Service life prediction of organic coatings: electrochemical impedance spectroscopy vs actual service life

Electrochemical impedance spectroscopy (EIS) is used to derive an expression for predicting the service life of organic coating in a C4-type environment (industrial and costal areas with moderate salinity) as defined in ISO 12944 standard for paints and varnishes—corrosion protection of steel structures by protective paint systems. Three coating systems with a record of 2, 5, and 10 years of durability were selected for the study. The selection was also based on proven composition and dry film thickness (DFT) of the coatings as per ISO 12944. Electrochemical impedance measurements of the paint-coated panels were carried out by exposing the coated mild steel panels without scribe in different corrosive environments such as immersion in NaCl solution, neutral salt spray, etc. Neutral salt spray exposure was found to be the most severe corrosive environment among all the three coating systems. In most of the cases, EIS gave early indication of coating failure when compared to visual defects such as blistering and over-film corrosion.     

Effect of pro‐oxidants on biodegradation of polyethylene (LDPE) by indigenous fungal isolate,Aspergillus oryzae

Proxidant additives represent a promising solution to the problem of the environment contamination with polyethylene film litter. Pro‐oxidants accelerate photo‐ and thermo‐oxidation and consequent polymer chain cleavage rendering the product apparently more susceptible to biodegradation. In the present study, fungal strain, Aspergillus oryzae isolated from HDPE film (buried in soil for 3 months) utilized abiotically treated polyethylene (LDPE) as a sole carbon source and degraded it. Treatment with pro‐oxidant, manganese stearate followed by UV irradiation and incubation with A. oryzae resulted in maximum decrease in percentage of elongation and tensile strength by 62 and 51%, respectively, compared with other pro‐oxidant treated LDPE films which showed 45% (titanium stearate), 40% (iron stearate), and 39% (cobalt stearate) decrease in tensile strength. Fourier transform infrared (FTIR) analysis of proxidant treated LDPE films revealed generation of more number of carbonyl and carboxylic groups (1630–1840 cm⁻¹ and 1220–1340 cm⁻¹) compared with UV treated film. When these films were incubated with A. oryzae for 3 months complete degradation of carbonyl and carboxylic groups was achieved. Scanning electron microscopy of untreated and treated LDPE films also revealed that polymer has undergone degradation after abiotic and biotic treatments. This concludes proxidant treatment before UV irradiation accelerated photo‐oxidation of LDPE, caused functional groups to be generated in the polyethylene film and this resulted in biodegradation due to the consumption of carbonyl and carboxylic groups by A. oryzae which was evident by reduction in carbonyl peaks. Among the pro‐oxidants, manganese stearate treatment caused maximum degradation of polyethylene. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Computational Fluid Dynamics Modeling for Urea Hydrolysis in a Batch Reactor for Flue Gas Conditioning

A computational fluid dynamics (CFD) model is proposed to simulate urea hydrolysis for ammonia synthesis as a safe feed stock to flue gas conditioning in thermal power plants. A series of parametric studies to investigate flow rates, thermal boundary conditions, and reactor geometry was performed and operating conditions and reactor geometry were optimized. Detailed 3D flow, heat, and chemistry simulations of ammonia were carried out with predicted conversions comparable to measurements and the dependence of the experiments on the reaction parameters was evaluated. Through simulation under the same conditions the output was generated and compared to the experimental plot. Profiles of temperature and flow patterns were successfully achieved through simulation.     

Synthesis and water absorbency of crosslinked superabsorbent polymers

A series of novel copolymer superabsorbents based on monomer acrylamide (AM), potassium methacrylate (KMA), and 2‐hydroxyethyl methacrylate (HEMA) were prepared by copolymerization using ammonium persulfate (APS) as an initiator and N,N‐methylenebisacrylamide (MBA) as a crosslinking agent. The synthetic variables (the monomer concentration, crosslinker concentration, and initiator concentration) were also studied. The experimental results of superabsorbent polymers (SAPs) show a better absorbency in both water and NaCl solutions. The copolymers were characterized by IR spectroscopy. The water retention in the soil was enhanced using the above superabsorbents. The use of SAPs for the growth of groundnut plants was also investigated. SAPs can be considered for water‐managing materials for agriculture and horticulture purposes in desert and drought‐prone areas. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1795–1801, 2002     

Cellulose acetate and sulfonated polysulfone blend ultrafiltration membranes. I. Preparation and characterization

Modification of polymeric membrane materials by incorporation of hydrophilicity results in membranes with low fouling behavior and high flux. Hence, Polysulfone was functionalized by sulfonation and ultrafiltration membranes were prepared based on sulfonated polysulfone and cellulose acetate in various blend compositions. Polyethyleneglycol 600 was employed as a nonsolvent additive in various concentrations to the casting solution to improve the ultrafiltration performance of the resulting membranes. The total polymer concentration, cellulose acetate, and sulfonated polysulfone polymer blend composition, additive concentration, and its compatibility with polymer blends were optimized. The membranes prepared were characterized in terms of compaction, pure water flux, membrane resistance, and water content. The compaction takes place within 3–4 h for all the membranes. The pure water flux is determined largely by the composition of sulfonated polysulfone and concentration of additive. Membrane resistance is inversely proportional to pure water flux, and water content is proportional to pure water flux for all the membranes. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1749–1761, 2002     

Direct Ink-Jet Printing of Vertical Walls

Direct jet printing can assemble ceramic powder into a three dimensional shape by firing droplets of ink through a nozzle to build a multiple layered structure. As with stereolithography and selective laser sintering, the surface texture is expected to witness the layered assembly. The ability to create vertical walls by direct ink-jet printing was explored using a test piece based on a maze. The structure and topography are discussed in terms of droplet spreading and drying.     

Microwave-Assisted Synthesis of Fine Particle Oxides Employing Wet Redox Mixtures

Interaction of electromagnetic radiation with a physical mixture of metal nitrates and amides/hydrazides is observed to initiate high-temperature reactions, useful for realizing several high-temperature ceramic materials. A judicious choice of such redox mixtures undergoes exothermic reactions when they couple with microwave radiation. The coupling of electromagnetic radiation with metal salts and amides/hydrazides depends on the dielectric properties of the individual components in the reaction mixture. The approach has been used to prepare γ-Fe₂O₃, Fe₃O₄, MgCr₂O₄, α-CaCr₂O₄, and La_0.7Ba_0.3MnO₃.     

Mechanically robust and thermally enhanced sand-polyacrylamide-2D nanofiller composite hydrogels for water shutoff applications

Herein, we report a facile preparation method for mechanically robust and thermally enhanced sand-polyacrylamide (PAM)-2D-nanofillers composite hydrogels and their application in water shutoff. To prepare the sample, 4 wt% of aqueous PAM solution is mixed with organic cross-linkers of hydroquinone (HQ) and hexamethylenetetramine (HMT) in a 1:1 weight ratio and aqueous potassium chloride (KCl) solution and with a specific amount of 2D-nanofillers such as commercial graphene (CG) nanosheets or boron nitride nanoparticles (BN NPs). A specific amount of the above solution is added to sand, well mixed, and subsequently cured at 150°C for 8 h. The prepared composite hydrogels were characterized by Fourier-transform infrared spectroscopy (FT-IR) for chemical composition and X-ray diffraction (XRD) for successful hydrogel coating onto the sand particles. Thermal stabilities of the samples have been evaluated by differential scanning calorimetry (DSC). Mechanical properties (storage modulus [G′]; loss modulus [G″]; gel strength (G′/G″); and damping factor [G″/G′]) of the samples were determined using dynamic mechanical analyses. The thermal stability of the samples has reached as high as 193.4°C, while the gel strength is found to be a maximum of 16.2. The water swelling ratio for the composite hydrogel has reached a maximum of 1100% within 1 h.     

CFD modeling of multiphase flow distribution in catalytic packed bed reactors: scale down issues

Flow maldistribution in either a bench-scale or commercial scale packed bed is often responsible for the failure of the scale down unit to mimic the performance of the large reactor. The modeling of multiphase flow in a bench-scale unit is needed for proper interpretation of reaction rate data obtained in such units. Understanding the mechanism of flow maldistribution is the first step to avoiding it. In order to achieve this objective, computational fluid dynamic (CFD) simulations of multiphase flow under steady state and unsteady state conditions in bench-scale cylindrical and rectangular packed beds are presented for the first time. The porosity distribution in packed beds is implemented into CFD simulation by pseudo-randomly assigned cell porosity values within certain constraints. The flow simulation results provide valuable information on velocity, pressure, and phase holdup distribution.     

The role of synthetic and natural fillers on three‐body abrasive wear behaviour of glass fabric–epoxy hybrid composites

Polymer matrix composites are a promising candidate in tribological applications due to possibility of tailoring their properties with special fillers. The comparative performance of Glass–Epoxy (G‐E) composites with influence of synthetic fillers such as graphite (Gr) and silicon carbide (SiC) and biobased natural filler jatropha oil cake (JOC) was experimentally investigated. All the composites were fabricated using vacuum‐assisted resin infusion (VARI) technique. The mechanical properties were studied in accordance with ASTM standards. The three‐body abrasive wear studies were carried out with rubber wheel abrasion tester as per ASTM‐G65 standard. Two different loads namely 22 N and 32 N with different abrading distances viz, 135, 270, 405, and 540 m are test parameters. The results reveal that addition of JOC in G‐E composites has significant influence on wear under varied abrading distance/load. Further, it was found that SiC filled G‐E composites exhibited better wear resistance compared to Gr/JOC filled G‐E composites. The operating wear mechanisms have been studied by using scanning electron microscopy. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012