Rheological Properties of Copolyester Liquid Crystalline Melts. I. Capillary Rheometry

Jerman, Robert; Baird, Donald G.

doi:10.1122/1.549645

Cited by 102 publications

(21 citation statements)

References 2 publications

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“…In order to further simplify the theory, Ericksen linearized Eqs. (1) and (4) with respect to the rate-of-deformation tensor. For the purposes of this study, the nonlinear stress equations will be conserved, but the linear director equations will be used.…”

Section: Ericksen's Transversely Isotropic Fluid Theorymentioning

confidence: 99%

Studies on the Transient Shear Flow Behavior of Liquid Crystalline Polymers

Viola¹,

Baird²

1986

Journal of Rheology

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SynopsisAn understanding of the flow behavior of liquid crystalline polymers (Lep's) is of immense practical value because of the potential to form high modulus materials from these polymers. These fluids exhibit a high degree of structure even in the quiescent state, as evidenced by their ability to transmit polarized light. In an effort to understand how the structure changes during flow, we have carried out a study on the transient shear flow properties of two thermotropic copolyesters of 60-and SO-mole % para-hydroxybenzoic acid (PHB) and polyethyleneterephthalate (PET) and a lyotropic system of poly-p-phenyleneterephthalamide (PPT) in 100% sulfuric acid. In one of the first theories concerned with the flow behavior of liquid crystalline fluids, which was proposed by Ericksen, the transient flow properties are all predicted to be due to changes in orientation of a director which describes the orientation of packets of rod-like molecules. Stress growth, interrupted stress growth, and stress relaxation experiments are carried out on the three LCP's and at first sight are in qualitative agreement with the predictions of Ericksen's theory. However, wide angle X-ray scattering analysis of quenched samples subjected to shear flow along with annealing experiments on oriented samples indicate that these materials do not orient readily in shear flow. Furthermore, orientation generated during extensional flow relaxes at a rate much faster than is indicated by the interrupted stress growth experiments. It is concluded that the stress growth response of LCP's is due to a disruption of a domain structure which exists within the fluid rather than to orientation changes of the domains of rod-like molecules.

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Section: Ericksen's Transversely Isotropic Fluid Theorymentioning

confidence: 99%

Studies on the Transient Shear Flow Behavior of Liquid Crystalline Polymers

Viola¹,

Baird²

1986

Journal of Rheology

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Section: -13mentioning

confidence: 99%

“…For example, the melt viscosities of thermotropic liquid crystalline polymers (LCPs) possessing an isotropic melt state were significantly lower than structurally similar polymers. [14][15][16] In addition, LCPs were also attached importance to their high modulus and a very low thermal expansion in their direction of the macroscopic orientation.A series of thermotropic liquid crystalline poly(aryl ether ketones) copolymers have been prepared since Bennett and Farris firstly reported a kind of thermotropic liquid crystalline poly(aryl ether ketones) copolymers based on 4, 4 0 -biphenol, bulky substituted hydroquinone and 4, 4 0 -difluorobenzophenone in 1994. …”

mentioning

confidence: 99%

Synthesis and Thermotropic Liquid Crystalline Behavior of Novel Main-Chain Poly(aryl ether ketones) Copolymer Containing Phthalazinone Moiety and Biphenyl Mesogen

Sun

Wang

Jin

et al. 2007

Polym J

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A novel thermotropic liquid crystalline poly(aryl ether ketones) copolymer containing phthalazinone moiety and biphenyl mesogen named P-5050 was developed by a mild solution polycondensation reaction. The thermotropic liquid crystalline properties were characterized by the means of differential scanning calorimetry (DSC), polarized light microscopy (PLM) and wide-angel X-ray diffraction (WAXD). A thread-like texture was achieved when P-5050 was annealed at 320 C for 1 h, and a typical schlieren texture was observed when shear forces were induced at that temperature. The crystalline-to-liquid crystalline transition (T m ) and the liquid crystalline-to-isotropic phase transition (T i ) appeared in both the first cooling and second heating DSC thermograms. The glass transition temperature (T g ) was 160C and the value for 5% weight loss temperature was 510 C in nitrogen from DSC and TGA determinations, respectively. 2-13It is well-known that liquid crystalline properties are particularly valuable in the applications of high performance engineering materials. For example, the melt viscosities of thermotropic liquid crystalline polymers (LCPs) possessing an isotropic melt state were significantly lower than structurally similar polymers. [14][15][16] In addition, LCPs were also attached importance to their high modulus and a very low thermal expansion in their direction of the macroscopic orientation.A series of thermotropic liquid crystalline poly(aryl ether ketones) copolymers have been prepared since Bennett and Farris firstly reported a kind of thermotropic liquid crystalline poly(aryl ether ketones) copolymers based on 4, 4 0 -biphenol, bulky substituted hydroquinone and 4, 4 0 -difluorobenzophenone in 1994.

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“…22, No. 4,1990 which give the correct ordering '1c > '1. > '1b for low molecular weight liquid crystals and C is the dimensionless concentration (= c/ c *).…”

Section: Theorymentioning

confidence: 99%

“…3,4 The production of ultrahigh strength/high modulus fibers spun from nematic solutions of macromolecules is a topic of interest. Specially the fiber made of poly(p-phenylene tereph thalami de) (PPTA) shows very excellent physical properties.…”

mentioning

confidence: 99%