Structure and Properties of Poly(butylene terephthalate)/Thermoplastic Polyester-Based Elastomer Blends

Studies on structure and properties of blend films composed of Poly(butylene terephthalate) (PBT) and thermoplastic polyester-based elastomers (TPC) were done. Tensile tests and structural measurements were carried out using dumbbell specimens processed from melt-pressed films. Three kinds of TPC having different composition ratios of hard and soft segments were used, and the blend ratios were changed systematically. Tensile modulus was found to be expressed using the ratio of Poly(tetramethylene glycol) (PTMG) of soft segment and PBT by weight%. Effect of composition ratio of TPC on tensile modulus, however, could not be distinguished by weight% evaluation. Infrared spectroscopic analysis gave three linear relations between tensile modulus and TPC composition ratio. Thermal and viscoelastic analysis revealed that TPC with large average number of molecular chain of hard segment showed good compatibility with PBT homo polymer. In this case, melting point of PBT crystal moved to the lower temperature side with increase of TPC content, while melting point attributed to hard segment crystal slightly increased. Lamella structure in spherulitic crystals composed of PBT homo polymer and hard segment PBT crystal of TPC was thought to be influenced by compatibility characteristics due to blending.Basic behaviors of structure and properties for blend polymers composed of PBT and TPC having same composition of PBT as hard segment were clarified.