Effect of surface treatment on pet spinning and the yarn property

To evaluate the effect of spin finishes on spun poly(ethylene terephthalate) (PET) yarn, a series of spin finish oils with different wetting properties were prepared by adding various wetting agents to three basic spin finish recipes and then applied onto the PET yarns. Variations of the tensile strength at 60% elongation (BE60) of the yarns were evaluated together with the corresponding dynamic contact angles of the PET film and on-line spin finish distribution (Rossa SD) on the PET yarn. A decreased BE60 was found when the wetting power increased. This indicates that spin finishes have diffused into the fiber core and, therefore, reduced the fiber strength. In addition, an inverse relationship between Rossa SD and BE60 is established for each spin finish with different wetting power. Comparing with the spin finish distribution, we conclude that wetting power of the wetting agent in the spin finish is the dominate factor for the plasticization of the PET yarn and, therefore, for the reduction of the yarn strength.