Desarrollo y caracterización de biocomposites enfibrados procedentes de recursos renovables. Estudio de su degradación en tierra

El propósito de la presente Tesis Doctoral es estudiar y predecir las características y la biodegradabilidad de diferentes biocomposites desarrollados a partir de materiales biodegradables procedentes de fuentes renovables. Para ello, se emplean dos termoplásticos de base almidón como matrices poliméricas (Mater-Bi KE03B1 y Mater-Bi NF01U ), que se refuerzan con distintas fibras naturales (algodón, cáñamo, kenaf, lino y yute) con el fin de mejorar sus propiedades mientras están en servicio, al tiempo que se mantiene su biodegradabilidad. Las fibras naturales, las matrices poliméricas y los biocomposites reforzados se caracterizan con el objetivo de estudiar de la influencia de cada fibra natural en las propiedades de la matriz polimérica. Para ello se emplea una metodología basada en el Análisis Espectroscópico (FTIR-ATR), Mecánico (Ensayos de Tensión), Morfológico (SEM) y Térmico (DMTA, TGA, DSC). Así mismo se establecen correlaciones entre la composición química de las fibras naturales y las propiedades de los biocomposites reforzados. La degradabilidad de las matrices poliméricas y de los biocomposites se evalúa mediante enasayos de degradación en tierra y de absorción en agua. La hidrólisis de las matrices poliméricas y de los biocomposites se estudia como étapa previa a su biodegradación en tierra. Ambos procesos, la degradación en tierra y la absorción de agua se monitorizan mediante cambios en las propiedades térmicas. En particular, los parámetros térmicos de control escogidos son: las temperaturas de inicio y máxima velocidad de termodegradación como marcador de la estabilidad térmica; y las energías de activación de cada proceso de descomposición, puesto que este parámetro permite discernir los cambios en los entornos moleculares que facilitan o dificultan el proceso de termodegradación. Estos estudios de degradación, se complementan con análisis morfológicos y espectroscópicos. Finalmente, se confirma que el Mater-Bi NF y el Mater-Bi KE aumentan sus aplicaciones cuando se refuerzan con fibras naturales al mismo tiempo que mantienen su capacidad para degradarse en el momento en el que finaliza su vida útil. En el diseño del biocomposite, la selección de una u otra fibra natural como material de refuerzo dependerá de las propiedades finales requeridas.Moriana Torró, R. (2010). Desarrollo y caracterización de biocomposites enfibrados procedentes de recursos renovables. Estudio de su degradación en tierra [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/8958Palanci

Thermal analysis applied to the characterization of degradation in soil of polylactide: I. Calorimetric and viscoelastic analyses

An accelerated soil burial test has been performed on a commercial polylactide (PLA) for simulating non-controlled disposal. Degradation in soil promotes physical and chemical changes in polylactide properties, which can be characterized by Thermal Analysis techniques. Physical changes occurred in polylactide due to the degradation in soil were evaluated by correlating their calorimetric and viscoelastic properties. It is highly remarkable that each calorimetric scan offers specific and enlightening information. Degradation in soil affects the polylactide chains reorganization. A multimodal melting behavior is observed for buried PLA, degradation in soil also promotes the enlarging the lamellar thickness distribution of the population with bigger average size. Morphological changes due to degradation in soil lead to an increase in the free volume of the polylactide chains in the amorphous phase that highly affected the bulk properties. Thermal Analysis techniques provide reliable indicators of the degradation stage of polylactide induced by degradation in soil, as corroborated by molecular weight analysis

Reinforcing capability of cellulose nanocrystals obtained from pine cones in a biodegradable poly(3-hydroxybutyrate)/poly(e-caprolactone) (PHB/PCL) thermoplastic blend

[EN] In this work, different loads (3, 5 and 7 wt%) of pine cone cellulose nanocrystals (CNCs) were added to films of poly(3-hydroxybutyrate)/poly(epsilon-caprolactone) (PHB/PCL) blends with a composition of 75 wt% PHB and 25 wt % PCL (PHB75/PCL25). The films were obtained after solvent casting followed by melt compounding in an extruder and finally subjected to a thermocompression process. The influence of different CNCs loadings on the mechanical, thermal, optical, wettability and disintegration in controlled compost properties of the PHB75/PCL25 blend was discussed. Field emission scanning electron microscopy (FESEM) revealed the best dispersion of CNCs on the polymeric matrix was at a load of 3 wt%. Over this loading, CNCs aggregates were formed enhancing the films fragilization due to stress concentration phenomena. However, the addition of CNCs improved the optical properties of the PHB75/PCL25 films by increasing their transparency and accelerated the film disintegration in controlled soil conditions. In general, the blend with 3 wt% CNCs offers the best balanced properties in terms of mechanical, thermal, optical and wettability.This research was supported by the Ministry of Economy and Competitiveness MINECO through the gran number MAT2014-59242-C2-1-R. D. Garcia-Garcia wants to thank the Spanish Ministry of Education, Culture and Sports for the financial support through a FPU grant number FPU13/06011.Garcia-Garcia, D.; Balart, R.; Strömberg, E.; Moriana, R. (2018). Reinforcing capability of cellulose nanocrystals obtained from pine cones in a biodegradable poly(3-hydroxybutyrate)/poly(e-caprolactone) (PHB/PCL) thermoplastic blend. European Polymer Journal. 104:10-18. https://doi.org/10.1016/j.eurpolymj.2018.04.036S101810

Thermal analysis applied to the characterization of degradation in soil of polylactide: II. On the thermal stability and thermal decomposition kinetics

The disposal stage of polylactide (PLA) was assessed by burying it in active soil following an international standard. Degradation in soil promotes physical and chemical changes in the polylactide properties. The characterization of the extent of degradation underwent by PLA was carried out by using Thermal Analysis techniques. In this paper, studies on the thermal stability and the thermal decomposition kinetics were performed in order to assess the degradation process of a commercial PLA submitted to an accelerated soil burial test by means of multi-linear-non-isothermal thermogravimetric analyses. Results have been correlated to changes in molecular weight, showing the same evolution as that described by the parameters of thermal stability temperatures and apparent activation energies. The decomposition reactions can be described by two competitive different mechanisms: Nucleation model (A2) and Reaction Contracting Volume model (R3). The changes in the kinetic parameters and kinetic models are in agreement with the calorimetric and dynamic-mechanical-thermal results, presented in the Part I of the study

Optimizing the yield and physico-chemical properties of pine cone cellulose nanocrystals by different hydrolysis time

[EN] Cellulose nanocrystals (CNCs) were isolated for the first time from pine cones (PC) by alkali and bleaching treatments and subsequent sulfuric acid hydrolysis (64 %) at 45 ºC. The influence of the hydrolytic reaction time (30, 45 and 90 min) on the yield, chemical composition and structure, and thermal stability of CNCs was evaluated. The removal of non-cellulosic constituents during the alkaline and bleaching treatment resulted in high pure cellulosic fibres. The isolation of CNCs from these cellulosic fibres at different reaction times was verified by the nano-dimensions of the individual crystals (< 3 and <335 nm of average diameter and length, respectively). The highest yield (15%) and the optimum CNCs properties in terms of aspect ratio, thermal stability and crystallinity were obtained for an extraction time of 45 min. PC appeared to be a new promising source of cellulose fibres and CNCs with potential to be applied as reinforcement in composites and for food-packaging.This work was supported by the Ministry of Economy and Competitiveness (MINECO) [MAT2014-59242-C2-1-R]. D. García-García wants to thanks the Spanish Ministry of Education, Culture and Sports for their financial support through an FPU Grant [FPU13/06011].Garcia-Garcia, D.; Balart, R.; López-Martínez, J.; Ek, M.; Moriana, R. (2018). Optimizing the yield and physico-chemical properties of pine cone cellulose nanocrystals by different hydrolysis time. Cellulose. 25(5):2925-2938. https://doi.org/10.1007/s10570-018-1760-0S2925293825

Improved Mechanical, Thermal, and Hydrophobic Properties of PLA Modified with Alkoxysilanes by Reactive Extrusion Process

[EN] An eco-friendly strategy for the modification of polylactic acid (PLA) surface properties, using a solvent-free process, is reported. Reactive extrusion (REX) allowed the formation of new covalent bonds between functional molecules and the PLA polymeric matrix, enhancing its mechanical properties and modifying surface hydrophobicity. To this end, the PLA backbone was modified using two alkoxysilanes, phenyltriethoxysilane and N-octyltriethoxysilane. The reactive extrusion process was carried out under mild conditions, using melting temperatures between 150 and 180 degrees C, 300 rpm as screw speed, and a feeding rate of 3 kg center dot h(-1). To complete the study, flat tapes of neat and functionalized PLA were obtained through monofilament melt extrusion to quantify the enhancement of mechanical properties and hydrophobicity. The results verified that PLA modified with 3 wt% of N-octyltriethoxysilane improves mechanical and thermal properties, reaching Young's modulus values of 4.8 GPa, and PLA hydrophobic behavior, with values of water contact angle shifting from 68.6 degrees to 82.2 degrees.This research work was funded by the Conselleria d'Economia Sostenible, Sectors Productius, Comerc i Treball de la Generalitat Valenciana through IVACE. Project references: GREENFILS, IMAMCI/2019/1 and BIOREX, IMAMCI/2020/1.Torres, E.; Gaona, A.; García-Bosch, N.; Muñoz, M.; Fombuena, V.; Moriana, R.; Vallés Lluch, A. (2021). Improved Mechanical, Thermal, and Hydrophobic Properties of PLA Modified with Alkoxysilanes by Reactive Extrusion Process. Polymers. 13(15):1-16. https://doi.org/10.3390/polym13152475S116131

Antioxidant and antibacterial effects of natural phenolic compounds on green composite materials

[EN] The aim of this study is to establish the thermal performance of a biocomposite (Arbofill kokos (R)), stabilized with different natural phenolic additives, to check the antioxidant capacity of the resulting compounds. Different phenolic compounds (thymol, carvacrol, a-tocopherol, and tannic acid) were used as biobased additives and the concentrations ranged between 0.5 wt% and 2 wt%. The results obtained were compared with formulations containing a typical industrial petroleum-based antioxidant agent (octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate). Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the antioxidant performance of the selected natural additives. The antimicrobial effect of these natural phenolic compounds was also studied by analyzing the growth of bacterial colonies. The comparison between the natural phenolic compounds and the petroleum-based antioxidant compound showed good antioxidant action for natural phenolic compounds; in all the mixtures of biocomposite and antioxidant agent the oxidation onset temperature (OOT) increased in a remarkable way, but the highest stabilization effect was achieved with a-tocopherol with provides a % increase on OOT of about 45%. With regard to antibacterial activity of the different natural phenolic compounds, thymol, and carvacrol showed interesting antibacterial properties against Staphylococcus aureus. POLYM. COMPOS., 2012. (c) 2012 Society of Plastics EngineersThis work is part of the project IPT-310000-2010-037, "ECOTEXCOMP: Research and development of textile structures useful as reinforcement of composite materials with marked ecological character" funded by the "Ministerio de Ciencia e Innovacion," with an aid of 189540.20 euros, within the "Plan Nacional de Investigacion Cientifica, Desarrollo e InnovacionTecnologica 2008-2011" and funded by the European Union through FEDER funds, Technology Fund 2007-2013, Operational Programme on R+D+i for and on behalf of the companies." Also, Generalitat Valenciana Ref: ACOMP/2012/087 is acknowledged for financial support. J.M. Espana thanks to the Universitat Politecnica de Valencia (UPV) its financial support through an FPI-UPV grant.España Giner, JM.; Fages, E.; Moriana Torró, R.; Boronat Vitoria, T.; Balart Gimeno, RA. (2012). Antioxidant and antibacterial effects of natural phenolic compounds on green composite materials. Polymer Composites. 33(8):1288-1294. https://doi.org/10.1002/pc.22254S1288129433

Integral Fractionation of Rice Husks into Bioactive Arabinoxylans, Cellulose Nanocrystals, and Silica Particles

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Sustainable Chemistry & Engineering, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acssuschemeng.8b06692[EN] Rice husk is an important agricultural byproduct that has not been exploited yet to full capacity for advanced applications. The feasibility of obtaining high-value products such as bioactive hemicelluloses and cellulose nanocrystals (CNCs) from rice husk is here demonstrated in a cascade biorefinery process using subcritical water extraction (SWE) prior to bleaching and acid hydrolysis and compared to traditional alkali pretreatments. The proposed SWE process enables the isolation of bioactive arabinoxylans with phenolic acid moieties, thus preserving their antioxidant and antibacterial properties that are lost during alkaline conditions. Additionally, SWE can be combined with subsequent bleaching and acid hydrolysis to obtain CNCs with large aspect ratio, high crystallinity, and thermal stability. The hydrothermal process also enables the recovery of silica particles that are lost during the alkali step but can be recovered after the isolation of the CNCs. Our biorefinery strategy results in the integral valorization of rice husk into their molecular components (bioactive arabinoxylans, cellulose nanocrystals, and silica particles), which can be used as additives for food applications and as reinforcing agents in biocomposite materials, respectively.The authors thank the Ministerio de Economía y Competitividad (Spain) for the financial support provided through Project AGL2016-76699-R. Author Raquel Requena thanks the Ministry of Education, Culture and Sport (Spain) for the FPU (FPU13/03444) Grant. This research work was also financed with a Short Term Scientific Mission of the COST Action FP1405.Requena-Peris, R.; Jiménez Quero, A.; Vargas, M.; Moriana Torró, R.; Chiralt A.; Vilaplana Domingo, FJ. (2019). Integral Fractionation of Rice Husks into Bioactive Arabinoxylans, Cellulose Nanocrystals, and Silica Particles. ACS Sustainable Chemistry & Engineering. 7(6):6275-6286. https://doi.org/10.1021/acssuschemeng.8b06692S627562867

The effect of pine cone lignin on mechanical, thermal and barrier properties of faba bean protein films for packaging applications

In the present work, faba bean protein (FBP) films plasticized with glycerol and reinforced with different amounts (2.5, 5.0, 7.5 and 10% by weight of FBP) of lignin extracted from pine cones (PL) have been obtained by solution casting. The results obtained showed an elongation at break of 111.7% with the addition of 5% PL to the FBP film, which represents an increase of 107% compared to the FBP control film. On the other hand, it was observed by thermogravimetric analysis (TGA) that the incorporation of lignin improved the thermal stability of the FBP film, leading to an increase in the protein degradation temperature, being this increase higher in the sample film reinforced with 10% PL. The barrier properties of the FBP films were also affected by the presence of lignin, leading to a decrease in water vapor permeability (WVP) in comparison to the unreinforced film. The results show that the sample reinforced with 2.5% PL had the lowest WVP value, with a reduction of 25% compared to the control film. Chemical analysis by Fourier transform infrared spectroscopy (FTIR) confirmed the formation of intramolecular interactions between lignin and proteins which, together with the inherent hydrophobicity of lignin, resulted in a decrease of the moisture content in the films reinforced with PL. This research work has allowed the development of biobased and biodegradable films with attractive properties that could be of potential use in sectors such as packaging

Effect of starch and fibre on faba bean protein gel characteristics

Faba bean is a promising alternative to soybean for production of protein-rich plant-based foods. Increased understanding of the gelling behaviour of non-soy legumes can facilitate development of novel plant-based foods based on other legumes, such as faba bean. A mixture design was used in this study to evaluate the effect of different proportions of protein, starch and fibre fractions extracted from faba beans on gelation properties, texture and microstructure of the resulting gels. Large deformation properties, in terms of fracture stress and fracture strain, decreased as fibre and/or starch replaced protein. In contrast, Young\u27s modulus and storage modulus increased with substitution of the protein. Light microscopy revealed that for all gels, protein remained the continuous phase within the region studied (65–100% protein fraction, 0–35% starch fraction, 0–10% fibre fraction in total flour added). Swollen and deformed starch granules were distributed throughout the mixed gels with added starch. Leaked amylose aggregated on starch and fibre surfaces and in small cavities (&lt;1 μm) throughout the protein network. No clear difference between samples in protein network structure was observed by scanning electron microscopy. The reduction in large deformation properties was tentatively attributed to inhomogeneities created by the added starch and fibre. The increase in small deformation properties was hypothesised to be affected by water adsorption and moisture stability through the starch and fibre, increasing the effective protein concentration in the surrounding matrix and enhancing the protein network, or potentially by starch granules and fibre particles acting as active fillers reinforcing the gel structure