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  • Chemical Engineering  (21)
  • Organic Chemistry  (11)
  • 1995-1999  (32)
  • 1
    Electronic Resource
    Electronic Resource
    Block copolyetherester. Part 3: Preparation of block copolyetheresters by a terephthalic acid process in the presence of salts (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 190-194 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The block copolyetheresters with hard segments of poly(butylene terephthalate) and soft segments of poly(tetramethylene ether) were prepared by a terephthalic acid (TPA) process in the presence of some salts. The preparations of a block copolyetherester under various conditions were first studied in a 1 L stainless steel reactor to find the best method. Then, the preparations of four block copolyetheresters were run in a pilot plant comprising a 200 L polyesterification reactor and a 200 L polymerization reactor under the suitable condition. The presence of some salts reduced the formation of tetrahydrofuran (THF), and also reduced the total reaction time in the pilot plant. The thermal properties and various mechanical properties of the block copolytheresters prepared by the pilot plant were investigated to evaluate the feasibility of this method.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350212
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  • 2
    Electronic Resource
    Electronic Resource
    Destruction and removal of toluene and MEK from gas streams with silent discharge plasmas (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1325-1330 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effectiveness of applying silent discharge plasmas (SDP) for destroying and removing volatile organic compounds (VOCs) from gas streams is experimentally evaluated with a laboratory-scale reactor. The VOCs selected for study include toluene and methyl ethyl ketone (MEK). Direct collision with energetic electrons and reaction with generated gas-phase radicals are two major mechanisms responsible for destruction and removal of VOCs from gas streams. Operating parameters investigated include applied voltage, gas residence time, and temperature and composition of the gas stream. Experimental results indicate that the removal efficiency of toluene and MEK achieved with SDP can be enhanced by operating the system at a higher gas temperature and applied voltage due to the generation of more energetic electrons and radicals. O2 is essential for removing VOCs from gas streams with SDP. More than 80% removal efficiencies were achieved with this system for both toluene and MEK. SDP can potentially serve as an alternative control technology for removing VOCs from gas streams.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430521
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  • 3
    Electronic Resource
    Electronic Resource
    Fracture toughness of acrylonitrile-butadiene-styrene by J-integral methods (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1433-1439 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The fracture toughness of acrylonitrile-butadiene-styrene (ABS) was determined by three J-integral methods, ASTM E813-81, E813-87, and by hysteresis. The critical J values (J1c) obtained are fairly independent of the specimen thickness, ranging from 10 to 15 mm. ASTM E813-81 and hysteresis methods result in comparable J1c values, whereas the ASTM E813-87 was ∼40% to 50% higher. The critical displacement determined from the plots of hysteresis (energy or ratio) and the true crack grow length vs. displacement are close. This indicates the critical displacement determined by the hysteresis method is indeed the displacement at onset of crack initiation, and the corresponding J1c represents a physical event of crack initiation. The elastic storage energy. The input energy minus the hysteresis energy, is the most important factor in determining the onset of crack initiation. The critical elastic storage energy (at the beginning of crack growth) was found close to the J1c obtained from the E813-81 or the hysteresis method.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760351803
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  • 4
    Electronic Resource
    Electronic Resource
    Simultaneous monitoring of the enantiomeric purities of both substrate and product in the enzymatic resolution of (R,S)-2-acetoxy-3-bromopropyl para-toluenesulfonate by HPLC chiral column chromatography (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 7 (1995), S. 20-22 
    Details
    ISSN: 0899-0042
    Keywords: Chiralcel OD column ; direct reaction monitoring ; β-blocker intermediate ; Amano lipase AK ; enantiomeric excess ; timolol ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The enantiomeric purities of both substrate, 2-acetoxy-3-bromopropyl para-toluenesulfonate (I), and product, 2-hydroxy-3-bromopropyl p-toluenesulfonate (II) were examined in one analysis. The enzymatic resolution was conducted by Amano lipase AK and the enantiomeric excess as well as the conversion rate were monitored by HPLC analysis utilizing a Chiralcel OD column. After 7 h of reaction, HPLC results indicated that the enantiomeric purities of both substrate (I) and product (II) were greater than 95% and the conversion rate was around 55%. © 1995 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530070104
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  • 5
    Electronic Resource
    Electronic Resource
    Pharmacokinetics of ibutilide and its enantiomers in dogs (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 8 (1996), S. 18-23 
    Details
    ISSN: 0899-0042
    Keywords: racemate ; enantiomer ; bioavailability ; pharmacokinetic ; ibutilide ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ibutilide fumarate, a new drug for the treatment of cardiac arrhythmias, contains a stereogenic center bearing a secondary alcohol group. Several single dose and multiple dose studies of racemic ibutilide or its enantiomers were performed by the oral and intravenous routes in dogs. A chiral assay was used to examine racemization and the individual enantiomer pharmacokinetics. Following low oral or intravenous doses (approximately 0.3 mg/kg), the pharmacokinetics of the enantiomers were nearly identical, with no substantial chiral conversion. Both enantiomers exhibited high clearance rates, large volumes of distribution, and low oral bioavailability. As the dose increased, pharmacokinetic differences between the enantiomers were observed. The greatest differences (3-fold) were seen after oral administration at 4 mg/kg, indicating that first-pass metabolism of ibutilide was highly enantioselective at high doses. The clearances of the enantiomers differed by up to 34% at 5 mg/kg followed intravenous administration of the racemate. At high doses, other non-linear pharmacokinetic behavior was also apparent. The intravenous clearance of ibutilide declined from 5.3 L/h/kg at 0.3 mg/kg to 3.7 L/h/kg at a dose of 5 mg/kg. The absolute oral bioavailability of the racemate increased from 2% at 0.3 mg/kg to as much as 84% at 5 mg/kg. © 1996 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Theoretical studies on the acid-catalysed aromatization of benzene-cis-1,2-dihydrodiolsDetermination of Reactivity by MO Theory, Part 92. For Part 91, see Reference 1. (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 127-131 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Theoretical studies on the acid-catalysed dehydration of 15-substituted dihydrodiols were carried out using the AM1 method. In agreement with the experimental results, the rate-limiting step is dehydration of the protonated diols, R+, and the o-phenol-forming pathway (path 1) is favoured both kinetically and thermodynamically over m-phenol product formation. The transition state for path 1 (TS 1) is found to be at an early position (ca 23% progress) along the reaction coordinate and a better correlation of the rate constant is obtained with σ+. Three resonance forms can exist for the benzenonium intermediate but the contribution of one form is dominant in the later TS, which resembles the cationic intermediate. The contribution of the other two, however, weakens the σ+ effect of +M subsituents. The σP correlation of the rate constant in acid solution is therefore suggestive of a later TS resembling the cationic intermediate which is stabilized by solution.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080213
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  • 7
    Electronic Resource
    Electronic Resource
    Theoretical studies on the reactions of substituted phenolate anions with formate estersDetermination of Reactivity by MO Theory. Part 91. For Part 90, see Ref. 1. (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 325-334 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Semiempirical MO (PM3) studies are reported on the reactions of 18 substituted phenolate anions with m-(MNPF), p-(PNPF) and 3,4-dinitrophenyl formates (DNPF). The mechanistic change from rate-limiting formation to breakdown of the anionic intermediate (T-) can occur in the gas phase, especially for MNPF, at approximately an equal proton affinity (PA) of the nucleophile and leaving group phenolates, i.e. ΔPA = 0 as the PA of the phenolate anion is decreased. In solution, however, owing to the low stability of T and a greater stabilization by solvation of the transition state for the breakdown step (TS2), all three formate esters are predicted to proceed by a concerted mechanism, which is in agreement with the experimental results. The low stability of T can be ascribed to the relatively high electron affinity of the phenolate anions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080502
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  • 8
    Electronic Resource
    Electronic Resource
    Experimental and theoretical studies of shrinkage, warpage, and sink marks of crystalline polymer injection molded parts (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1222-1230 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An integrated theory and computer program were developed in this study for simulation of shrinkage, warpage, and sink marks of crystalline polymer injection molded parts. The basic theory considers the following items: (1) mold cooling analysis; (2) analysis of the polymeric filling, packing, and cooling processes; (3) viscoelastic behavior of polymeric fluid; (4) influence of thermal and mechanical properties of polymer; (5) pressure-volume-temperature relationship of polymer; (6) crystallization kinetics of crystalline polymer; and (7) solid mechanics analysis. Considered are the origins of defects, e.g. nonuniform cooling process, nonuniform volume shrinkage, flow-induced residual stress, thermal induced residual stress, and crystallization behavior. The boundary element and the finite difference method were applied toward calculating the mold cooling analysis for obtaining the temperature profile at the cavity surface as the boundary conditions in filling and packing analysis. A hybrid finite-element and finite-difference methods were employed for simulating the injection molding filling, packing, and cooling processes. A control volume method was applied towards both finding the melt front position and also calculating the temperature and pressure profile at any instant during the filling process. A modified Tait equation provided a description of the pressure-volume-temperature relationship of crystalline polymers. The Malkin's kinetics model was employed to describe the behavior of polymer crystallization. The flow-induced and thermal induced-residual stresses employed as the initial conditions in the solid mechanics analysis were obtained with the linear thermo-viscoelastic model. The displacements, including the thickness direction of part, which could not be calculated by the traditional bending moment method, were solved by using the numerical solid mechanics analysis with the three dimensional finite element method. These methods were applied to predict the shrinkage, warpage, and sink marks of crystalline polypropylene and amorphous ABS for the plate cavity. Both the qualitative results for the theoretical prediction correlated sufficiently with the experimental data. The theoretical results were also correlated using the commercial software C-MOLD.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760351505
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  • 9
    Electronic Resource
    Electronic Resource
    Blends of thermotropic liquid crystalline polyesters and poly(butylene terephthalate): Thermal, mechanical, and morphological properties (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1605-1614 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Blends of poly(butylene terephthalate) (PBT) with three different thermotropic liquid crystalline polyesters (TLCPs) were prepared. The first TLCP (HBH-6) consists of diad aromaticester type mesogenic units and the hexamethylene spacers along the main chain, and the second (TB-S6) is a wholly aromatic polyester TLCP having alkoxy side groups on the terephthaloyl moiety. The last (TR-4,6) is an LC copolymer comsisting of triad aromatic ester type mesogenic units and two differents spacers; tetramethylene and hexamethylene units. Blends of TLCP with PBT were melt spum at different LCP contents and differnt draw ratios to produce monofilaments. For the HBH-6/PBT and TB-S6/PBT blends, the ultimate tensile strength showed a maximum value at the 5 wt% level of LCP in the blends, and then it decreased when the LCP content was increased up to 20%. On the other hand, the initial modulus monotonically increased with increasing LCP content in all cases. The blends with TB-S6 showed the highest tensile properties of the three blends systems. This can be ascribed to the highest rigidity of the polymer chain, which still carries relatively long alkoxy substituents that promote sufficient adhesion between the LCP and PBT matrix. When compared with the PBT fiber itself, the fibers obtained from the 5% TB-S6/PBT blends exhibited an improvement in tensile strength by 〉 25% and in tensile modulus by ∼ 200%.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352006
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  • 10
    Electronic Resource
    Electronic Resource
    The hybrid FEM/FDM computer model for analysis of themeteirng section of a single-screw extruder (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 1748-1757 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A hybrid FEM/FEM computer model was employed n this studyfor simulating the non-newtonian, nonisothermal polymr melt fielt in the inetering section of a single-screw extruder. The pressure distribution in the screw surface was obtained by solving the generalized Reynolds equation. Instead of using the energy equation in Eulerian frame, a Lagrangian expression ws involved for stabilizing the numerical scheme. The temperature profiles wee obtained by finite difference discretizaton for the energy equation in such element. The screw surface with the screw channels and the flight lands could be modeled as a surface divided into small shell elements. To demonstrate aplicability, the results provided by the hybrid FEM/FDM were found to be similar to those of the 2D FDM for the trhermally developing flow, through Fenner's example. It can also ilustrate the leakage flow and the cross-channel effect in the screw pumping problem. The results from the Hybrid FEM/FDM revealed that if the clearance becomes too large, the volumetric flow rate would considerably decrease and the exist melt temperature would increase. In addtion, when the clearance is close to the normal design clearance, the leakage flow through the flight lands was found to be small. These computational results were observed to correlate with those of other experimental studies. Finally, the hybrid FEM/FDM approach can in principle be extended to the non-Newtonian, nonisothermal flow in a complex screw surface such as the barrier screw and the Maddock mixing head.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760352204
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