Diseño y caracterización de nuevos materiales compuestos polipropileno y madera: estudio del viniltrimetoxisilano como agente de acoplamiento

[Resumen] El objetivo principal es el estudio de las relaciones entre la estructura, el procesado, las propiedades mecánicas y la morfología de nuevos materiales compuestos polipropileno y madera. Incidiendo en la influencia de un nuevo agente de acoplamiento de tipo silano (viniltrimetoxisilano) y de determinados aditivos. Se selecciona la mejor formulación para la obtención de materiales compuestos, que con el aspecto de la madera, puedan emplearse en aplicaciones de exterior

Influence of the Hydrophilicity of Montmorillonite on Structure and Properties of Thermoplastic Wheat Starch/Montmorillonite Bionanocomposites

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] The increasing environmental pollution with petroleum-based plastics has advanced research on biodegradable polymers. Thermoplastic starch (TPS) is one promising candidate due to wide availability from various renewable sources, low cost and biodegradability. However, TPS has significant shortcomings, as high water sensitivity and low mechanical properties. An approach to overcome these drawbacks is adding nanofillers as reinforcement of the starch matrix. Among the nanofillers, montmorillonite clays have the advantages of a wide availability, low cost, versatility and environmental friendliness. Bionanocomposites based on wheat starch plasticized with glycerol and reinforced with three types of montmorillonite nanoclays, one natural (Cloisite Na+) and two organomodified (Cloisite 30B and Cloisite 10A), were prepared by melt processing. The effect of nanoclay type and amount on processing properties, thermal stability, dynamic mechanical properties and water absorption was widely investigated. The properties strongly depended on the dispersion state of the nanoclay in the TPS matrix. The dispersion improved with the hydrophilicity of the nanoclay. Cloisite Na+, the most hydrophilic nanoclay, was the most effective in reinforcing TPS, improving the thermal stability and the dynamic mechanical properties, and showing a greater resistance to water absorption in normal humidity environments. Bionanocomposites of TPS andCloisite Na+ can be a good alternative for use in packaging applications.Xunta de Galicia; ED431C 2019/1

Comportamiento de cristalización y fusión en compuestos de polipropileno y derivados de madera

[Resumen] Se ha analizado el comportamiento de cristalización bajo condiciones dinámicas e isotermas, y de fusión, del polipropileno isotáctico, iPP, como matriz semicristalina en compuestos binarios con polvo de madera, WF, a composiciones del 20% en peso de refuerzo vegetal, iPP/WF 80/20, y ternarios, iPP/WF/I, mediante la incorporación de un agente de interfase basado en un copolímero de etileno/ácido metacrílico, preparados mediante mezclado en fundido en extrusora de doble husillo. Tanto en el compuesto binario como en los compatibilizados o ternarios, el iPP presenta el polimorfo cristalino monoclínico α, independientemente de si la cristalización se realiza en condiciones dinámicas desde el fundido a velocidades de enfriamiento entre 1 y 20 grado.min-1, o en condiciones isotermas. La presencia del componente vegetal induce un ligero efecto nucleante sobre la cristalización isoterma del iPP, que se manifiesta en una disminución de las energías libres interfaciales basales y de la energía libre de nucleación y, por lo tanto, en un aumento de la velocidad global de cristalización. Por el contrario, la incorporación del agente de interfase, genera un fenómeno de compatibilización que se traduce en una disminución de la temperatura de cristalización del iPP, en un aumento de las energías libres interfaciales basales respecto del compuesto binario y, por lo tanto, en una reducción de la velocidad global de cristalización. Tanto en el caso del compuesto binario como en los ternarios, el comportamiento de fusión del iPP es función del subenfriamiento del sistema y no se ve prácticamente alterado por la presencia de la carga vegetal y del agente de interfase

Preparation and Characterization of Bionanocomposite Films Based on Wheat Starch and Reinforced With Cellulose Nanocrystals

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] In recent times, the attention of scientific community has been focusing on the replacement of petroleum-based polymers by others more environmentally friendly. In this sense, bionanocomposites based on glycerol-plasticized wheat starch and reinforced with cellulose nanocrystals (CNCs) were prepared by a solvent-casting process to obtain environmentally friendly films. The plasticization process was proven to be complete in the conditions used and no residual crystallinity was observed in any case. The incorporation of CNCs leads to materials with increased rigidity (about 1000% increment in modulus) which is related to a good filler-matrix interaction and to the formation of a rigid crystalline network of cellulose. This fact allowed also to improve the moisture resistance and the barrier properties (in both, oxygen and water vapor as permeant) of the bionanocomposite films due to the formation of a tortuous path, which prevent the gas diffusion. Moreover, the thermal stability of films was not affected by the filler incorporation. These improvements in the properties make these films susceptible to be used in short-time applications in the food packaging industry.Xunta de Galicia; ED431C 2019/17The research leading to these results received funding from the Xunta de Galicia Government: program of consolidation and structuring competitive research units [Grant number: ED431C 2019/17]. Funding for open access charge was provided by Universidade da Coruña/CISUG

Effect of different plasticizers on thermal, crystalline, and permeability properties of Poly(3–hydroxybutyrate–co-3–hydroxyhexanoate)films

Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) films were prepared using a cast film technique. Dioxane was chosen over other polymer solvents as it resulted in homogenous films with better morphology. Several plasticizers with different molecular weights and concentrations were added to the biopolymer solution prior to casting. Thermal, crystalline, and permeability properties were analyzed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and both water vapor and oxygen transmission rate analysis. In general, the addition of plasticizers decreased the glass transition temperature (Tg), cold crystallization temperatures (Tcc), melting temperatures, as well as crystallinity degrees and increased the crystallite sizes and water vapor and oxygen transmission rates. The use of isosorbide and low-molecularweight poly(ethylene glycol) (PEG) lowered the Tg around 30 C at the highest used concentration, also being the most effective in increasing the crystallite size. When considering isosorbide and low-molecular-weight poly(ethylene glycol) (PEG) as very good plasticizers for PHBH, the question of which plasticizer to use strongly relies on the desired PHBH application.Xunta de Galicia; GPC IN607B2019/10Xunta de Galicia; ED431C 2019/1

Preparation of Poly(vinyl Alcohol) Microparticles for Freeze Protection of Sensitive Fruit Crops

[Abstract] Poly(vinyl alcohol) (PVA) displays ice recrystallization inhibition (IRI) properties as many antifreeze proteins found in cold tolerant organisms. The molecular architecture and composition (molecular weight and distribution of pendant OH and acetate groups) have been studied to improve the antifreezing properties of PVA, suggesting that the molecular architecture of PVA plays an important role in IRI activity. The present work deals with the preparation of PVA microparticles using an alkaline treatment. The effect of PVA molecular weight on the morphology and antifreezeing properties of PVA microparticles was investigated. The antifreezeing property of PVA microparticles on the susceptibility of flower bud tissues to freeze damage was also evaluated. The alkaline treatment of an aqueous PVA solution produced stable polymer chain aggregates with spherical shapes. The average size of the PVA microparticles increased significantly with the increasing molecular weight of the PVA macromolecule precursor. The PVA microparticles inhibited the growth of ice crystals and blocked ice growth at concentrations as low as 0.01 % w/v. The effect of impeding ice crystal growth by preventing the joining of adjacent ice crystals is attributed to the larger size of the PVA particles adsorbed on the ice surface compared to the aggregated PVA macromolecules in saline solution. The thermal hysteresis activity of PVA macromolecules and microparticles was not detected by differential scanning calorimetry analysis. The PVA microparticles reduced the incidence of freeze injuries in flower bud tissues by 55% and their application, considering the low toxicity of PVA, has a high potential for freeze protection in fruit crops.Chile. Comisión Nacional de Investigación Científica y Tecnológica; ID16I10425Chile. Comisión Nacional de Investigación Científica y Tecnológica; ID16I20425Chile. Gobierno Regional del Biobío; R17A10003Chile. Agencia Nacional de Investigación y Desarrollo; ACE210016Chile. Agencia Nacional de Investigación y Desarrollo; ACE210012Chile. Comisión Nacional de Investigación Científica y Tecnológica; AFB170007This research was funded by projects CONICYT + FONDEF/tercer concurso IDeA en Dos Etapas del Fondo al Desarrollo Científico Y Tecnológico, FONDEF/CONICYT 2016 [grant numbers ID16I10425 and ID16I20425], CIPA, ANID Regional, GORE BIO BIO [grant number: R17A10003], ANID [grant numbers: ACE210016 and ACE210012] and CONICYT PIA/APOYO CCTE [grant number: AFB170007

Overexpression of ZePrx in Nicotiana Tabacum Affects Lignin Biosynthesis Without Altering Redox Homeostasis

[Abstract] Class III plant peroxidases (Prxs) are involved in the oxidative polymerization of lignins. Zinnia elegans Jacq. Basic peroxidase (ZePrx) has been previously characterized as capable of catalyzing this reaction in vitro and the role in lignin biosynthesis of several of its Arabidopsis thaliana homologous has been previously confirmed. In the present work, ZePrx was overexpressed in Nicotiana tabacum to further characterize its function in planta with particular attention to its involvement in lignin biosynthesis. Since Prxs are known to alter ROS levels by using them as electron acceptor or producing them in their catalytic activity, the impact of this overexpression in redox homeostasis was studied by analyzing the metabolites and enzymes of the ascorbate-glutathione cycle. In relation to the modification induced by ZePrx overexpression in lignin composition and cellular metabolism, the carbohydrate composition of the cell wall as well as overall gene expression through RNA-Seq were analyzed. The obtained results indicate that the overexpression of ZePrx caused an increase in syringyl lignin in cell wall stems, suggesting that ZePrx is relevant for the oxidation of sinapyl alcohol during lignin biosynthesis, coherently with its S-peroxidase nature. The increase in the glucose content of the cell wall and the reduction of the expression of several genes involved in secondary cell wall biosynthesis suggests the occurrence of a possible compensatory response to maintain cell wall properties. The perturbation of cellular redox homeostasis occurring as a consequence of ZePrx overexpression was kept under control by an increase in APX activity and a reduction in ascorbate redox state. In conclusion, our results confirm the role of ZePrx in lignin biosynthesis and highlight that its activity alters cellular pathways putatively aimed at maintaining redox homeostasis.Xunta de Galicia; ED431C 2018/57AG-U held an FPU grant from MECD (Spain) (FPU13/04835). This research was possible thanks to the funding of Xunta de Galicia (Spain) (ED431C 2018/57

Injectable hybrid hydrogels physically crosslinked based on carrageenan and green graphene for tissue repair

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] Injectable and biocompatible novel hybrid hydrogels based on physically crosslinked natural biopolymers and green graphene for potential use in tissue engineering are reported. Kappa and iota carrageenan, locust bean gum and gelatin are used as biopolymeric matrix. The effect of green graphene content on the swelling behavior, mechanical properties and biocompatibility of the hybrid hydrogels is investigated. The hybrid hydrogels present a porous network with three-dimensionally interconnected microstructures, with lower pore size than that of the hydrogel without graphene. The addition of graphene into the biopolymeric network improves the stability and the mechanical properties of the hydrogels in phosphate buffer saline solution at 37 °C without noticeable change in the injectability. The mechanical properties of the hybrid hydrogels were enhanced by varying the dosage of graphene between 0.025 and 0.075 w/v%. In this range, the hybrid hydrogels preserve their integrity during mechanical test and recover the initial shape after removing the applied stress. Meanwhile, hybrid hydrogels with graphene content of up to 0.05 w/v% exhibit good biocompatibility for 3T3-L1 fibroblasts; the cells proliferate inside the gel structure and show higher spreading after 48 h. These injectable hybrid hydrogels with graphene have promising future as materials for tissue repair.Xunta de Galicia; ED431C 2019/17Instituto de Salud Carlos III; CD21/00042Chile. CORFO; 22CVID-20683

Improvement of Endothelial Function by Gunnera Tinctoria Extract With Antioxidant Properties

[Abstract] Background: Gunnera tinctoria has been collected by Mapuche-Pewenche people for food and medicinal purposes. The high polyphenol content of methanolic extract from G. tinctoria leaves with chemical constituents such as ellagic acid and quercetin derivatives suggests its application to prevent endothelial dysfunction and oxidative stress. The aim of this study was to provide evidence of the protective effect of this extract on endothelial function by reducing oxidative stress induced by high D-glucose and H2O2, as well as by stimulating nitric oxide (NO) levels in human umbilical vein endothelial cells (HUVECs). Results: A methanolic extract with a high content of polyphenols (520 ± 30 mg gallic acid equivalents/g dry extract) was obtained from G. tinctoria leaves. Its main constituent was ellagic acid. The results of Ferric reducing antioxidant power and 2,2-diphenyl-1-picrylhydrazyl radical scavenging assays of the extract confirmed its antioxidant activity by inhibition pathway of radical species. The incubation of HUVECs with the extract decreased the apoptosis and reactive oxygen species (ROS) synthesis induced by high extracellular concentration of D-glucose or hydrogen peroxide. The extract increased endothelial NO levels and reduced vasoconstriction in human placental vessels. Conclusions: This study provides evidence about the antioxidant and endothelial protective properties of methanolic G. tinctoria leaf extract. The extract improves the availability of NO in HUVECs, inhibiting the production of ROS and vasoconstriction.Comisión Nacional de Investigación Científica y Tecnológica (Chile); 1191651InnovaChile; 13IDL223120Gobierno Regional del Biobío (Chile); R17A10003Comisión Nacional de Investigación Científica y Tecnológica (Chile); AFB170007Comisión Nacional de Investigación Científica y Tecnológica (Chile); EQM150025Comisión Nacional de Investigación Científica y Tecnológica (Chile); AFB170007Universidad de Concepción (Chile); VRID-Asociativo 213.A84.014-1.0Universidad de Concepción (Chile); VRID-Asociativo 217.033.110-1.0Universidad de Concepción (Chile); VRID-Enlace 216.033.108-1.0This work has been financed by Fondecyt Regular [Grant Number 1191651], InnovaChile [Grant Number 13IDL223120], CIPA, CONICYT Regional, GORE BIO BIO [Grant Number R17A10003], CONICYT PIA/APOYO CCTE [Grant Number AFB170007], Fondequip [Grant Numbers EQM150025 and AFB170007] and Universidad de Concepción, Chile [Grant Numbers VRID-Asociativo 213.A84.014-1.0, VRID-Asociativo 217.033.110-1.0, VRID-Enlace 216.033.108-1.0

Measurement of t(t)over-bar normalised multi-differential cross sections in pp collisions at root s=13 TeV, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

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