The glass–liquid transition (or glass transition for short) is the reversible transition in amorphous materials (or in amorphous regions within semicrystalline materials) from a hard and relatively brittle state into a molten or rubber-like state. An amorphous solid that exhibits a glass transition is called a glass. Supercooling a viscous liquid into the glass state is called vitrification, from the Latin vitreum, "glass" via French vitrifier.
Despite the massive change in the physical properties of a material through its glass transition, the transition is not itself a phase transition of any kind; rather it is a laboratory phenomenon extending over a range of temperature and defined by one of several conventions. Such conventions include a constant cooling rate (20 K/min) and a viscosity threshold of 1012 Pa·s, among others. Upon cooling or heating through this glass-transition range, the material also exhibits a smooth step in the thermal-expansion coefficient and in the specific heat, with the location of these effects again being dependent on the history of the material. However, the question of whether some phase transition underlies the glass transition is a matter of continuing research.
The glass-transition temperature Tg is always lower than the melting temperature, Tm, of the crystalline state of the material, if one exists.
Other articles related to "glass transition, glass, transition":
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... Alternatively, when hit hard and directly, it shatters like a silicate glass ... In addition, conventional rubber undergoes a glass transition, (often called a rubber-glass transition) ... that were being used well below their glass transition temperature on an unusually cold Florida morning, and thus could not flex adequately to form proper seals between sections of the two solid-fuel ...
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... One important application of DMA is measurement of the glass transition temperature of polymers ... Amorphous polymers have different glass transition temperatures, above which the material will have rubbery properties instead of glassy behavior and the stiffness of the material ... At the glass transition, the storage modulus decreases dramatically and the loss modulus reaches a maximum ...
Famous quotes containing the words transition and/or glass:
“A transition from an authors books to his conversation, is too often like an entrance into a large city, after a distant prospect. Remotely, we see nothing but spires of temples, and turrets of palaces, and imagine it the residence of splendor, grandeur, and magnificence; but, when we have passed the gates, we find it perplexed with narrow passages, disgraced with despicable cottages, embarrassed with obstructions, and clouded with smoke.”
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“Each day I live in a glass room
Unless I break it with the thrusting
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