Multifunctional layered double hydroxide (LDH) based epoxy nanocomposites

As one of the most important thermosetting polymers, epoxy resin (EP) has acquired wide application in the fields of coating, adhesive, electronic/electrical insulation, carbon fiber composites and etc. EP possesses many outstanding advantages, such as low shrinkage, high thermal and mechanical stabilities and excellent solvent and chemical resistance. However, like most of polymeric materials, high flammability of EP is its main fatal drawback, which has severely restricted the application fields required a remarkable flame-retardant standards. Thus, the flame retardancy of epoxy resins continues to remain as a very important area of research for polymer chemists and material engineers. Such research is also highly encouraged by the polymer industries because of huge economic and sociological casualties involved each year in fire accidents. Among the various methods of improving flame retardancy of polymeric materials, incorporation of flame retardants is a very commonly used one. The present work and the relevant reporting involve the investigation of a relatively new fascinating nano-filler, known as layered double hydroxide (LDH) as potential flame retardant for polymers composites. The basic reason for selecting LDH or more specifically magnesium-aluminum based LDH (Mg-Al–LDH) is their typical metal hydroxide-like chemistry and conventional clay-like layered crystalline structure. The current dissertation containing: •Functionalization of LDH; Multi-modifiers’ systems composed by bio-based modifiers such as hydroxypropyl-sulfobutyl-beta-cyclodextrin sodium (sCD) and its hybridized form with chalcone species (fCD), taurine (T), phytic acid (Ph), and dodecylbenzenesulfonate (DBS) were fabricated in this thesis, each designed for specified feature, aiming at developing high performance fire retardant epoxy nanocomposites. •Preparation and characterization of functionalized LDH based epoxy nanocomposites; Based on these functionalized LDHs, bisphenol A epoxy resin and diamino diphenyl sulfone (DDS), and utilizing multi step mixing method followed by appropriate curing process, series functionalized LDH/Epoxy nanocomposites have been developed. •Structural Properties relationship; The structural morphology of LDH/epoxy nanocomposites was investigated by transmission electron microscopy (TEM) and wide-angle X-ray scattering (WAXS), revealing that multi-modified LDH based epoxy nanocomposites showed much better dispersion state than the epoxy composites containing un-modified LDH or single modifier modified LDH. In contrast to conventional LDHs based epoxy composites, the functionalized LDH based epoxy nanocomposites show significantly improvement on both flame retardancy, such as passing UL94 V0 rating and significant reduction of peak of heat release rate, total heat release, total smoke, etc. and well maintenance on impact, flexural, micro-mechanical and anti-UV properties. Such multifunctional nano-hybrid will provide a promising solution to develop various functional epoxy-based composites for advanced applications.Como uno de los polímeros termoestables más importantes, resina epoxi (EP) ha adquirido una amplia aplicación en los campos de recubrimiento, adhesivos, aislamiento eléctrico / electrónico, materiales compuestos de fibra de carbono y etc. EP posee muchas ventajas excepcionales, tales como baja contracción, alta térmica y estabilidades mecánicas y excelente disolvente y resistencia química. Sin embargo, como la mayoría de los materiales poliméricos, alta inflamabilidad de EP es su principal inconveniente fatal, que ha restringido severamente la aplicación campos requieren un notable estándares ignífugos. Por lo tanto, la resistencia a la llama de resinas epoxi sigue siendo como un área muy importante de la investigación para los químicos de polímeros e ingenieros de materiales. Este tipo de investigación es también muy animado por las industrias de polímeros debido a enormes bajas económicas y sociológicas que participan cada año en accidentes de fuego. Entre los diversos métodos para mejorar llama retardancia de materiales poliméricos, la incorporación de los retardantes de la llama es muy comúnmente usada. El presente trabajo y el informe correspondiente implican la investigación de un nuevo y fascinante nano-relleno relativamente, conocido como de doble capa de hidróxido (LDH) como potencial retardante de llama para polímeros compuestos. La razón básica para la selección de LDH o LDH más basada en específicamente de magnesio-aluminio (Mg-Al-LDH) es su química típica hidróxido como el metal y la estructura cristalina capas similar a la arcilla convencional. La tesis actual que contiene: • La funcionalización de la LDH; Los sistemas Multi-modificadores 'compuestas por modificadores de origen biológico, tales como hidroxipropil-sulfobutil-beta-ciclodextrina de sodio (SCD) y su forma hibridado con especies chalcona (FCD), taurina (T), el ácido fítico (Ph) y dodecilbencenosulfonato (DBS ) fueron fabricados en esta tesis, cada uno diseñado para la función especificada, con el objetivo de desarrollar de alto rendimiento nanocompuestos epoxi retardante de fuego. • Preparación y caracterización de nanocompuestos epoxi funcionalizados LDH basada; En base a estos LDHs funcionalizados, sulfona de bisfenol A resina epoxi y diamino difenil (DDS), y utilizando el método de mezclado de múltiples fases seguido por el proceso de curado apropiado, se han desarrollado series funcionalizado nanocompuestos LDH / epoxi. • Relación Propiedades Estructurales; La morfología estructural de nanocompuestos de LDH / epoxi se investigó por microscopía electrónica de transmisión (TEM) y de amplio ángulo de dispersión de rayos X (WAXS), revelando que LDH basado nanocompuestos epoxi multi-modificado mostraron mucho mejor estado de dispersión de los materiales compuestos epoxi que contienen ONU LDH modificado o solo LDH modificado modificador. En contraste con los materiales compuestos epoxi basadas LDHs convencionales, los nanocompuestos de LDH epoxi basada funcionalizados muestran una mejora significativa tanto en resistencia a la llama, tales como pasar calificación V0 UL94 y una reducción significativa del pico de la tasa de liberación de calor, la liberación total de calor, el humo total, etc. y bien el mantenimiento de las propiedades de impacto, flexión, micro-mecánicos y anti-UV. Tal multifuncional nano-híbrido proporcionará una solución prometedora para desarrollar diversos materiales compuestos a base de epoxi funcionales para aplicaciones avanzadas.Financial support for the work described in this dissertation by EU 7th Framework Programme through the project ECOFIRE-NANO (reference: 321951).Programa de Doctorado en Ciencia e Ingeniería de MaterialesPresidente: Juan Baselga Llidó.- Secretario: Santiago Gómez Ruiz.- Vocal: Carlos Daniel Gonzales Martíne

Sustainable and photoresponse triboelectric nanogenerators based on 2D-gC3N4 and agricultural wastes

Two bio-friendly and photoactive triboelectric nanogenerators (TENG) are introduced, employing sustainable and biocompatible materials as functional components. The TENGs utilize corn husk and coconut coir fibers as the positive layers and incorporate two-dimensional graphitic carbon nitride (g-C3N4) nanosheets as negative layers. Upon simple biomechanical forces, the optimized devices fabricated from corn husk and coconut fibers produce a maximum output voltage of 630 V and 581 V, respectively. Under short-circuit conditions, the measured current was approximately 0.79 mA for corn husk-TENG and 11.47 mA for coconut fibers-TENG. Also, the maximum output power of 131 mW and 1980 mW were achieved over a 2 × 2 cm2 area of corn husk-TENG and coconut fibers-TENG. The TENGs were also tested under blue commercial lights and UV light, and an increase of approximately 1.5 times was observed in the output voltages of both TENGs under UV light. These g-C3N4-based TENGs perform superior under UV illumination and can be used as nanogenerators and active photosensors. This paper proposes two eco-environmentally friendly and robust electronic devices for energy harvesting and photo-sensing applications based on two agricultural wastes, corn husk, and coconut coir fibers

Development of a triboelectric nanogenerator for joining of silver nanorods

On account of their excellent properties, 2D nanostructures beyond graphene, such as MoS2, have extensive applications. Given their quantum confinement effects, MoS2 monolayers could efficiently trap electrons as an intermediate layer between friction and electrode in triboelectric nanogenerators (TENGs) and successfully hinder their recombination and air breakdown, increasing their output. With the help of this phenomenon, a TENG called PS+PS/MoS2-AHSG (PPMA) TENG is fabricated with an open-circuit voltage of ≈1200V and a short-circuit current of 0.74mA, and a maximum power of 11.27mW. PPMA TENG consists of transparent polystyrene (PS) and PS/MoS2 as negative contact and storage layers. Also, the positive layer is a novel Alyssum homolocarpum seed gum (AHSG) layer, which is a natural polymer. This TENG could successfully light up 115 commercial light-emitting diodes. PPMA TENG exhibits exceptional mechanical robustness so that after a decrease in its outputs, heating would activate the self-healing mechanism, and the surface charge density could reach from 0.428 to 0.874 µC m−2, which is 82% of the initial value. To demonstrate the practical applications of PPMA TENG as a high-voltage sustainable power source, it is successfully employed to perform a dielectrophoretic assisted welding of silver nanorods

A critical review of the current progress of plastic waste recycling technology in structural materials

One of the main environmentally threatening factors is plastic waste which generates in great quantity and causes severe damage to both inhabitants and the environment. Commonly, plastic waste generated on the land ends up in water bodies, resulting in detrimental solid impacts on the aquatics via poisoning and flooding the marine ecosystem. Exploring various approaches to convert plastic wastes into new products known as an efficient way to manage them and to enhance the sustainability of the environment, discussed in this article. Moreover, The limitation of the application of plastic waste for construction purposes is also considered. It is wind up that the usage of plastic waste for construction purposes will significantly rectify the sustainability of our environment and also be regarded as a trustworthy source of materials for applying in conventional materials such as concrete and asphalt

Effect of nitrogen and oxygen doped carbon nanotubes on flammability of epoxy nanocomposites

To overcome the flammability of epoxy resins, novel nitrogen (CNₓ) and oxygen (COₓ) doped CNT were synthesized via CVD method and epoxy nanocomposites at 2 wt.%. constant loading were prepared by three roll milling and cured. The structures of the nanotubes were confirmed by XRD, XPS, SEM and Raman and it was found a very high aspect ratio especially for COₓ. Thermal degradation as well as glass transition temperatures and elastic moduli were measured by TGA, DSC and DMTA. The flammability of epoxy nanocomposites was studied by microscale combustion calorimetry (MCC) and limiting oxygen index (LOI) determination. Results showed that the fire retardant properties of nanocomposites improved significantly specially for COₓ, which presented a very high LOI (35%) and a homogeneous and uniform surface after burning. This effect was tentatively attributed to the very high aspect ratio of COₓ tubes.Authors wish to acknowledge financial support from Spanish Ministerio de Economía y Competitividad under grant MAT2014-57557-R. Authors also wish to thank Dr. Sofía M. Vega-Díaz for her invaluable help with XPS interpretatio

Green Flexible Triboelectric Nanogenerators Based on Edible Proteins for Electrophoretic Deposition

Abstract The next generation of wearable electronics for internet of things (IoT) systems, and green energy harvesting require electrically conductive materials with high flexibility, conductivity, and being environmentally friendly. In this study, three biopolymers, cow's milk, soy milk, and egg white liquid, are investigated and compared as spin‐coated positive layers in triboelectric nanogenerators (TENGs). Superior results are obtained using egg white liquid as a novel liquid conductor with comparable conductivity and high transparency. After investigating various disposable polymers as substrates, sandpaper is used to improve the output performance of the proposed egg white liquid based TENG (EW‐TENG). The maximum output power density, voltage, and current of the EW‐TENG are 328.84 mW cm−2, 1720 V, and 16.05 mA, respectively. The fabricated EW‐TENG, with an area of 4 × 4 cm2, can directly illuminate 55 high‐power blue LEDs and can adequately perform an electrophoretic deposition of ZnO nanoparticles on copper layers without microcracks. The potential distribution of the EW‐TENG obtained by COMSOL Multiphysics software is consistent with the experimental results. Herein, an eco‐environmentally friendly, flexible, and lightweight electronic device for energy harvesting and electrophoretic deposition applications is proposed

Synthesis of a Fe₃O₄ Nanosphere@Mg–Al Layered-Double-Hydroxide Hybrid and Application in the Fabrication of Multifunctional Epoxy Nanocomposites

Layered double hydroxide (LDH) is regarded as a prominent flame-retardant nanoadditive for polymers. However, the flame-retardant efficiency of a LDH depends strongly on its dispersion state and composition. Usually, modification or functionalization of a LDH is crucial to obtaining high-performance polymer nanocomposites. In order to develop multifunctional epoxy nanocomposites, in this study a LDH was first modified by biobased flame-retardant species, phytic acid (Ph) and (hydroxypropyl)­sulfobutyl-β-cyclodextrin sodium (CDBS), and subsequently decorated by Fe₃O₄ nanoparticles to obtain a Fe₃O₄ nanosphere@LDH hybrid. Results obtained from size distribution and transmission electron microscopy revealed that the Fe₃O₄ nanoparticles with an average size of 8 nm were well decorated on the LDH platelet. The Fe₃O₄-decorated LDH hybrids facilitated their dispersion within an epoxy matrix, as indicated in X-ray diffraction. The incorporation of an as-prepared Fe₃O₄@Ph-CDBS-LDH hybrid into epoxy resin (EP) not only improved the flame-retardant properties but also endowed EP with increased thermal conductivity. Specifically, the peak heat release rate and total smoke production of the EP composite with 8 wt % Fe₃O₄@Ph-CDBS-LDH were decreased by 55% and 34%, respectively, in comparison to those of pristine EP, and the UL-94 V0 rating requirement can be met. The investigation provides a promising approach for the preparation of multifunctional LDH hybrids and related high-performance polymer nanocomposites by just using a functionalized nanomaterial

Renewable Cardanol-Based Surfactant Modified Layered Double Hydroxide as a Flame Retardant for Epoxy Resin

A biobased modifier (cardanol-BS) was successfully synthesized from renewable resource cardanol via the ring-opening of 1, 4-butane sultone (BS). Cardanol-BS modified layered double hydroxide (m-LDH) was developed through a one-step coprecipitation method and subsequently incorporated into epoxy resins (EPs) with different loadings using a combined technique of three-roll mill and ultrasonication. As a comparison, a pristine LDH/EP composite was also prepared using the same procedure. The XRD result indicated that the interlayer spacing of m-LDH was about 5-fold enlarged compared with that of pristine LDH. As a result, the enlarged interlayer spacing of m-LDH facilitated the homogeneous dispersion of the nanoadditive in the epoxy matrix, as evidenced by TEM and XRD results. The flame retardant properties were improved with the increase of the m-LDH loading. With only 6 wt % m-LDH, the EP composite reached a limiting oxygen index (LOI) of 29.2% and UL-94 V0 rating. The peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) values of EP/m-LDH-6% were decreased by 62%, 19%, and 45%, respectively, compared to those of pure EP. In contrast, pristine LDH did not show so high an efficiency as m-LDH in terms of the reduced PHRR, THR, and TSP, and also the EP/LDH-6% composite exhibited no rating in the UL-94 vertical burning test. These findings supported that the flame retardant behavior increased with improved dispersion of nanofiller in the polymer matrix. The well-dispersed m-LDH nanofillers were beneficial to improving the quality of char residue, which effectively inhibited flammable volatiles escaping from the interiors and served as an effective thermal insulation layer to shield the underlying matrix from the exterior heat irradiation