Modification of melt memory effect by addition of poly(butylene terephthalate) to thermoplastic polyester elastomer

The structure and properties of a thermoplastic polyester elastomer (TPEE) containing a small amount of poly (butylene terephthalate) (PBT) were investigated by focusing on the residual crystals in the molten state. When the pure TPEE was extruded at a slightly higher temperature than its melting point, the crystallization rate increased. This phenomenon has been called the melt memory effect and has been attributed to unmolten crystals that act as nuclei. The addition of PBT widened the temperature range of the melt memory effect, because PBT crystals were present at the higher temperatures. Moreover, the addition of PBT induced phase separation, leading to a decrease in the dissolution of hard segments in the soft matrix. As a result, the glass transition temperature of the soft matrix decreased. Furthermore, the modulus at room temperature increased with good rubber elasticity.