Structures and properties of newly synthesized semi-aromatic polyamide thermoplastic elastomers

Abstract

Novel semi-aromatic polyamide thermoplastic elastomers (TPAEs) were synthesized with a hard-segment poly(dodecamethylene terephthalate/dodecamethylene isophthalamide (PA12T/12I) oligomer and soft segment poly(tetramethylene glycol) (PTMG) via a facile “two-step” melt polycondensation method. The effects of the proportion of 12T to 12I in the hard segments on the crystallization behavior and mechanical properties of the TPAEs were investigated systematically. The results show that the glass transition temperature (T_g) of the polyamide-rich phase increases with an increase in terephthalic acid (TPA). Meanwhile, two isomeric acids (TPA and IPA) are regulated in the hard segments to elevate the Young's modulus, tensile strength, and toughness of the TPAEs to 145.9 MPa, 40.8 MPa, and 136.5 kJ m⁻³, respectively. Furthermore, TPAE-6 (60%TPA) exhibits outstanding high-temperature mechanical properties: the Young's moduli went up to 90.2, 58.4, 40.1, and 24.5 MPa at 40, 60, 80, and 100 °C, respectively, and the tensile stress (strain = 500%) went up to 33.8, 23.9, 18.6, and 11.1 MPa at 40, 60, 80, and 100 °C, respectively. Importantly, such outstanding high-temperature mechanical properties have not been reported previously. Hence, we propose the introduction of aromatic structures as an accessible method to improve the heat resistance of thermoplastic elastomers which are expected to provide reliability and long service life for elevated temperature applications.