Industrial fibers can be segmented into two parts: natural fibers (flax, wool, cotton, etc.) and man-made fibers (rayon, acetate, polyester, etc.). Man-made fibers are also classified into cellulose based and synthetic. One of the most common processes for the production of fibers from synthetic polymers is melt spinning. During this process, the filaments produced after spinning will be stretched and thermally stabilized in order to achieve the desired structural properties such as denier, tenacity, elongation and shrinkage (a schematic of the melt spinning process can be seen in Figure 1). The amount of draw applied to the filaments affects the properties of the resulting yarn. Also, the morphology of the fiber produced is related to crystallinity and orientation. POY (partially oriented yarn) refers to multi-filament yarns that are only partially draw during the melt spinning, and the spinning speed is usually 2500-5000 m / min. Less molecular orientation of partially-oriented yarns(POY) than less fully drawn yarns (FDY) results in less strength and uniformity and more elongation of these yarns. Therefore, POY yarns are not directly suitable for weaving purposes due to their lack of dimensional stability and are stretched during the texturing stage to increase the strength of the filaments. Therefore, POY yarns are used as basic yarns in the production of textured yarns (DTY, ATY and ITY) and fully drawn yarns (FDY).
Schematic diagram of melting spun
As mentioned, one of the common methods for produced POY fibers is melt spinning. In melt spinning process, filaments are stretched about five times their normal length to ensure uniformity, strength and increasing length. POY yarn has weaker mechanical properties than FDY yarn. This yarn is used in texturing for the production of textured yarns and is finally used for weaving and warp knitting. POY yarns are produced in two modes, shiny and semi-shiny and they have the ability to be dyed, are multi-filament, and are marketed by packaging on the bobbin. China and India are the largest exporters of POY yarn. In 2018, about 1 million dollars in international exports were recorded for POY yarn, with Iran also importing millions of dollars. POY yarn is used to make a variety of clothing, including shirts, men’s suits and more. Compared to POY, fabrics woven from FDY yarn have higher mechanical properties and FDY yarn can be used directly in knitting. DTY yarn cannot be used directly for knitting and requires final finishing.
POY: partially oriented yarn
DTY: draw textured yarn
FDY: fully drawn yarn
PSF: polyester staple fiber
PSY: polyester staple yarn
ITY: intermingle yarn