This is a guest post by Harry Mercer where he shares some ideas on denim product developments.
1) More Softness In Fabrics Made With Open-End Yarn: Ring spun yarns are preferred in denim because of a feel that is more soft than open-end. The softness of open-end denim can be raised to the level of ring yarns in the warp by reducing the twist. For example, in a 14 ounce denim, the warp yarns are often a 7 Ne with about 470 turns per meter in the open end yarn. This can be reduced to about 415 to 420, with almost no loss of weaving efficiency and little decrease in fabric strength. The face of the fabric with the warp yarns is the important side for an appealing touch. However, if the weft yarns are made with a similar low twist, the fabric strength will suffer. This method has been used in 3 denim operations that I have advised with excellent market acceptance. In one company it was found that after mercerizing, the washed garments were softer than ring spun. Also, by reducing the twist in the warp, yarn production is faster and less expensive.
2) Making Denim With A Flatter Appearance: Almost all denim operations have tried flat finishing which is usually a form of wet-treatment with sodium hydroxide on the fabric. The results are variable messy with a great deal of water and energy consumption for the flat finishing. A super flat denim can be produced only with fabric construction, avoiding the additional processing steps which in some companies includes a de-sizing process as well as the sodium hydroxide application, both requiring heavy consumption of water and steam energy in drying. This can be avoided by constructing the fabric with yarns having opposite twist directions Yarn can have either a Z-twist (to the right) or an S-twist. For example, by using the standard Z-twist yarn in the warp and S-twist in the weft, the twill will be diminished, producing a fabric with a flatter appearance than any type of flat finish. S-twist yarns are not often available, but are easy to produce on ring spinning equipment by a simple change of gear direction. The problem in producing them is that when the ring bobbins are wound onto yarn packages for use in warping and weaving, a special attachment in winding is needed for the different twist direction.
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