posted on 2024-02-12, 13:03authored byHan Dong, Jie Dong, Xiuting Li, Xin Zhao, Qingsong Xu, Jialin Zhang, Qinghua Zhang
To improve the heat resistance of
polyimide (PI) fibers
for application
in harsh environments and establish a correlation among the chemical
structure, fabrication performance, and material properties, a simple
and rigid diamine, p-phenylenediamine (p-PDA) was incorporated into the Kapton-type PI synthesized from pyromellitic
dianhydride and 4,4-diaminodiphenylmethane (ODA). The comprehensive
properties of these co-PI fibers were systematically investigated
to assess the impact of p-PDA addition. Two-dimensional
wide-angle X-ray diffraction (WAXD) was used to investigate the evolution
of the aggregation structure of the co-PI fibers during the processing.
The thermogravimetric analyzer (TGA) test shows that the incorporation
of p-PDA improves the heat resistance of polyimide
fibers, with the 10 wt % weight loss temperature (T10%) ranging from 582 to 605 °C and the maximum decomposition
temperature (Tmax) of 611–635 °C
for the co-PI fibers with different p-PDA contents.
Additionally, the potential degradation mechanism of the PI fibers
was examined by utilizing pyrolysis-gas chromatography/mass spectrometry
(Py-GC/MS) and other thermal analyses. By introducing p-PDA, the content of O element (ether bond in ODA) in the system
decreases, leading to a reduction in oxygen free radicals from ODA
during the decomposition process of polyimides. The decrease in active
species can cause a decrease in the decomposition rate and improve
the heat resistance of the polyimide fibers. The study of the thermal
decomposition mechanism of polyimides provides a valuable foundation
for the preparation of high-performance polymer fibers with enhanced
thermal resistance and excellent overall performance.