GTTM - Glass Transition Temperature Test

This is quoted for ceramic frits and is derived from the graph produced by a dilatometer. The line (representing increasing thermal expansion) climbs steeply as temperature increases. When the transition point is reached an inflection (direction change) in the curve occurs, after this the expansion increases more rapidly until the material reaches the softening point. That point is the peak of the curve, after that the line drops off vertically and melting proceeds.

This is equal to the sintering point in the HMA test.

Simple dilatometric curve produced by a dilatometer

Dialometric chart produced by a dilatometer. The curve represents the increase in thermal expansion that occurs as a glass is heated. Changes in the direction of the curve are interpreted as the transformation (or transition) temperature, set point and softening point (often quoted on frit data sheets). When the thermal expansion of a material is quoted as one number (on a data sheet), it is derived from this chart. Since the chart is almost never a straight line one can appreciate that the number is only an approximation of the thermal expansion profile of the material.

Variables

TP - Value (V)

Value in degrees: e.g. 560C

Related Information

Links

URLs	http://www.answers.com/topic/glass-transition-temperature?cat=technology Glass Transition Temperature at answers.com
URLs	http://en.wikipedia.org/wiki/Glass_transition Glass Transition Temperature at Wikipedia
Tests	Heating Microscope Analysis for Frits
Tests	Heating Microscope Analysis
Tests	Frit Softening Point In ceramics, this is the temperature at which a glaze or glass begins to flow, ceasing to exhibit the properties of a solid.
Tests	Co-efficient of Linear Expansion In ceramics, glazes expand with increasing temperature. Being brittle materials, they must be expansion-compatible with the body they are on.
Typecodes	Material Tests Test conducted primarily on materials use to make bodies or glazes.
Projects	Frits
Glossary	Frit Frits are used in ceramic glazes for a wide range of reasons. They are man-made glass powders of controlled chemistry with many advantages over raw materials.

By Tony Hansen
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