Tough and Excellent Heat-Resistant Semiaromatic Polyamide Elastomer Containing Hierarchical Bonds: Synthesis and Synergistic Molecular Design

Thermoplastic polyamide elastomers (TPAEs) presenting outstanding mechanical properties and good heat resistance can serve as superior performers for engineering fields in elevated temperatures. However, there are no suitable polyamide elastomers that can comprehensively meet these requirements. Here, two kinds of isomeric diamines were used to regulate structure and performance for TPAEs, and newly synthesized TPAEs were constructed with hard segments containing strong bonds and weak bonds, which satisfy the demands of application in elevated temperatures. The results show that the melting temperature (Tm) and Vicat softening temperature (VST) of the resultant elastomers increase with the ratio of p-xylylenediamine (PXD) with a polyamide-rich phase increase. Meanwhile, when 60% of PXD was introduced, the TPAE exhibits an excellent tensile strength (34.8 MPa), toughness (157.8 MJ/m3), and Young's modulus (86.1 MPa), which are much superior to the commercial product Pebax@5533 (tensile strength, 25.7 MPa; toughness, 133.3 MJ/m3; Young's modulus, 71.5 MPa). In particular, it is worth mentioning that in contrast with the Pebax@5533 sample the TPAE-60% sample exhibits much better heat resistance and mechanical property stability in elevated temperatures. This work provides a facile method to develop high-performance TPAE materials by a synergistic molecular design in hard segments and paves the way for the development of ultraheat-resistant and tough TPAE elastomers, which can be applied in the sealing field especially for harsh conditions (such as high temperature and high stress).