Infrared spectra of jute stick bleached with sodium chlorite and hydrogen peroxide

Jute stick was bleached with sodium chlorite and alkaline hydrogen peroxide solutions. The infrared (IR) spectra of bleached samples and jute stick were analyzed and compared. The bleached samples were characterized by higher absorbance intensity ratios (A_v/A₂₉₀₀) of the bands attributed to hemicellulose. Among the bleached samples the chlorite-bleached sample showed higher intensity for the bands mentioned. The bands attributed to lignin are either absent or very weak in the chlorite-bleached jute stick as compared to that of peroxide-bleached jute stick, although some residual lignin was present in the substrate. The 1635 cm^?1 band attribute to the vibration of adsorbed water molecules in the noncrystalline regions in cellulose appears as a sharp peak in chlorite-bleached jute stick and as a shoulder in peroxide-bleached jute stick. This can be attributed to the difference in the nature of the two bleaching processes.     

Hydration of fly ash-portland cements

Hydration products of fly ash-portland cements were studied with x-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM) as part of a continuing research effort to understand the pozzolanic activity of fly ashes. It was found that the amount of calcium hydroxide crystals in the cement pastes is diminished due to the addition of fly ash to the cement. Ettringite was produced in the early age, and the consumption of sulfate by the formation of ettringite was accelerated by the addition of fly ash. A partial conversion of ettringite to monosulfate within the first 7 days of hydration in the fly ash-portland cement pastes, but the formation of ettringite continued to form up to at least 28 days of hydration in the pastes without fly ash. Examination of the fly ash bearing pastes showed, in all cases, varying amounts of calcium hydroxide and unreacted portland cement, with minor quartz and gehlenite hydrate. It appears that hydration reactions actually occur in the fly ash cement pastes more or less on a particle-by-particle basis.     

The effect of w/c ratio and curing temperature on the permeability of hardened cement paste

The importance of concrete permeability is discussed relative to its effect on durability. Experimental studies were made of the effect of water/cement ratio and curing temperature on the porosity, pore size distribution and permeability of cement pastes. Although total porosities of samples cured at 60°C are smaller than in those cured at 27°C, the pore volume larger than 750Å radius is greater in the 60°C samples and is related to higher permeabilities also in the latter.     

29Si and 27Al MAS-NMR of NaOH-Activated Blast-Furnace Slag

b²⁹Si and ²⁷Al MAS-NMR were performed on NaOH-activated blast-furnace slag to better characterize the amorphous and poorly crystalline phases which occur in this system. The unreacted glass has a mainly dimeric silicate structure represented by a broad ²⁹Si peak (FWHM = 15 ppm) centered at –74.5 ppm [ Q ¹], with aluminum present exclusively in tetrahedral coordination. Upon reaction with 5M NaOH ( w/s = 0.4), three new ²⁹Si peaks with widths of ca. 2 ppm are formed at -78.5 Q ¹, –81.4 [ Q ²(1Al)J, and -84.3 [ Q ²]. Relative peak areas indicate a mostly dimeric silicate structure for the tobermorite-like C─S─H layers, with roughly a third of the bridging sites occupied by aluminum, and less than 10% by silicon. In addition to the tetrahedrally coordinated aluminum substituted in the C─S─H structure, ²⁷Al MAS-NMR reveals the presence of aluminum in octahedral sites, which is attributed to the aluminate phase (C,M)₄AH₁₃. ²⁹Si results indicate rapid initial consumption of the glass, with roughly a third of the glass reacting within the first day and another third consumed over the following 27 days.     

Synthesis and structure-activity relationship of the isoindolinyl benzisoxazolpiperidines as potent,selective, and orally active human dopamine D4 receptor antagonists

A new class of potent dopamine D(4) antagonists was discovered with selectivity over dopamine D(2) and the alpha-1 adrenoceptor. The lead compound was discovered by screening our compound collection. The structure-activity relationships of substituted isoindoline rings and the chirality about the hydroxymethyl side chain were explored. The isoindoline analogues showed modest differences in potency and selectivity. The S enantiomer proved to be the more potent enantiomer at the D(4) receptor. Several analogues with greater than 100-fold selectivity for D(4) over D(2) and the alpha-1 adrenoreceptor were discovered. Several selective analogues were active in vivo upon oral or intraperitoneal administration. A chiral synthesis starting from either D- or L-O-benzylserine is also described.     

Reinforcing effect of silica on the properties of styrene butadiene rubber–reclaim rubber blend system

Incorporation of silica into styrene butadiene rubber (SBR)–reclaim rubber (RR) blend system was carried out by sol–gel technique and conventional method. A well known silica coupling agent bis(3‐triethoxysilyl propyl) tetrasulfide was found to affect the curing characteristics and mechanical properties of SBR/RR vulcanizate. Here, the effect of RR on silica reinforcement was studied for different SBR/RR blend system. Silica incorporation by conventional mechanical mixing in absence of TESPT showed a much higher tensile properties than that of silica incorporated by the in situ sol–gel reaction of tetraethoxy silane both in presence and absence of TESPT. Studies of equilibrium swelling in a hydrocarbon solvent were also carried out. ATR study indicates that RR forms bond with silica particles due to the presence of active functional site on RR. The amount of silica incorporated by sol–gel reaction was determined through thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) studies further indicate the coherency and homogeneity in the silica filled SBR/RR vulcanizate. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 957–968, 2006     

Mechanical and dynamic mechanical studies of epoxy/VAc‐EHA/HMMM IPN–jute composite systems

Epoxy [50:50 mixture of Di‐Glycidyl Ether of Bis‐Phenol A (DGEBA) and Epoxidized Novolac (EPN)] was solution blended with Vinyl Acetate‐2‐ Ethylhexylacrylate (VAc‐EHA) resin in aqueous medium, in varying weight fractions, with Hexamethoxymethylmelamine (HMMM) as a crosslinker and data was compared with a control. The present work was aimed to optimize the tensile strength, dynamic mechanical strength, impact strength, and toughness by preparing a blend followed by jute composites of a semi‐ and full interpenetrating network (IPN). In control experiments epoxy alone was crosslinked (semi‐IPN), whereas the DGEBA‐EPN and VAc‐EHA/HMMM were crosslinked separately (full‐IPN), using jute as the substrate for making composites. Composites of full‐IPN systems of epoxy/VAc‐EHA system had higher moduli and UTS than the semi‐IPN systems. Dynamic mechanical study showed that full‐IPN systems have higher T_g values than semi‐IPN systems. The impact strength increases with increasing proportions of VAc‐EHA copolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 958–963, 2004     

Organoclays for soil remediation: Adsorption of 2,4-dichlorophenol on organoclay/aquifer material mixtures studied under static and flow conditions

A column material containing organophilic clay particles was developed for soil remediation. 2,4-dichlorophenol adsorption on aquifer material with an effective particle diameter d < 1 mm and various partially modified dioctadecyldimethylammonium–montmorillonite/aquifer material mixtures were studied under static and flow conditions. The 2,4-dichlorophenol adsorption on the aquifer material was negligible. On organoclay/aquifer material mixtures the adsorption capacity increased with increasing organoclay content and the adsorption isotherms could be fitted by the Freundlich equation. In columns filled with organoclay/aquifer material mixtures, the 2,4-dichlorophenol retardation increased with increasing organoclay content up to 1% (w / w). Above 1.5–2.0% (w / w) the permeability of the column material decreased. The HYDRUS_1D model, which solves the convection–dispersion equation for solute transport, was used in a forward and inverse mode to simulate 2,4-dichlorophenol breakthrough in the columns. The simulations revealed that 2,4-dichlorophenol transport exhibited an additional kinetic effect not observed in the batch experiments.     

Degumming and refining practices in the U.S.

The “state of the art” of degumming and refining crude vegetable oils in the U.S. is discussed with reference to (a) production volumes and significant quality characteristics of oils processed; (b) processes and equipment for degumming, refining, and waterwashing the oils, illustrated by diagrams and flow charts; and (c) key process controls and analytical testing requirements for each unit operation.