Drawing-Induced Crimp Formation and Wettability of Four-Lobed Side-by-Side PBT/PET Bicomponent Fibers

PBT/PET side-by-side bicomponent fibers form helical crimp structures under thermal or mechanical stress, though the mechanism behind mechanically induced crimping remains unclear. In this study, four-lobed cross-sectional PBT/PET side-by-side bicomponent fibers were produced and subjected to drawing from 1.6 to 4.0 times at 80 °C to induce crimping. Increasing draw ratios significantly enhanced fiber tenacity (from 0.64 to 3.91 cN/dtex) and reduced crimp radius (from 2.05 mm to 0.64 mm). A predictive crimp curvature model integrating Denton's crimp theory and a four-element viscoelastic model was established, with corrected results achieving an R² of 0.9951. Additionally, four-lobed fibers showed better wettability, with a static contact angle 3.56° lower than that of circular fibers. This work provides theoretical guidance for high-performance self-crimping fiber design.