Effects of UV degradation on surface hydrophobicity, crack, and thickness of MWCNT-based nanocomposite coatings

Surface degradation is a common problem in polymeric coatings when they are exposed to sunlight, moisture, and oxygen. In order to reduce their surface degradation, thus keeping the coatings’ original properties, multi-wall carbon nanotubes (MWCNTs) were added, and the coatings were exposed to UV light and salt fog for various lengths of time. At 0 days of UV exposure, contact angle values of 0%, 0.25%, 0.5%, 1%, and 2% MWCNT-based nanocomposite coatings of 75 μm (∼3 mil) thickness were between 85° and 89°. However, after 16 days of UV exposure, contact angle values of the same samples were reduced to 11°, 13°, 34°, 50°, and 54°, respectively. Longer UV exposures resulted in several microcracks on the surface of the coated samples in the absence of nanoscale inclusions, while very minimal cracks or degradation appeared on the MWCNT-loaded samples. Test results also showed that UV exposure along with salt fogging reduced the coating thickness up to 24% at 0% CNTs; in contrast, this reduction was only 7% with a 2% MWCNT coating. These results clearly indicate that MWCNTs added to polymeric coatings reduce UV degradation, lessen surface cracks, protect the film thickness, and hence increase the lifetime of the polymeric coatings.     

Synthesis,characterization and application of Azadirachta indica juss (neem oil) fatty amides (AIJFA) based polyurethanes coatings: A renewable novel approach

Number of diethanol amides has been developed by scientist using various vegetable oils and not from neem seed oil. Most of the research work on neem seed oil has explored its applications in pharmaceutical and pesticides fields. This paper representing new area of application of neem seed oil for polymeric resin, in which we attempted to synthesize the neem seed oil based poly(urethane fatty amides) by reaction of neem oil fatty amide (AIJFA) with trimer of isophorone diisocyanate (IPDI). Spectral study of AIJFA was carried out by using FT-IR and ¹H NMR techniques. Molecular weight of AIJFA was determined by gel permeation chromatography (GPC). Fatty acid composition of neem seed oil was obtained by gas chromatographic method. The coatings applied on mild steel plates were evaluated by determining coating properties, chemical and corrosion resistances. TGA study of coatings showed higher thermal stability to AIJFA based PU coatings compared to normal urethane and alkyd coatings.     

Atomic force microscopy, scanning electron microscopy and electrochemical characterization of Al alloys, conversion coatings, and primers used for aircraft

Characterization of the metal–coating interface is crucial to the understanding and prediction of the performance of corrosion protective coatings. To date, such characterization has been incomplete and performed on a scale of measurement that gives little microscopic-scale information. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) have the ability to provide such information. We present in this work the use of such methods to examine the interface between steel and marine coatings and to image the surface of untreated aircraft aluminum alloys. We have also imaged these aircraft alloys after chromate/phosphate pretreatment. AFM and SEM have also been used to investigate the changes in surface morphology, which accompany changes in the samples due to exposure. Electrochemical noise methods, electrochemical impedance spectroscopy measurements, and Prohesion^TM testing were performed in parallel with the AFM/SEM measurements. The results, along with implications for aircraft coatings, are discussed.     

Synthesis,characterization and assessment of poly(urethane-co-pyrrole)s derived from castor oil as anticorrosion coatings for stainless steel

Electrically conductive and organic-solvent soluble poly(urethane-co-pyrrole)s (CPUPYs) were prepared by oxidative polymerization of pyrrole with a hydroxyl-terminated polyurethane prepolymer in the presence of ceric (IV) ammonium nitrate. Direct electrodeposition of CPUPYs from their appropriate solvent on the surface of stainless steel working electrode by continuous cycling potential between −0.8 and 1.8 V vs. Ag/AgCl with a scan rate of 0.03 V/s led to smooth, strongly adhered and insoluble coatings. All materials were characterized by conventional spectroscopic methods, and their physical and viscoelastic properties were evaluated. The corrosion protection properties of the CPUPYs-coated stainless steels were measured by Tafel polarization and electrochemical impedance spectroscopy. A substantial lower corrosion current, higher corrosion potential and higher charge transfer resistance values of CPUPYs-coated steels were recorded and comparisons were made with those properties of bare steel as well as parent polyurethane and neat polypyrrole-coated stainless steel. Excellent anticorrosive efficacy of newly developed CPUPYs-coated steel was achieved.     

Cross-linking agents for the protection of lyocell against fibrillation: synthesis, application and technical assessment of 2,4-diacrylamidobenzenesulphonic acid

A novel, colourless, water soluble, anionic cross-linking agent, 2,4-diacrylamidobenzenesulphonic acid, has been synthesised, applied to lyocell by a pad–steam method and the wet abrasion resistance measured. The agent furnished cross-linked lyocell fibres with good wet abrasion resistance and stable lyocell–agent bonds to subsequent hot exhaust reactive dyeing conditions. Surprisingly, the fibre–agent bonds showed some instability to polyester dyeing conditions at pH 4.5 and 5.0. This is rationalised in terms of hydrolysis of the amide bond ortho to the sulphonic acid group via a neighbouring group participation mechanism.     

Preparation and characterization of light curable hybrid coating: Its potential application for dental restorative material

The objective of this study was to synthesize a dual-functional light curable resin by the reaction between acrylated cycloaliphatic epoxy resin and 3-isocyanatopropyltrimethoxysilane and investigate the performance of this oligomer in the preparation of resin-based composite restoratives. FT-IR and ²⁹Si-NMR were used to characterize the structure of the hybrids. The char yields of the hybrids increased with inorganic content comes from TEOS (tetraethylorthosilicate) and synthesized SiUA oligomers. Gel content of polymeric films was found to be between 95% and 98%. Swelling was found to be between 3.1% and 3.8%. Weight loss of coated human teeth in synthetic saliva solution was found to be among 1% and 2%. There was a systematic increase in the modulus and tensile strength with the increase of inorganic content. On the other hand, elongation at break did not changed. Prepared hybrid coating materials exhibited improvement in tensile properties and hardness, when photo chemically cured.     

Preparation,characterization and application of Al2O3 nanoparticles for the protection of boiler steel tubes from high temperature corrosion

In this study, α-Al₂O₃ nanoparticles were prepared using a simple sol-gel method. Synthesized nanoparticles with NiCrAlY alloy were used as coating layer for high temperature corrosion control of boiler tubes in absence and presence of fuel ash. Thermal plasma technique was used for coating process. Corrosion rates of austenitic stainless steel tubes were evaluated via weight loss technique as a function of temperature. Prepared α-Al₂O₃ nanoparticles and surface morphology of austenitic stainless steel tubes were characterized by XRD, SEM and EDS analyses. The results show that the corrosion rate increases with increasing temperatures, in absence and presence of coating. Maximum coating efficiency was 82 and 88% in absence and presence of fuel ash respectively.     

Design,preparation, and characterization of new high-refractive index hybrid organic–inorganic polysiloxanes: Innovative coatings for optoelectronic applications

The current demand for high-refractive index materials is very high due to their importance in optoelectronic applications. Such materials already exist in the market, but they present many disadvantages. They might contain toxic metals; their preparation can be challenging or produce high quantity of waste. Consequently, there is an urgent need to produce new friendly coatings with high-refractive index. Hybrid organic–inorganic polysiloxanes can offer a solution to this problem. They can be easily prepared from nontoxic alkoxy silanes using the sol–gel chemistry process. Herein, a series of new hybrid polysiloxanes are synthesized from the monomer 1–(2–(triethoxysilyl)ethyl)triphenylsilane and other silanes. The preparation of the macromolecules is optimized at both stages of the sol–gel process. The polymers are characterized by gel permeation chromatography and NMR spectroscopy. Spin coating of the materials on silicon wafers, followed by film thickness and refractive index measurements, indicates that the new polysiloxanes can have refractive indexes as high as 1.6 with thicknesses varying from 2200 to 3700 nm. Consequently, it is expected that the new materials described in this report are valuable for optoelectronic applications such as high-dielectric constant (high-k) gate oxides, interlayer high-k dielectrics, or high-refractive index abrasion resistant coatings.     

Hydrophobically graded polyester polyol acrylate polymers: Synthesis,characterization, and microencapsulation of sulfamethoxazole for controlled release application

Polyester polyol macromers were prepared by using diacid‐diol condensation reaction using succinic acid as the acid component and polyethylene glycol 200 (PEG 200) as the diol component. Replacing PEG 200 with increasing amounts of butanediol resulted in macromers, which upon acrylation of end hydroxy groups and polymerization resulted in polymers with graded hydrophobicity depending on the amount of butanediol present in the polymer. These polymers showed expected trends in water equilibrium swells, equilibrium water contact angles, and in vitro degradation times depending on the amount of modification with butanediol. These polymers were used to microencapsulate sulfamethoxazole as a model drug and the in vitro delivery of the drug also followed the expected trend depending on the polymer hydrophobicity. Thus, it was shown that it is possible to prepare polyesters of graded properties by judicious selection of diacids and diols. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4058–4065, 2006     

A complete testing environment for the automated parallel performance characterization of biofuel cells: design,validation, and application

We present a complete testing environment for the parallel performance characterization of biofuel cells. Besides rapid-assembly electrode fixtures and an aseptic electrochemical reactor, it comprises a 24-channel electrical testing system that bridges the gap between simple load resistors and costly multi-channel potentiostats. The computer-controlled testing system features active current control to enable the forced operation of half-cell electrodes, whereas galvanic isolation between individual channels ensures interference-free operation of multiple fuel cells immersed in a common testing solution. Implemented into the control software is an automated procedure for the step-wise recording of polarization curves. This way, performance overestimation due to a too fast increase in load current can be circumvented. As an applicational example, three abiotically catalyzed glucose fuel cells are characterized simultaneously in a common testing solution. Complete disclosure of the electrical system (incl. printed circuit board layout, control software, and circuit diagrams) in the online supplementary material accompanying this paper allows researchers to replicate our setup in their lab and can serve as inspiration for the design of similar systems adapted to specific requirements. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis,characterization, and application of hetarylazo disperse colorants: Preparation and properties of ink-jet inks with active agents for polyester printing

The synthesis and characterization of two hetarylazo disperse colorants are described. These compounds were used for the preparation of ink-jet inks with and without active agents for polyester printing. The viscosity, conductivity, surface tension, and pH of these inks were studied over a period of time and discussed with respect to their structure and the active agent content. The particle size and particle size distribution of a representative ink containing a new synthesized hetarylazo compound were measured. All the prepared inks were proved to be suitable for ink-jet printing in terms of their particle size. Viscosity , surface tension, conductivity, and pH values of all inks, with and without active agent, were monitored over a period of 90 days and were related to the ink stability. The same properties were measured for an ink preparation with a commercial dye for comparison. The inks containing the new synthesized dyes were found to be more advantageous regarding most of the above properties, i.e., surface tension, viscosity, and conductivity. Contrarily pH values of all the preparations were unacceptable for ink-jet inks. The ink compositions containing the new synthesized compounds were applied by exhaustion (dyed) on polyester fabric. Fastness properties of the dyed polyester samples were excellent to very good in most cases. Color measurements of the dyed fabric were also performed. A qualitative determination of the aroma-active agent adsorbed on the fiber by the exhaustion method was achieved by the GC-MS method. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and application of fluorocarbon polymer/SiO2 hybrid materials,part 2: Water and oil repellent processing for cotton fabrics by sol–gel method

This research employed different procedures for out water and oil repellent finish on cotton fabrics with fluorocarbon copolymer or its hybrid materials. The experimental results indicated that fabrics processed with fluorocarbon copolymer have larger contact angle for water and oil repellent finish, and the fabric processed with simultaneous bathing of fluorocarbon copolymer/TEOS is the strongest but has poorer softness. Furthermore, when processing with chemical compounds, the processes or orders had little effect on the fabric's angle of contact and bleaching, but had more significant influence on strength. Regarding to washing fastness, after ten‐time water washing, the angle of contact of processed fabrics decreased by about 3%. Overall, the fabric pretreated with TEOS, followed by fluorocarbon polymer, had the best balance of physical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3019–3024, 2007     

Novel magnetic polyamic hydrazide nanocomposite: Preparation,characterization, and application for the removal of cd2+ and pb2+ from industrial wastes

In this work, a novel polymer polyamic hydrazide (PAH) was synthesized via the reaction of terephthalohydrazide with pyromelitic dianhydride. The obtained PAH was characterized with nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared (FT‐IR) spectroscopy and elemental analysis. Finally, a novel magnetic nanocomposite was prepared by immobilization of PAH on the Fe₃O₄ nanoparticles in water. The prepared magnetic nanocomposite was successfully used for selective removal of Pb²⁺ and Cd²⁺ ions from industrial wastes and the effects of affecting parameters on the adsorption capacity of the magnetic nanocomposite adsorbent for the removal of Pb²⁺ and Cd²⁺ from model aqueous solutions were investigated. The maximum adsorption capacities of Pb²⁺ and Cd²⁺ were found to be 138.9 and 103.1 mg g^?1, respectively. The kinetics and mechanism of the adsorption of Pb²⁺ and Cd²⁺ on the surface of the prepared nanocomposite were studied and it was found that complex formation between active sites of the surface of the nanocomposite and metal ions is the possible mechanism for adsorption of metal cations. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42538.     

Poly(N‐vinylpyrrolidone‐co‐2‐acrylamido‐2‐methylpropanesulfonate sodium): Synthesis,characterization, and its potential application for the removal of metal ions from aqueous solution

In the current study, poly(N‐vinylpyrrolidone‐co‐2‐acrylamido‐2‐methylpropanesulfonate sodium), poly(VP‐co‐AMPS), was prepared and used for the removal of Cu²⁺, Cd²⁺, and Ni²⁺ ions via a polymer‐enhanced ultrafiltration (PEUF) technique. The copolymer was synthesized by radical polymerization in an aqueous medium with a comonomer feed composition of 50:50 mol %. The molecular structure of the copolymer was elucidated by ATR‐FTIR and ¹H NMR spectroscopy, and the average molecular weight was obtained by GPC. The copolymer composition was determined to be 0.42 for VP and 0.58 for AMPS by ¹H NMR spectroscopy. The copolymer and homopolymers exhibited different retention properties for the metal ions. PAMPS exhibited a high retention capacity for all of the metal ions at both pH values studied. PVP exhibited selectivity for nickel ions. Poly(VP‐co‐AMPS) exhibited a lower retention capacity compared to PAMPS. However, for poly(VP‐co‐AMPS), selectivity for nickel ions was observed, and the retention of copper and cadmium ions increased compared to PVP. The homopolymer mixture containing PAMPS and PVP was inefficient for the retention of the studied metal ions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41272.