Miscibility of polymethylmethacrylate and polyethyleneglycol blends in tetrahydrofuran

The miscibility of polymethylmethacrylate (PMMA) and polyethyleneglycol (PEG) blends in tetrahydrofuran (THF) has been investigated by viscosity, density, refractive index, and ultrasonic velocity studies. Various interaction parameters such as polymer–solvent and blend–solvent interaction parameters and heat of mixing have been calculated using the viscosity, density, and ultrasonic velocity data. The results indicated the existence of positive interactions in the blend polymer solutions and that they are miscible in THF in the entire composition range. The study also revealed that variation in the temperature does not affect the miscibility of PMMA and PEG blends in THF significantly. The presence of hydrogen bonding in the blends in the solid state has also been indicated by FTIR studies. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Experimental study and hydrodynamic modeling of countercurrent liquid–solid system with batch liquid

It is known that a transient effluent outlet concentration is obtained with a batch of adsorbent solids in any operation. A preferred steady state outlet concentration can be achieved with a continuous flow of solids. In the present work, information on pressure profiles, the total pressure drop across the column and holdup of solids are experimentally obtained for various solid flow rates, particle sizes and densities in a countercurrent liquid–solid system. These experimental results are compared with the prediction obtained using a phenomenological model containing continuity and momentum balance equations. The dominant drag force term was expressed in terms of various drag equations. The drag expression developed by Foscolo et al. (1983 Foscolo, P. U., Gibilaro, L. G., and Waldram, S. P. (1983). A unified model for particulate expansion of fluidized beds and flow in fixed porous media, Chem. Eng. Sci., 38(8), 1251–1260.[Crossref], [Web of Science ®] , [Google Scholar]) could predict the axial profiles of pressure drop and holdup, and the effect of various parameters on total pressure drop and solid holdup most satisfactorily.     

Failure pressure estimations on a solid propellant rocket motor with a circular perforated grain

This paper presents analytical as well as finite element estimations of the failure pressure of a typical rocket motor, which is modelled as a body of a HTPB-based propellant material enclosed by a thin-walled flexible casing of 15CDV6 steel. The estimations are based on non-linear analyses, using stress–strain curves generated from the uniaxial tension specimens of the propellant as well as casing materials. Solid propellant being viscoelastic in nature, stress–strain curves generated at different strain rates have been used in the analysis. It is noted that the failure pressure of the rocket motor slightly increases in the presence of propellants. As the grain web thickness decreases, due to propellant burning the failure pressure slightly reduces and approaches the value of the maximum pressure in the hydroburst test of the motor case at the end of the propellant burning.     

Preparation and performance evaluation of poly (ether-imide) incorporated polysulfone hemodialysis membranes

Biocompatible Polysulfone (PSf) hemodialysis membranes were prepared by phase inversion technique using poly (ether-imide) (PEI) as the modification agent and Polyethylene glycol (PEG-200) as the pore former. The effect of PSf/PEI blend ratio on the morphology, hydrophilicity, water content, porosity, glass transition temperature, mechanical strength, biocompatibility and permeation rate of the prepared membranes were studied and were found to be improved significantly by the incorporation of PEI in the dope solution. The scanning electron microscopy (SEM) studies revealed that, incorporation of PEI resulted in the formation of spongy sub-layer and increased the connectivity of pores between sub-layer and bottom layer. The water content and permeation rate of the membranes of PSf/PEI blend membranes were increased considerably indicating the enhancement of hydrophilicity and it was supported by lower contact angle values of the blend membranes. The existence of single well defined Tg over entire composition established the compatibility between the components in blend membranes. The biocompatibility of membranes was investigated through protein adsorption, platelet adhesion and thrombus formation on the membrane surface. Anticoagulant activity of PSf/PEI blend membranes was evaluated by measuring the activated partial thrombin time (APTT), prothrombin time (PT), thrombin time (TT) and fibrinogen time (FT). The results revealed that antithrombogenicity of PSf/PEI blend membranes was increased significantly. The efficiency of these membranes in removal of urea, creatinine and vitamin B₁₂ were studied and found to be improved for blend membranes. Thus, it is worth mentioning to note that, the biocompatible PSf/PEI blend membranes prepared in this study would offer immense potential in hemodialysis.     

Recycled waste paper—A new source of raw material for electric double-layer capacitors

For the first time, a new carbon–carbon composite electrode material for supercapacitors is prepared by simple KOH activation of waste newspaper. The amorphous nature and surface morphology of the carbon composite are investigated by X-ray diffraction (XRD), N₂ adsorption/desorption and scanning electron microscopy. The surface area and pore diameter are 416 m² g⁻¹ and 5.9 nm, respectively. Electrochemical characteristics are evaluated by cyclic voltammetry (CV) and charge–discharge tests in 6.0 M KOH at a 1 mA cm⁻² current density. The CV results reveal a maximum specific capacitance of 180 F g⁻¹ at a 2 mV s⁻¹ scan rate and the data explore a development of new use for waste paper into a valuable energy storage material.     

Electrochemical characterization of polythiophene-coated steel

In situ electropolymerization leading to polythiophene coating has been found to be a new option for providing corrosion protection to mild steel surface. The polythiophene coating thus coated has been diagnosed through polarization and AC impedance analysis, which has demonstrated the passivation role of conducting polythiophene coating. The determination of volume fraction, water uptake and delamination area have been used to further support the corrosion protection of conducting polythiophene coating.     

HON-DESTRUCTIVE EXTRACTION IECHANIS1 OF BITUMINOUS COALS USING K-IETBTL-2-PY1LR0LID0NE

ABSTRACT

A technique whereby substantial portions of bituminous coals are extracted, non-destructively using N-Methyl-2-Pyrrolidone under mild conditions (202° C and 1 atm pressure) was previously reported. Herein, a parametric study on the extraction step is presented and a possible mechanism on the extraction is proposed. The extent of extraction shows little dependence on the solvent-to-coal ratio, coal particle size and treatment time whereas coal type and treatment temperature significantly affect the extent of extraction. Extractions for 26 different coals are reported and the results show reasonable correlation with the ratio of the volatile matter to fixed carbon (VM/FC), i.e. the inverse of the fuel ratio of the coal.

A postulated mechanism of extraction is based on the assumption of the two-phase structure of coal. Electron Paramagnetic Resonance (EPR) studies of the raw coal, and unextracted and extracted species support the proposed mechanism and lend support to the two-phase model of coal structure. The ratio (VM/FC) seems to be a fundamental parameter which relates coal properties to the accessibility of extractable components in the coal matrix.     

Failure Assessment on a Strip Biaxial Tension Specimen for a HTPB-Based Propellant Material

This paper indicates the possibility of assessing the failure of a strip biaxial tension specimen from the non-linear stress-strain behaviour of a uniaxial tension specimen which is useful for characterizing the propellant material. In order to examine the adequacy of the analytical and finite element methods, test data existing on a HTPB-based propellant material is used. Failure predictions on a strip biaxial tension specimen are found to be in reasonably good agreement with test results.     

HON-DESTRUCTIVE EXTRACTION IECHANIS1 OF BITUMINOUS COALS USING K-IETBTL-2-PY1LR0LID0NE

A technique whereby substantial portions of bituminous coals are extracted, non-destructively using N-Methyl-2-Pyrrolidone under mild conditions (202° C and 1 atm pressure) was previously reported. Herein, a parametric study on the extraction step is presented and a possible mechanism on the extraction is proposed. The extent of extraction shows little dependence on the solvent-to-coal ratio, coal particle size and treatment time whereas coal type and treatment temperature significantly affect the extent of extraction. Extractions for 26 different coals are reported and the results show reasonable correlation with the ratio of the volatile matter to fixed carbon (VM/FC), i.e. the inverse of the fuel ratio of the coal.

A postulated mechanism of extraction is based on the assumption of the two-phase structure of coal. Electron Paramagnetic Resonance (EPR) studies of the raw coal, and unextracted and extracted species support the proposed mechanism and lend support to the two-phase model of coal structure. The ratio (VM/FC) seems to be a fundamental parameter which relates coal properties to the accessibility of extractable components in the coal matrix.