Tg Glass transition temperature - Thermoplastic polymers, elastomers and additives

It is the temperature at which a polymer changes from a rigid and brittle to a soft and malleable state, is present only in amorphous polymers and is different for each polymer, this transition temperature is known as the glass transition temperature (Tg) . The glass transition is a typical property of the amorphous portion of a semicrystalline solid. At low temperatures, the regions in which the polymer is amorphous are in the vitreous state and the molecules have little mobility since the only allowed movement is a weak vibratory movement and, therefore, the polymer is hard, rigid and fragile. If the polymer is heated, when it reaches the glass transition temperature, the molecules can start to move and, therefore, the polymer is rubbery and shows softness and flexibility. The transitions must be considered as the effect of the excitation, due to the increase of the temperature, of the vibratory or rotational movements of the atoms, atomic groups and chain segments.