Abstract: SEM, X-ray powder diffraction, Fourier transform infrared spectroscopy and differential thermal analysis were used to study the surface morphology, aggregation structure, chemical structure and heat resistance of PBT fibers in supercritical CO₂ fluid at different temperatures. The SEM investigation showed that due to plasticization and swelling actions, the oligomers remained in the inner phase of PBT fiber migrated to the surfaces of the fiber during the fluid treatment from supercritical CO₂ fluid; the higher fluid temperature is, the more obvious the phenomenon is. However, when the fluid temperature is higher than 100 ℃, oligomers reduced under enhanced dissolution in the supercritical fluid medium.

XRD analysis revealed that with the increased fluid temperature, the crystallinity of PBT fiber was decreased in a general tendency. FTIR investigation indicated that the treatment of supercritical CO₂ fluid under different temperature didn’t affect the chemical structure of the fiber evidently, but could bring some effects on the chemical environments of chain segment and functional groups, as well as their arrangements and the supramolecular structure. Fluid media with different temperatures can affect the macroscopic thermal stability of PBT fibers, and the effect is obvious when the fluid temperature is 8 0 ℃.

Key words: PBT fiber; supercritical CO₂ fluid; structure; crystallinity; property