Blends of poly(trimethylene terephthalate) (PTT) and poly(buthylene terephthalate)
(PBT) in the amorphous state were miscible in all of the blend compositioins studied, as evidenced
by a single, composition-dependent glass-transition temperature observed for each blend
composition. The variation in the glass-transition temperature was well-predicted by the Gordon-
Taylor equation, with the fitting parameter being 1.37. The cold-crystallization (peak) temperature
increased with increasing PBT content in the blends. The subsequent melting endotherms after melt
crystallization exhibited melting point depression behavior in which the observed melting
temperatures decreased with an increasing amount of minor component of the blends. LHW and
NLHW were used to determine the equilibrium melting temperature of the blends. The values of
the overall crystallization rate parameters for these blends were all found to increase with
decreasing crystallization temperature, suggesting that these blends crystallized at low temperatures
faster than that at high temperatures. As the content of PBT was further increased, these values
dramatically decreased. This result is similar to that observed in the growth rate. From LH
secondary nucleation theory, PTT ,PBT and their blends showed the transition temperatures
between regime III and II about 194oC. Banded spherulites were observed for PTT/PBT blends.
The spacing of bands of PTT increases with increasing Tc. The body of spherulite texture is more
open with increasing PBT content. In addition, the boundary of spherulite is also changed with
composition.