Shrinkage characteristics of poly( ethylene terephthalate), nylon-6 and polypropylene yarns

Abstract

<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:minor-latin;="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">The thermal shrinkage characteristics of well-oriented multifilament yarns prepared by drawing low-oriented yarn (LOY) and partially-oriented yarn (POY) of each of the three polymers, viz. poly(ethylene terephthalate) (PET), nylon-6 and polypropylene (PP) have been found to differ in three respects. First, the shrinkage of POY-based yarns is higher than that of LOY-based yarns in PET and PP multifilament yarns while the reverse is the case with nylon-6 yarns. This behaviour is predominantly because the drawing stresses for LOY and POY samples are significantly different. Second, the shrinkage of undrawn nylon-6 and PP yarns is lower than the shrinkage of their drawn counterparts, but the shrinkage of undrawn PET yarns is higher, apparently because in the case of PET considerable crystallization occurs on drawing. Third, the shrinkage of nylon-6 yarns in boiling water is more than that in silicone oil. This is apparently due to the fact that nylon-6 absorbs considerable amount of water. The studies also establish the importance of drawing rate as a source of residual stress and thermal shrinkage.</span>