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  • 1
    Electronic Resource
    Electronic Resource
    Primary normal-stress difference for two liquid crystalline copolyesters (1986)
    Springer
    Rheologica acta 25 (1986), S. 275-286 
    Details
    ISSN: 1435-1528
    Keywords: Liquid crystalline copolyester ; shear flow ; negative primary normal-stress difference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The primary normal-stress difference,N 1, was determined in both steady and transient shear flow experiments for thermotropic copolyesters of 60 and 80 mole% p-hydroxybenzoic acid (PHB) and polyethylene terephthalate (PET).N 1 was observed to be negative for the 80 mole% system at low shear rates and temperatures below 332 °C (a tensile stress, e.g. σ11 is taken here to be positive). At higher shear rates and for temperatures above 332 °C,N 1 was found to be positive. Values ofN 1 for the 60 mole% pHBA/PET system were always positive over the same range of shear rates. Although it is not certain as to the origin of the negative values, a probable cause is small density changes upon the inception of flow as well as the existence of a solid phase or some texture development in the melt. However, it is shown that it is thermodynamically admissible for liquid crystalline fluids to exhibit negative values ofN 1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01357954
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  • 2
    Electronic Resource
    Electronic Resource
    Dependence of the primary normal-stress difference coefficient on molecular weight for concentrated solutions of rodlike molecules (1980)
    Springer
    Rheologica acta 19 (1980), S. 183-186 
    Details
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Summary The primary normal-stress difference has been measured for concentrated solutions of rodlike and flexible chain polyamides. The solutions studied here consist of poly-p-phenyleneterephthalamide (PPT) which is believed to be rodlike in 100% H2SO4 and the flexible chain polyamide, polyhexamethylene adipamide (nylon 6.6), which is also dissolved in 100% sulfuric acid. For the PPT solutions the primary normal-stress difference coefficient in the limit of zero shear rate (ψ 1(0)) is observed to be proportional toM w 12.9 whereM w is the weight average molecular weight. For concentrated solutions of nylon 6.6,ψ 1(0) is found to be proportional toM w 7.6 which is in reasonable agreement with values reported for other flexible chain polymers. These data point out that there are some interesting differences in the primary normal stress differences for rodlike and flexible chain polymers and at the same time provide support of the recent theoretical predictions ofDoi andEdwards for concentrated solutions of entangled rodlike molecules.
    Notes: Zusammenfassung Es wurde die erste Normalspannungsdifferenz an konzentrierten Lösungen von stäbchenförmigen und flexiblen kettenförmigen Polyamiden bestimmt. Die untersuchten Lösungen bestehen aus Poly-p-Phenylenterephthalamid (PPT), bei dem man eine stäbchenförmige Konfiguration annimmt, bzw. aus Polyhexamethylenadipamid (Nylon 6.6), welches als flexibles Kettenmolekül gelöst ist, beide in 100%iger Schwefelsäure. Bei den PPT-Lösungen findet man für den ersten Normalspannungs-Koeffizienten in der Grenze verschwindender Schergeschwindigkeit (ψ 1 (0)) eine Proportionalität mitM w 12,9 , woM w das Gewichtsmittel des Molekulargewichts darstellt. Bei konzentrierten Lösungen von Nylon 6.6 findet man dagegen forψ 1(0) Proportionalität mitM w 7,6 , was in vernünftiger Übereinstimmung mit den Ergebnissen anderer Autoren bei verschiedenen flexiblen Kettenmolekülen ist. Diese Ergebnisse zeigen, daß zwischen der ersten Normalspannungsdifferenz von stäbchenförmigen und flexiblen kettenförmigen Polymeren interessante Unterschiede bestehen, und stützen zugleich die neuerlichen theoretischen Voraussagen vonDoi undEdwards bezüglich konzentrierter Lösungen ineinander verhängter stäbchenförmiger Moleküle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01521929
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization and processing of blends of polyethylene terephthalate with several liquid crystalline polymers (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 519-526 
    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 an engineering thermoplastic, poly(ethylene terephthalate) (PET), and two liquid crystalline polymers (LCPs) viz., copolyesters of PET and parahydrox-ybenzoic acid (PHB) in 40/60 mole percent (LCP60) and in 20/80 mole percent (LCP80) were prepared. A blend of LCP60 and LCP80 in 50/50 weight percent (LCP60-80) was blended with PET. Both flat films and rods were extruded and their properties examined. The morphology of the films investigated using Scanning Electron Microscopy (SEM) revealed that the LCP phase remained as dispersed droplets in the PET matrix. In spite of the lack of fibrillation in these films, the mechanical properties were enhanced to some extent with a maximum at 10 weight percent of the LCP phase. However, in the case of the rods thin fibrils of the LCP phase of the order of 1 μm in diameter were observed provided the composition of the LCP was 20 weight percent or greater. This success In achieving fibrillation is through to be due to the extensional flow fields present at the entrance of the capillary die and the fact that a short L/D ratio die was used. Differential Scanning Calorimetry (DSC) thermograms of the extruded films indicated that the LCP phase may act as a nucleating agent for the crystallization of PET. Rheology of the blends revealed that the complex viscosity of the blends is not much different from that of pure PET. This is attributed to the partial miscibility of the two components. Based on the DSC results and residence times in the extruder, it is concluded that no significant transesterification reactions appear to have: taken place in the blends. The rheology is studied further with respect to the cooling behavior of the pure components and factors important to the fibrillation of the LCP phase and the formation of in-situ reinforced composites are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300904
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  • 4
    Electronic Resource
    Electronic Resource
    Pressure gauge handbook. By P. W. Harland, Editor, Marcel Dekker, Inc., 1985, 292 pp. (1988)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 525-525 
    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.690340326
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  • 5
    Electronic Resource
    Electronic Resource
    The effect of thermal history on the rheology and texture of thermotropic liquid crystalline polymers (1987)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 27 (1987), S. 816-822 
    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: This paper is concerned with the effect of thermal history on the rheology of three liquid crystal copolymers. The polymers were heated to temperatures above their melting points and then cooled down. During the cooling cycle, the dynamic mechanical properties were monitored. It was found that these properties remained unchanged at temperatures as low as 30°C below the normal melting points for two copolyesters of 60 mole percent p-hydroxybenzoic acid (PHB) and 40 mole percent poly(ethylene terephthalate) (PET) (60-40 PHB/PET) and 80 mole percent PHB and 20 mole percent PET (80-20 PHB/PET). For a copolymer of PHB and 2,6-dihydroxynaphthaic acid, there was a gradual increase in the properties with decreasing temperature. However, at a critical temperature all three systems exhibit a sudden increase In dynamic mechanical properties. The kinetics of solidification were also monitored, and it was found that at temperatures well below the melting point, it took 4 to 6 min before the solidification process impeded flow. Extrusion studies on these materials were also carried out, and it was observed that in this supercooled state, the polymers exhibited significant die swell. The samples also exhibited a fibrous texture and were more oriented than when extruded isothermally above the melting point.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760271108
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamic rheological properties of polyetherimide/polyetheretherketone/liquid crystalline polymer ternary blends (1994)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1492-1496 
    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 dynamic rheological properties of poly(etherimide)/poly(etheretherketone)/liquid crystalline polymer (LCP) ternary blends were measured in order to correlate these properties with the morphology obtained after extrusion. The viscosity radio, ηd/ηm, where ηd = disperse phase viscosity and ηm = matrix viscosity, had to be redefined. Below 50 wt% LCP, ηd = ηLCP, ηm = ηPEEK+PEI and ηd/ηm 〈 1. Above 50 wt% LCP, ηd = ηPEEK+PEI, ηm = ηLCP and ηd/ηm 〉 1. Fibrillar morphologies were obtained in both cases, except below a concentration of 20 wt% LCP. At low concentrations of LCP the ternary blends had lower viscosities than the component polymers, showing a flow promotion effect of the LCP on the PEI- and PEEK-rich phases.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760341909
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  • 7
    Electronic Resource
    Electronic Resource
    The development of molecular orientation and morphological texture in thermotropic copolyesters (1985)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 25 (1985), S. 888-895 
    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: Liquid crystalline polymers can be processed to form high strength/modulus materials. In processing these materials, it is apparent that molecular orientation is an important factor in determining the physical strength of the processed materials. In this study a systematic investigation was carried out to determine how a thermotropic copolyester of parahydroxybenzoic acid (PHB) and polyethylene terephthalate (PET) responds to two basic types of flows: shear and extensional flow. This was accomplished by preparing sheared and extended samples under controlled conditions of temperature and flow history. Sheared disks were prepared using a disk and plate geometry of a Rheometrics Mechanical Spectrometer (RMS model 605), while extended ribbons were prepared using a slit die attached to an Instron capillary rheometer. Two copolymerer compositions of 60 mole percent and 80 mol percent PHB were investigated. The sheared disks and extended ribbons were investigated for molecular orientation and morphological textures using wide angle x-ray scattering (WAXS) and scanning electron microscopy (SEM) analysis, respectively. It was found that extensional flow has a greater capacity for orienting such materials than shear flow. Samples annealed at their softening points for 1 minute (240°C for the 60 mole percent PHB/PET copolymer and 300°C for the 80 mole percent PHB/PET copolymer) showed no significant loss of orientation, indicating that once orientation is produced it may remain in the melt for a long period of time. Sheared samples prepared by shearing the sample while cooling showed significantly higher degrees of orientation than those not cooled while being sheared. This may indicate that a minimum stress level exists for the production of orientation in shear flow.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760251405
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  • 8
    Electronic Resource
    Electronic Resource
    Rheology of a textured fluid consisting of poly(ethylene terephthalate) and nylon 6,6 (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 845-859 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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 rheology and development of the texture of immiscible polymer blends based on poly(ethylene terephthalate) (PET) and nylon 6,6 at composition ratios of 75/25, 50/50, and 25/75 w/w PET/nylon 6,6 were studied. The blends were prepared by mixing in an extruder and by dry blending and mixing between cone-and-plate fixtures in a nitrogen atmosphere. The rheology of these blends was found to be a function of both polymer degradation and the two-phase morphology. An accelerated degradation rate in air was observed for the 75/25 and 50/50 w/w PET/nylon 6,6 blends relative to the neat polymers while the blend at a weight ratio of 25/75 w/w PET/nylon 6,6 displayed a rate of degradation similar to that of the neat polymers. The values of the steady shear viscosity (η), |η*| storage modulus (G′), and steady-state first normal stress difference (N1) for melt-blended 75/25 and 50/50 w/w PET/nylon 6,6 samples were lower than those of the neat polymers and were determined to be a consequence of the higher rate of degradation of these blends during extrusion relative to that of the neat polymers. The role played by the two-phase nature on the blends was observed for all samples prepared by dry blending and mixing in cone-and-plate fixtures under a nitrogen atmosphere and for the melt-blended 25/75 w/w PET/nylon 6,6 blend. The two-phase nature of the dry-blended samples and the extruded 25/75 w/w PET/nylon 6,6 sample resulted in values of |η*|, η, G′, and N1 which were higher than those of the neat polymers. Transient behavior observed for the blends using stepwise changes of shear rate was found to superimpose when plotted in reduced form, indicating that at rates lower than the longest relaxation time of the neat polymers there was no intrinsic time constant associated with the deformation of the interface in the blends. © 1996 John Wiley & Sons, Inc.
    Additional Material: 18 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Capillary and slit flow behavior of concentrated solutions of a rod-like polymer (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 521-527 
    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: This paper is concerned with the flow behavior of isotropic solutions of the rod-like polymer, poly(p-phenyleneterephthalamide) (PPT), in 100 percent sulfuric acid. Studies include entry flow visualization in a slit die and solution fracture, and die swell in capillaries and a slit die. It was observed that solutions of PPT exhibit nearly negligible die swell, a slip-stick type of fracture that disappears at high shear rates, and radial entry flow patterns similar to Newtonian fluids. Fracture was associated with the plateau in the shear stress vs shear rate curve. Because values of the wall shear stress (τw.) obtained from capillary measurements were in good agreement with those obtained from a cone-and-plate rheometer and values of the loss modulus (G″) obtained from small-strain dynamic oscillatory measurements, it is believed that the rheological properties lead to the flow instability. These results are in agreement with the predictions of a recent theory by Doi and Edwards for concentrated solutions of rod-like molecules. Data are also presented for a flexible chain polyamide, nylon 6,6, in 100 percent H2SO4 for the purpose of comparing the flow characteristics of rigid and flexible chain polymers.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760220902
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  • 10
    Electronic Resource
    Electronic Resource
    Sandwich injection molding of thermotropic copolyesters and filled polyester (1983)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 23 (1983), S. 632-636 
    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: Mold filling studies have shown that thermotropic liquid crystalline copolyesters of p-hydroxybenzoicacid (PHB) and polyethyleneterephthalate (PET) fill by an advancing front mechanism similar to flexible chain polymers. The structure and orientation developed during filling as determined on solid specimens by an etching method, X-ray diffraction, and shrinkage study on thin microtomed samples appear to be most pronounced at the surface. Based on this information copolymers of 60 and 80 mole percent PHB/PET were co-injection molded with filled PET under various processing conditions. Because of the low viscosity of the copolyesters, they readily coated filled PET under most processing conditions to give a sheath/core structure. The bending modulus of co-injection molded bars with as little as 35 percent PHB/PET was as high as the sample consisting of 100 percent liquid crystalline copolyester. Electron micrographs of fracture surfaces revealed excellent adhesion between the two polymers.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760231108
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