SALS, WAXS and mechanical properties of heat-treated thermotropic polymers

Adriana Reyes-Mayer, Bonifacio Alvarado-Tenorio, Angel Romo-Uribe, Michael Jaffe

    Research output: Contribution to journalArticlepeer-review

    5 Scopus citations

    Abstract

    The influence of heat treatment on the texture, microstructure and tensile mechanical properties of extruded thin films of a series of high-performance thermotropic liquid crystal polymers (LCPs) was investigated. LCPs based on random units of hydroxybenzoic acid (B), hydroxynaphthoic acid (N), terephthalic acid (TA) and biphenol (BP) were kindly supplied by the former Hoechst Celanese Corp as 50 μm thick extruded tapes. The LCPs, denoted B-N, COTBP and RD1000, have B and N as common comonomers and vary the other comonomers. Thus, this study also enables the investigation of the influence of monomer composition on microstructure and mechanical properties. Heat treatments were carried out at temperatures close to the solid-to-nematic transition (Ts→n) for periods up to 5 h, under dry air conditions. The thermal treatment produced either two endotherms or a small increase of Ts→n (B-N and RD1000), or increased significantly Ts→n (COTBP). Moreover, when heat treatment was carried out approximately 40°C below the respective Ts→n, the mechanical Young's modulus, E, along the extrusion axis, increased for all LCPs. Strikingly, for COTBP, E increased over 100% relative to the as-extruded film. The results also showed that the optimum treatment time for improving the Young modulus, under dry air atmosphere, was between 3 and 4 h. Wide-angle X-ray scattering showed a significant sharpening of crystalline reflections and concentration of the 002 meridional reflection as a result of thermal treatment, suggesting the elimination of defects and a better alignment of the molecular chains along the extrusion axis. This would explain the increase in tensile modulus.

    Original languageEnglish (US)
    Pages (from-to)1029-1039
    Number of pages11
    JournalPolymers for Advanced Technologies
    Volume24
    Issue number12
    DOIs
    StatePublished - Dec 2013

    All Science Journal Classification (ASJC) codes

    • Polymers and Plastics

    Keywords

    • Copolyesters
    • Dynamic mechanical analysis
    • Mechanical relaxation
    • Thermotropic LCP
    • X-ray scattering

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