Glass transition temperature of different fibe

Glass transition temperature:

the glass transition temperature is the temperature at which an amorphous solid becomes soft upon heating or brittle upon cooling. The glass transition temperature is lower than the melting point of its crystalline form, if it has one.

Melting temperature:

Melting point, the temperature at which a substance changes from solid to liquid state.

The temperature response of linear polymers may be viewed as divided into three distinctly separate segments:

1. Above T_{m :}

In this segment, the polymer remains as a melt or liquid whose viscosity would depend on molecular weight and on the temperature of observation.

2. Between T_m and T_g :

This domain may range between near 100% crystalline and near 100% amorphous chain molecular clusters depending on the polymer structural regularity and on experimental conditions.  The amorphous part behaves much like super cooled liquid in this segment.  The overall physical behaviour of the polymer in this intermediate segment is much like a rubber.

3. Below T_g :

The polymer material viewed as a glass is hard and rigid, showing a specified coefficient of thermal expansion.  The glass is closer to a crystalline solid than to a liquid in behavioural pattern in terms of mechanical property parameters.  In respect of molecular order, however, the glass more closely resembles the liquid.  There is little difference between linear and cross linked polymer below T_g.

T_m and T_gValues of Several Polymers:

Polymer	Repeat Unit	Tm, 0C	Tg, 0C
Polyethylene	– CH2 – CH2 –	137	-115,-60
Polyoxymethylene	– CH2 – O –	181	-85,-50
Polypropylene (isotactic)	– CH2 – CH (CH3) –	176	- 20
Polyisobutylene	– CH2 – C (CH3)2 –	44	- 73
Polybutadine (1, 4 cis)	– CH2 – CH = CH – CH2 –	2	- 108
Polyisoprene (1, 4 cis), (NR)	– CH2 – C(CH3) = CH – CH2 –	14	- 73
Poly (dimethyl siloxane)	– OSi (CH3)2 –	- 85	- 123
Poly (vinyl acetate)	– CH2 – CH (OCOCH3) –	---	28
Poly (vinyl chloride)	– CH2 – CH Cl –	212	81
Polystyrene	– CH2 – CH (C6H5) –	240	95
Poly (methyl methacrylate)	– CH2 – C(CH3)( COOCH3) –	200	105
Poly tetrafluoroethylene	– CF2 – CF2 –	327	126
Poly caprolactam (Nylon 6)	– (CH2)5 CONH –	215	50
Poly(hexamethylene adipamide) (Nylon 66)	–HN(CH2)6-NHCO–(CH2)4CO –	264	53
Poly (ethylene terephthalate)	– O(CH2)2 – OCO – (C6H4) CO –	254	69
Poly (ethylene adipate)	– O(CH2)2 – OCO – (CH2)4 CO –	50	-70
Cellulose triacetate		306	49-478
Cellulose trinitrate		700	53
Ethyl cellulose			43
Natural rubber		36	-73
Polybutyl acrylate		47	-54
Polyvinyl carbazole		>320	150
Polyvinylidene chloride		190	-18