Structure-property relationship of blended cotton yarns made from low and high tenacity fibers

The tensile response of staple yarns is usually determined by their structu re and the mechanical properties of their constituent fibers. Yam structure is influenced by the radial disposition of fibers along the yam length, co mmonly known as migration, and the packing density of the fibers in the yam cross section. These, in turn, are affected by fiber properties, yam facto rs, and the dynamics of preparatory and spinning processes. Yam structure d evelopment is further complicated when the yam is spun from blends of diffe rent fiber types because the blending method usually profoundly influences the position and orientation of the fibers in the yam matrix. This investig ation is concerned with the effect of fiber properties and yam structure on the tensile properties of ring spun yarns made from a 50:50 blend of high (Pima) and low (Upland) tenacity cotton fibers spun using intimate and draw frame blending techniques. The drawframe blended yam in this work is produc ed by arranging all high tenacity fiber slivers in the center of the drawfr ame creel to determine if preferential positioning in the core of the yam h elps to improve the strength of drawframe blended yam compared with intimat e blended yarns. The findings reveal that intimate blended yam has better t ensile strength than drawframe blended yam, even though more high strength Pima cotton fibers are positioned in the core of the yam. This is because n on-uniform fiber distribution resulting from blending of different fibers a ffects the migratory behavior of fibers. The tensile failure of such yarns is governed by the mode of fiber breakage and fiber slippage as determined by the yam structure-fiber distribution and migration-rather than predomina ntly by fiber breakage compared with strength.