Characterization of thermotropic liquid crystalline polyester/polycarbonate blends

miscibility, rheology, and free volume behavior

Tsung Tang Hsieh, Carlos Tiu, Kuo Huang Hsieh, George P. Simon

Research output: Contribution to journalArticleResearchpeer-review

28 Citations (Scopus)

Abstract

Miscibility, rheology, and free volume properties of blends of thermotropic liquid crystalline polymers (TLCPs) (Vectra A950) and polycarbonate (PC) are studied in this work. Despite the unusual increase in Tg of the PC phase, the blends are found to be generally immiscible. Transesterification may occur during blending and be the cause of the increase of Tg of the PC phase and the partial miscibility of the blends at high TLCP concentrations. With regard to the melt rheology of these materials, according to a three-zone model, dynamic moduli of Vectra A950 show plateau- and transition-zone behavior, while PC exhibits terminal-zone behavior. The blends show only terminal-zone behavior at low Vectra A950 contents (≤50%) and terminal- and plateau-zone behavior at higher Vectra A950 contents. The relaxation time of Vectra A950 is much longer than PC and the blends have relaxation times greater than additivity. Both the complex and steady shear viscosities of the blends increase with the addition of Vectra A950. This is attributed to interfacial association, which retards the reorientation and alignment of the Vectra A950 phase in the molten state. The Cox-Merz rule holds true for PC but not for Vectra A950 and the blends. Free volume properties on an angstrom scale evaluated by positron annihilation lifetime spectroscopy (PALS) indicate that Vectra A950 has smaller, fewer free volume cavities than PC and the variation of free volume behavior in the blends can be explained in terms of blend miscibility. The measured densities of the blends agree well with the free volume fractions of the blends determined from PALS.

Original languageEnglish
Pages (from-to)2319-2330
Number of pages12
JournalJournal of Applied Polymer Science
Volume77
Issue number10
DOIs
Publication statusPublished - 1 Sep 2000

Cite this

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title = "Characterization of thermotropic liquid crystalline polyester/polycarbonate blends: miscibility, rheology, and free volume behavior",
abstract = "Miscibility, rheology, and free volume properties of blends of thermotropic liquid crystalline polymers (TLCPs) (Vectra A950) and polycarbonate (PC) are studied in this work. Despite the unusual increase in Tg of the PC phase, the blends are found to be generally immiscible. Transesterification may occur during blending and be the cause of the increase of Tg of the PC phase and the partial miscibility of the blends at high TLCP concentrations. With regard to the melt rheology of these materials, according to a three-zone model, dynamic moduli of Vectra A950 show plateau- and transition-zone behavior, while PC exhibits terminal-zone behavior. The blends show only terminal-zone behavior at low Vectra A950 contents (≤50{\%}) and terminal- and plateau-zone behavior at higher Vectra A950 contents. The relaxation time of Vectra A950 is much longer than PC and the blends have relaxation times greater than additivity. Both the complex and steady shear viscosities of the blends increase with the addition of Vectra A950. This is attributed to interfacial association, which retards the reorientation and alignment of the Vectra A950 phase in the molten state. The Cox-Merz rule holds true for PC but not for Vectra A950 and the blends. Free volume properties on an angstrom scale evaluated by positron annihilation lifetime spectroscopy (PALS) indicate that Vectra A950 has smaller, fewer free volume cavities than PC and the variation of free volume behavior in the blends can be explained in terms of blend miscibility. The measured densities of the blends agree well with the free volume fractions of the blends determined from PALS.",
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Characterization of thermotropic liquid crystalline polyester/polycarbonate blends : miscibility, rheology, and free volume behavior. / Hsieh, Tsung Tang; Tiu, Carlos; Hsieh, Kuo Huang; Simon, George P.

In: Journal of Applied Polymer Science, Vol. 77, No. 10, 01.09.2000, p. 2319-2330.

Research output: Contribution to journalArticleResearchpeer-review

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T2 - miscibility, rheology, and free volume behavior

AU - Hsieh, Tsung Tang

AU - Tiu, Carlos

AU - Hsieh, Kuo Huang

AU - Simon, George P.

PY - 2000/9/1

Y1 - 2000/9/1

N2 - Miscibility, rheology, and free volume properties of blends of thermotropic liquid crystalline polymers (TLCPs) (Vectra A950) and polycarbonate (PC) are studied in this work. Despite the unusual increase in Tg of the PC phase, the blends are found to be generally immiscible. Transesterification may occur during blending and be the cause of the increase of Tg of the PC phase and the partial miscibility of the blends at high TLCP concentrations. With regard to the melt rheology of these materials, according to a three-zone model, dynamic moduli of Vectra A950 show plateau- and transition-zone behavior, while PC exhibits terminal-zone behavior. The blends show only terminal-zone behavior at low Vectra A950 contents (≤50%) and terminal- and plateau-zone behavior at higher Vectra A950 contents. The relaxation time of Vectra A950 is much longer than PC and the blends have relaxation times greater than additivity. Both the complex and steady shear viscosities of the blends increase with the addition of Vectra A950. This is attributed to interfacial association, which retards the reorientation and alignment of the Vectra A950 phase in the molten state. The Cox-Merz rule holds true for PC but not for Vectra A950 and the blends. Free volume properties on an angstrom scale evaluated by positron annihilation lifetime spectroscopy (PALS) indicate that Vectra A950 has smaller, fewer free volume cavities than PC and the variation of free volume behavior in the blends can be explained in terms of blend miscibility. The measured densities of the blends agree well with the free volume fractions of the blends determined from PALS.

AB - Miscibility, rheology, and free volume properties of blends of thermotropic liquid crystalline polymers (TLCPs) (Vectra A950) and polycarbonate (PC) are studied in this work. Despite the unusual increase in Tg of the PC phase, the blends are found to be generally immiscible. Transesterification may occur during blending and be the cause of the increase of Tg of the PC phase and the partial miscibility of the blends at high TLCP concentrations. With regard to the melt rheology of these materials, according to a three-zone model, dynamic moduli of Vectra A950 show plateau- and transition-zone behavior, while PC exhibits terminal-zone behavior. The blends show only terminal-zone behavior at low Vectra A950 contents (≤50%) and terminal- and plateau-zone behavior at higher Vectra A950 contents. The relaxation time of Vectra A950 is much longer than PC and the blends have relaxation times greater than additivity. Both the complex and steady shear viscosities of the blends increase with the addition of Vectra A950. This is attributed to interfacial association, which retards the reorientation and alignment of the Vectra A950 phase in the molten state. The Cox-Merz rule holds true for PC but not for Vectra A950 and the blends. Free volume properties on an angstrom scale evaluated by positron annihilation lifetime spectroscopy (PALS) indicate that Vectra A950 has smaller, fewer free volume cavities than PC and the variation of free volume behavior in the blends can be explained in terms of blend miscibility. The measured densities of the blends agree well with the free volume fractions of the blends determined from PALS.

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EP - 2330

JO - Journal of Applied Polymer Science

JF - Journal of Applied Polymer Science

SN - 0021-8995

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