Abstract
The fictive temperature (Tf) was defined by Tool in the 1940s as a measure of glassy structure. Tf is generally measured on heating and can be calculated from the enthalpy overshoot in calorimetric studies using a method developed by Moynihan. Prior work has demonstrated that the limiting fictive temperature (Tf′) is similar to Tg (measured on cooling) and depends on the cooling rate in a manner consistent with the Williams-Landel-Ferry (WLF) relationship. Theoretically, the limiting fictive temperature should not depend on heating rate, but this has been experimentally verified only for a very limited range of heating rates. Here, rapid-scanning chip calorimetry and conventional differential scanning calorimetry (DSC) are combined to investigate Tf′ for polystyrene over a broad range of heating rates ranging from 0.017 to 3000 K/s after cooling at different rates. The results show that Tf′ depends on cooling rate following the WLF equation. On the other hand, Tf′ is not a function of heating rate, consistent with theoretical predictions, in spite of the change in the magnitude and placement of the enthalpy overshoot.
Original language | English |
---|---|
Pages (from-to) | 123-127 |
Number of pages | 5 |
Journal | Thermochimica Acta |
Volume | 603 |
DOIs | |
State | Published - Mar 10 2015 |
Keywords
- Cooling and heating rate dependence
- Glass transition temperature
- Limiting fictive temperature
- Polystyrene
- WLF equation