Research subject: In recent years, various filament cross-sectional shapes have been employed in the production of synthetic multifilament yarns to achieve diverse applications and properties. In this study, the effect of round and rectangular cross-sectional shapes of polyethylene terephthalate (PET) multifilament yarns on the physical and crimp properties of melt-spun and draw-textured yarns was investigated.
Research approach: Partially oriented yarns (POY) were produced using an industrial melt-spinning machine, and draw-textured yarns (DTY) were prepared with an industrial frictional false-twist texturizing machine under identical conditions. All yarn samples with round and rectangular cross-sectional shapes were analyzed in terms of linear density, thermal shrinkage, degree of crystallinity, and tensile properties (strength, elongation at break, and initial modulus). For DTY yarns, additional tests were conducted to evaluate crimp properties (crimp shrinkage, crimp modulus, and crimp stability), resiliency, and the ratio of tension after the twisting zone to tension before the twisting zone (T2/T1). Furthermore, X-ray diffraction was performed on textured yarn samples to examine the fiber microstructure.
Main results: The results revealed that differences in the tensile properties and thermal shrinkage of POY yarns with both cross-sectional shapes were small, despite being statistically significant. However, greater variations were observed in DTY yarns. The DTY yarn with a rectangular cross-sectional shape exhibited higher resiliency than that with a round cross-section. Conversely, the DTY yarn with a round cross-sectional shape demonstrated superior crimp properties, which can be attributed to its higher crystallinity and, consequently, greater softness and texturability compared to the rectangular cross-sectional shape.