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  • Chemical Engineering  (9)
  • 1995-1999  (5)
  • 1975-1979  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Pressure fluctuations and particle dispersion in liquid fluidized beds (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1164-1169 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420429
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  • 2
    Electronic Resource
    Electronic Resource
    A simple approach to determining three-dimensional screw characteristics in the metering zone of extrusion processes using a total shape factor (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 274-283 
    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: It is of great importance in designing extruders to predict the screw characteristics, that is, the throughput in terms of the screw speed and the pressure gradient along the down-channel direction. The screw characteristics depend on the extruder geometry, the operating conditions, and material properties of non-Newtonian fluids. This paper suggests a simple approach to determining the screw characteristics for a three-dimensional flow in a channel with a finite aspect ratio (ratio of a width to a depth, W/H) by introducing a Total Shape Factor (Ft) to correct a two-dimensional flow analysis for a channel with an infinite aspect ratio. In the present study, the Total Shape Factor (Ft) was defined as a ratio of a net flow rate obtained by the three-dimensional analysis to that by the two-dimensional analysis. In the proposed approach, the quantity, ∂Ft/∂(H/W), which turns out to be almost constant, offers important information for understanding the effects of the flights. Threfore, ∂Ft/∂(H/W) is extensively reported in this paper in terms of several dimensionless parameters. This simple approach with such a database will be very useful for extruder designers to predict screw characteristics.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350308
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  • 3
    Electronic Resource
    Electronic Resource
    Enhanced polycarbonate toughness. I: Measurement methodology (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 471-476 
    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 JIC values for core-shell-particle-toughened polycarbonate were determined at different temperatures and at 0, 2.5, 5.0, 7.5, and 10.0 phr particle content by six similar methods, using compact tensile specimens. At the 2.5 phr toughener level, the JIC values ranged from 2878 to 6100 J/m2, and at 7.5 phr, they ranged from 6125 to 10,760 J/m2, dependent only upon how the same JI-Δ a data were interpreted. This indicates that more work will be required before a reliable method of JIC measurement that can be applied to tough polymers is achieved.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350603
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  • 4
    Electronic Resource
    Electronic Resource
    Enhanced polycarbonate toughness. II: Mechanisms (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 477-482 
    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: Glassy shell-rubbery core polymer particles, 0.1 to 0.2 μm in diameter, increase the plane strain JIC values of 3.175 mm thick polycarbonate from 3.05 kJ/m2 (no particles) to 9.5 kJ/m2 (7.5 phr particles) at 23°C. Some modest decreases in these values are caused by tests at -20°C in samples 9.525 and 3.175 mm thick. If only the particle concentration is varied, JIC increases monotonically to 7.5 phr (by wt), then levels off or decreases slightly at 10.0 phr. The total volume of 1 to 2 μm diameter cavities formed in the matrix by the apparently unbonded particles behaves similarly; cavity volume and JIC are directly related. With increasing particle concentration the tensile modulus is unchanged, the yield stress and strain decrease modestly, the strain at fracture decreases appreciably, and the heat recoverable orientation in the fractured samples decreases. Few cavities are formed. The particles reduce the extent of shear deformation in the tensile samples.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350604
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  • 5
    Electronic Resource
    Electronic Resource
    Polyurethane - polystyrene interpenetrating polymer networks (1975)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 15 (1975), S. 339-342 
    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: Two component interpenetrating polymer networks (IPN) of the SIN type (simultaneous interpenetrating networks), composed of a polystyrene network (crosslinked with divinyl benzene) and a polyester-polyurethane network (crosslinked with trimethylolpropane), were made. Electron microscopy and glass-transition measurements showed that phase separation had resulted with some interpenetration, presumably occurring at the boundaries. At a composition of about 75 percent polyurethane, a phase inversion occurred, the continuous phase being polystyrene at polyurethane compositions of less than 75 percent. The stress-strain properties and hardness measurements agreed with these results. Enhanced tensile strength was observed in the IPN's in a concentration range where modulus reinforcement was not evident. A small enhancement in tear strength and thermal stability was also noted.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760150503
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of molecular weight distribution on fatigue crack propagation in poly(methyl methacrylate) (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 145-150 
    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: It is well established that both molecular weight (M) and its distribution (MD) affect many polymer properties such as mechanical behavior. Thus studies have shown that fatigue life is enhanced by increases in M. Research here has shown that with notched specimens fatigue crack propagation (FCP) rates are dramatically decreased by increasing M, even when the M is high enough that the static fraeture energy has essentially reached its asymptotic limit. In this study, specimens of poly(methyl methacrylate) containing either high- or low-M tails were prepared and characterized. The earlier finding that FCP rates are inversely related to average M was confirmed, but specific effects of M distribution were observed. At constant Mn, a low-M tail had little effect on FCP resistance, while a high-M tail improved FCP resistance of polymers whose average M was too low for effective entanglements. Thus with high-M tails, it was possible to test specimens whose average M's were too low to permit machining. It is proposed that the effects noted are due to relative stabilization or destabilization of crazes ahead of the crack.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190218
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  • 7
    Electronic Resource
    Electronic Resource
    Fatigue crack propagation in poly(methyl methacrylate): Effect of molecular weight and internal plasticization (1977)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 17 (1977), S. 194-203 
    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: In spite of the importance of fatigue behavior in engineering plastics, relatively few fundamental studies have been made of the effects of polymer structure, molecular weight, composition, and morphology on fatigue crack propagation (FCP). As, part of a broad program for the study of such effects, the role of molecular weight and internal plasticization has been studied in poly(methyl methacrylate) (PMMA) which had been specially prepared and characterized with respect to molecular weight, dynamic mechanical behavior, and, in some cases, stress-strain response. As expected, values of fracture toughness, Kc, varied considerably as the molecular weight was rai ed, from 0.7 MPa, √m at Mv = 1.0 × 105 to 1.1 at Mv, = 4.8 × 106. However, a specific effect of fatigue was noted: over the same range of Kc, values of FCP rate decreased by two orders of magnitude as molecular weight was; increased. It is proposed that this high sensitivity is due to differences in the degree of chain disentanglement effected by the cyclic loading, with consequent differences in the strength of the craze preceding the crack. With PMMA plasticized internally with a low level (10 percent) of n-butyl acrylate (nBA), the FCP rate and Kc, were similar to those of controls, with very high rates shown. At higher nBA levels (up to 30 percent), the sensitivity of FCP rate to stress intensity factor range decreased considerably, Kc, increased by 30 percent and the pre-exponential constant in the growth rate law increased. Plasticization weakens the polymer but at high degrees leads to enough hysteretic heating to induce local creep and crack blunting.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760170308
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  • 8
    Electronic Resource
    Electronic Resource
    Tensile, impact and fatigue behavior of an amine-cured epoxy resin (1978)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 1093-1100 
    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: Although crosslinked networks are commonly used as adhesives and composite matrixes, structure-property relationships are not as well established as with thermoplastics. For this reason, an extensive study was begun to systematically examine effects of stoichiometry, morphology, and distribution of crosslink density on viscoelastic behavior and ultimate properties. The system selected was based on a bisphenol-A-type epoxy cured with methylene dianiline. This paper describes and discusses results obtained for resins in which the amine/epoxy ratio ranged between 0.7 and 2.2. In agreement with reports by others, the tensile strength, modulus, and ultimate elongation were relatively insensitive to stoichiometry but did not show slight maxima or minima when the amine was somewhat in excess. Impact strengths, tensile energies-to-break and fracture toughness were, in contrast, quite sensitive, though the patterns of each differed significantly. Both fracture toughness and the stress intensity factor required to drive the crack at a given rate varied directly with the amine/epoxy ratio, as did estimates of the characteristic flaw size. Fatigue striations were observed on the fracture surfaces and corresponded to the incremental advance of the crack in one loading cycle.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760181410
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  • 9
    Electronic Resource
    Electronic Resource
    Gas permeation and viscoelastic deformation of prepregs in composite manufacturing processes (1995)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 16 (1995), S. 370-377 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Gas permeation and creep deformation of a commercial prepreg, which exhibits viscoelastic characteristics, were investigated as a function of time, temperature, and consolidation pressure. Experiments using a prepreg stack demonstrated that the material exhibited a linear viscoelastic bulk deformation under vacuum/autoclave pressure and furthermore, the in-plane gas flow exhibited non-Darcian flow behavior with a permeation hysteresis. This behavior was viewed and analyzed by two viscoelastic relaxation processes: (1) bulk dimensional relaxation, and (2) microscopic pore structure rearrangement. A modified standard linear solid (SLS) viscoelastic model was used to interpret the creep compliance and dynamic gas permeability utilizing two independent relaxation parameters. By visual investigation of pore sizes and their distribution, air permeation was found to take place mostly through the interlaminar porosity network for the prepreg system examined.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750160505
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