Glass transition temperature transformation range

The lower limit of the elastic range, the glass transition temperature, can be easily determined by refractometric, volumetric, or other well known methods. The upper limit suffers from an exact definition the transition from the fixed liquid to the liquid state occurs without transformation. But as the viscosity decreases exponentially with the temperature it is very convenient to define a 1 flow-temperature by penetrometer measurements. If the rate of temperature rise is kept constant, this temperature is reproducible within 1° or 2°C. The penetrometer indicates a temperature where macroscopically one would call the substance liquid. ... 

From the curve presented in Fig. 2.25 we can deduce that the glass transition temperature is around 72°C, the crystallization temperature at 125°C and the melting temperature at 250°C. Note that in all three cases there is a range of temperatures at which the transition occurs. To compute the heat of fusion during the ramp-up, we need to find the area between Q and the base-line for the endothermic deviation around the melting point, between 210 and 260°C. To do this we, must first transform the temperature scale to time by dividing it by the heating rate as... 

IL are generally glass-transforming materials whose useful liquid ranges are boxmded by their glass transition temperatures at the lower end and their decomposition temperatures at the higher end. 

Goyal and co-workers [10] in their Fourier-transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) investigation of the thermal stability of N-phenyl substituted aromatic-aliphatic and of aromatic amides derived from 4,4-dianilodiphenyl showed that the aromatic-aliphatic polyamides had glass transition temperatures in the range 76-116 °C, whilst the aromatic polyamides had transition temperatures of 207-255 °C. The polymers were thermally stable, and had decomposition temperatures in excess of 400 °C in air. 

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