Semiaromatic Polyamides Containing Carboxyl Unit: Synthesis and Properties

In this work, 2-(bis­(4-hydroxyphenyl)­methyl)­benzoic acid (BHPBA) was prepared by hydrolysis of phenolphthalein with addition of ferrous powder. Afterward, semiaromatic polyamides (SAPs) with varied carboxyl group content were prepared from BHPBA and the bisphenol 1,1-bis­(4-hydroxyphenyl)-1-phenylethane (BHPPE) as well as 1,6-N,N′-bis­(4-fluorobenzamide)­hexane (BFBH). It was found that they all exhibited glass transition temperatures (T g’s) of 159.6–180.7 °C. The resultant copolymers could be hot compressed into films, which showed a failure strength of 60–70 MPa. Additionally, high storage moduli (1.0–1.6 GPa) were observed at 150 °C, indicating the good thermal mechanical performance for these resultant semiaromatic polyamides (SAPs). Interestingly, such copolymers can be used as the compatibilizer of composites of PA6T/carbon fiber (CF) in the case of the carboxyl group in the main chain, which was beneficial for the improvement of their interfacial adhesion force.