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  • 1
    Electronic Resource
    Electronic Resource
    Letters to the editor (1976)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 22 (1976), S. 815-815 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690220436
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  • 2
    Electronic Resource
    Electronic Resource
    A kinetic approach for polymer solution data (1968)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 14 (1968), S. 61-68 
    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 phenomenological theory previously prsented for describing the rheological properties of non-Newtonian materials was applied to two polymer solution systems. The basic shear diagram is needed over a wide range of shear rates and polymer concentrations, and such data are not readily available; however, what could be found supported the analysis. In order to confirm the theory further, ten solutions of polymethylmetacrylate in diethyphthalate with concentrations up to 55% were investigated at 40°C. The results indicated that the forward and reverse orders were 1 and 2 respectively and that the two parameters of the theory (a susceptibility to shear term and an equilibrium type of constant) were constant over the range of concentrations investigated. The flow data were reproduced to within a few percent for all solutions, although the errors were large for the very dilute concentration, where experimental difficulties precluded obtaining reliable data. The method allows correlation of polymer solution data over the range from lower to upper Newtonian viscosities and over a wide concentration range.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690140114
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  • 3
    Electronic Resource
    Electronic Resource
    Momentum transfer in climbing film flow in annular duct (1967)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 13 (1967), S. 326-334 
    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 characteristics of upward gas-liquid flow in a vertical annular duct were investigated. The flow regime studied was the climbing film regime in which water flowed as a film up the inner core of the annulus while air flowed in the annular space, the outer wall of the annulus remaining dry. Friction losses, air velocity distributions, and film characteristics were studied, the latter by photographing the climbing film through the transparent outer tube. Friction loss and film thickness were correlated with Lockhart-Martinelli parameters, X, Φ, and RL. The presence of the climbing film caused the point of maximum velocity of the air profile to move toward the outer tube, indicating that the film created a rough wall condition. The inner portion of the velocity profile was correlated by Nikuradse's rough tube equation, while the outer portion was correlated by a logarithmic equation which previous workers have reported for single-phase flow. Kapitza's theory of wave formation was applied to the climbing film and was found to predict reasonable values for the mean film thickness. However, it failed to predict reliable values for the wavelength of surface waves.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690130224
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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Kinetic studies on shear degradation of polystyrene during extrusion (1978)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 812-816 
    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: Kinetic studies on shear degradation of a polystyrene (M̄n = 115,700 and P̄n = 1113) during extrusion in a model extruder were made at different temperatures (170, 190, 210, and 230°C) and shear stresses (340,406, and 472 g/cm2) for determination of rate constants for degradation, reaction order, and effects of temperature and stress on the rate constants. Mechanical energy and effective activation energy (E*) of bond rupture were related to temperature and applied stress. The following results were obtained. The degradation process is found to be satisfied by a second order reaction over the temperatures and stresses studied with respect to the changes in number average chain length (Pt - P∞), thus -dP/dt = k(Pt - P∞)2, where k is a reaction rate constant and t and ∞ refer to degradation times. The mechanical energy of bond rupture has a maximum and the rate constant a minimum at about 180°C, indicating that the least effective temperature for mechanical degradation is about 180°C. E* decreases with increasing applied stress (τ) as a linear relationship, i.e., E* = EA - ατ. At τ = 0, E* becomes equal to the activation energy for thermal degradation with the value EA = 48.6 kcal/mole which agrees well with literature data. Temperature and stress effects on the rate constant are well expressed for our study by the Arrhenius equation proposed by Zhurkov, et al., i.e., k = A exp[-(Ea - ατ)/RT] where A and α are coefficients.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760181012
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