Toughening of Epoxy Resin with Solid Amine Terminated Poly （ethylene glycol） Benzoate and Effect of Red Mud Waste Particles

An investigation was carried out to modify the toughness of triethylene tetramine cured DGEBA （diglycidyl ether of bisphenol-A） resin using solid amine terminated poly （ethylene glycol） benzoate （ATPEGB） as modifier with and without red mud waste particles. The solid ATPEGB modifier synthesized from the acid catalyzed esterification reaction of poly （ethylene glycol） （PEG） and 4-amino benzoic acid was characterized by Fourier transform infrared spectroscopy （FT-IR） and ^1H-NMR （nuclear magnetic resonance） spectroscopies, viscosity measurements, and solubility parameter calculation. The unfilled and red mud waste filled modified epoxy networks were evaluated with impact, adhesive, tensile, flexural and thermal properties by differential scanning calorimetry （DSC）, thermogravimetric （TG） and dynamic mechanical analysis （DMA）. The effect of modifier concentration and red mud waste particles on toughening behavior was also investigated. The optimum properties were obtained at 12.5 phr （parts per hundred parts of resin） concentration of the modifier. The ATPEGB modified cured epoxy was thermally stable up to 315℃. The morphology on fracture surfaces of cured epoxy was also analyzed by scanning electron microscopy （SEM）.     

Preparation and properties of poly(N-vinylcarbazole) and MWCNT nanocomposites

N-vinylcarbazole (NVC) was polymerized in bulk through the interaction of multi-walled carbon nanotube (MWCNT) without any extraneous catalyst. A PNVC-MWCNT composite was isolated by MeOH precipitation of a polymerization system containing NVC and MWCNT at melting temperature of the monomer. The inclusion of PNVC in the composite was endorsed by the FTIR study. TG analysis revealed the thermal stability trend as MWCNT > PNVC-MWCNT composite > PNVC. DTA showed two exothermic peaks at 427 degrees C and 607 degrees C in the PNVC-MWCNT composite. Transmission electron microscopic analyses of MWCNT revealed presence of tubular MWCNT particles with diameters in nm range while the corresponding analysis for the composite showed the formation of spherical dark polymer particles encapsulating cylindrical MWCNT moieties with some ends of uncoated MWCNT tubes (light shades) protruding out of the dark spherical particles. Scanning electron microscopic analysis revealed presence of tubular CNT particles entangled with the composite particles of irregular shapes and sizes. XRD analysis revealed no additional crystalline peaks for PNVC in the composite. In contrast to PNVC homopolymer (10(-12)-10(-16) S/cm), the dc conductivity values of the composite varied form 1.3 to 33 S/cm depending upon the weight ratio of MWCNT and PNVC in the composite. Current-voltage characteristics of the composite showed a linear variation and conductivity-temperature studies revealed an increase in conductivity by 35% in the temperature range 150-220 degrees C.     

Conducting nanocomposites of poly(N-vinylcarbazole) with single-walled carbon nanotubes

The in situ solid-state polymerization of N-vinylcarbazole (NVC) at an elevated temperature in the presence of single-walled carbon nanotubes (SWCNTs) leads to the formation of new types of composite materials, the morphology and properties of which were characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and electrical property measurements. FTIR spectroscopy and XPS studies confirmed the ability of SWCNTs to initiate the in situ polymerization of NVC monomers. FE-SEM and TEM results showed the coating of the outer surfaces of SWCNTs by the PNVC hompolymer with separation of individual SWCNTs from the bundles. Thermogravimetric analysis revealed a moderate improvement in the thermal stability of the nanocomposites at a higher temperature region relative to the base polymer. The electrical conductivity of neat polymer dramatically improved in the presence of SWCNTs. For example, dc electrical conductivity increased from 10(-16)-10(-12) S x cm(-1) for neat PNVC to approximately 10(-6) S x cm(-1) for nanocomposite containing 9 wt% SWCNTs.     

Investigation of mechanical factor of soil reinforced with four types of fibers: An integrated experimental and extreme learning machine approach

ABSTRACT

This study investigates and compares mechanical factor (a dimensionless parameter and defined as the ratio of the compressive strength of fiber reinforced soil to that of unreinforced soil) for soils reinforced with four different fibers (three natural fibers and one synthetic fiber). An integrated methodology was utilized, including 351 laboratory experiments for obtaining data and Extreme Learning Machine (ELM) technique for developing functional relationships between mechanical factor and soil and fiber parameters. Soils reinforced with synthetic fiber (Polypropylene) and with natural fibers exhibited different characteristics when subjected to the same variation in soil parameters. This phenomenon can be attributed to the differences in surface morphology and water absorption capability of Polypropylene comparative to other natural fibers. Polypropylene–soil composite shows the maximum sensitivity to the soil moisture. It also shows the least sensitivity toward soil density and fiber content among all tested fiber–soil composites.     

Simulation of abrasive flow machining process for 2D and 3D mixture models

Improvement of surface finish and material removal has been quite a challenge in a finishing operation such as abrasive flow machining (AFM). Factors that affect the surface finish and material removal are media viscosity, extrusion pressure, piston velocity, and particle size in abrasive flow machining process. Performing experiments for all the parameters and accurately obtaining an optimized parameter in a short time are difficult to accomplish because the operation requires a precise finish. Computational fluid dynamics (CFD) simulation was employed to accurately determine optimum parameters. In the current work, a 2D model was designed, and the flow analysis, force calculation, and material removal prediction were performed and compared with the available experimental data. Another 3D model for a swaging die finishing using AFM was simulated at different viscosities of the media to study the effects on the controlling parameters. A CFD simulation was performed by using commercially available ANSYS FLUENT. Two phases were considered for the flow analysis, and multiphase mixture model was taken into account. The fluid was considered to be a Newtonian fluid and the flow laminar with no wall slip.     

Electro-conductive Palmyra Fibers By In Situ Polymerization of Pyrrole

Palmyra (Borassus flabellifer L.) is one of the natural fruit fibers that are available in plenty. This fiber has many advantages, such as biodegradability, renewability, low density, and low cost, which offer greater opportunities to develop new applications. Imparting electrical conductivity to this fiber may open up avenues for various novel applications. In the present study, Palmyra fibers are made electro-conductive by in situ chemical polymerization of pyrrole with FeCl₃ oxidant and PTSA dopant. Prepared electro-conductive fibers show average electrical resistivity 2.96 kΩ cm^?1. A positive correlation is found between fiber-length and electrical resistance, whereas a negative correlation is found in between fiber-diameter and electrical resistance. FTIR study is conducted to understand the chemical interaction between lingo-cellulose and polypyrrole. Tensile properties and thermal degradation behavior of the prepared electro-conductive fibers are evaluated, and significant deterioration of both tensile properties and thermal stability is observed. Due to this reason, these electro-conductive fibers are unsuitable for mechanical processing and high-tech applications. But the response of these fibers in different pH solution is investigated, and their possible application as a pH sensor has been explored.     

Production of Low-P Steel

Production of low phosphorus steel using the basic oxygen steelmaking process is conventionally achieved by maintaining a highly basic slag. This leads to high flux consumption, generates a large volume of slag and restricts recycling of the slag due to presence of free lime. The environmental impact goes further, since the calcined lime involves depletion of a mineral resource, consumption of fossil fuels and release of CO₂. However, recent studies indicate that adequate dephosphorisation is possible in the BOF even if the slag basicity is reduced from the current practice (3.3–3.6) to a level of 2.7–2.8. Phosphorus partitioning deviates considerably from equilibrium and post stirring of bath helps in lowering bath phosphorus. Induction furnace is widely used to produce structural grade steel. Since lining is usually acidic, effective phosphorus removal is not achieved. But using basic lining reasonably low phosphorus steel could be produced.     

Kinetics of phase transfer catalyzed reduction of nitrochlorobenzenes by aqueous ammonium sulfide: Utilization of hydrotreater off-gas for the production of value-added chemicals

The reduction of nitrochlorobenzenes (NCBs) was carried out in an organic solvent, toluene, under liquid–liquid mode with phase transfer catalyst, tetrabutylammonium bromide (TBAB). The selectivity of chloroanilines (CANs) was found to be 100%. The reaction rate of m-nitrochlorobenzene (MNCB) was found to be highest among the three NCBs followed by o- and p-nitrochlorobenzene (ONCB and PNCB). The reactions were found to be kinetically controlled with apparent activation energies of 22.8, 19.6 and 9.4 kcal/mol for ONCB, PNCB and MNCB, respectively. The effects of different parameters such as TBAB concentration, NCB concentration, sulfide concentration, ammonia concentration, and elemental sulfur loading on the conversion and reaction rate of NCBs were studied to establish the mechanism of the reaction. The rate of reaction of NCBs was found to be proportional to the concentrations of the catalyst and NCBs and to the cube of the concentration of sulfide. A generalized empirical kinetic model was developed to correlate the experimentally obtained conversion versus time data for the three NCBs.