Glass Transition Temperature Of PET Research Articles

EFFECT OF STRETCHING ON DICHROISM OF POLY (ETHYLENE TEREPHTHALATE) AND POLYPROPYLENE AT HIGH TEMPERATURES

Dichroic value of poly (ethylene terephthalate) (PET) and polypropylene (PP) films dyed with C. I. Disperse Yellow 7 was measured at high temperatures in order to investigate the influences of draw ratio and temperature of stretching on the thermal change of the dichroism.When the break appearing in the plot of D versus temperature was plotted against the D measured at room temperature, a linear relation was observed. This leads us to conclude that the glass transition temperature of PET rises linearly with increase in the degree of amorphous orientation.As for the PP film the following results were obtained:(1) Three transition points were observed above Tg at T0 (38_??_50°C), T1 (74_??_85°C) and T3 (108_??_120°C).(2) T1 and T3 are nearly constant independently of the value of D, while T0 drops at first and then rises with increase in D through a minimum value at D=0.7_??_0.8.(3) T1 and T3 decrease systematically with increase in the content of atactic fraction, hence, tacticity has a great influence on the mobility of PP segment.