Yarns Now that you have the fibers what do you do next?

Spinning

Different connotation for natural & manufactured fibers –Natural: making long yarn from short fibers –Manufactured: making fibers and yarn simultaneously Sometimes manufactured fibers are “chopped” up into short fibers and then treated as if they were natural fibers

Manufactured Fibers - Spinning

Summary of Major Fiber Spinning Methods WET DRYMELT Polymer before spinningsolution molten Spinning Environmentsolutionwarm aircool air Examplerayonacetate, acrylicpolyester, nylon Manufactured Fibers - Summary

Natural Fibers - Twisting Fibers are put in a parallel bundle and the bundle is drawn down and twisted to form a yarn 2 competing effects –Cohesion: friction as fibers are pressed into one another produces strength –Obliquity: fibers can carry the most load along their axis; twisting causes the fiber axis and yarn axis to be different

Twist Direction No effect on yarn strength Can affect other properties –Untwisting in larger structures –Fabric thickness

Complex Yarn Structures Very large textile structures can be built up by twisting together other structures. For example, two or more single yarns can be twisted together to form a plied yarn; two or more plied yarns twisted together form a cord; two or more cords form a cable ad infinitum. The twist in each of the parts is alternated so, for example, if the twist in the single yarn is 'Z', the plied yarn will have 'S', the cord 'Z'; the cable 'S' … The twist is alternated to help prevent the larger structure from untwisting.

Yarn Numbering Systems Direct (N D ) –Our “old friends” from linear density –As yarn gets larger its yarn number increases –Usually used with manufactured yarns N D = NDND S denier (N d )9000 m/g tex (N t )1000 m/g decitex/dtex (N dt )10000 m/g

Yarn Numbering Systems Indirect (N I ) –As yarn gets larger its yarn number decreases –Usually used with twisted yarns NINI S English cotton (N e ) 840 yd/lb worsted (N w )560 yd/lb woolen run (N wr )1600 yd/lb N I =