Effect of Annealing on Creep Behavior and Density Fluctuations in Polycarbonate Investigated Using Time-Resolved SAXS/WAXS

This study examines the effect of annealing on the creep behavior and density fluctuations of polycarbonate (PC) using time-resolved small- and wide-angle X-ray scattering (SAXS/WAXS). As-molded PC showed accelerated creep and necking at stresses above 51.7 MPa, while annealed PC exhibited greater structural stability, fracturing without accelerated creep. SAXS revealed anisotropic density fluctuations in as-molded PC during deformation, marked by abnormal butterfly scattering patterns, which intensified upon necking. Fitting analyses identified Debye–Bueche and Ornstein–Zernike–Debye (OZD) components, with annealed PC showing suppressed OZD fluctuations and reduced molecular orientation, indicating that annealing stabilizes molecular chains and delays deformation-induced changes. Furthermore, invariant Q analysis demonstrated that density fluctuations in as-molded PC increased sharply during accelerated creep and then relaxed, whereas in annealed PC, fluctuations rose steadily until fracture.