L'Energia en context

Presentem el material didàctic L'energia en context, un projecte elaborat i experimentat pel grup de treball Scientia Omnibus, un equip de professors/es de secundària de diverses especialitats de ciències. Consta de 3 unitats didàctiques amb un enfoc CTS (ciència - tecnologia - societat) adreçades a alumnat del segon cicle d'ESO que tracten els continguts curriculars relacionats amb l'energia. L'elecció d'aquest tema com a eix vertebrador de tot el projecte s'ha realitzat per la rellevància social i personal que té a la nostra societat. Les estratègies didàctiques clau del projecte són la contextualització de la ciència escolar i el treball cooperatiu. També fomenta la interacció social i l'autonomia d'aprenentatge de l'alumnat, utilitzant diversos tipus d'activitats (estudis de casos, recerques, problemes, etc.)

L'Energia en context

Presentem el material didàctic L’energia en context, un projecte elaborat i experimentat pel grup de treball Scientia Omnibus, un equip de professors/es de secundària de diverses especialitats de ciències. Consta de 3 unitats didàctiques amb un enfoc CTS (ciència – tecnologia – societat) adreçades a alumnat del segon cicle d’ESO que tracten els continguts curriculars relacionats amb l’energia. L’elecció d’aquest tema com a eix vertebrador de tot el projecte s’ha realitzat per la rellevància social i personal que té a la nostra societat. Les estratègies didàctiques clau del projecte són la contextualització de la ciència escolar i el treball cooperatiu. També fomenta la interacció social i l’autonomia d’aprenentatge de l’alumnat, utilitzant diversos tipus d’activitats (estudis de casos, recerques, problemes, etc. )

Development and Characterization of Electrospun Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Biopapers Containing Cerium Oxide Nanoparticles for Active Food Packaging Applications

Food quality is mainly affected by oxygen through oxidative reactions and the proliferation of microorganisms, generating changes in its taste, odor, and color. The work presented here describes the generation and further characterization of films with active oxygen scavenging properties made of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) loaded with cerium oxide nanoparticles (CeO2NPs) obtained by electrospinning coupled to a subsequent annealing process, which could be used as coating or interlayer in a multilayer concept for food packaging applications. The aim of this work is to explore the capacities of these novel biopolymeric composites in terms of O2 scavenging capacity, as well as antioxidant, antimicrobial, barrier, thermal, and mechanical properties. To obtain such biopapers, different ratios of CeO2NPs were incorporated into a PHBV solution with hexadecyltrimethylammonium bromide (CTAB) as a surfactant. The produced films were analyzed in terms of antioxidant, thermal, antioxidant, antimicrobial, optical, morphological and barrier properties, and oxygen scavenging activity. According to the results, the nanofiller showed some reduction of the thermal stability of the biopolyester but exhibited antimicrobial and antioxidant properties. In terms of passive barrier properties, the CeO2NPs decreased the permeability to water vapor but increased the limonene and oxygen permeability of the biopolymer matrix slightly. Nevertheless, the oxygen scavenging activity of the nanocomposites showed significant results and improved further by incorporating the surfactant CTAB. The PHBV nanocomposite biopapers developed in this study appear as very interesting constituents for the potential design of new active organic recyclable packaging materials.Authors thank the funding received from the EU H2020 BBI JU USABLE PACKAGING project—836884 and also from the Spanish Ministry of Science and Innovation, project PID2021-128749OB-C31.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2021-001189-S).Peer reviewe

Effect of graphene nanoplatelets on the dielectric permittivity and segmental motions of electrospun poly(ethylene-co-vinyl alcohol) nanofibers

[EN] The influence of the addition of graphene nanoplatelets (GNPs) on the intra/inter ¿ molecular segmental motions of poly(ethylene-co-vinyl alcohol) (EVOH) was assessed by means of dielectric thermal analysis (DETA). The relaxation spectra were studied in terms of the dielectric permittivity (¿¿) and the dielectric loss tangent (tan ¿) at wide ranges of frequency (from 10¿2 to 107 Hz) and temperature (from -150 to 140 °C). Two relaxation zones were disthinguished. Below the glass transition temperature (Tg), two ß-relaxations were observed, which are characteristic local modes of mobility of the EVOH side groups, and related to the influence of the different surroundings of ethylene or vinyl alcohol units. At higher temperatures, the dielectric ¿-relaxation in the vicinities of the glass transition of EVOH was determined. The thermal activation of the ß-relaxations was explained by an Arrhenius model, and showed activation energies (Ea) around 55 and 80 kJ·mol¿1. The ¿-relaxation was explained by the Vogel-Fulcher-Tammann-Hesse (VFTH) model. The study of the segmental dynamics showed an increase in the dynamic fragility parameters with the addition of GNPs. The permittivity was increased at preferential concentrations of GNPs. In particular, the addition of GNPs up to 0.5 wt% increased the dielectric permittivity of the electrospun EVOH/GNPs nanocomposite fibers, specially at low frequencies.The authors would like to thank the European Regional Development Funds (ERDF) and the Spanish Ministry of Science, Innovation, and Universities (MICIU) for the concession of the Research Projects ENE2017-86711-C3-1-R and RTI2018-097249-B-C21. The UPV authors would also like to thank the Chilean Economic Development Agency (CORFO) the economic support in the frame of the project 13CEI2-21839. This research was also funded by the EU H2020 YPACK (773872) and USABLE (BBI-JTI-2018-836884) projects. Torres-Giner is a recipient of a Juan de la Cierva-Incorporación contract (IJCI-2016-29675) from MICIU. Universitat Politècnica de València is acknowledged for the post-doctoral aid for R. Teruel-Juanes, under the PAID-10-19 SUB.1 SP20190049 scholarship.Badia, JD.; Teruel Juanes, R.; Echegoyen, Y.; Torres-Giner, S.; Lagarón, JM.; Ribes-Greus, A. (2021). Effect of graphene nanoplatelets on the dielectric permittivity and segmental motions of electrospun poly(ethylene-co-vinyl alcohol) nanofibers. Polymer Degradation and Stability. 183:1-9. https://doi.org/10.1016/j.polymdegradstab.2020.109404S1918

L'Energia en context

Presentem el material didàctic L'energia en context, un projecte elaborat i experimentat pel grup de treball Scientia Omnibus, un equip de professors/es de secundària de diverses especialitats de ciències. Consta de 3 unitats didàctiques amb un enfoc CTS (ciència - tecnologia - societat) adreçades a alumnat del segon cicle d'ESO que tracten els continguts curriculars relacionats amb l'energia. L'elecció d'aquest tema com a eix vertebrador de tot el projecte s'ha realitzat per la rellevància social i personal que té a la nostra societat. Les estratègies didàctiques clau del projecte són la contextualització de la ciència escolar i el treball cooperatiu. També fomenta la interacció social i l'autonomia d'aprenentatge de l'alumnat, utilitzant diversos tipus d'activitats (estudis de casos, recerques, problemes, etc.)

Electrospun Active Biopapers of Food Waste Derived Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with Short-Term and Long-Term Antimicrobial Performance

© 2020 by the authors.This research reports about the development by electrospinning of fiber-based films made of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) derived from fermented fruit waste, so-called bio-papers, with enhanced antimicrobial performance. To this end, different combinations of oregano essential oil (OEO) and zinc oxide nanoparticles (ZnONPs) were added to PHBV solutions and electrospun into mats that were, thereafter, converted into homogeneous and continuous films of ~130 μm. The morphology, optical, thermal, mechanical properties, crystallinity, and migration into food simulants of the resultant PHBV-based bio-papers were evaluated and their antimicrobial properties were assessed against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in both open and closed systems. It was observed that the antimicrobial activity decreased after 15 days due to the release of the volatile compounds, whereas the bio-papers filled with ZnONPs showed high antimicrobial activity for up to 48 days. The electrospun PHBV biopapers containing 2.5 wt% OEO + 2.25 wt% ZnONPs successfully provided the most optimal activity for short and long periods against both bacteria.The Spanish Ministry of Science and Innovation (MICI) through the RTI2018-097249-B-C21 program number and the EU H2020 YPACK (reference number 773872) and FODIAC (MSCA-RISE-2017-778388) projects funded this research.Peer reviewe