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Differential scanning calorimetry can be used to measure a number of characteristic properties of a sample. Using this technique it is possible to observe fusion and crystallization events as well as glass transition temperatures T g. DSC can also be used to study oxidation, as well as other chemical reactions. [15] [16] [19]
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.
CTE of the glassy state is low, while at the glass transition temperature (Tg) increased degrees of molecular segmental motion are released so CTE of the rubbery state is high. Changes in an amorphous polymer may involve other sub-Tg thermal transitions associated with short molecular segments, side-chains and branches.
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 ...
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.
The glass transition temperature (Tg) can be defined by the temperature at which an amorphous polymeric material undergoes a reversible transition from a hard, solid state to a more rubbery state, as determined as inflection point of the heat capacity-temperature curve recorded by differential scanning calorimetry (DSC). In the determination ...
Vitrification (from Latin vitrum 'glass', via French vitrifier) is the full or partial transformation of a substance into a glass, [1] that is to say, a non-crystalline or amorphous solid. Glasses differ from liquids structurally and glasses possess a higher degree of connectivity with the same Hausdorff dimensionality of bonds as crystals: dim ...
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