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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
    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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  • 4
    Electronic Resource
    Electronic Resource
    Mechanical properties of in situ composites based on partially miscible blends of polyetherimide and liquid crystalline polymers (1993)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 14 (1993), S. 214-223 
    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: Results related to the mechanical properties of in situ composites based on partially miscible blends of polyetherimide (Ultem) and liquid crystalline polymers (HX1000 and HX4000) are discussed. It is observed that, at least in terms of the tensile and flexural modulus, there is a positive deviation from the law of mixtures. These results are analyzed and an attempt is made to explain the origin of this synergistic behavior based upon morphological data. The behavior of these partially miscible systems is compared to that of an immiscible system (Ultem/Vectra) and also that of glass-reinforced Ultem. Using blends subjected to two passes through a single screw extruder, and thereby increasing the mixing history of the Ultem/HX4000 blend, led to improved dispersion but did not lead to any measurable improvement, within experimental error, in the tensile modulus or ultimate strength (though the toughness was enhanced). The dynamic creep compliance was measured and the creep behavior with composition and temperature is discussed. The data seem to suggest that a number of factors (including partial miscibility, the properties of the specific LCP chosen as the reinforcement and the final blend morphology) all interact in a complex and as yet undetermined manner to produce the enhanced mechanical properties.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750140306
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  • 5
    Electronic Resource
    Electronic Resource
    Composites based on drawn strands of thermotropic liquid crystalline polymer reinforced polypropylene (1995)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 16 (1995), S. 330-345 
    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: This paper is concerned with the use of two thermotropic liquid crystalline polymers (TLCPs), HX1000 and Vectra B950, to reinforce a thermoplastic matrix of polypropylene (PP). The goal was to pregenerate the optimal TLCP reinforcement in PP and then process the material at a lower temperature than the melting point of the TLCP to form a composite structure. Specifically, strands of the blend were produced using a dual extrusion process, which resulted in the formation of axially continuous TLCP fibrils within the PP matrix. It was found that the mechanical properties of the strands were greatly improved by increased draw ratio and that optimal reinforcement, as predicted by the rule of mixtures, could be achieved. Initial studies indicated that injection molding and sheet extrusion of the pelletized strands caused the TLCP phase to agglomerate and deform, which resulted in a reduction of the mechanical property enhancement. However, the TLCP fibrillar morphology in the pregenerated strands was maintained during compression molding, which resulted in uniaxial composites with properties equal to or greater than properties of the strands. In addition, composites were made using compression molding in which strands were randomly oriented prior to consolidation to show the limits of properties possible in composites produced from the pregenerated strands. It was found that this process could be used to produce composites in which the mechanical properties were isotropic in the plane of the sample and approached the properly limits predicted by composite theory. Additionally, it was found that many of the mechanical properties of the VB/PP materials were greatly enhanced by the addition of a maleated PP throughout the composite forming process.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750160411
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  • 6
    Electronic Resource
    Electronic Resource
    Comparison of experimental data with the numerical simulation of planar entry flow: Role of the constitutive equation (1990)
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 10 (1990), S. 373-400 
    Details
    ISSN: 0271-2091
    Keywords: Comparison ; Experimental ; Simulation ; Planar entry flow ; Viscoelastic ; Convergence ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The goal of this research was to determine whether there is any interaction between the type of constitutive equation used and the degree of mesh refinement, as well as how the type of constitutive equation might affect the convergence and quality of the solution, for a planar 4:1 contraction in the finite eiement method. Five constitutive equations were used in this work: the Phan-Thien-Tanner (PTT), Johnson-Segalman (JS), White-Metzner (WM), Leonov-like and upper convected Maxwell (UCM) models. A penalty Galerkin finite element technique was used to solve the system of non-linear differential equations. The constitutive equations were fitted to the steady shear viscosity and normal stress data for a polystyrene melt. In general it was found that the convergence limit based on the Deborah number De and the Weissenberg number We varied from model to model and from mesh to mesh. From a practical point of view it was observed that the wall shear stress in the downstream region should also be indicated at the point where convergence is lost, since this parameter reflects the throughput conditions. Because of the dependence of convergence on the combination of mesh size and constitutive equation, predictions of the computations were compared with birefringence data obtained for the same polystyrene melt flowing through a 4:1 planar contraction. Refinement in the mesh led to better agreement between the predictions using the PTT model and flow birefringence, but the oscillations became worse in the corner region as the mesh was further refined, eventually leading to the loss of convergence of the numerical algorithm. In comparing results using different models at the same wall shear stress conditions and on the same mesh, it was found that the PTT model gave less overshoot of the stresses at the re-entrant corner. Away from the corner there were very small differences between the quality of the solutions obtained using different models. All the models predicted solutions with oscillations. However, the values of the solutions oscillated around the experimental birefringence data, even when the numerical algorithm would not converge. Whereas the stresses are predicted to oscillate, the streamlines and velocity field remained smooth. Predictions for the existence of vortices as well as for the entrance pressure loss (ΔPent) varied from model to model. The UCM and WM models predicted negative values for ΔPent.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/fld.1650100403
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  • 7
    Electronic Resource
    Electronic Resource
    Dilute solution properties of poly(1,4-phenylene terephthalamide) in sulfuric acid (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 16 (1978), S. 61-70 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The intrinsic viscosity [η] of dilute solutions of poly(1,4-phenylene terephthalamide) (PPPT) is found to depend strongly on sulfuric acid strength, exhibiting a maximum at about 100% H2SO4. This behavior instigated measurements of [η] and light scattering from dilute solutions of unfractionated PPPT in concentrated (≈96%) and 100% H2SO4. From [η] and weight-average molecular weight Mw relationships, Mark-Houwink exponents a were determined to be 1.36 in 96.6% and 1.62 in 100.2 ± 0.2% H2SO4, indicating that the PPPT molecule can undergo considerable expansion in 100% H2SO4. For the case of 100% H2SO4, a noticeable polyelectrolyte effect is observed in the reduced viscosity versus concentration curves. This result suggests that the repulsive charges generated along the PPPT backbone may be responsible for the change in configuration of PPPT upon increasing the acid strength from 96.6% to 100% H2SO4. It is pointed out that there is considerable experimental difficulty in measuring consistent values of Mw, and this may be the reason for the variation among published data.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.170160106
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  • 8
    Electronic Resource
    Electronic Resource
    Mechanical properties of in-situ composites based on partially miscible blends of glass-filled polyetherimide and liquid crystalline polymers (1993)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 33 (1993), S. 808-818 
    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 use of inorganic (glass) fiber reinforcement to enhance the mechanical properties and reduce the anisotropy of in situ composites based on blends of liquid crystalline polymers (LCPs) with polyetherimide (PEI) is discussed. It was found that the tensile and flexural moduli are increased and the anisotropy is reduced with increasing grass content (when compared at equivalent LCP weight fractions). The creep compliance of the PEI/LCP composites is reduced upon the addition of glass fibers. However, the disadvantage is that the processability worsens upon addition of glass fibers to the PEI/LCP in situ composites. The effect of adding glass reinforcement on the ultimate tensile strength is less clear, because the data do not show any consistent trend. Similarly, the elongation at break and toughness do not show any consistent improvement upon addition of glass reinforcement. Morphological studies show that there is considerable difference between the size and texture of the reinforcing glass fibers and LCP microfibrils.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760331305
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  • 9
    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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  • 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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