Epoxy-Based Composites

Epoxy-based composites are used in automotive and aerospace applications because of their high strength-to-weight ratio, high stiffness-to-weight ratio, and good resistance to wear and corrosion. This book presents research on epoxy-based composites and their applications. It explains methods of preparing and testing these composites, including the hand lay-up technique, compression molding, and others. This book is useful for industrialists, undergraduate and postgraduate students, research scholars, and scientists

Recent advances in carbon-based polymer nanocomposites for electromagnetic interference shielding

Carbon-based nanoparticles have recently generated a great attention, as they could create polymer nanocomposites with enhanced transport properties, overcoming some limitations of electrically-conductive polymers for high demanding sectors. Particular importance has been given to the protection of electronic components from electromagnetic radiation emitted by other devices. This review considers the recent advances in carbon-based polymer nanocomposites for electromagnetic interference (EMI) shielding. After a revision of the types of carbon-based nanoparticles and respective polymer nanocomposites and preparation methods, the review considers the theoretical models for predicting the EMI shielding, divided in those based on electrical conductivity, models based on the EMI shielding efficiency, on the so-called parallel resistor-capacitor model and those based on multiscale hybrids. Recent advances in the EMI shielding of carbon-based polymer nanocomposites are presented and related to structure and processing, focusing on the effects of nanoparticle’s aspect ratio and possible functionalization, dispersion and alignment during processing, as well as the use of nanohybrids and 3D reinforcements. Examples of these effects are presented for nanocomposites with carbon nanotubes/nanofibres and graphene-based materials. A final section is dedicated to cellular nanocomposites, focusing on how the resulting morphology and cellular structures may generate lightweight multifunctional nanocomposites with enhanced absorption-based EMI shielding propertiesPostprint (author's final draft

From Gd2O3suspension to nanocomposite: Synthesis, properties and radiation protection

This study provides details for the design, preparation of an environmentally friendly, clinically safe and lightweight radiation protective shield made ofGd2O3/epoxy nanocomposite (Gd-nanocomposite) which is proposed as an alternative to traditional toxic lead (Pb)-based aprons for diagnostic X-ray protection. In theory, this particulate nanocomposite can possess significant features of both inorganic particles and organic polymeric matrices. However, in practice, its performance does not simply depend on the sum of the individual contributions of characteristics of the constituent phases but on the interaction of their inner interfaces and the homogeneous dispersion of inorganic particles in the polymer matrix. The miniaturization of inorganic particles to nanoscale before mixing with an organic matrix has been considered as an effective way to improve the interface of the dispersion phase. Unfortunately, homogeneous dispersion has still not yet been achieved in this type of material due to the coalescence of nanoparticles resulting from the large surface area of nanoparticles and their chemical incompatibility with the matrix. The effect of inter-particle forces arising from adsorbed typical cationic and anionic surfactants on the morphology of the ball milled gadolinium oxide (Gd2O3) is investigated to attain the optimal conditions for interface improvement between Gd2O3 particles and an epoxy matrix. The experimental outcomes are interpreted in terms of the stabilization and interaction mechanisms of the fine washed Gd2O3 particles (size diameter \u3c1μm) in an aqueous medium under the variation of the surface forces arising from adsorbed surfactants. The point of zero charge or isoelectric point (IEP) of ball milled Gd2O3 particles suspension is at pH 11. In the presence of adsorbed anionic SDS (Sodium dodecyl sulphate), the particles are refined together with numerous 2D nanowire or nano-rod particles at pH ~ 8. In contrast, the coarser particles are found when cationic CTAB (Cetyl trimethylammonium bromide) is used to modify the Gd2O3 surface. This is invoked from organic shell formed by the high adsorbability of negatively charged heads of SDS into the bare positive charge density of the particle. This capping agent acts as (i) a steric barrier preventing the agglomeration or rewelding of the powder during nanoparticle preparation and (ii) an intermediate adhesive that enhances the miscibility of the particle and liquid matrix, thereby improving the particle dispersion in the organic matrix. VI Based on the above outcomes, an optimal geometric design of a non-lead based X-ray protective material with lightweight per volume unit is prepared. A plateau with 28-30% increments in the value of fracture toughness (KIC (Mpa.m1/2)) is observed with a specific addition of 0.08 to 0.1 volume fraction (ϕs) of SDS-encapsulated Gd2O3 particles in pure epoxy. The same quantity of particles also optimally raises the critical strain energy release rate (GIC (J.m-2)) and Young’s modulus (E (MPa)) of epoxy by approximately 22-24% and 18-25% respectively. A 16 mm thick sheet of fabricated filled composite at ϕs of 0.08 and 0.1 can shield greater than 95% (0.5 mm Pb-equivalence) and 99% (1 mm Pb-equivalence) respectively of a primary X-ray beam in the range of 60-120kVp. At the same X-ray attenuation (99% attenuation), the specimen is 7, 8.5, and 16 times lighter than wood, glass, and concrete respectively. At 0.5 mm Pb-equivalence, the composite also has 4.5-19.4% less weight per unit area than current commercial non-lead products

Development of microcellular conductive foams based on polyetherimide with graphene nanoplatelets

Tesi per compendi de publicacions, amb diferents seccions retallades per drets de l'editor.Premi Extraordinari de Doctorat, promoció 2018-2019. Àmbit d’Enginyeria IndustrialThe aim of this dissertation was to develop and investigate novel cellular foams based on polyetherimide (PEI) and carbonbased nanoparticles such as, graphene nanoplatelets (GnP) and carbon nanotubes (CNT), using two main foaming methods; One being water vapour induced phase separation (WVIPS) method and the other being one-step foaming through dissolution of carbon dioxide (CO2) at its supercritical state. WVIPS method consists of initial preparation of polymer-solvent solution and nucleation of cells through phase separation due to water vapour absorption. The dissolution of supercritical CO2 (scCO2) in a high-pressure vessel has been used in order to consequently force a sudden expansion of the nanocomposite precursor in a one-step pressure drop which results in formation of cells. In WVIPS method, the concentration of the polymer in solvent during mixture showed to have a great impact on the morphology of the foams. Additionally, the composition seems to have various effect on the cellular structure. When a blend of PEI with polyamide-imide (PAI) was prepared using this method, the cellular formation evolved drastically depending on the amounts of PAI added to the mixture. Moreover, the incorporation of GnP and CNT seem to have affected the cellular structure and morphology with various levels of impact depending on whether the ultrasonication of the nanoparticles was applied. Using the one-step scCO2 dissolution foaming method, foams were obtained with homogenous closed-cell structure. The incorporation of GnP did not seem to affect the cellular structure of the PEI foams. However, the application of ultrasonication, melt mixing and one-step foaming seem to have induced a proper level of particle dispersion which was confirmed by X-ray diffraction analysis. The studies of mechanical properties of foams prepared via WVIPS method suggested that the densities of the foams alter their viscoelastic behaviour in a direct manner. Additionally, the mechanical behaviour followed a similar increasing trend by incrementing the amount of graphene content. Surprisingly, this behaviour changed when using CNT as reinforcement; A clear decreasing trend was observed in specific storage modulus of the foams by increasing the amount of CNT. Moreover, considering the case of polymeric blends, the mechanical behaviour seem to have been affected vastly by the structural changes. The PEI/PAI polymer composition played a key role in determination of the cellular structure and therefore, the eventual mechanical behaviour of these foams. The foams prepared through scCO2 dissolution showed an increasing trend of normalized modulus (Enorm) with increasing the density and a rise in specific modulus (Espec) with increasing the GnP volume fraction. In an overall view, the nanoparticles provided a general delay in degradation temperatures of the nanocomposite foams which could provide the possibility of their application in high temperature environments. Significant enhancements were achieved regarding the electrical conductivity of the foams. The ultrasonication of the nanoparticles have provided the possibility to increase the value of electrical conductivity by six orders of magnitude from 1.8 × 10E-7 S/m to 1.7 × 10E-1 S/m for foams containing 10 wt% of GnP. The foams with 1/1 ratio of GnP and CNT reached an electrical conductivity value of 8.8 × 10E-3 S/m containing only a total amount of 2 wt% in nanoparticles.El objetivo de esta tesis doctoral fue desarrollar e investigar nuevas espumas celulares basadas en polieterimida (PEI) y nanopartículas basadas en carbono, como son las nanopartículas de grafeno (GnP) y los nanotubos de carbono (CNT). Para ello se utilizó dos métodos principales de formación de espumas, uno de ellos fue el método de separación de fases inducida por vapor de agua (WVIPS) y el otro consistió en la formación de espuma en un solo paso mediante la disolución de dióxido de carbono (CO2) en su estado supercrítico. El método WVIPS consiste en la preparación inicial de la solución de polímero-disolvente y la nucleación de las células a través de la separación de fases debido a la absorción del vapor de agua. La disolución de CO2 supercrítico (scCO2) se aplicó en un reactor para forzar consecuentemente una expansión repentina del precursor nanocompuesto en una caída de presión en un paso que dio como resultado la formación de células. En el método WVIPS, la concentración del polímero en el disolvente durante la mezcla mostró un gran impacto sobre la morfología de las espumas. Las espumas preparadas con una menor concentración de polímero en el disolvente dieron como resultado, espumas más ligeras con tamaños medios de células mayores. Además, la composición parece tener diversos efectos sobre la estructura celular. Cuando se preparó una mezcla de PEI con poliamida-imida (PAI) usando este método, la formación celular evolucionó drásticamente dependiendo de la fracción de PAI añadida a la mezcla. Por otra parte, la incorporación de GnP y CNT parece haber afectado la estructura celular y la morfología en diferentes niveles de impacto dependiendo de si se aplicó la ultrasonicación de las nanopartículas o no. Usando el método de espumación por disolución de scCO2 en un paso, espumas con homogeneidad estructural y con celdas cerradas fueron obtenidas. Sin embargo, la aplicación de ultrasonidos, mezcla en fusión y espumación en un solo paso parece haber inducido un nivel adecuado de dispersión de partículas que se confirmó mediante análisis de difracción de rayos X. Los estudios de las propiedades mecánicas de las espumas preparadas mediante el método WVIPS sugirieron que las densidades de las espumas alteran su comportamiento viscoelástico de manera directa. Además, el comportamiento mecánico sigue una tendencia similar al aumentar la fracción de grafeno. Sorprendentemente, este comportamiento cambia cuando se usa CNT como refuerzo; Se observó una clara tendencia decreciente en el módulo de almacenamiento específico con el aumento de la cantidad de CNT. Además, considerando el caso de las mezclas poliméricas, el comportamiento mecánico parece haber sido afectado enormemente por los cambios estructurales. La composición del polímero PEI / PAI desempeñó un parte clave en la determinación de la estructura celular y, por lo tanto, el comportamiento mecánico final de estas espumas. Las espumas preparadas a través de la disolución de scCO2 mostraron una tendencia creciente de módulo normalizado (E´norm) con el aumento de la densidad y un aumento en el módulo específico (E´spec) con el aumento de la fracción volumétrica de GnP. De forma general, las nanopartículas proporcionaron un retraso general en las temperaturas de degradación de las espumas nanocompuestas que podrían proporcionar la posibilidad de su aplicación en entornos de alta temperatura. Se lograron mejoras significativas con respecto a la conductividad eléctrica de las espumas. La ultrasonicación de las nanopartículas proporcionó la posibilidad de aumentar el valor de la conductividad eléctrica en seis órdenes de magnitud desde 1,8 × 10E-7 S/m hasta 1,7 × 10E-1 S/m en espumas que contienen 10% en peso de GnP. Las espumas con proporción 1/1 de GnP y CNT alcanzaron un valor de conductividad eléctrica de 8,8 × 10E-3 S/m que contenía solo un 2% en peso de nanopartícularAward-winningPostprint (published version

Defence Applications of Polymer Nanocomposites

The potential opportunities promised by nanotechnology for enabling advances in defence technologies are staggering. Although these opportunities are likely to be realised over a few decades, many advantages are currently being explored, particularly for defence applications. This review provides an insight into the capabilities offered by nanocomposites which include smart materials, harder/lighter platforms, new fuel sources and storage as well as novel medical applications. It discusses polymer-based nanocomposite materials, nanoscale fillers and provides examples of the actual and potential uses of nanocomposite materials in defence with practical examples.Defence Science Journal, 2010, 60(5), pp.551-563, DOI:http://dx.doi.org/10.14429/dsj.60.57

Photoactive Properties of Nanostructured Titania Modified Polyurethanes

In order to enhance both the photoactivity and physical/mechanical properties of titania/polyurethane (PU) nanocomposites, in-situ polymerization and film casting were investigated. Both self-degrading PU foams and self-cleaning PU coatings were prepared. Functional monomers were prepared usingDMPA (2,2-dimethylolpropionic acid) functionalized anatse TiO2 and P25 for integration into polyurethane foam with a grafting-from synthetic method. This technique was found to successfully reduce the agglomeration effect of titania nanoparticles inside the foams. In addition, the photodegradation rate was enhanced by \u3e 120% over unmodified foam at an optimized loading of 3wt% DMPA functionalized anatase TiO2. The presence of DMPA functionalized P25 nanoparticles produced an increase in the degradation rate of 66% over the unmodified foam at an optimized 1wt% loading. SiO2 encapsulated anatase and rutile TiO2 nanoparticles were successfully synthesized via a modified Stöber process, and integrated into polyurethane coatings. The SiO2 encapsulation enhanced the anatase TiO2 nanoparticle distribution as well as the photocatalytic activity of the polyurethane nanocomposites when the loading weight of SiO2 was lower than 3.25wt%. By increasing the SiO2 amount on the titania surface, the contact angle of the coatings increased from 75 to 87 for anatase phase and 70 to 78 for rutile phase. The Young\u27s Modulus was also increased from 1.06GPa to 2.77GMPa for anatase phase and 1.06GPa to 2.17GPa for rutile phase, attributed to the silica layer giving better integration. The thermal conductivity of the polyurethane coatings was also successfully decreased by encapsulating SiO2 on the titania surface, which has applications for next generation high performance coatings. In addition to nanospheres, TiO2 nanofibers were synthesized via an environmental friendly supercritical CO2 method and nanotubes were prepared via a hydrothermal reaction. They were encapsulated with silica via the modified Stöber process, then integrated into polyurethane coatings. With more of SiO2 coated on the nanofibers’ surface, the photocatalytic activity, UV absorbance, and hydroxyl radical formation decreased due to the shielding effect of the SiO2 layers. In contrast, with more SiO2 coated on the nanotubes’ surface, the formed material was more photoactive at first and then became less active later. These effects in part are attributed to the surface area changes. With these modified nanofibers and nanotubes, the polyurethane coatings were found to exhibit similar photoactivity trend. The mechanical strength was enhanced and the hydrophobicity of coatings was maintained upon exposure to UV irradiation. Nanofiber shaped TiO2 xerogel was synthesized via environmental friendly approach with supercritical CO2 (ScCO2), which when mixed within polyurethane coatings through film casting method and the coatings remain transparent. The coordination between Ti and the carboxylic acid group was investigated showing a bidentate coordination. The TiO2 xerogel nanofibers were found to possess high UV absorbance with high UV shielding properties when integrated into polyurethane coatings. They also were found to influence the thermicity while increasing the reflective index, hence allowing more IR transfer through the coatings faster

Engineered quantum dots for EVA nanocomposite films and TiO2 photocatalysts

Light absorbing inorganic nanoparticles in transparent plastics such as poly(ethylene-co-vinyl acetate) (EVA) are of enormous interest in emerging solar materials, including photovoltaic (PV) modules and commercial greenhouse films. Quantum dots (QDs) have the potential to absorb UV light and selectively emit visible light. However, how to stabilize the QDs for long product life spans without blinking while enabling their easy integration into polymer systems is lacking. This work examines different approaches for loading mesoporous silica encapsulated QDs into EVA polymer films which can control plant growth in greenhouses or enhance PV panel efficiencies. Highly luminescent CdS and CdS-ZnS core-shell QDs with 5 nm sizes were synthesized using a modified facile approach based on the pyrolysis of single molecule precursor. To make both the bare and core-shell structure QDs more resistant against photochemical reactions, a mesoporous silica layer was grown onto the QDs through a modified reverse microemulsion technique. Silica encapsulated QDs were then melt-mixed with EVA pellets using a twin-screw extruder and pressed into thin films with controlled thickness. A novel supercritical carbondioxide (scCO2) processing method was also explored that utilizes scCO2 to disperse silica encapsulated core-shell quantum dots into EVA. The novel photo-stable light selective films show high visible light and decreased UV transmission. Also, silica layer showed improved infrared and thermal wavebands retention in the films. Beside polymer nanocomposites, a facile process has also been developed to covalently link QDs to TiO2 nanowires through a bifunctional organic linker that enhanced photoctalytic property and stability of nano TiO2

Polymer Based Nanocomposites as Multifunctional Structure for Space Radiation Shielding: A Study of Nanomaterial Fabrications and Evaluations

Radiation shielding in space missions is critical in order to protect astronauts and other payloads from radiation damage. Low atomic-number materials such as hydrogen are proved to be efficient in shielding ionizing radiations, but the relatively poor thermal and mechanical properties compared to metallic alloys has limited their applications. Conventional material aluminum (Al) is widely used in space applications as structural and radiation shielding material. However, the issues related to heavy weight and extra secondary radiation generation make pure metals not suitable for modern space radiation shielding. Currently, conventional shielding materials including Al, high density polyethylene (HDPE), and water have been jointly applied as radiation shielding parts on spacecraft. Disadvantages such as low thermal properties (HDPE), high atomic number (Al) and complex maintenance system (water) have resulted in heavy load and high-cost in space missions. One approach to replace high atomic number metals is deploying hydrogen rich polymers enhanced with nanofillers associating mechanically strong composite carbon fiber reinforce plastic (CFRP) that has been proposed in this research. Polymer based nanocomposite can achieve improved physical properties such as thermal properties, while at the same time it can provide adequate radiation shielding function with lower weight and less secondary radiation generation. By reviewing nanotechnologies for radiation shielding, multi-walled carbon nanotube (MWCNT) and bismuth oxide (Bi2O3) nanoparticle were carried out to enhance properties of poly(methyl-methacrylate) (PMMA). The role of nanofillers embedded in PMMA matrix, in terms of radiation shielding effectiveness, were experimentally evaluated by comparing the proton transmission properties and secondary neutron production of the PMMA/MWCNT nanocomposite and electron transmission properties of PMMA/MWCNT/Bi2O3 nanocomposite with pure PMMA and Al. The results indicate that the addition of MWCNT in PMMA matrix can not only further reduce the secondary neutron production of the pure polymer, but also show significant reduction in weight compared to Al. Furthermore, the adoption of Bi2O3 illustrates reduced areal density of nanocomposite over Al under the same electron radiation energies. However, enhanced thermal properties of nanocomposite is required to make it a potential candidate for radiation shielding in space applications. As a result, an optimization of nanocomposites and methods to apply its multiple functions onto CFRP structure have been accomplished. After all, a prototype was designed and produced with improved properties of nanocomposite. The low-cost component has shown potentials to replace conventional radiation shielding material Al alloys with high ratio of radiation shielding effectiveness and weight

Fabrication of functional micro/nano-carbon composites based on structural design for electromagnetic shielding （構造設計による機能性マイクロ・ナノコンポジットの開発および電磁波遮蔽への応用）

信州大学(Shinshu university)博士（工学）この博士論文は、次の学術雑誌論文を一部に使用しています。COMPOSITES SCIENCE AND TECHNOLOGY. 172:108-116 (2019); doi:10.1016/j.compscitech.2019.01.013. © 2019 Elsevier Ltd.MATERIALS LETTERS. 245:98-102 (2019); doi:10.1016/j.matlet.2019.02.101. © 2019 Elsevier Ltd.RSC ADVANCES. 9(17):9401-9409 (2019); doi:10.1039/c9ra00028c. © The Royal Society of Chemistry 2019.MATERIALS LETTERS. 236:116-119 (2019); doi:10.1016/j.matlet.2018.10.101. © 2018 Elsevier B.V.ThesisYAN YONGJIE. Fabrication of functional micro/nano-carbon composites based on structural design for electromagnetic shielding　（構造設計による機能性マイクロ・ナノコンポジットの開発および電磁波遮蔽への応用）. 信州大学, 2019, 博士論文. 博士（工学）, 甲第715号, 令和01年09月30日授与.doctoral thesi