Low-surface-energy materials based on polybenzoxazines for surface modification of textiles

The benzoxazine monomers, 3-tert-butyl-3,4-dihydro-8-allyl-2H-1,3-benzoxazine (Benz-m) and 2,2-bis(3-methyl-3,4-dihydro-2H-1,3-benzoxazinyl) propane (Benz-b) were synthesized successfully using Mannich reaction. The formation of the monomer was confirmed by ¹H NMR and FTIR spectroscopy. Both the monomers were coated onto cotton fabric and the fabric samples were then dried at 60°C and cured at 120°C for varying time period. During the curing process, monomer was converted to polybenzoxazine by ring-opening polymerization of oxazine ring. In the Raman spectra, presence of the characteristic absorption bands due to benzoxazine structure at 952, at 1037 and at 1348?cm^?1 even after curing at 120°C for 2?h, suggested incomplete ring opening of benzoxazine to form polybenzoxazine. Also, the lack of durability of the finish to washing appears be due to the mild conditions of curing. Therefore, the application of Benz-b monomer was investigated on polyester (PET) fabric, which could be subjected to higher temperature however for shorter duration. The water and oil (ethylene glycol) repellency was measured to determine the hydrophobicity and oleophobicity of the finish on PET fabric. It was found that there was a marked improvement in the durability to laundry when compared with the treated cotton samples. This study provides a unique and easy method to prepare a low-surface-energy material through a simple thermal treatment procedure without using fluoro polymers or silicones.     

Estimation of theaflavin content in black tea using electronic tongue

Biochemical components like theaflavins (TF) play very important role in the quality of finished CTC (cut, torn, and curled) variety of tea. TF are known to provide characteristic astringency to the taste of finished CTC tea. The quality indicators like brightness, briskness, strength, color and overall quality of tea liquor are also due to the amount of TF present. A positive correlation is normally observed between the amount of TF and the quality scores of finished tea. Biochemical tests that yield the percentage of TF are often time consuming, require meticulous effort of sample preparation, storage and measurement. This paper proposes an alternative approach of quality evaluation of CTC tea by predicting the amount of TF that may be present in a given tea sample, using a voltammetric electronic tongue.     

Adsorption of surfactant during chemical enhanced oil recovery

Surfactant is extensively used as chemicals during chemical enhanced oil recovery (CEOR) process. Effectiveness of surfactant CEOR process depends on several parameters like formation of micro emulsion, ultra-low interfacial tension (IFT) and adsorption of surfactant. First two parameters enhance the effectiveness while the last parameter reduces the effectiveness. Micro emulsions are highly desirable for CEOR due to its low interfacial tension (IFT) value and higher viscosity. In this research the size of the emulsions were studied with particle size analyzer to study the liquid–liquid absorption process and the entrapment of oil drops inside surfactant drop. Initially, the average surfactant drop size was found to be 100 nm, after mixing the surfactant slug with reservoir crude, the size was increase up to 10 times. It signifies the formation of micro emulsion between surfactant and oil. Another attempt was done in this research to study the adsorption mechanism of surfactant on reservoir rock. The process of adsorption was studied by Langmuir and Freundlich isotherm to understand the adsorption phenomena. In this study, it was found that the adsorption follows Freundlich isotherm and the adsorption phenomena was chemical for surfactant flooding process. In chemical adsorption phenomena, the rate of adsorption is high because, surfactant molecules are adsorbed layer after layer by the rock surface. Use of alkali along with surfactant reduces adsorption of surfactant since, alkali blocked the active clay sites before interacting with surfactant and hence the adsorption isotherm was found to be Langmuir and phenomena was physical adsorption.     

Top gate ZnO-Al2O3 thin film transistors fabricated using a chemical bath deposition technique

ZnO thin films were prepared by a simple chemical bath deposition technique using an inorganic solution mixture of ZnCl₂ and NH₃ on glass substrates and then were used as the active material in thin film transistors (TFTs). The TFTs were fabricated in a top gate coplanar electrode structure with high-k Al₂O₃ as the gate insulator and Al as the source, drain and gate electrodes. The TFTs were annealed in air at 500 ℃ for 1 h. The TFTs with a 50 μm channel length exhibited a high field-effect mobility of 0.45 cm²/(V·s) and a low threshold voltage of 1.8 V. The sub-threshold swing and drain current ON-OFF ratio were found to be 0.6 V/dec and 10⁶, respectively.     

Efficient organic solvent and oil sorbent co-polyesters: Poly-9-octadecenylacrylate/methacrylate with 1-hexene

In this work, highly absorbent cross linked co-polymer gels of cis-9-octadecen-1-ol with acrylic/methacrylic acid and 1-hexene in different molar ratios were synthesized by thermal polymerization techniques and studied. The polymers were characterized by Fourier Transform-Infrared Spectroscopy, Thermogravimetric analysis and Scanning Electron Microscopy techniques. Their non-ionic nature was verified with the help of transport number measurement by Wagner polarization technique. The polymers were found to have very high swelling capacities in organic solvents like chloroform, tetrahydrofuran, ethanol, diethylether, thiophene, pyridine, and benzene. These gels show maximum swelling for chloroform which reaches up to 750%. The swelling capacities for different oils like kerosene, gasoline, engine oil, and silicon oil, are also favorable. The swelling kinetics confirmed that the swelling followed second order kinetics. The chloroform retention time was also checked which established that the gels can be recycled and reused again and again. An experiment showing removal of kerosene from kerosene/water mixture is also performed. This confirms that these gels can be used in removing organic contaminants and oil from water and can help in water purification and environmental cleanup purposes.     

Three-dimensional sodium phosphinates derived from a bis-functionalized phosphinic acid

The synthesis and crystal structures of two three-dimensional sodium phosphinates are reported. While [Na₂{(CH₂OH)₂PO₂}₂(H₂O)]_n (1) is formed from the direct reaction of bis(hydroxylmethyl)phosphinic acid with NaOH, the addition of 1,10-phenanthroline to the above reaction mixture results in the formation of [Na₂{(CH₂OH)₂PO₂}₂]_n (2). The basic structural unit of the 3D polymeric networks in both 1 and 2 is a dimeric Na₂L₂ moiety. In case of 1, these units are interconnected through coordination via phosphoryl and alcoholic oxygen atoms to eventually result in a three-dimensional network. However in the case of 2, only the phosphoryl oxygen is responsible for gluing the Na₂L₂ dimeric units into a three-dimensional framework.     

Agar immobilized yeast cells in tubular reactor for ethanol production

Saccharomyces cerevisiae cells were immobilized in agar gel and used in a tubular reactor for conversion of cane molasses to ethanol at 30 degrees C, pH 4.5. Reactor was used in a continuous operation to test the operational stability and ethanol productivity. After 100 days of continuous fermentation at a dilution rate of 0.67 hr-1, some deactivation of cells was observed, but ethanol productivity was recovered by reactivating the cells by sparging air intermittently. It was found that intermittent reactivation during continuous operation was very important for satisfactory performance of the reactor. During operation, gel beads maintained their rigidity. Maximum ethanol concentration (94.9 g/L) was obtained with a feed containing 255 g/L reducing sugar, at a dilution rate of 0.2 hr-1. Maximum volumetric productivity (79.5 g ethanol /L/hr), specific ethanol productivity (0.58 g ethanol/g cells/hr), specific sugar uptake rate (1.12 g sugar/g cells/hr) and ethanol yield coefficient (0.43 g ethanol/g sugar) were obtained with a feed containing 195 g/L reducing sugar at a dilution rate of 1.33 hr-1.     

D.C. electrical properties of vacuum-deposited CdTe films

The current-voltage characteristics of vacuum-deposited CdTe films were studied as a function of film thickness (2500–13000 Å) at various temperatures (0–110°C). The d.c. conduction mechanism was explained using a modified Poole-Frenkel equation.     

Composites from compounding wood fibers with recycled high density polyethylene

The development of composites consisting of wood fibers and recycled plastics offers not only an opportunity to utilize an abundant natural resource but also a means to alleviate the serious plastics disposal problem. In this work, aspen fibers are incorporated into recycled high density polyethylene with a co-rotating inter-meshing twin-screw extruder to study processing-property relationships. Tensile, impact, and flexural strengths are measured as functions of fiber concentration. The effects of fiber pretreatment, screw configuration, and compounding temperature on the properties of composites are discussed.