There is no latent heat of glass transition. The temperature keeps going up. But the temperature doesn't go up at the same rate above the Tg as below it. ... Because the glass transition involves change in heat capacity, but it doesn't involve a latent heat, this transition is called a second order transition.

Is the glass transition a second order?

The glass transition is not considered a first-order phase transition, but a kinetic phenomenon or a second-order transition. The glass transition is a temperature range over which the amorphous regions change from a brittle glassy state to a flexible rubbery state as they are heated.

Why do polymers undergo glass transition?

In the glassy state, the motion of the red molecule in the schematic diagram below would NOT occur. When the amorphous regions of a polymer are in the glassy state, it generally will be hard, rigid, and brittle. If the polymer is heated it eventually will reach its glass transition temperature.