scholarly journals Curing of Functionalized Superhydrophobic Inorganic/Epoxy Nanocomposite and Application as Coatings for Steel

Coatings ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 83
Author(s):  
Mohamed H. Wahby ◽  
Ayman M. Atta ◽  
Yasser M. Moustafa ◽  
Abdelrahman O. Ezzat ◽  
Ahmed I. Hashem
Keyword(s):  
Adhesion Strength ◽  
Lattice Structure ◽  
Salt Spray ◽  
Contact Angles ◽  
Inorganic Nanoparticles ◽  
Crystalline Lattice ◽  
Epoxy Coatings ◽  
Epoxy Networks ◽  
Chemical Structures ◽  
Steel Surfaces

Superhydrophobic epoxy nanocomposites coatings with superior mechanical and adhesion strength are targeted to increase epoxy coating performance and to protect steel corrosion in aggressive environment. The present work prepared hydrophobic organic modified inorganic nanoparticles (NPs) based on magnetite, titanium dioxide and silver capped with epoxide oleic, linoleic and linolenic fatty acids. Their chemical structures, thermal stability, crystalline lattice structure, morphology and particles sizes distribution were determined using different tools. The curing exothermic reactions and thermal mechanical properties of the cured commercial epoxy with polyamine hardener were evaluated in the presence of the modified NPs to investigate their effect on the curing mechanism and crosslinking densities of the cured epoxy networks. The adhesion strength, abrasion resistance, seawater contact angles and seawater salt spray resistances of the cured epoxy coatings were evaluated on the steel surfaces. The obtained results confirm that the increasing weight contents of the modified NPs embedded into epoxy networks via chemical linking affect the adhesion, superhydrophobicity and anticorrosion performances of the cured epoxy coatings on the steel surfaces.

scholarly journals New Imidazolium Ionic Liquids from Recycled Polyethylene Terephthalate Waste for Curing Epoxy Resins as Organic Coatings of Steel

Coatings ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1139
Author(s):  
Ayman M. Atta ◽  
Hamad A. Al-Lohedan ◽  
Abdelrahman O. Ezzat ◽  
Nourah I. Sabeela
Keyword(s):  
Polyethylene Terephthalate ◽  
Epoxy Resins ◽  
Salt Spray ◽  
Thermal Characteristics ◽  
Weight Ratio ◽  
Organic Coatings ◽  
Imidazolium Ionic Liquid ◽  
Pet Waste ◽  
Chemical Structures ◽  
Steel Surfaces

Imidazolium ionic liquid (IIL) was prepared from aminolysis of polyethylene terephthalate (PET) waste with pentaethylenehexamine (PEHA) to apply as hardener of epoxy resin. Its purified chemical structures, thermal stability, and thermal characteristics were identified as well as amino phthalamide aminolyzed products. The thermal, thermomechanical, and mechanical properties of the cured epoxy resins with different weight percentages of IIL were investigated to optimize the best weight ratio to obtain homogeneous networks. The adhesion, durability, and corrosion resistance of the cured epoxy resins on the steel surfaces were tested to confirm that the best weight ratio of epoxy: IL was 2:1. This ratio achieved higher adhesion strength and salt spray resistance to seawater extended to 1500 h.

scholarly journals Using Graphene-Based Composite Materials to Boost Anti-Corrosion and Infrared-Stealth Performance of Epoxy Coatings

Nanomaterials ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1603
Author(s):  
Meng-Jey Youh ◽  
Yu-Ren Huang ◽  
Cheng-Hsiung Peng ◽  
Ming-Hsien Lin ◽  
Ting-Yu Chen ◽  
...  
Keyword(s):  
Electrochemical Impedance ◽  
Graphene Nanosheets ◽  
Salt Spray ◽  
Corrosion Current ◽  
Filler Concentration ◽  
Epoxy Coatings ◽  
Corrosion Properties ◽  
Water Contact ◽  
Different Temperatures ◽  
Thermal Signature

Corrosion prevention and infrared (IR) stealth are conflicting goals. While graphene nanosheets (GN) provide an excellent physical barrier against corrosive agent diffusion, thus lowering the permeability of anti-corrosion coatings, they have the side-effect of decreasing IR stealth. In this work, the anti-corrosion properties of 100-μm-thick composite epoxy coatings with various concentrations (0.01–1 wt.%) of GN fillers thermally reduced at different temperatures (300 °C, 700 °C, 1100 °C) are first compared. The performance was characterized by potentiodynamic polarization scanning, electrochemical impedance spectroscopy, water contact angle and salt spray tests. The corrosion resistance for coatings was found to be optimum at a very low filler concentration (0.05 wt.%). The corrosion current density was 4.57 × 10−11 A/cm2 for GN reduced at 1100 °C, showing no degradation after 500 h of salt-spray testing: a significant improvement over the anti-corrosion behavior of epoxy coatings. Further, to suppress the high IR thermal signature of GN and epoxy, Al was added to the optimized composite at different concentrations. The increased IR emissivity due to GN was not only eliminated but was in fact reduced relative to the pure epoxy. These optimized coatings of Al-GN-epoxy not only exhibited greatly reduced IR emissivity but also showed no sign of corrosion after 500 h of salt spray test.

scholarly journals Bonding of Selected Hardwoods with PVAc Adhesive

2020 ◽  
Vol 11 (1) ◽  
pp. 67
Author(s):  
Ján Iždinský ◽  
Ladislav Reinprecht ◽  
Ján Sedliačik ◽  
Jozef Kúdela ◽  
Viera Kučerová
Keyword(s):  
Adhesion Strength ◽  
Cold Water ◽  
Ph Value ◽  
Water Extract ◽  
Solid Wood ◽  
Contact Angles ◽  
Water Contact ◽  
Ph Values ◽  
Positive Tendency ◽  
The Impact

The bonding of wood with assembly adhesives is crucial for manufacturing wood composites, such as solid wood panels, glulam, furniture parts, and sport and musical instruments. This work investigates 13 hardwoods—bangkirai, beech, black locust, bubinga, ipé, iroko, maçaranduba, meranti, oak, palisander, sapelli, wengé and zebrano—and analyzes the impact of their selected structural and physical characteristics (e.g., the density, cold water extract, pH value, roughness, and wettability) on the adhesion strength with the polyvinyl acetate (PVAc) adhesive Multibond SK8. The adhesion strength of the bonded hardwoods, determined by the standard EN 205, ranged in the dry state from 9.5 MPa to 17.2 MPa, from 0.6 MPa to 2.6 MPa in the wet state, and from 8.5 MPa to 19.2 MPa in the reconditioned state. The adhesion strength in the dry state of the bonded hardwoods was not influenced by their cold water extracts, pH values, or roughness parallel with the grain. On the contrary, the adhesion strength was significantly with positive tendency influenced by their higher densities, lower roughness parameters perpendicular to the grain, and lower water contact angles.

scholarly journals Hydrophilicity Improvement of Polymer Surfaces Induced by Simultaneous Nuclear Transmutation and Oxidation Effects Using High-Energy and Low-Fluence Helium Ion Beam Irradiation

Polymers ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 2770
Author(s):  
Jung Woo Kim ◽  
Seung Hwa Yoo ◽  
Young Bae Kong ◽  
Sung Oh Cho ◽  
Eun Je Lee
Keyword(s):  
Surface Texture ◽  
Ion Irradiation ◽  
Ion Beam ◽  
High Energy ◽  
Contact Angles ◽  
Polymer Chains ◽  
Polymer Surfaces ◽  
Water Contact ◽  
Chemical Structures ◽  
Nuclear Transmutation

Two commodity polymers, polystyrene (PS) and high-density polyethylene (HDPE), were irradiated by high-energy He ion beams at low fluence to examine the wettability changes at different fluences. The water contact angles of the PS and HDPE surfaces were reduced from 78.3° to 46.7° and 81.5° to 58.5°, respectively, upon increasing the fluence from 0 to 1 × 1013 He2+/cm2 for irradiation durations ≤4 min. Surface analyses were performed to investigate these wettability changes. Surface texture evaluations via scanning electron and atomic force microscopies indicated non-remarkable changes by irradiation. However, the chemical structures of the irradiated polymer surfaces were notable. The high-energy He ions induced nuclear transmutation of C to N, leading to C–N bond formation in the polymer chains. Further, C–O and C=O bonds were formed during irradiation in air because of polymer oxidation. Finally, amide and ester groups were generated by irradiation. These polar groups improved hydrophilicity by increasing surface energies. Experiments with other polymers can further elucidate the correlation between polymer structure and surface wettability changes due to high-energy low-fluence He ion irradiation. This method can realize simple and effective utilization of commercial cyclotrons to tailor polymer surfaces without compromising surface texture and mechanical integrity.

scholarly journals Modified Epoxy with Chitosan Triazine Dihydrazide Derivatives for Mechanical and Corrosion Protection of Steel

Coatings ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1256
Author(s):  
Ayman M. Atta ◽  
Ayman El-Faham ◽  
Hamad A. Al-Lohedan ◽  
Abdelrahman O. Ezzat
Keyword(s):  
Exothermic Reaction ◽  
Epoxy Coatings ◽  
Thermal Stabilities ◽  
Chemical Structures ◽  
Curing Characteristics ◽  
Mechanical Adhesion ◽  
Molecular Masses ◽  
Amine Groups ◽  
Surface Morphologies ◽  
Modified Epoxy

Modification of the curing exothermic reaction of epoxy resin with polyamine (PA) hardeners by new chemically bonded fillers to improve the mechanical properties and anticorrosion performances of the epoxy coatings is the main goal for wide applications of epoxy coatings. In this work, the chemical structure of chitosan was modified with triazine hydrazide moiety that contains primary, secondary, and tertiary amine groups to act as activator and dangling chain linkers during the curing of epoxy/PA system. Different molecular masses of chitosan were modified with triazine dihydrazide moiety (Ch-TH2), and their chemical structures and surface morphologies were identified. Their thermal stabilities were investigated, and the grafting percentages with triazine hydrazide were determined from thermal analysis. Different weight percentages of Ch-TH2 ranged from 1 to 10 Wt. % were added to the epoxy/PA system, and their curing characteristics, such as heat enthalpy and glass transition temperature, were determined from non-isothermal dynamic scanning calorimetric thermograms. The effects of molecular masses, triazine dihydrazide %, and Ch-TH2 Wt. % on the mechanical, adhesion and anticorrosive properties of the cured epoxy/PA coatings for steel were investigated. The optimum Ch-TH2 Wt. % was selected from 3 to 6 Wt. % to improve the mechanical, adhesion, and anticorrosive properties of the cured epoxy/PA coatings.

scholarly journals Assessment of Anti-Corrosion Performances of Coating Systems for Corrosion Prevention of Offshore Wind Power Steel Structures

Coatings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 970 ◽  
Author(s):  
Sung-Hyun Eom ◽  
Seong-Soo Kim ◽  
Jeong-Bae Lee
Keyword(s):  
Wind Power ◽  
Adhesion Strength ◽  
Marine Environment ◽  
Power Plants ◽  
Salt Spray ◽  
Steel Structures ◽  
Offshore Wind ◽  
Coating System ◽  
Fracture Type ◽  
Offshore Wind Power

The anti-corrosion performance of coating systems (cathode protection, organic coating, and duplex coating) applied to prevent the corrosion of offshore wind power plants was assessed. As an assessment method, the adhesion strength of each coating system was evaluated after exposing the coatings to the marine environment and an indoor salt spray test. It was confirmed that the adhesion strength varied depending on the exposure period, and the deterioration of adhesion strength was related to the fracture type of each coating layer. In addition, the fracture type of each coating system was analyzed and the adhesion strength was corrected according to the fracture type. The corrosion rates after exposure to the marine environment and indoor salt spray were compared and examined using the corrected values.

Nanoengineered Superhydrophobic Surfaces to Prevent Adhesion of Listeria monocytogenes for Improved Food Safety

2020 ◽  
Vol 63 (5) ◽  
pp. 1401-1407
Author(s):  
Bog Eum Lee ◽  
Youngsang You ◽  
Won Choi ◽  
Eun-mi Hong ◽  
Marisa M. Wall ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Listeria Monocytogenes ◽  
Biofilm Formation ◽  
Electrochemical Etching ◽  
Contact Angles ◽  
Bacterial Attachment ◽  
Superhydrophobic Surfaces ◽  
List Type ◽  
Ptfe Film ◽  
Steel Surfaces

HighlightsNanoporous superhydrophobic surfaces were fabricated using electrochemical etching and Teflon coating.Adhesion of Listeria monocytogenes to the nanoengineered stainless steel surfaces was reduced.Self-cleanable food-contact surfaces prevent bacterial attachment and subsequent biofilm formation.Abstract. Bacterial attachment on solid surfaces and subsequent biofilm formation is a significant problem in the food industry. Superhydrophobic surfaces have potential to prevent bacterial adhesion by minimizing the contact area between bacterial cells and the surface. In this study, stainless steel-based superhydrophobic surfaces were fabricated by manipulating nanostructures with electrochemical etching and polytetrafluoroethylene (PTFE) film. The formation of nanostructures on stainless steel surfaces was characterized by field emission scanning electron microscopy (FESEM). The stainless steel surfaces etched at 10 V for 5 min and at 10 V for 10 min with PTFE deposition resulted in average water contact angles of 154° ±4° with pore diameters of 50 nm. In addition, adhesion of Listeria monocytogenes was decreased by up to 99% compared to the bare substrate. These findings demonstrate the potential for the development of antibacterial surfaces by combining nanoporous patterns with PTFE films. Keywords: Electrochemical etching, PTFE, Nanoengineered surface, L. monocytogenes, Superhydrophobic.

scholarly journals STUDIES ON AMPHIBIAN YOLK

1963 ◽  
Vol 18 (1) ◽  
pp. 135-151 ◽  
Author(s):  
Shuichi Karasaki
Keyword(s):  
Fine Particles ◽  
Lattice Structure ◽  
Hexagonal Lattice ◽  
Superficial Layer ◽  
Crystalline Lattice ◽  
Main Body ◽  
Embryonic Cells ◽  
Amphibian Species ◽  
Ca 50 ◽  
Band Spacing

The yolk platelets of mature eggs and young embryonic cells of all amphibian species studied (Rana pipiens, Triturus pyrrhogaster, Diemictylus viridescens, Rana nigromaculata, and Bufo vulgaris) have a superficial layer of fine particles or fibrils (ca. 50 A in diameter), a central main body with a crystalline lattice structure, and an enclosing membrane approximately 70 A in thickness. Electron micrographs of the main body reveal hexagonal net (spacing ca. 70 A), square net (spacing ca. 80 A), and parallel band (spacing from 35 to 100 A but most frequent at ca. 70 A) patterns. The crystalline structure is believed to be a simple hexagonal lattice made of closely packed cylindrical rods. Each rod is estimated to be about 80 A in diameter and 160 A in length.

Fabrication and Wettability Analysis of Hydrophobic Stainless Steel Surfaces With Microscale Structures From Nanosecond Laser Machining

2018 ◽  
Vol 6 (3) ◽  
Author(s):  
Cong Cui ◽  
Xili Duan ◽  
Brandon Collier ◽  
Kristin M. Poduska
Keyword(s):  
Stainless Steel ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Surface Structures ◽  
Laser Machining ◽  
Nanosecond Laser ◽  
Static Contact ◽  
Submicron Structures ◽  
Steel Surfaces ◽  
Hierarchical Multiscale

In this work, nanosecond laser machining is used to fabricate hydrophobic 17-4 PH stainless steel surfaces with microscale and submicron structures. Four surface structures were designed, with microscale channels and pillars (100 μm pitch size) of uniform heights (100 μm) or alternating heights (between 100 μm and 50 μm). During fabrication, the high-power laser beams also created submicron features on top of the microscale ones, leading to hierarchical, multiscale surface structures. Detailed wettability analysis was conducted on the fabricated samples. Measured static contact angles of water on these surfaces are over 130 deg without any coating, compared to ∼70 deg on the original steel surface before laser machining. Slightly lower contact angle hysteresis was also observed on the laser machined surfaces. Overall, these results agree with a simple Cassie–Baxter model for wetting that assumes only fractional surface area contact between the droplet and the surface. This work demonstrates that steel surfaces machined with relatively inexpensive nanosecond laser can achieve excellent hydrophobicity even with simple microstructural designs.

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