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  • 1
    Digitale Medien
    Digitale Medien
    Maximum pressure developed by solid conveying force in screw extruders (1975)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 15 (1975), S. 29-34 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: There are two distinct solid conveying theories that can be applied to plasticating screw extruders. One is Darnell and Mol's theory based on a solid-to-solid friction model and the other is Chung's theory based on a viscous shearing model. The two theories predict very different solid conveying performances for a same set of conditions. In this paper, the maximum pressures that can be developed inside plasticating screw extruders by the solid conveying force are calculated using each of the two theories. Comparison of the results may shed some light on the applicability of each theory for a particular extrusion operation.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760150105
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  • 2
    Digitale Medien
    Digitale Medien
    Plasticating single-screw extrusion theoryPresented before the 28th Annual Technical Conference of the Society of Plastics Engineers, New York, N. Y., May, 1970. (1971)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 11 (1971), S. 93-98 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Various solid conveying, melting, and metering theories developed for plasticating screw extrusions are reviewed. Some recommendations for improving the present melting theories are presented. It is pointed out that the overall performance of a screw extruder can be predicted only by combining the solid-conveying, melting and metering theories into a complete mathematical package because the three functions of a screw extruder depend on each other and cannot be separated. A suggestion is made on how to combine these three theories.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760110204
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  • 3
    Digitale Medien
    Digitale Medien
    Compressibility of polyethylene melts at low pressures (1971)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 15 (1971), S. 1277-1281 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Branched polyethylene has quite different rheological and physical properties from its linear homologue. Despite their many different properties, the densities of linear and branched polyethylene melts at atmospheric pressure have been reported to be identical at all temperatures. However, it was not known whether their melt densities at a given temperature would also be identical at all pressures. In this investigation, the compressibilities of one linear and two branched polyethylene melts at 160°C, 190°C, and 220°C were studied, and it was found that they had an identical compressibility over the present experimental pressure range of ca. 0-455 psi (0-31 atm). Both the specific volume and the density at each temperature could be very accurately expressed as linear functions of pressure for this pressure range. Time-dependent compressive property was not observed within the present low pressure range.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1971.070150521
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  • 4
    Digitale Medien
    Digitale Medien
    The concept of solid solvent as a processing aid (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 2739-2751 
    Details
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The concept of solid solvent entails the use of low-molecular weight crystalline materials (LMC) as a processing aid. A LMC as an ideal solid solvent mixed into a polymer is expected to become a solvent for the polymer at high processing temperatures, reducing the melt viscosity and thus enhancing the processability, but to become a nonsolvent for the polymer at low use temperatures precipitating out of the polymer without adversely affecting the properties of the polymer. The feasibility of such a concept was examined using acetanilide as a potential solid solvent for polystyrene (PS) and two ABA-type block copolymers containing PS end blocks. Acetanilide demonstrated the essential features required of a solid solvent supporting the concept of solid solvent. It had a high solubility in PS at high temperatures very effectively reducing the melt viscosity of PS and the block copolymers, and it precipitated out of PS at low temperatures although it had an undesirably high residual solubility. The concept of solid solvent appears to be a viable one.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/app.1986.070310828
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  • 5
    Digitale Medien
    Digitale Medien
    Melting behavior of solid polymers on a metal surface at processing conditions (1978)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 711-720 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The melting or plasticating behavior of seven commercial polymers (high density polyethylene, low density polyethylene, polypropylene, polyoxymethylene copolymer, polystyrene, poly(methyl methacrylate), and polycarbonate (PC) was investigated using an experimental apparatus specifically designed to measure the melting rate and the viscous shear stress of a solid polymer on a steel surface under precisely controlled conditions of temperature, velocity, pressure and sample width comparable to actual processing. The melting rate (per unit polymer solid/metal contact area) was found to increase with increasing temperature for all polymers except PC, to decrease with increasing sample width and to increase less than proportionally to velocity. Pressure increased the melting rate somewhat for most of the polymers. The viscous shear stress decreased with increasing temperature for all polymers except PC, decreased with increasing sample width and increased with increasing velocity. Pressure generally increased the viscous shear stress. PC showed an unusual behavior with a maximum in the melting rate near 4200°F(215.5°C) and also a maximum in the viscous shear stress near 445°F (229.4°C). The present melting model could be examined unequivocally for the first time using our experimental results. Comparison of our experimental results with the predictions of the present melting model clearly indicates the inadequacy of the present melting model, Our experimental results will provide a basis for rational development of a reliable melting model.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760180906
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  • 6
    Digitale Medien
    Digitale Medien
    Effects of lubricants on the second fusion behavior of rigid polyvinyl chloride (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 1110-1116 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Rigid polyvinyl chloride (RPVC) is thermally unstable and difficult to process. The processibility of RPVC compounds markedly depends on the type and level of lubricants present. Lubricants are compounded into RPVC powder and the resulting dry blend is either directly converted into the final product requiring the resin to fuse only once, or pelletized first followed by conversion into the final product in a subsequent operation requiring the resin to fuse twice. The effects of lubricants on the first fusion have been well studied but little is known about the second fusion. We studied the effects of eleven common lubricants on the second fusion of a RPVC master, batch at three levels of concentration at several temperatures., The lubricants were compunded with the RPVC powder, the dry blends molded into one-inch cube samples, and the molded samples fused under shearing conditions comparable to the actual processing. We found that the effects of the lubricants on the second fusion were generally the same as those on the first fusion. Apparently, the properties of the lubricants and their interactions with the RPVC resin are not altered by the first fusion history.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760191508
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  • 7
    Digitale Medien
    Digitale Medien
    On the scale-up of plasticating extruder screws (1984)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 626-632 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: In the most commonly used scale-up method of plasticating extruder screws, the screw channel depth is increased by the square root of the diameter ratio while the screw RPM is decreased by the square root of the diameter ratio such that the output rate increases proportionally to the square of the diameter ratio. This scale-up method, largely based on the pumping function of the screw, often leads to a higher melt temperature, a higher screw horsepower consumption per unit output rate and an inferior melt quality from the larger diameter screw. Analysis of the common scale-up method reveals that, although the shear rate in the melt is kept constant, the average residence time and the peripheral screw speed are increased for the larger diameter screw. Our recent study on the melting mechanism also reveals that the melting capacity increases less than the pumping capacity. A detailed examination of the common scale-up method in this paper shows that the pumping capacity and the solid conveying capacity increase more than necessary while the melting capacity increases insufficiently.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760240904
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  • 8
    Digitale Medien
    Digitale Medien
    Screw horsepower dependence on screw speed and size - theory and experiment (1974)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 28-37 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Within a normal operating range of extruders, it has been well established that the output increases nearly proportionally to the screw speed but the screw horsepower increases more than proportionally to the screw speed, making the screw HP difficult to predict. It has been also known in scale-up of extruders that the output may be predicted with reasonable accuracy but the screw HP is difficult to predict. No sound theoretical or empirical method predicting screw HP in a scale-up calculation has been offered heretofore. Since a screw performs solid conveying, melting and pumping (or metering) functions simultaneously, any theoretical analysis of screw HP has to consider all three extrusion theories; solid conveying theory, melting theory and pumping theory. In this paper, semi-theoretical equations for predicting screw HP as a function of screw speed and size are developed. Experiments are conducted to test the utility of these equations and the implications of the experimental results on extrusion theories are discussed.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760140106
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  • 9
    Digitale Medien
    Digitale Medien
    Friction and its effect on the mechanical- to-thermal energy conversion during extrusion of poly(vinylidene chloride) (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 1261-1269 
    Details
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Solid state friction reduction has been found to be an effective method for extrusion stabilization of a high coefficient of friction (COF) thermally sensitive polymer. A poly(vinylidenechloride) copolymer (PVDC) was studied alone and blended with various polyolefins to change its frictional behavior. COF of the polymer rubbing on a metal surface was measured under conditions typical of an extrusion process. These results correlated well with the measured mechanical energy consumed during extrusion. Of the polyolefins studied, high and low density polyethylene were found to be very effective for lowering friction and improving extrusion performance of the PVDC. Polypropylene was found to be much less effective. Interface temperature where melting occurs due to frictionally generated heat has been experimentally shown to be a function of COF and the bulk metal temperature.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pen.760331906
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  • 10
    Digitale Medien
    Digitale Medien
    Nature of melt rheological transition in a styrene-butadiene-styrene block copolymer (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 545-553 
    Details
    ISSN: 0098-1273
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Our laboratory previously reported the observation of a high temperature, melt rheological transition in a styrene-butadiene-styrene (S:7 × 103 and B:43 × 103) block copolymer from the highly elastic, nonlinear viscous behavior typical of a multiphase structure to linear viscous behavior with insignificant elasticity typical of a single-phase structure. We have investigated the precise nature of this melt rheological transition in the 7S-43B-7S sample by measuring the dynamic viscoelastic properties at more than 11 temperatures, including several in the transition region. A new procedure was developed for accurately measuring the sample temperature in a Weissenberg rheogoniometer. The transition is found to start at about 140°C and proceed over a narrow transition region from 140 to about 150°C. Data at all temperatures superimpose onto a single master curve only at high reduced frequencies. At low reduced frequencies, two characteristic branches of the master curve are formed. The data at temperatures below the transition region superimpose onto the upper branch where the dynamic viscosity η′(ω) is a strong function of ω, whereas the data at temperatures above the transition region superimpose onto the lower branch where η′(ω) is independent of ω. The data at temperatures within the transition region fall between the upper and lower branches, ordered according to their temperature positions. The apparent flow activation energy is found to be constant at about 22.8 kcal/mole below the transition region, but appears to decrease to about 17.4 kcal/mole above the transition region. The narrowness of the rheological transition far above the glass transition temperature of the polystyrene domains and the limiting linear viscoelastic behavior at low frequencies above the transition suggest an accompanying morphological transition rather than a gradual weakening of the polystyrene domains.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pol.1978.180160316
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