alvarez, Ruben; Castillo, Juan R.; Gayoso Lopez, Jorge; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓN; Caracterización y Validación. MecánicosMulti Jet Fusion (MJF), an innovative additive manufacturing (AM) technique in the field of Powder Bed Fusion (PBF) developed by Hewlett-Packard (HP) Inc. (Palo Alto, CA, USA), has been designed to produce polymer parts using thermoplastic-based powders, primarily focusing on polyamide 12 (PA12). Employing a layer-by-layer approach, MJF enables the rapid production of intricate components, reportedly up to 10 times faster than other AM processes. While the mechanical properties of MJF-printed PA12 and the impact of build orientation on those properties have already been explored in various studies, less attention has been given to the mechanical performance of MJF-printed PA12 components under complex loads and accurate predictive models. This contribution aims to assess the applicability of a constitutive model based on a transversely isotropic behaviour under linear elastic deformation for predicting the mechanical response of MJF-printed PA12 parts through numerical simulations. Both uniaxial tensile and shear tests were carried out on printed samples to determine the elastic properties of MJF-printed PA12, with additional testing on printed complex handle-shaped parts. Finally, a numerical model was developed to simulate the mechanical tests of the handles. Results from tests on printed samples showed that MJF-printed PA12, to some extent, behaves as a transversely isotropic material. Furthermore, using a constitutive model that assumes a transversely isotropic behaviour under linear elastic deformation for predicting the mechanical response of MJF-printed PA12 parts in numerical simulations could be a reasonable approach, provided that the material stress levels remain within the linear range. However, the particularities of the stress-strain curve of MJF-printed PA12 complicate determining the elasticity-to-plasticity transition point.Item Bio-Based Phosphate-Containing Polyester for Improvement of Fire Reaction in Wooden Particleboard(2023-03) Svensson, Ingemar; Butron, Amaia; Puyadena, Maddalen; González, Alba; Irusta, Lourdes; Barrio, Aitor; BIOECONOMÍA Y CO2A new phosphate-containing bio-polyester based on glycerol and citric acid was synthesized and evaluated as fire-retardant (FR) in wooden particleboards. Phosphorus pentoxide was used to first introduce phosphate esters in the glycerol followed by esterification with citric acid to produce the bio-polyester. The phosphorylated products were characterized by ATR-FTIR, 1H-NMR and TGA-FTIR. After polyester curing, they were grinded and incorporated in laboratory produced particleboards. The fire reaction performance of the boards was evaluated by cone calorimeter. An increased char residue was produced depending on the phosphorus content and the THR (Total Heat Release), PHRR (Peak of Heat Release Rate) and MAHRE (Maximum Average of the Rate of Heat Emission) were considerably reduced in presence of the FRs. Highlights: Phosphate containing bio-polyester as fire retardant in wooden particle board; Fire performance is improved; Bio-polyester acts in the condensed and gas phases; Additive effectiveness similar to ammonium polyphosphate.Item Carbon nanotubes and graphene into thermosetting composites: Synergy and combined effect(2018-07-20) Prolongo, S. G.; Moriche, R.; Ureña, A.; Flórez, S.; Gaztelumendi, I.; Arribas, C.; Prolongo, M. G.; POLIMEROSThis work analyzes the morphology and behavior of hybrid composites reinforced with carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). In order to avoid the weak interface of laminar nanofillers, GNPs were functionalized with amine groups. Different tendencies were observed as a function of the measured property. Storage modulus showed a synergic trend, being the stiffness of hybrid CNT/GNP/epoxy composites higher than the corresponding ones measured in neat epoxy composites reinforced with CNTs or GNPs. In contrast, the thermal and electrical conductivity increased with the nanofiller addition, the final value of the mentioned properties in the hybrid composites was strongly influenced by specific graphitic nanofiller. Neat GNP/epoxy composites showed the highest thermal conductivity, while neat CNT/epoxy composites presented the highest electrical conductivity. This behavior is explained by the observed morphology. All composites exhibited a suitable nanofiller dispersion. However, on hybrid GNP/CNT/epoxy composites, CNTs tend to be placed between nanoplatelets, forming bridges between nanoplatelets. This morphology implies a less effective electrical network, limiting the synergic effect in the properties, which requires percolation. In spite of this, the hybrid GNP/CNT/epoxy composites showed a better combination of properties than the neat composites.Item Cellulose and graphene based polyurethane nanocomposites for fdm 3d printing: Filament properties and printability(2021-03-01) Larraza, Izaskun; Vadillo, Julen; Calvo-Correas, Tamara; Tejado, Alvaro; Olza, Sheila; Peña-Rodríguez, Cristina; Arbelaiz, Aitor; Eceiza, Arantxa; BIOECONOMÍA Y CO23D 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.Item Characterization of Comb Shaped MAA-co-PEGMA Copolymers Synthesized by Free-Radical Polymerization(2020-12) Emaldi, Iñaki; Agirre, Amaia; Etxeberria, Agustin; Erkizia, Edurne; Dolado, Jorge S.; Leiza, Jose R.; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNMethacrylic acid-co-polyethylene glycol methacrylate (MAA-co-PEGMA) copolymers (also known as MPEG-type polycarboxylate ether (PCE) superplasticizers) present comb-shaped microstructure and they are generally used as dispersants of inorganic particles in cementitious formulations. Application properties of the PCEs strongly depend on the molecular structure and therefore accurate characterization of the microstructure is necessary to fully understand the structure–property relationship. In this work, MAA-co-PEGMA copolymers with various lateral size chain lengths and homogeneous copolymer compositions are synthesized by starved-feed semibatch copolymerization. Molar mass and radius of gyration distributions and monomer sequence distribution are measured using size exclusion chromatography coupled with multi angle light scattering (SEC/MALS/refractive index, RI) and 1H and 13C NMR, respectively. Furthermore, it is proved that the experimental radius of gyration compares well with the prediction of a theoretical model for the radius of gyration that uses characteristic parameters of the microstructure of the PCEs (e.g., average molar masses). This confirms the accuracy of the measurements of the absolute molar masses for the MPEG-type PCEs synthesized by free-radical (co)polymerization.Item Correlations between rheological and thermal behaviour of TGDDM/m-PDA epoxy systems(1994-05) Imaz, J. J.; Valea, A.; Cortazar, M.; Mondragon, I.; Centros PRE-FUSION TECNALIA - (FORMER)Isothermal variation of viscosity has been investigated at various temperatures for an epoxy-aromatic amine system (TGDDM/m-PDA system). The variation of the extent of reaction during the curing process has been also determined by means of differential scanning calorimetry. Two different models were used to predict the viscosity during cure: a model based on a modified Williams-Landel-Ferry equation, and a percolation-gelation analogy. This analysis reflects that the reaction mechanism does not change with temperature in the studied range.Item Crystallization behavior of poly(L-lactic acid)-based ecocomposites prepared with kenaf fiber and rice straw(2010-06) Dobreva, T.; Perena, J. M.; Pérez, E.; Benavente, R.; García, M.; Tecnalia Research & InnovationSeveral composites of poly(L-lactic acid) (PLLA) with natural fibers (kenaf and rice straw) and pigments have been prepared and analyzed. The study of the thermal behavior has shown a rather important nucleation ability of these fillers for the crystallization of the PLLA component in the composites. Thus, the cooling from the melt of pure PLLA at 10°C/min leads to an almost completely amorphous sample, while a high crystallinity (around 60%) is exhibited by the sample PLLA and rice straw (PLLA-RS)-yellow under those conditions. The analysis of the isothermal crystallization from the melt indicates that a maximum rate of crystallization is obtained for all the samples at around 105°C, although the rate is three times faster for samples PLLA and kenaf fiber (PLLA-KF), PLLA-KF-red, and PLLA-RS, in comparison with pure PLLA. The rate is increased by another factor of three for sample PLLA-RS-yellow. The analysis of the melting temperatures and crystallinities as a function of the crystallization temperature shows that there is a break at around 115°C, which seems to be related to the formation of ordered crystals at higher temperatures and disordered ones at lower temperatures. Besides, the natural fibers are environmentally friendly and nonexpensive materials, and the higher crystallization rates of the composites will result in shorter production cycles of end-use articles.Item Curing of epoxy/carbon nanotubes physical networks(2012-03) Chapartegui, Maialen; Markaide, Nerea; Florez, Sonia; Elizetxea, Cristina; Fernandez, Mercedes; Santamaria, Anton; POLIMEROSA melt-mixing procedure has been used to disperse multi-walled carbon nanotubes (MWCNT) in an epoxy matrix. According to dynamic viscoelastic results, a physical network is formed for carbon nanotube concentrations of 0.3 weight per cent (wt%) and above. The temperature activated curing process is followed analyzing the evolution of the dynamic viscoelastic functions and the dielectric loss with time. Curing process from a physical to a chemical network is monitored. The presence of MWCNT accelerates curing, even when the rheological percolation is not reached (absence of physical network). Several hypotheses are considered to explain this result. Electrical conductivity decreases during cure, so lower electrical conductivities are found for cured MWCNT/epoxy samples than for dispersions: this is explained by a distortion of nanotubes physical network and a reduction of the ionic conductivity contribution of the liquid phase.Item Definition and assessment of an adhesively bonded composite reinforcement in fatigue for steel structures developped in Fasstbridge project(International Institute for FRP in Construction (IIFC), 2018) Chataigner, S.; Benzarti, K.; Foret, G.; Caron, J. F.; Gemignani, G.; Brugiolo, M.; Birtel, V.; Lehmann, F.; Calderon, I.; Piniero, I.; Ferrier, Emmanuel; Benzarti, Karim; Caron, Jean-Francois; Tecnalia Research & Innovation; E&I SEGURAS Y RESILIENTESOne of the aims of Infravation project called FASSTbridge (Fast and effective Solution for the Strengthening of existing steel bridges) is to develop a specific reinforcement system dedicated to the preventive fatigue reinforcement of steel bridges. The proposed system relies on the use of an adhesively bonded composite plate. The adhesive has been specifically formulated by Collanti Concorde within the project to respect the required fulfillments of the studied application. It is combined with a commercially available composite plate. The communication will first give insight of the required properties of the adhesive, the composite plate, and the overall system for the considered application. Based on these requirements and existing literature and standards on the topic, the chosen experimental plan will be described. It includes investigations on the adhesive before curing, the adhesive after curing, the composite plate, and the whole reinforcing system. Both short term and durability investigations were carried out by the different partners implied within the projects. The obtained results will be presented, and allowed verifying the system properties. The participation of different partners to the experimental campaign also gives insight of the encountered dispersion, and allowed studying different parameters that may affect the capacities. The reinforcement system has been applied on a real bridge in Spain.Item Development of a Novel Biobased Polyurethane Resin System for Structural Composites(2022-10-27) Echeverria-Altuna, Oihane; Ollo, Olatz; Larraza, Izaskun; Elizetxea, Cristina; Harismendy, Isabel; Eceiza, Arantxa; Tecnalia Research & Innovation; POLIMEROSPolyurethanes 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.Item Development of Flame-Retardant Polylactic Acid Formulations for Additive Manufacturing(2024-04) Aguirresarobe, Robert; Calafel, Itxaso; Villanueva, Sara; Sanchez, Alberto; Agirre, Amaia; Sukia, Itxaro; Esnaola, Aritz; Saralegi, Ainara; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNPolymeric materials, renowned for their lightweight attributes and design adaptability, play a pivotal role in augmenting fuel efficiency and cost-effectiveness in railway vehicle development. The tailored formulation of compounds, specifically designed for additive manufacturing, holds significant promise in expanding the use of these materials. This study centers on poly(lactic acid) (PLA), a natural-based biodegradable polymeric material incorporating diverse halogen-free flame retardants (FRs). Our investigation scrutinizes the printability and fire performance of these formulations, aligning with the European railway standard EN 45545-2. The findings underscore that FR in the condensed phase, including ammonium polyphosphate (APP), expandable graphite (EG), and intumescent systems, exhibit superior fire performance. Notably, FR-inducing hydrolytic degradation, such as aluminum hydroxide (ATH) or EG, reduces polymer molecular weight, significantly impacting PLA’s mechanical performance. Achieving a delicate balance between fire resistance and mechanical properties, formulations with APP as the flame retardant emerge as optimal. This research contributes to understanding the fire performance and printability of 3D-printed PLA compounds, offering vital insights for the rail industry’s adoption of polymeric materials.Item Development of self-contained microcapsules for optimised catalyst position in self-healing materials(2020-01-20) Rodriguez, Raquel; Bekas, Dimitrios G.; Flórez, Sonia; Kosarli, Maria; Paipetis, Alkiviadis S.; POLIMEROSSelf-contained microcapsules for use in self-healing epoxy resin are successfully synthesized by suspension polymerization process. The microencapsulation of an epoxy resin using Polymethylmethacrylate (PMMA) as a shell material and the location of scandium triflate (Sc(OTf)3) as the catalyst into microcapsules shell during the microencapsulation processes is presented (PMMA/Sc(OTf)3-walled microcapsules). Spherical microcapsules of 80 μm in diameter with a liquid core content of 30 wt% (determined by HPLC) are produced. Catalyst location on microcapsules are assessed qualitatively by SEM-EADS and quantitatively by TGA showing high yields (⁓70 wt%). The evaluation of the healing efficiency was assessed in terms of fracture toughness recovery. PMMA/Sc(OTf)3-walled microcapsules showed an increased healing efficiency than that of conventional PMMA-walled capsule. The healing efficiency of the PMMA-walled capsules was 46.7 and 55.1% when the system healed at 80 and 120 °C, respectively. However, in the case of PMMA/Sc(OTf)3-walled microcapsules healing efficiency increased to 57.5 and 79.1% for the same healing temperatures.Item Development of unsaturated polyester matrix - Carbon Nanofibers Nanocomposites with Improved Electrical Properties(2010-08-01) Monti, M.; Terenzi, A.; Natali, M.; Gaztelumendi, I.; Markaide, N.; Kenny, J. M.; Torre, L.; POLIMEROSIn this work, the dispersion of carbon nanofibers (CNFs) in an unsaturated polyester (UP) resin was performed by mean of the calendering process. The calendering process allows to obtain good dispersion of the nanoparticles, and, with respect to the other techniques, is also possible to scale it up at the industrial level. Optimization of the calendering conditions for the processing was carried out as a first step of this study. Optimization, in this case, means to reach the best dispersion level, as rapidly as possible and with the lowest amount of styrene evaporation. The dispersion level reached was investigated by the technique of scanning electron microscopy. The investigation on electric conductivity of the nanocomposites at different CNF concentrations has revealed that the electrical percolation threshold exists at around 0.3 wt %, where electrical conductivity switches from 10-13 to 10-7 S/cm. The rheologicalcharacterization has been performed to verify if the improved electrical properties are obtained at the expense of loss of workability, that is a significant increase of viscosity. Eventually, a mechanical characterization was carried out. VC 2010 Wiley Periodicals, Inc.Item Direct Acrylation of Soybean Oil and the Influence of the Acrylation Degree on Waterborne Acrylic Systems(2024-08) Perez, Beatriz; Blanco, Noelia; Villaverde, Haizea; Echeverria, Oihane; Gomez de Miranda, Olga; Rodriguez, Raquel; POLIMEROS; BIOECONOMÍA Y CO2; PRINTEXThe direct acrylation of soybean oil was investigated by the activation of soybean oil’s (SO’s) internal fatty unsaturation with acidic catalysts. The effect of the catalyst and the reactant ratio with respect to the unsaturation and reaction time on the direct acrylation process were explored. ASO (acrylated soybean oil) with acrylation degrees (the number of acrylate molecules introduced in a triglyceride molecule) between 1.6 and 2.55 were obtained. The effect of the ASO acrylation degree on copolymerization processes was investigated. The resulting monomers were successfully copolymerized with meth(acrylate) monomers by the miniemulsion polymerization process, favoring the droplet nucleation mechanism and showing conversions higher than 97%. The acrylic–ASO copolymers presented lower Tg and higher hydrophobicity and oleophobicity than the acrylic copolymer.Item Effect of aryl phosphates on toxicity of combustion gases of flame‐retardant polycarbonate/acrylonitrile butadiene styrene blends according to EN 45545 railway standard(2022-03-09) Sánchez, Alberto; Villanueva, Sara; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNIn this study, the toxicity of combustion gases of polycarbonate/acrylonitrile butadiene styrene (ABS) blends that include aryl phosphates as flame-retardants (FRs) was analyzed according to the European railway standard EN 45545-2 (NBS chamber + FTIR). FRs have a significant influence on the evolution of the toxicity of gases generated during the combustion process. In the experiment, the asphyxiant hydrogen cyanide (HCN) was detected at the beginning of combustion (4 min of testing) as a product of ABS degradation. CO was generated throughout the test (8 min) because of the incomplete combustion of both the ABS and PC fractions. The presence of aryl phosphates promoted the inhibition of the flame. The reaction of PO radicals in the gas phase resulted in OH scavenging and a higher release of HCN and CO. The results suggest that aryl phosphates act in the first 4 min and do not have an effect later. FRs with lower thermal stability exhibited lower heat release and flame propagation but generated more toxic gases. This effect is attributed to the higher activity of the flame-retardant in the gas phase. Further, additional fire performance parameters, including thermal stability (thermogravimetric analysis), flammability (UL94), and heat and smoke generation (cone calorimeter), were studied. It was found that aryl phosphates reduced the fire hazard, prevented the spread of the flame, reduced heat generation, increased the time to ignition, and, at the same time, promoted the emission of toxic gases that differ in function of the selected flame-retardantItem Effect of Cellulose Nanofibers’ Structure and Incorporation Route in Waterborne Polyurethane–Urea Based Nanocomposite Inks(2022-11) Larraza, Izaskun; Vadillo, Julen; Calvo-Correas, Tamara; Tejado, Alvaro; Martin, Loli; Arbelaiz, Aitor; Eceiza, Arantxa; BIOECONOMÍA Y CO2In 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.Item Effect of different thermal treatments on the mechanical performance of poly(L-lactic acid) based eco-composites(2010-04-15) Dobreva, T.; Benavente, R.; Pereña, J. M.; Pérez, E.; Avella, M.; García, M.; Bogoeva-Gaceva, G.; Tecnalia Research & InnovationPLLA-based eco-composites reinforced with kenaf fiber and rice straw and containing red or yellow pigments have been studied. The mechanical behavior of the composites was tested by DMTA at two different annealing temperatures (65°C and 85°C) and times (15 min and 120 min) as well as at two preparation conditions: vacuum drying and long time at room temperature. A decrease of microhardness was observed during the water absorption tests. Moreover, the rice straw-based composites absorbed more water than the kenaf-ones. Generally, the dyed NFs composites presented better water resistance than undyed ones. The pigments improved the adhesion and led to better mechanical performance. The natural fibers favored the cold crystallization process of PLLA and shifted the cold crystallization peak temperature to lower values, as it was confirmed by DSC measurements. The values of tensile storage modulus obtained after different preparation condition were strongly affected by the process of physical ageing. According to, tan d parameter, the samples stored at room temperature for a long time showed the highest amorphous content. The PLLA eco-composite reinforced with kenaf fibers, dyed with the red pigment, and annealed at 85°C for 2 h displays the best mechanical properties.Item Effect of Different Types of Electrospun Polyamide 6 Nanofibres on the Mechanical Properties of Carbon Fibre/Epoxy Composites(2018-10-25) Monteserín, Cristina; Blanco, Miren; Murillo, Nieves; Pérez-Márquez, Ana; Maudes, Jon; Gayoso, Jorge; Laza, Jose; Aranzabe, Estíbaliz; Vilas, Jose; Tecnalia Research & Innovation; PRINTEX; Caracterización y Validación. MecánicosDelamination and brittle matrix fracture have long since been the biggest problems in fibre-reinforced composites. Recently, the incorporation of electrospun nanofibre veils has been shown to be an effective method for improving the mechanical properties of these composites, without causing process problems and negatively affecting other mechanical properties. Thus, these nanofibres have the potential to be used as thickness-reinforcing materials in composites. This paper investigates the effect of incorporating standalone electrospun nanofibre veils made of two different types of polyamide 6 (PA6) on the mechanical properties of carbon fibre/epoxy composites. The influence of positioning the electrospun veils at different interlaminar positions of the laminate has also been investigated.Item Effect of enzyme lignin oxidation by laccase on the enzymatic-mechanical production process of lignocellulose nanofibrils from mechanical pulp(2024-04) Henríquez-Gallegos, Sergio; Albornoz-Palma, Gregory; Andrade, Andrea; Filgueira, Daniel; Méndez-Miranda, Alejandro; Teixeira Mendonça, Regis; Pereira, Miguel; BIOECONOMÍA Y CO2The use of endoglucanase enzymes as pretreatment of high-yield pulps to produce lignocellulose nanofibrils (LCNFs) has garnered increasing interest at both industrial and scientific levels. However, the lignin present in the lignocellulosic fibers hinders the enzymatic treatment reducing the efficiency of the further fibrillation process. This work postulates that modifying the structure of the residual lignin in the pulp can help to improve LCNF production. Laccase-mediator system (LMS) was evaluated to promote lignin oxidation of pressurized groundwood pulp from Pinus radiata previous to a treatment with endoglucanases and mechanical refining to produce LCNFs. As a result, it was observed that the LMS treatment improved the accessibility of the endoglucanase enzyme in the fibers, increasing their efficiency. Furthermore, it was observed a reduction in residual lignin and an increment in acidic groups in the LMS treated pulps facilitated the mechanical fibrillation process, enabling the production of LCNFs with a high aspect ratio. It was also observed that the pulps treated with a laccase-endoglucanase combination allowed to production of LCNF suspensions with zeta potential values sufficient for the nanofibrils not to form aggregates and to be considered stable (< − 25 mV).