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Influence of type of compatibilizer on the rheological and mechanical behavior of LCP/TP blends under different stationary and nonstationary shear conditions

Authors

  • Susana Filipe,

    1. IPC-Institute for Polymers and Composites, University of Minho, Polymer Engineering Department, Campus de Azurém, 4800-058 Guimarães, Portugal
    2. Materials Science Department and CENIMAT, New University of Lisbon, Campus da Caparica, 2829-516 Caparica, Portugal
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  • João M. Maia,

    1. IPC-Institute for Polymers and Composites, University of Minho, Polymer Engineering Department, Campus de Azurém, 4800-058 Guimarães, Portugal
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  • Ana Duarte,

    1. Materials Science Department and CENIMAT, New University of Lisbon, Campus da Caparica, 2829-516 Caparica, Portugal
    2. ICTPOL, IST — Chemical Department, Torre Sul, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
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  • Catarina R. Leal,

    1. ISEL, Polytechnical Institut of Lisbon, Scientific Area of Physics, Rua Conselheiro Emídio Navarro, 1, 1949-014 Lisboa, Portugal
    2. C.F.M.C., Lisbon University, Av. Prof. Gama Pinto 2, P-1649-003 Lisboa, Portugal
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  • Maria T. Cidade

    Corresponding author
    1. Materials Science Department and CENIMAT, New University of Lisbon, Campus da Caparica, 2829-516 Caparica, Portugal
    • Materials Science Department and CENIMAT, New University of Lisbon, Campus da Caparica, 2829-516 Caparica, Portugal
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Abstract

The addition of small amounts of liquid-crystalline polymers to thermoplastics leads to the formation of in situ–reinforced materials, with improved processability and mechanical properties. Nevertheless, the lack of adhesion between the thermoplastic and the liquid-crystalline polymer often occurs, thus requiring the use of compatibilizers. In this case, the results of several previous works show that there is an improvement of strength, usually accompanied by a decrease of toughness and, thus, the interest of LCP/TP blends for industrial applications will certainly increase if both strength and toughness are obtained. Additionally, the emphasis of previous studies has been on the evaluation of the properties of the blend under stationary conditions and not under non-stationary ones, which are, in fact, those most relevant to processing sequences. Thus, the present work focuses on the influence of type of compatibilizer on the mechanical and rheological properties of polypropylene/LCP blends under nonstationary conditions. In terms of mechanical properties, the traditional increase of tensile strength was obtained for all compatibilizers, which was essentially due to the formation, during processing, of thinner and longer fibrils of LCP dispersed in the matrix than those observed for the noncompatibilized blends. Additionally, an improvement of the impact strength and flexural modulus was also observed for the blend in which a compatibilizer with an elastomeric nature was used. Rheologically, the experiments most sensitive to the structure were those performed in transient shear, with an increase of the transient stress (in the form of an overshoot) of different magnitudes being observed for the different compatibilizers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 694–703, 2005

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