Superhydrophobic Coatings Of Wax And Polymers Sprayed From Supercritical Solutions

The possibility of using supercritical carbon dioxide (scCO2) as the primary solvent in a spray process for producing superhydrophobic surfaces have been examined in this work. Using scCO2 as solvent will have considerably lower environmental impact compared to an organic solvent since scCO2 is considered a green solvent as it is non-toxic, non-flammable and recyclable. To be able to work at the pressures needed to reach the supercritical state of carbon dioxide, a high-pressure technique called rapid expansion of supercritical solutions (RESS) has been used to produce the coatings. Fluorinated compounds are often used when producing superhydrophobic coatings due to their intrinsic water repellent properties, but generally these compound do not degrade in nature. Due to this, a wax and a biodegradable polymer have been used as the coating materials in this work. Two RESS set-ups were used to spray a polymer from solutions of scCO2 and acetone. The first system was based on a continuous flow of the solvent mixture and the polymer particles were collected on silica surfaces. Some of the coatings had superhydrophobic properties and the limitation with this technique was the loss of particles between the nozzle and the surface. In the second set-up, RESS was combined with electrostatic deposition (ED) to improve the particle collection. Different processing parameters were examined and most of the RESS-ED sprayed surfaces were superhydrophobic. This was demonstrated by high contact angles against water, low contact angle hysteresis and low tilt angles at which a water droplet rolls off the surface. It was also shown that the surface structures created when spraying using RESS-ED induced the important two-level roughness that was needed to achieve superhydrophobicity. A semi-continuous process for scaling-up the RESS system when spraying the wax has been developed. Temperature and pressure was investigated to find the highest solubility of the wax in scCO2, and 250 bar and 67 °C resulted in the largest amount of sprayed wax. It was also shown that the system is suitable for spray-coating the wax on different substrates such as glass, paper, aluminium etc. since all of these surfaces showed superhydrophobic properties. The wear resistance of the coatings were examined by different methods. Scratch resistance, vertical compression and the friction between the surface and a finger were analysed. The polymer coated surfaces showed a larger robustness compared with the wax surfaces in the scratch tests. The superhydrophobicity was lost for the wax coatings exposed to compression loads above 59 kPa and in the frictions test, one finger stroke over the coating destroyed the surface roughness. Finally, the wax surfaces were investigated as coating barriers to protect steel from corrosion. The superhydrophobic coating was stable up to 10 days before corrosion of the steel started.

This book guides readers through superhydrophobic coating fabrication and thier application, representing the latest significant advances in this important topic.

The recent huge developments in nanotechnology and surface science are allowing the production of multifunctional coatings materials combining different properties: corrosion-protective actions, aesthetic functions, hydrophobic properties, self-healing abilities, etc. Moreover the increasing attention to environmental issues is driving the development of new systems, joining advanced performance with high sustainability, which can be better understood using new highly efficient experimental techniques. This frame is inducing us to consider the advances in organic coatings (the skin of materials) as one of the most interesting and promising innovation fields in material science and technology, with important consequences, not only considering fundamental aspects in science, but also for industrial applications, positively affecting everyday life. The aim of this Special Issue is to provide an update of the most advanced research in this area, showing the innovation trends and promoting further research for better properties of new coating materials.

Abstract: Superhydrophobic coatings are widely applicable, e.g., as self-cleaning surfaces or water-oil separation membranes, yet their wider usage is impeded due to costs of fabrication, size, or substrate limitation. Spray-coating is a versatile coating procedures and might offer a good solution for the fabrication of these superhydrophobic coatings, due to the fact that coatings can be fabricated on various materials in a simple, fast, and inexpensive manner. Most procedures rely on hybrid coatings of hydrophobized nanoparticles and a polymeric matrix, which have several drawbacks including the easy loss of nanoparticles and difficult waste handling. Here, the fabrication of the superhydrophobic material, called Fluoropor, for the first time, by spray-coating on various substrates including metals, tissues, concrete, and glass is presented. It is fabricated by spray-coating a mixture of a highly fluorinated monomer blended with porogens followed by photopolymerization. The superhydrophobicity of the material relies on the porous structure on the micro-/nanoscale across the bulk material and does not require any nanoparticles. Excellent self-cleaning ability of these coatings, resistance against thermal and abrasive impact, and their application as oil-water separation membranes are shown. This versatile applicability is highly promising for real-world application as self-cleaning coatings or oil-water separating membranes

This book investigates the enhancement of properties of acacia wood and its surface treatment for high strength bio-composites. It describes the tensile, flexural and impact strength, surface behaviour, morphological analysis, infrared spectral functional analysis, thermal properties analysis and dielectrical properties of acacia wood bio-composites. It reports efforts on the optimization of fabrication techniques to prepare acacia wood reinforced bio-composites based on PLA, PHA, Etc. The book also reports on environmental impact analysis of acacia wood bio-composites. A special chapter is dedicated to the nano-enhancement of acacia wood bio-composites and their possible use in applications in terms of sustainability and economics.

Nanocellulose Based Composites for Electronics presents recent developments in the synthesis and applications of nanocellulose composites in electronics, highlighting applications in various technologies. Chapters covers new trends and challenges in a wide range of electronic applications and devices. Significant properties, safety, sustainability, and environmental impacts of the electronic devices are included, along with the challenges of using nanocellulose-based composites in electronics. This book is an important reference for materials scientists and engineers configuring and designing processes for the synthesis and device fabrication of nanocellulose composites in electronics. Explores how to utilize nanocellulose fibers and nano-crystalline cellulose substances to synthesize materials with designed functionalities Outlines the major production processes for nanocellulous composites Discusses the major challenges that need to be surmounted in order to effectively use nanocellulous composites for electronics

This book addresses two critical problems that plague materials that make up components in both desalination and cooling water systems: corrosion, and fouling. The book addresses various types and components of industrial desalination technologies with solutions for controlling corrosion, scaling and biofouling. Issues unique to desalination systems, vital for the production of clean water, are considered as well. Green technologies are discussed throughout, along with environmental and economic considerations. The book presents solutions to the problems encountered by internal and external parts of these systems and will aid professionals that design, operate, and maintain them. It will be valuable to professionals in the materials, corrosion, electrochemical and wastewater industries, as well as chemical engineers. Addresses the corrosion issues facing the conventional and modern water desalination systems; Discusses the causes and remediation of problems caused by corrosion, scaling, and biofouling in water treatment; Offers green solutions, thereby minimizing environmental impact while increasing control and productivity of water systems; Suitable for professionals working with water desalination plants, materials scientists and corrosion engineers.