The structure of thermotropic copolyesters

Sawyer, Linda C.; Jaffé, Michael

doi:10.1007/bf00547924

Cited by 246 publications

(148 citation statements)

References 42 publications

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“…Microstructure SEM micrographs of the cryofractured surfaces of Vectran_rGO nanocomposites were acquired in order to assess the dispersion of GO lamellae achieved during the nanocomposite preparation. Figure 5a shows a micrograph of the unfilled matrix, evidencing the peculiar fibrillar morphology of Vectran [48,49]. Because this morphology is preserved also when the nanofiller is present in the polymer matrix, the evaluation of the filler dispersion and distribution within the matrix is a rather difficult task for filler amount of 1 wt% (Figure 5b).…”

mentioning

confidence: 99%

Liquid crystalline polymer nanocomposites reinforced with in-situ reduced graphene oxide

Pedrazzoli¹,

Dorigato²,

Conti³

et al. 2015

Express Polym. Lett.

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Abstract. In this work liquid-crystalline polymer (LCP) nanocomposites reinforced with in-situ reduced graphene oxide are investigated. Graphene oxide (GO) was first synthesized by the Hummers method, and the kinetics of its thermal reduction was assessed. GO layers were then homogeneously dispersed in a thermotropic liquid crystalline polymer matrix (Vectran ® ), and an in-situ thermal reduction of GO into reduced graphene oxide (rGO) was performed. Even at low rGO amount, the resulting nanocomposites exhibited an enhancement of both the mechanical properties and the thermal stability. Improvements of the creep stability and of the thermo-mechanical behavior were also observed upon nanofiller incorporation. Furthermore, in-situ thermal reduction of the insulating GO into the more electrically conductive rGO led to an important surface resistivity decrease in the nanofilled samples.

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mentioning

confidence: 99%

Liquid crystalline polymer nanocomposites reinforced with in-situ reduced graphene oxide

Pedrazzoli¹,

Dorigato²,

Conti³

et al. 2015

Express Polym. Lett.

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“…High-strength and high-stiffness LCP fibres, e.g. Kevlar and Vectran, have been developed and commercialized (Sawyer, 1984;Sawyer & Jaffe, 1986, 1991. However, these types of materials are normally highly anisotropic and the enhancement of the mechanical performance in one direction is usually achieved at the expense of the properties in the other directions.…”

Section: Introductionmentioning

confidence: 99%

Structure and morphology of the in situ composites of a liquid crystalline polymer and polycarbonate

Xiao

Lin

Yee

et al. 1997

Journal of Microscopy

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SummaryIn situ composites were prepared via melt blending of a liquid crystalline polymer (LCP) and polycarbonate using a twin screw extruder. The structure and morphology of these composites were analysed using both transmission electron microscopy (TEM) and scanning electron microscopy. The LCP phases were able to orientate and form in situ submicrometre fibres during the extrusion and postextrusion drawing. TEM images as well as selected-area diffraction patterns were obtained from the materials. The effects of both composition, i.e. LCP content, and postextrusion draw-down ratio on the development of the in situ formed LCP fibres were studied in detail. A skin-core morphological differentiation is observed in these materials where well-defined LCP fibres of higher aspect ratios were formed in the skin region. However, a significant amount of unelongated LCP particles were found coexisting with the less well-defined fibres in the core region of the extrudates. This skin-core differentiation was found to be dependent on the composition and the processing conditions, e.g. draw ratio. In this instance, electron microscopy is proven to be a powerful technique not only for direct observation of the formation, dimensions and morphology of the in situ LCP fibres, but also for the qualitative and quantitative characterization of the molecular orientation and crystalline structures in these fibres using selected-area electron diffraction. It is observed that the skin-core differentiation becomes more distinct in the in situ composites containing a higher percentage of LCP but diminishes when the material is processed at higher post-extrusion draw ratio.

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“…In larger bulk parts that are produced by processes such as injection molding, the orientation is limited to a thin surface layer. 1 The bulk of the part is unoriented because the shear field that is responsible for the orientation dies out quickly as one moves away from the wall of the mold.…”

Section: Introductionmentioning

confidence: 99%

Processing of polymers in high magnetic fields

Douglas¹,

Smith²,

Benicewicz³

et al. 1996

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Many organic molecules and polymers have an anisotropic diamagnetic susceptibility, and thus can be aligned in high magnetic fields. The presence of liquid crystallinity allows cooperative motions of the individual molecules, and thus the magnetic energy becomes greater than the thermal energy at experimentally obtainable field strengths. Our work has determined the effect of magnetic field alignment on the thermal expansion and mechanical properties of liquid crystalline thermosets in the laboratory. Further advances in magnet design are needed to make magnetic field alignment a commercially viable approach to polymer processing.

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The structure of thermotropic copolyesters

Cited by 246 publications

References 42 publications

Liquid crystalline polymer nanocomposites reinforced with in-situ reduced graphene oxide

Liquid crystalline polymer nanocomposites reinforced with in-situ reduced graphene oxide

Structure and morphology of the in situ composites of a liquid crystalline polymer and polycarbonate

Processing of polymers in high magnetic fields

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