Review on the Use of Nanofillers in Polyurethane Coating Systems for Different Coating Applications

Polyurethane (PU) is the most common, versatile and researched material in the world. It is widely used in many applications such as medical, automotive and industrial fields. It can be found in products such as furniture, coatings, adhesives, construction materials, Paints, elastomers, insulators, elastic fibres, foams, integral skins, etc. because it has extraordinary properties and the facility to tailor-made various formulations according to property requirement using different raw materials which are available. Though the material is having fascinating properties the material is also associated with various problems such as inferior coating properties. Inorganic pigments and fillers are dispersed in organic components and binders to improve different properties of the coating. This paper is intended to review the various nanofillers used in different PU coating systems. It gives a general introduction about the various fillers and it's classification, Mechanism by which the filler enhances the mechanical properties of the materials, various factors which affect the properties of the coatings. Various methods of incorporation of fillers in the coating systems are discussed. Various nanofillers such as SiO2(Silicon Dioxide), TiO2(Titanium Dioxide), AL2O3(Aluminium Oxide), antimony doped tin oxide (ATO), BaSO4(Barium Sulphate), FE2O3(Ferric Oxide) as well as carbon nanotubes, graphene derived fillers and nano-diamonds are discussed in detail. The importance and effect of surface modification of fillers to enhance coating properties are also discussed along with challenges associated with polyurethane coatings and future trends

Rational design of mesoporous materials with Core/shell structures with applications for sustainability

Les matériaux mésoporeux sont devenus des nanomatériaux d’une grande importance, et le contrôle des structures des matériaux mésoporeux est essentiel pour une variété d'applications pratiques. Les matériaux «cœur/coquille» structurés sont un type de matériaux hybrides qui non seulement possèdent les propriétés des composants individuels, mais présentent également de effets synergiques entre le «cœur» et la «coquille». La conception de matériaux mésoporeux et «cœur/coquille» structurés pour les appliquer avec succès dans la pratique devrait être une force de progrès importante pour le développement continu. Cette thèse se concentre principalement sur deux aspects: (1) une conception de matériaux mésoporeux «cœur/coquille» structurés en vue de résoudre les problèmes de synthèse, qui entravent leurs nouvelles applications et (2) l'application de matériaux mésoporeux dans la capture du CO2 cyclique pour améliorer la durabilité des sorbants de CO2 en prenant avantage du concept de «cœur/coquille». Visant le cyclage de l’hydroxyde de calcium, une technologie attrayante pour la capture du CO2 à grande échelle, nous avons établi un nouveau mésoporeux «cœur/coquille» structuré à base de CaO qui présentait une grande stabilité et d'excellentes performances de résistance à l’attrition, attribuées aux avantages des matériaux mésoporeux et à la configuration de «cœur/coquille». Notre procédé de fabrication peut être facilement réalisé à grande échelle et répond aux exigences de la circulation entre des réacteurs en lit fluidisé. Les nanoparticules métalliques ont normalement tendance à se coaguler ensemble dans des réactions catalytiques, et sont difficiles à séparer. Par conséquent, nous avons démontré une synthèse de microsphères Fe3O4@C-Pd@mSiO2 à composants multiples et polyvalentes avec une structure «cœur/coquille» bien définie et des nanoparticules catalytiques de Pd confinées, et ayant des canaux mésoporeux ordonnés et facilement accessibles. Récemment, des méthodes diverses ont été proposées pour fabriquer un revêtement de matériaux mésoporeux sur un cœur par un processus de «soft-templating». Cependant, les diamètres des mésopores générés sont généralement très faibles (< 3 nm), ce qui peut limiter leurs nouvelles applications. Ici, nous avons réalisé la synthèse de microsphères «cœur/coquille» structurées superparamagnétiques possédant une coquille externe de silice mésoporeuse ordonnée à larges pores (4,5 nm), en adoptant un copolymère tribloc comme agent tensioactif directeur de structure.Mesoporous materials, especially ordered ones have become ones of great importance nanomaterials, which possess regular, uniform and interpenetrating mesopores in nanoscale. Morphology and texture controls towards mesoporous materials are critical for a variety of practical applications, the ultimate goal of which are the realization of their functional design. Core/shell composite materials are a type of functional hybrid materials which not only possess the properties of the individual components, but also exhibit some new or synergistic effects between the core and the shell. The design of mesoporous materials with unique core/shell configuration and multifunctions to make them successfully applied in practice, should be an important driving force for the continuous development of current material science. This thesis mainly focuses on two aspects: (1) careful design of core/shell structured mesoporous materials in order to solve the problem and difficulty in synthesis, which hinders their further applications and (2) application of mesoporous materials in cyclic CO2 capture to enhance the durability of CO2 sorbents by taking advantage of the core/shell concept. Aiming at the calcium looping cycle, an attractive technology for large-scale CO2 capture, we have prepared novel mesoporous core/shell structured CaO-based sorbents which exhibit highly stable cyclability and excellent attrition-resistance performances, attributed to advantages of both mesoporous materials and unique core/shell configuration. Our fabrication method could easily be realized in large-scale and meet the requirements of circulating fluidized bed reactors. Owing to their high surface energies, metallic nanoparticles normally tend to aggregate together during catalytic reactions, and their separation from a complex heterogeneous system is another obstacle. In this regards, we have demonstrated a facile and versatile synthesis of multicomponent and multifunctional microspheres Fe3O4@C-Pd@mSiO2 with well-defined core/shell structures, confined catalytic Pd nanoparticles and accessible ordered mesopore channels. Recently, various methods have been proposed for coating mesoporous shells on cores by soft-templating process. However, the generated mesopores are usually very small (< 3 nm), which may limit their further applications. In this work, we have accomplished the synthesis of superparamagnetic core/shell structured microspheres possessing an outer shell of ordered mesoporous silica with large pores (4.5 nm) by adopting triblock-copolymer Pluronic P123 as soft-template

Application of ultrasound in twin-screw extrusion and microinjection molding: improvements of properties of processed materials and nanocomposites : polymers and biopolymers

Pla de Doctorat Industrial, Generalitat de Catalunya, Aplicat embargament fins el dia 22 de novembre de 2022The plastics industry is in constant evolution looking to improve the properties of new materials and performance in different applications. Currently, the environmental impact associated with the use of plastics is one of the main concerns for the society. It was reflected in regulations at European level such as SUP Directive, Green Deal or studies such as Patents for tomorrow's plastics by European Patent Office on the trends reflected in research on alternative materials to conventional plastic. In order to transfer these new and more sustainable alternatives to an industrial and realistic environment, first applied research has to be carried out on both the development and processes of the materials to optimize their performance. In this thesis study, applied research was carried out using ultrasound technology on different nanocomposites and their transformation processes. Advances in the application of ultrasound for different transformation processes have been studied previously to ensure the approach of the practical study. This study focuses on the application of ultrasound in the process of obtaining new formulations by compounding extrusion and in injection molding, specifically in microinjection. The application of nanotechnology in the development of new materials will allow an improvement in performance and will open a range of new possibilities and applications. To explore the potential of ultrasonic molding (USM) technology, a preliminary process stability study was performed with polypropylene. The evaluation was carried out from a mechanical point of view, in which it was shown that, with an optimization of the process parameters and a correct design approach of the components with the nodal point allow a stability close to production was allowed. To deepen into the potential of USM technology in synergy with new nanocomposite formulations, a comparative study with the conventional microinjection process was performed. Two different nanocomposites based on a biopolymer matrix of poly 3-hydroxybutyrate with Cloisite 20 (organic modification), and with Cloisite 116 (unmodified) were studied. This research reveals that the USM technology, is stable obtaining micro-pieces, maintaining the chemical structure of the initial biocomposite without degrading and homogeneously achieving an exfoliation of both nanoclays. Conventional microinjection did show slight changes in the level of degradation and chemical structure, highlighting that it was not possible to micro-mold samples of the material with the unmodified nanoclay. The stabilization of the compounding extrusion assisted by an ultrasound system has been studied, with a design of a single component that allows the new approach to work in continuous condition and on pre-industrial equipment. Due to the success of the new component, it was possible to carry out the study of new formulations of polypropylene loaded with two different nanoclays (Cloisite 20 and Garamite 1958) and glass bubbles. The new nanocomposites reached the mechanical properties of a conventional material used for door panels in the automotive sector, but with a reduced density. The aim was to demonstrate that it is possible to reduce the weight of plastic components used in the automotive industry and reduce CO2 emissions for a standard vehicle. The research carried out in this thesis work has opened a new field of application to nanocomposites for weight reduction with improved mechanical properties when high level of dispersion is reached. In addition, the potential of USM technology for micro-molding applications has been demonstrated, showing high stability without material degradation during the process, and good dispersion of nano-reinforcements.El sector del plástico está en continuo cambio en busca de mejorar sus propiedades y rendimiento en diferentes aplicaciones. Actualmente. el impacto ambiental asociado al uso de los plásticos es una de las principales preocupaciones en el ámbito social. Se puede ver reflejado en regulaciones a nivel europeo como SUP Directive. Green Deal o estudios como el que efectúa la Oficina de Patentes Europeas Patents for tomorrow's plastics sobre las tendencias que reflejan las investigaciones en materiales alternativos al plástico convencional. Para poder llevar a un ambiente industrial y realista estas nuevas alternativas más sostenibles. primero se ha de llevar a cabo una investigación aplicada tanto del desarrollo de los materiales como de los procesos que pueden optimizar su rendimiento. En este estudio de tesis se lleva a cabo una investigación aplicada sobre diferentes nanocompuestos y sus procesos de transformación que pueden ser mejorados con la tecnología de ultrasonidos. Se ha estudiado los avances en la aplicación de ultrasonidos para diferentes procesos de transformación con el objetivo de enfocar correctamente el estudio práctico. Este estudio centra la aplicación de los ultrasonidos en el proceso de obtención de nuevas formulaciones por extrusión compounding y en el moldeo por inyección, concretamente en microinyeccion. La aplicación de nanotecnología en el desarrollo de nuevos materiales permitirá una mejora del rendimiento y abrirá un abanico de nuevas posibilidades y aplicaciones. Para explorar el potencial de la tecnología de microinyección por ultrasonidos (USM}, se realizó un estudio preliminar de estabilidad del proceso con un polipropileno. La evaluación fue llevada a cabo desde un punto de vista mecánico, en el que se demostró que con una optimización de los parámetros de proceso y un enfoque de diseño correcto de los componentes que hacen intervenir el punto nodal, se puede alcanzar un nivel de estabilidad cercano a producción. Para profundizar en el potencial de la tecnología USM en sinergia con nuevas formulaciones de nanocompuestos, se realizó un estudio comparativo con el proceso de microinyección convencional. Dos nanocompuestos basados en una matriz del biopolímero poli 3-hidroxibutirato con Cloisite 20 (modificación orgánica). Y con Cloisite 116 (sin modificar) fueron estudiados. Este estudio revela que la tecnología USM además de ser estable en la obtención de micropiezas, mantiene la estructura química del biocompuesto inicial sin llegar a degradación y alcanzando homogéneamente la exfoliación de ambas nanoarcillas. La microinyección convencional si mostro ligeros cambios a nivel de degradación y estructura química, destacando que no fue posible micromoldear muestras del material con la nanoarcilla sin modificar. La estabilización del proceso de extrusión compounding asistida por ultrasonidos ha sido estudiado, diseñando un componente único que permite al sistema de ultrasonidos trabajar en régimen continuo en equipos preindustriales. Gracias al éxito del nuevo componente, se ha podido llevar a cabo el estudio de nuevas formulaciones de polipropileno argado con dos nanoarcillas diferentes (Cloisite 20 y Garamite 1958) y esferas huecas. Los nuevos nanocompuestos alcanzaron las propiedades mecánicas de un material empleado para paneles de puerta en el sector automoción, pero con una densidad reducida. El objetivo fue demostrar que se puede reducir el peso de los componentes plásticos empleados en automoción y reducir las emisiones de CO2 para un vehículo estándar. La investigación llevada a cabo en este trabajo de tesis ha permitido abrir un nuevo campo de aplicación a los nanocompuestos para reducción de densidad con buenas propiedades mecánicas cuando la dispersión es alta. Además, se ha demostrado el potencial de la tecnología USM para aplicaciones de micromoldeo, mostrando alta estabilidad sin degradación del material durante el proceso, y buena dispersión de los nano-refuerzos.Polímers i biopolímer

High Performance Reinforced Hemp-Lime Nanocomposite Construction Materials

The aim of the project is to develop high performance, lightweight, durable, and environmentally friendly construction materials. Construction materials should have high compressive and flexural strength, low porosity, low thermal conductivity, low shrinkage and high water vapour permeability (breathability). The following materials were selected to achieve this aim; lime was selected as the base matrix material with hemp (fibres and shives) and wood glue (Poly vinyl acetate, PVAc). Specially selected nanomaterials were used as fillers. The properties of the developed material were used to design an eco-friendly wall consisting of a central 'Core' which will be the load bearing element, highly insulative layers with low thermal conductivity 'Insulators' and outer rendering materials for enhanced aesthetics purpose and breathability 'Renders'. The research conducted in this project enabled a number of different construction materials to be developed, each exhibiting their own characteristics to enable the aims and objectives of the project to be achieved. A summary of the findings is as follows: A load bearing wall requires relatively high compressive and flexural strengths of about 5 MPa and 4.0 MPa, respectively or higher. The 'Core' material designed consisted of 10 wt. % hemp fibres, 12 % PVAc/L, 4 wt. % nZnO (nanozinc oxide) and lime (NHL5, which its quantity was 1 kg for each batch of 4 samples for the whole project) and prepared using air curing method. The compressive strength was 17.7 MPa and the flexural strength was greater than 7.0 MPa, which were the highest results of strength throughout the project. The same mentioned mixture (10 wt. % hemp fibres, 12 % PVAc/L, 4 wt. % nanozinc oxide of lime) was cured using 'Oven-drying', the strengths in compression and flexure were still considerable, being 10 MPa and 4 MPa respectively which were more than the minimum limit of loadbearing material. This material, therefore, due to its high compressive strength, used as the 'Core' load bearing element of the proposed wall in the absence of a timber framework. The 'Insulator' was developed using a water removal 'Solvent exchange' technique and the mixture was 20 wt. % hemp shives, 12 % PVAc/L, 4 wt. % nanozinc oxide and lime. The thermal conductivity was 0.06 W/mK, much lower than that of pure lime which was 0.16 W/mK. The 'Insulator' will be applied in two layers, one on either side of the 'Core'. The 'Render' was developed using lime and 4 wt. % nanozinc oxide by wt. of lime and cured via air curing. It possessed a low porosity (18 %) in comparison to that of pure lime (36.4 %) and low thermal conductivity, (0.13 W/mK) in comparison to pure lime 0.16 W/mK cured by solvent exchange. Shrinkage was lowest in a Render material containing 4 % wt. nZnO, averaging 750 microstrain (μs) compared to the control sample (lime only) of 2428 μs. Chopped fibres, PVAc and nanozinc oxide were used for the first time with lime and no other examples of this exist in the literature (in the best knowledge of the researcher). Water vapour permeability (breathability), which is a beneficial property for construction materials was generally enhanced by using nanomaterials and the optimum breathability was achieved by adding 2 wt. % nanoclay to lime. The results achieved were used to design an eco-friendly wall in accordance with the Building Regulations. The U-value target was 0.18 W/m2K and the results show that a decrease in thickness of 40 mm could be achieved by using optimum materials V developed in this project in comparison to traditional hemp shives/Lime walls, in addition to eliminating timber studding which is normally required to provide support to non-loadbearing lime based walls

Comprehensive survey on nanobiomaterials for bone tissue engineering applications

One of the most important ideas ever produced by the application of materials science to the medical field is the notion of biomaterials. The nanostructured biomaterials play a crucial role in the development of new treatment strategies including not only the replacement of tissues and organs, but also repair and regeneration. They are designed to interact with damaged or injured tissues to induce regeneration, or as a forest for the production of laboratory tissues, so they must be micro-environmentally sensitive. The existing materials have many limitations, including impaired cell attachment, proliferation, and toxicity. Nanotechnology may open new avenues to bone tissue engineering by forming new assemblies similar in size and shape to the existing hierarchical bone structure. Organic and inorganic nanobiomaterials are increasingly used for bone tissue engineering applications because they may allow to overcome some of the current restrictions entailed by bone regeneration methods. This review covers the applications of different organic and inorganic nanobiomaterials in the field of hard tissue engineering

Nanoparticle Filled Polymeric Systems for Gas Barrier and Flame Retardant Properties

Polymer composite gas barrier and fire retardant properties were studied in this investigation. An increase in the gas barrier property was observed by adding silicate nanotubes or clay nanoparticles into polymeric systems. Oxygen permeability, diffusivity, solubility and water vapor permeability were determined for polyimide/silicate nanocomposites with 0 to 9.99% (vol/vol) filler loading. Both oxygen and water vapor permeability for the system gradually decreased when adding increasing amounts of nanofiller up to 4.50% (vol/vol) and increase again after that. The permeability decrease was caused by both the diffusivity and solubility coefficient changes, although diffusivity (the tortuous factor) is the main reason of permeability deduction. Other than polyimide systems, high aspect ratio mica filled LLDPE/LDPE multilayer materials were used for gas barrier property improvement. Multilayer coextrusion is an attractive approach for creating designed particulate-filled nanocomposite polymer film structures with enhanced gas barrier properties. Multilayered materials were annealed above the melting temperature of the polymers to activate interdiffusion and to concentrate the mica platelets in the filled LLDPE layers. SEM, TEM and WAXS analysis were employed to probe the films’ layer morphology and the platelet orientation/dispersion in the nanocomposite blends and nanoparticulate filled multilayer systems. The oxygen barrier of the blends and multilayer composites were measured and related to their morphologies. It was shown particle concentrated multilayering leads to an enhancement in oxygen barrier properties as compared to the as-received multilayer materials and nanocomposite blends with the same mineral compositions. Mica LLDPE/LDPE multilayers were tested for flammability. The multilayer technique and moving boundary effect causes further improvement of the flame retardant properties due to the particle concentration in the LLDPE layers. Although clay and various other types of nanoparticles have been reported and used as flame retardant materials, this study marks the first time nanoparticles were used as flame retardant materials in co-extruded multilayer systems. Flame retardant properties of the blends and multilayer composites were measured and related to the morphological observations. It was shown that multilayer materials have decreased peak heat release rate and enhanced char formation as compared to nanocomposite blends with the same mineral compositions. Flame retardant materials, zinc acetate (ZnAc), zinc undecylenate (ZnUnd) and Zinc stearate (ZnSt), were studied for thermal degradation and flame retardant properties on standard epoxy/amine systems. The zinc salts had improved flame retardant properties (decreased peak heat release rate (PHRR), smoke emission and improved char formation) on epoxy/amine systems and the flame retardant efficiency order was ZnAc, ZnUnd and ZnSt. The char of ZnUnd epoxy/amine composites, with surface protecting zinc oxide layers, formed a better physical barrier for the flame. SEM and X-ray were used to further understand the mechanism of zinc salts on flame retardant properties

Rational Design of Next-generation Nanomaterials and Nanodevices for Water Applications

Despite the fact that nanotechnology has been present for a few decades, there is a big gap between how nanotechnology is perceived and what nanotechnology can truly offer in all sectors of water. The question to be answered is 'what more can we expect from nanotechnology' in the water field? The rational nano-design starts with well-defined problem definitions, necessitates interdisciplinary approaches, involves 'think-outside-the-box', and represents the future growth point of environmental nanotechnology. However, it is still largely new to the educated public and even scientists and engineers in water fields. Therefore, it is the purpose of this book to promote the concept of rational nano-design and to demonstrate its creativity, innovation, and excitement. This book presents a series of carefully selected rationally designed nano- materials/devices/surfaces, which represent drastically different, ground-breaking, and eye-opening approaches to conventional problems to embody the concept of nano-design and to illustrate its remarkable potential to change the face of the research in water industry in the future. Each of the book contributors is world-renowned expert in the burgeoning field of rational nano-design for applications. Rational Design of Next-generation Nanomaterials and Nanodevices for Water Applications is intended for undergraduates, graduates, scientists and professionals in the fields of environmental science, material science, chemistry, and chemistry engineering. It provides coherent and good material for teaching, research, and professional reference

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

Nanostructural Materials with Rare Earth Ions: Synthesis, Physicochemical Characterization, Modification and Applications

This Special Issue of "Nanostructural Materials with Rare Earth Ions: Synthesis, Physicochemical Characterization, Modification and Applications" is related to studies of nanometer-sized materials doped and co-doped with rare earth ions and the creation of periodically ordered nanostructures based on single nanoparticles. A small particle size implies a high sensitivity and selectivity. These new effects and possibilities are mainly due to the quantum effects resulting from the increasing ratio of surface-to-volume atoms in low-dimensional systems. An important factor in this context is the design and fabrication of nanocomponents displaying new functionalities and characteristics for the improvement of existing materials, including photonic materials, conductive materials, polymers and biocomposites. With this concept in mind, the aim of the Special Issue is to publish research on innovative materials and their applications.Topics to be covered in this Special Issue include, but are not limited to, the following: Technology and applications of nanomaterials with rare earth ions; Advanced physicochemical properties, characterization and modification of nanomaterials with rare earth ions; Novel active materials, especially organic and inorganic materials, nanocrystalline materials, nanoceramics doped and co-doped with rare-earth ions with bio-related and emerging applications; Magnetic properties of nano-sized rare-earth compounds; Applications of nano-sized rare-earth-doped and co-doped optical materials