High Speed SSA Thermal Fractionation and Limitations to the Determination of Lamellar Sizes and Their Distributions

Authors

  • Arnaldo T. Lorenzo,

    1. Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Apartado 89000, Caracas 1080-A, Venezuela
    Search for more papers by this author
  • Maria L. Arnal,

    1. Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Apartado 89000, Caracas 1080-A, Venezuela
    Search for more papers by this author
  • Alejandro J. Müller,

    Corresponding author
    1. Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Apartado 89000, Caracas 1080-A, Venezuela
    • Grupo de Polímeros USB, Departamento de Ciencia de los Materiales, Universidad Simón Bolívar, Apartado 89000, Caracas 1080-A, Venezuela.
    Search for more papers by this author
  • Adriana Boschetti de Fierro,

    1. Institut für Polymerforschung, GKSS-Forschungszentrum Geesthacht GmbH, 21502 Geesthacht, Germany
    Search for more papers by this author
  • Volker Abetz

    1. Institut für Polymerforschung, GKSS-Forschungszentrum Geesthacht GmbH, 21502 Geesthacht, Germany
    Search for more papers by this author

Abstract

Summary: The technique of successive self-nucleation and annealing (SSA) has been applied using differential scanning calorimetry (DSC) to a model hydrogenated polybutadiene prepared by anionic polymerization and to a commercial Ziegler-Natta ethylene/1-butene copolymer. Here, it is shown that the use of high scanning rates (50 °C · min−1) in the SSA protocol can reduce the thermal fractionation time to only 78 min in length (if 6 fractions are produced with a fractionation window of 5 °C), taking into consideration the need to compensate the increment in heating rates by reducing the sample mass. This time is much shorter than those previously achieved by thermal fractionation in the literature, where fractionation times of 12 or 24 h are common. Potentially, much higher rates could be employed by further reducing the fractionation times by SSA. For the first time, a distribution of lamellar thicknesses has been obtained by transmission electron microscopy after SSA fractionation and compared to distributions calculated by the Thomson-Gibbs equation. It is shown that the results are highly dependent on the equilibrium melting temperatures employed in the calculations, and it is recommended that the values of lamellar thicknesses obtained are checked by comparing with methylene sequence lengths derived from calibration measurements available in the literature. The Thomson-Gibbs equation is useful for comparing lamellar thickness distributions obtained by SSA with different polymers only on a semi-quantitative basis.

original image

Rate and mass compensation as a way to reduce fractionation time employing SSA.

Ancillary