Tg (glass transition temperature)

The glass transition temperature (Tg) is the temperature at which a material like glass or certain plastics changes from a brittle, rubbery state to a softer, more flexible form. Below Tg, the material's molecules are relatively fixed, making it hard and fragile. Above Tg, the molecules can move more freely, allowing the material to bend or stretch without breaking. Tg is important in engineering and manufacturing because it determines the temperature range where a material can be used effectively without losing its desired properties.