glass transition


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Glass transition

The transition that occurs when a liquid is cooled to an amorphous or glassy solid. This can occur only if the cooling rate is fast enough to prevent crystallization which would otherwise occur if time had been sufficient for the sample to reach true equilibrium at each temperature. Since the crystal is invariably the thermodynamically stable low-temperature phase, the glass transition corresponds to a transition from a high-temperature liquid into a nonequilibrium meta-stable low-temperature solid. See Amorphous solid, Crystal, Viscosity

For many organic and polymeric systems, the difficulty of molecular packing and the steric hindrances are sufficient to prevent crystallization, and glass formation in these systems is relatively easy. In other systems, for example, metallic systems, rapid quench rates on the order of 106 K/s (2 × 106 °F/s) may be necessary to avoid crystallization, suggesting that any system can be quenched from the liquid state to an amorphous glassy state assuming that the system can be cooled rapidly enough.

glass transition

[′glas tran‚zish·ən]
(physics)
The transition that occurs when a liquid is cooled to an amorphous or glassy solid.
(physical chemistry)
The change in an amorphous region of a partially crystalline polymer from a viscous or rubbery condition to a hard and relatively brittle one; usually brought about by changing the temperature. Also known as gamma transition; glassy transition.
References in periodicals archive ?
In amorphous polymers, the glass transition is the major event that separates molten from solidified material.
KUWAIT, Aug 27 (KUNA) -- The Kuwait Institute for Scientific Research (KISR) has registered an unprecedented patent for measurement of glass transition temperatures of polymers.
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The ink composition includes a mono-functional monomer having a glass transition point of -30[degrees]C or lower, and a polyfunctional monomer having a glass transition point of 0[degrees]C or lower.
They cover density, thermal properties, and the glass transition temperature of glasses; infrared spectroscopy; Raman spectroscopy; Brillouin light scattering; neutron diffraction techniques for structural studies; X-ray diffraction from glass; X-ray absorption fine structure (SAFS) spectroscopy and glass structure; nuclear magnetic resonance spectroscopy; advanced dipolar solid-state nuclear magnetic resonance spectroscopy; and atom probe tomography.
The effect of glass transition on coating impedances during a short period of exposure to heat source was insignificant.
More specifically, chemists and physicists have struggled to describe key aspects of the glass transition, such as the concept of molecular "cages" that form as the temperature drops and the surface begins to harden.
However their low thermal stability (low glass transition temperature) or their tendency to crystallize prevent their use in OLED products.
The product's glass transition temperature Tg is -30 AC.
1c) and from this step the characteristic values, glass transition temperature ([T.
Chemists and physicists who specialize in glass present a range of modern theoretical and experimental views of the glass transition and relaxations in glassy systems, phenomena that have perplexed scientists, artisans, and artists since ancient times.
First, the surface temperature of the hinge must exceed the glass transition temperature of the material, which is the point at which the material begins to soften.