glass transition temperature
Quick Summary
The glass transition temperature ((T_g)) is a crucial concept in materials science, particularly for polymers and amorphous solids. It marks the temperature range where a material transitions from a rigid, glassy state to a more flexible, rubbery state.12
In an amorphous polymer, molecules are randomly arranged. Below (T_g), these molecules vibrate with low energy, essentially frozen in place, creating the glassy state. As the temperature increases and reaches (T_g), molecular motion becomes more energetic, leading to a significant increase in volume and a transition to a rubbery state where the polymer exhibits elasticity.1
This transition is not a sharp melting point but a gradual process occurring over a temperature range. The exact (T_g) can vary depending on the material's composition and cooling rate. For instance, rubbers have (T_g) below room temperature, explaining their elasticity, while plastics require heating above their (T_g) to become moldable.12
Ask Britannica AI about this topic
Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.
- industrial glassThe glass transformation range
…in Figure 1 is the glass transition temperature, or Tg; this would be located at the lower end of the transformation range.) In crystallization, on the other hand, the transition from liquid to solid takes place with essentially a discontinuous change in volume. In Figure 1 this abrupt transition is…
Read More…in Figure 1 is the glass transition temperature, or Tg; this would be located at the lower end of the transformation range.) In crystallization, on the other hand, the transition from liquid to solid takes place with essentially a discontinuous change in volume. In Figure 1 this abrupt transition is…
Read More - industrial glassViscosity
65 poise, the annealing point by 1013 poise, and finally the strain point by 1014.5 poise. Upon further cooling, viscosity increases rapidly to well beyond 1018 poise, where it can no longer be measured meaningfully. (The softening point and working point of the major oxide glass families are…
Read More65 poise, the annealing point by 1013 poise, and finally the strain point by 1014.5 poise. Upon further cooling, viscosity increases rapidly to well beyond 1018 poise, where it can no longer be measured meaningfully. (The softening point and working point of the major oxide glass families are…
Read More
- chemistry of industrial polymersAmorphous and semicrystalline
…this occurs is called the glass transition temperature; in the volume-temperature diagram it is indicated by the vertical dashed line labeled Tg, which intersects the amorphous and semicrystalline curves at points f and b. In the rubbery state above Tg, polymers demonstrate elasticity, and some can even be molded into…
Read More…this occurs is called the glass transition temperature; in the volume-temperature diagram it is indicated by the vertical dashed line labeled Tg, which intersects the amorphous and semicrystalline curves at points f and b. In the rubbery state above Tg, polymers demonstrate elasticity, and some can even be molded into…
Read More 
plasticPhysical states and molecular morphologies…which is set by the glass transition temperature or the melting temperature of the particular polymer. Below a certain temperature, known as the glass transition temperature (Tg), the molecules of a polymer material are frozen in what is known as the glassy state; there is little or no movement of…
Read More…which is set by the glass transition temperature or the melting temperature of the particular polymer. Below a certain temperature, known as the glass transition temperature (Tg), the molecules of a polymer material are frozen in what is known as the glassy state; there is little or no movement of…
Read More- elastomerPolymers and elasticity
…are glassy below a characteristic glass transition temperature (Tg), which ranges from as low as −125 °C (−195 °F) for an extremely flexible molecule such as polydimethyl siloxane (silicone rubber) to extremely high temperatures for stiff, bulky molecules. For both PS and PMMA, Tg is approximately 100 °C (212 °F).
Read More…are glassy below a characteristic glass transition temperature (Tg), which ranges from as low as −125 °C (−195 °F) for an extremely flexible molecule such as polydimethyl siloxane (silicone rubber) to extremely high temperatures for stiff, bulky molecules. For both PS and PMMA, Tg is approximately 100 °C (212 °F).
Read More