Influence of temperature and imidization method on the structure and properties of polyimide fibers prepared by wet spinning

A polyamic acid (PAA) based on 4,4′-bis(4-aminophenoxy)diphenyldiamine and 1,3-bis-(3′,4-dicarboxyphenoxy)benzene dianhydride was synthesized. PAA fibers were prepared by wet spinning. Subsequent cyclization of PAA units was achieved using chemical or thermal imidization. The influence of the imidization method and process conditions on the chemical structure, porosity, morphology, thermal and mechanical properties of polyimide (PI) fibers was studied. Thermal imidization was carried out in the temperature range from 60 to 300 °C at different process durations. The degree of imidization of PI fibers was studied by IR spectroscopy. The structure and properties of PI fibers were studied by scanning electron microscopy, thermal analysis, and by measuring the stress-strain properties.