VISCOELASTIC PROPERTIES OF POLY(PIVALOLACTONE)

The viscoelastic properties of poly(pivalolactone) (PPL) have been investigated in the linear range using stress-relaxation and dynamic-mechanical measurements. Under the conditions that the sample was isotropic and insensitive to relative humidity, Ferry's reduction method was applied without using translations along the vertical axis. A horizontal shift factor was determined at each temperature, which satisfactorily agreed with the WLF equation in the transition region. The apparent activation energy of PPL was temperature dependent and passed through a maximum near Tg whose value was found to be 369 ± 3 K. The relaxation spectrum was calculated according to the first method of approximation of Schwarzl and Staverman, and it was found to be flat with a complicated fine structure. Two absorption peaks were determined. The low-temperature γ peak, around 300 K, was ascribed to a relaxation process in the crystalline phase of the polymer while the high-temperature β peak was related to the glass-transition process. © 1979, American Chemical Society. All rights reserved.