Synthesis of a New Diisocyanate-Based Polyurethane

A new polyurethane was prepared by polycondensation reaction of the α, 4-diisocyanate anisole with polypropylene glycol. Synthetic procedures for the preparation of the new diisocyanate are described. The monomers and the polymers formed therefrom are characterized by IR and NMR spectral data. Thermal stability of the polymer was studied by thermogravimetry.     

Second-Order Correction for Convective Wall Plume in Power-Law Fluids Over an Isothermal Wall

This paper considers the steady-state free-convection flow arising from an infinitely long horizontal line source of heat embedded at the leading edge of a vertical isothermal surface when the ambient fluid is a non-Newtonian fluid, for moderately large values of the generalized Grashof numbers by the method of matched asymptotic expansion. The first- and second-order boundary layer equations are considered. In particular, the second-order corrections to account for the non-boundary layer effects have been predicted. A family of numerical solutions are reported for the power-law fluid behavior index, n, ranging from 0.4 to 1.5 and for Pr = 10 and 100.     

Free-Radical Graft Copolymerization of Polar Monomers on Low-Density Polyethylene Under Melt-Processing Conditions

Free-radical graft co polymerization of acrylic acid and ethyl methacrylate on low-density polyethylene (LDPE) was studied under simulated melt-processing conditions. Initiators benzoyl peroxide and dicumyl peroxide were evaluated for their grafting efficiency. Benzoyl peroxide was found to be an excellent catalyst for the grafting of both monomers, whereas dicumyl peroxide was quite ineffective. Effect of reaction time, initiator concentration, and reaction temperature was studied for benzoyl peroxide initiated graft co polymerization of the two monomers. The changes in the torque and temperature of the reaction melt in the course of the reaction were recorded. More or less quantitative grafting of both monomers could be achieved, using low initiator concentrations, in very short reaction times. The possibility of modifying LDPE during melt extrusion in the extruder itself has been clearly demonstrated. This would be a highly cost-effective way of diversifying the properties and applications of LDPE. Cross linking was found to be relatively higher in the graft co polymerization of acrylic acid but within acceptable limits. Possible mechanisms of this are discussed.     

Nanocomposites based on copolymers of fluorinated imide and polyhedral oligomeric silsesquioxane macromonomer: microstructure and morphology studies

Towards the development of copolymeric nanocomposites, N‐3(trifluoromethyl)phenyl‐7‐oxanorbornene‐5,6‐dicarboximide (TFI) monomer and a macromonomer of polyhedral oligomeric silsesquioxane (POSS) were synthesized. Ring‐opening metathesis polymerization to copolymerization of specified proportions of the two co‐monomers was carried out. All the monomers and polymers were characterized using Fourier transform IR analysis and ¹H and ²⁹Si NMR. Gel permeation chromatography shows that copolymeric nanocomposites have a lower average molar mass than a homopolymer of TFI (HTFI). TGA shows that the thermal stability of the copolymer is inversely proportional to the proportion of POSS units. DSC studies have demonstrated that the glass transition temperature (T_g) of a nanocomposite possessing 25 wt% POSS is at a higher temperature (180 °C) than that of HTFI (175 °C). Transmission electron microscopy and AFM images of copolymers are consistent with the self‐assembled spherical aggregation of POSS units, while X‐ray diffraction studies have confirmed the homogeneous dispersion of the same units within the nanocomposites. © 2012 Society of Chemical Industry     

Enrichment of glutaminase production by Bacillus subtilis RSP‐GLU in submerged cultivation based on neural network—genetic algorithm approach

BACKGROUND: Owing to the importance of glutaminase in biotech product production, its production with isolated Bacillus subtilis RSP‐GLU (MTCC 9727) was investigated. Fermentation factors play an important role in product enhancement. Hence, glutaminase production was optimized using an artificial neural network (ANN) coupled genetic algorithm (GA). RESULTS: A ‘6–12–1’ topology ANN was constructed to identify the nonlinear relationship between fermentation factors and enzyme yield. ANN‐predicted values were optimized for glutaminase production using a GA. The overall mean absolute predictive error (MAPE) and the mean square errors (MSE) were observed to be 0.00125 and 1.77 and 0.002 and 3.06 for training and testing, respectively. The goodness of neural network prediction (coefficient of R²) was found to be 0.996. The maximum interactive impact on glutaminase production was noted with rpm versus medium volume. The use of ANN–GA hybrid methodology resulted in a significant improvement (47%) in glutaminase yield. CONCLUSION: Five different optimum fermentation conditions out of 500 revealed maximum enzyme production. Glutaminase enzyme production in this Bacillus subtilis RSP‐GLU is strongly influenced by aeration of the fermentation. A hybrid ANN‐GA effectively identifies the different fermentation conditions for optimum production of enzyme in a given large set of conditions. Copyright © 2009 Society of Chemical Industry     

Low Cycle Fatigue Behavior of 316LN Stainless Steel Alloyed with Varying Nitrogen Content. Part I: Cyclic Deformation Behavior

In this study, the influence of cyclic strain amplitude on the evolution of cyclic stress–strain response and the associated cyclic deformation mechanisms in 316LN stainless steel with varying nitrogen content (0.07 to 0.22 wt pct) is reported in the temperature range 773 K to 873 K (500 °C to 600 °C). Two mechanisms, namely dynamic strain aging and secondary cyclic hardening, are found to strongly influence the cyclic stress response. Deformation substructures associated with both the mechanisms showed planar mode of deformation. These mechanisms are observed to be operative over certain combinations of temperature and strain amplitude. For strain amplitudes >0.6 pct, wavy or mixed mode of deformation is noticed to suppress both the mechanisms. Cyclic stress–strain curves revealed both single and dual-slope behavior depending on the test temperature. Increase in nitrogen content is found to increase the tendency toward planar mode of deformation, while increase in strain amplitude leads to transition from planar slip bands to dislocation cell/wall structure formation, irrespective of the nitrogen content in 316LN stainless steel.