Abstract: PGA fiber samples were prepared by different processes, and the samples were placed in a thermostatic chamber for two weeks. The PGA fiber samples with different strength retention rates were selected, and the aggregation structure of PGA fibers was studied by means of sound velocity method, DSC and XRD. The results show that under the experimental conditions, the preparation process and heat treatment of PGA fiber have certain effect on the strength retention of the fiber, in which, the relaxation heat treatment can improve the strength retention of the fiber; the crystallinity, crystal orientation and grain size have no obvious regular relation with strength retention rate; the sound velocity orientation factor of fiber samples was significantly correlated with strength retention rate, i.e. the lower the sound velocity orientation, and the higher the strength retention rate.

Key words: PGA; degradation property; structure; orientation; crystallinity