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Published online by Cambridge University Press: 10 February 2011
We report measurements of the temperature and pressure dependence of ultrasonic modulus in polystyrene between 340 and 550 K and applied pressures up to 775 bar. The real and imaginary parts of the modulus are analyzed within the Havriliak-Negami model and very good agreement is found over the entire temperature and pressure ranges. Using the Vogel-Tammann-Fulcher equation for the relaxation time, the Kauzmann temperature TK and the fragility parameter D of polystyrene were determined. The value of D indicates that polystyrene is a fragile-glass former.