Presentation on theme: "Woven Fabric Features Dr. Jimmy Lam Institute of Textiles & Clothing."— Presentation transcript:
Woven Fabric Features Dr. Jimmy Lam Institute of Textiles & Clothing
Learning Objectives n What are the fabric characteristics of woven fabric n How to distinguish between warp and weft yarn n The purpose of selvedges n Fabric density (warps per inch and wefts per inch) n Face and back of fabric
Woven Fabric Features n There are several features common to all woven fabrics. n Knowledge of these fabric characteristics are needed to understand fabric structure and suitability in particular end uses. n Can you name some of them?
Fabric Features n The features are: –Warp Yarn and Weft Yarn –Fabric selvedge –Yarns per inch (warp and weft) –Face and back of fabric –Top and bottom of fabric n Last but not the least, the material uses (cotton, wool or polyester) and fabric weight.
Warp and Weft Yarns n Generally, fabrics are cut with the warp yarns running the length of the garment, so designer needs to know the drapability of the fabric in the warp direction. n Fabric technician needs to tell between warp and weft yarn so that he can analysis the information such as fibre content, yarn count and twist.
Warp and Weft Yarns (II) n Warp yarns can be distinguished from weft yarn in the following ways: 1.Selvedge: the yarn parallel to the selvedge are in the warp direction; 2.Yarn count: warp yarns are usually thinner to reduce abrasion when passing through the loom. If the yarn contains both filament yarns and spun yarns, filament yarns will usually be the warp set. 3.Twist: Generally, spun warp yarns have more twist than spun weft yarns because warp yarn is thinner, and needs more twist to have sufficient strength to withstand the tensions during weaving process.
Warp and Weft Yarns (III) 4.Yarns per inch: the number of yarns per inch in warp set is higher than in weft set. This makes the fabric stronger in the lengthwise direction to withstand most of the tensions created in weaving and finishing processes. 5.Ply yarn: plied (two or three yarns) yarn will be stronger than the same single yarn, so that warp yarns are occasionally plied to give added strength while the weft yarns remain single. 6.Stiffness: in all spun yarn fabrics, the warp yarns are generally stiffer than weft yarns because the usually have more twist. In pure filament fabrics, the weft yarns are usually stiffer because they are thicker. A stiffer set of yarns will result in less fabric drapability. 7.Stripes: most woven stripes appear in the lengthwise direction because of cheaper produciton cost.
Selvedges (I) n The selvedge prevents the fabric from ravelling and the edges from tearing when the fabric is under stresses. n Normally, the selvedge area is made stronger than the body by using: Heavier warp yarns; more warp yarns per inch; piled warp yarns; greater twist for spun yarns and different weave
Selvedge (II) n There are three different types of selvedge produced by different sorts of looms: 1. Plain selvedge: created with shuttle loom from the same warp yarns and weave as the fabric body, but with higher number of warps per inch; 2. Fringed selvedge: created from cutting weft yarns on a shuttleless loom. To prevent unravelling, either leno weave is used or the ends are tucked back into fabric (tuck-in selvedge) 3. Fused selvedge: can be used when fabric has higher percent of thermoplastic fibre (polyester or nylon). The edges of the fabric are heated, causing the fibres to melt and fuse together. Fushed selvedge is harsh and stiff.
Selvedge Problem n If the selvedge warp yarns have greater shrinkage during finishing, a tight selvedge occurs, resulting in the puckering of an area near the fabric edge. n This will be a problem when the material is spread on the cutting table where the cloth does not lie flat. n Cutting off the selvedge to eliminate the stress on the fabric can eliminate the tight selvedge problem. n The loose edge can either be fused or glued by adhesive to prevent un ravelling.
Yarns per unit length (I) n This is the number of warp or weft yarns in a specific length. 1. E.g 108 X 58 : It means 108 warps yarn and 58 weft yarn in one inch. 2. E.g 60-square plain cloth : It means 60 ends and picks per inch 3. For a sheeting fabric, a total number of per square inch is given. 4. E.g 140-sheeting fabric: It means 70 ends and 70 picks per inch
Yarns per unit length (II) n Yarns per inch is also a measure of fabric quality. A higher number of yarns per inch gives the fabric following quality: 1. Higher strength: the breaking force for 20 yarns per inch is stronger than 10 yarns per inch 2. More weight: the weight of fabric depends on the weight of yarn 3. Better hand: More yarns grouped together produces an even surface which gives a smooth hand feel. 4. Yarn distortion: the chance for yarn to slide by rubbing action is reduced 5. Better abrasion resistance: more yarn groups together make them more compact, stronger and heavier and durable against abrasion.
Fabric face and back n Fabrics have face and back. The face side has better appearance and usually forms the outside of the garment. n The face and back of some fabrics can be distinguished by their weave and finishes. n For example, the face side of a satin fabric is shinier and smoother than the back side, and the coating finish is usually applied to the face side only
Discussion n What are the functions of fabric selvedges and name THREE different types of selvedges in woven fabric. n What are the difference between the warp yarn and weft yarn used in woven fabric, and why? n Which of the following fabrics is lightest, assuming each fabric is made with size 40/1 yarns? Why? –Fabric A: 100 x 70 Fabric C:110 x 70 –Fabric B: 90 x 90Fabric D:100 x 80