Giass transition temperature
1.GLASS TRANSITION TEMPERATURE:-
The temperature at which polymer experience the transition from rubbery to rigid state is termed as the 'Glass transition temperature'( Tg). The behaviour of a polymer is temperature sensitive. Glass transition temperature is also defined as the lowest temperature below which the polymer becomes hard and brittle and above which it becomes soft and flexible. The
polymer becomes too soft, that it behaves like a fluid called as the visco fluid state. The temperature at which the soft_ flexible polymer goes to the visco fluid state is called the melting temperature T m.
Factors Influencing Tg
1.Cross linking increases the Tg value.
2.Presence of bulky groups increases the Tg value.
3.Addition of plasticizer decreases the Tg value.
4.Polymers having strong intermolecular forces of attraction increases Tg value.
5.Polar side atoms or groups of atoms increases the Tg value.