Polymer Dynamics Studies with Flow Birefringence Method

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(1) An optical system was equipped to a tensile tester for simultaneous measurements of stress and birefringence of a polymeric film. The range of time for relaxation measurement was 1 - 10^4s and the range of temperature was 0 - 200ﾟC. An apparatus for simultaneous measurements of viscoelasticity and dynamic birefringence was developed by adding an optical system to a dynamic rheometer. The frequency range was 1 - 20OHz and the temperature range was 0 - 250 ﾟC.(2) A modified stress-optical rule was proposed to describe the stress and birefringence of amorphous polymers. The method was applied to polystyrene, poly- alpha -methylstyrene, polyarylate, polycarbonate, polysulfone, polyethersulfone, polyetherimide, and polyetherether ketone. For these polymers, the viscoelastic relaxation spectrum was revealed to consist of two components. The difference in temperature dependence of these components was revealed to be the origin of the complicated temperature dependence of viscoelasticity around the glass transition point.(3) The stress and birefringence were measured after an instantaneous large deformation and during a deformation at constant speed for polystyrene and polycarbonate. The yield phenomenon of such a glassy polymer was revealed to represent the yield of the enthalpic force due to the potential energy. The entropic force did not show any sign of yield phenomenon.