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The glass transition of a liquid to a solid-like state may occur with either cooling or compression. [10] The transition comprises a smooth increase in the viscosity of a material by as much as 17 orders of magnitude within a temperature range of 500 K without any pronounced change in material structure. [11]
The Flory–Fox equation relates the number-average molecular weight, M n, to the glass transition temperature, T g, as shown below: =, where T g,∞ is the maximum glass transition temperature that can be achieved at a theoretical infinite molecular weight and K is an empirical parameter that is related to the free volume present in the polymer sample.
Fragility characterizes how rapidly the viscosity of a glass forming liquid approaches a very large value approximately 10 12 Pa s during cooling. At this viscosity, the liquid is "frozen" into a solid and the corresponding temperature is known as the glass transition temperature T g. Materials with a higher fragility have a more rapid increase ...
The onset temperature of the transition zone, moving from glassy to rubbery, is known as the glass transition temperature, or T g. In the 1940s Andrews and Tobolsky [ 6 ] showed that there was a simple relationship between temperature and time for the mechanical response of a polymer.
In this way, the master curve can be applied to other temperatures. However, when the constants are obtained with data at temperatures above the glass transition temperature (T g), the WLF equation is applicable to temperatures at or above T g only; the constants are positive and represent Arrhenius behavior.
The Vogel–Fulcher–Tammann equation, also known as Vogel–Fulcher–Tammann–Hesse equation or Vogel–Fulcher equation (abbreviated: VFT equation), is used to describe the viscosity of liquids as a function of temperature, and especially its strongly temperature dependent variation in the supercooled regime, upon approaching the glass transition.
Because of that, amorphous materials have a characteristic threshold temperature termed glass transition temperature (T g): below T g amorphous materials are glassy whereas above T g they are molten. The most common applications are in the making of pottery , glass, and some types of food, but there are many others, such as the vitrification of ...
When the supercooled liquid is further cooled, it becomes a glass. [1] The temperature at which a polymer becomes a glass by fast cooling is called the glass transition temperature T g. At this temperature, viscosity reaches up to 10 13 poise depending upon cooling-rate.