Presentation on theme: "Introduction to Textile Fabric Basic Knitted Fabrics Dr. Abu Yousuf Department of Chemical Engineering & Polymer Science Shahjalal University of Science."— Presentation transcript:
Introduction to Textile Fabric Basic Knitted Fabrics Dr. Abu Yousuf Department of Chemical Engineering & Polymer Science Shahjalal University of Science & Technology Sylhet-3114, Bangladesh
Knitting is a method by which thread or yarn may be turned into cloth or other fine crafts. Knitting consists of consecutive loops, called stitches. As each row progresses, a new loop is pulled through an existing loop. The active stitches are held on a needle until another loop can be passed through them. This process eventually results in a final product, often a garment.thread or yarncloth Knitting may be done by hand or by machine. There exist numerous styles and methods of hand knitting.machine Knitting
How to cast on Casting on is simply the way that you get stitches onto the needle so that you can start knitting. Stitch: A single loop of yarn around an implement such as a knitting needle
Difference between woven and knitted fabrics 1) Fabric Construction –Woven fabric is at least made up of two separate groups of yarns (warp and weft) and knitted fabric can be made up of one yarn only. –Weaving is interlacing of 2 set of yarn to form a fabric. –Knitting is a process of converting yarn to fabric by forming a series of loops dependent on each other.
Difference between woven and knitted fabrics 2) Elasticity –Elasticity is the ability of the fabric to extend and recover to its original shape and length. –Knitted fabric has higher extensibility and instant recovery ability than woven fabric. up of one yarn only.
Difference between woven and knitted fabrics 3) Fabric Density and Cover –In general, woven fabric can be produced in extremely tight and higher coverage when compared with knitted fabric. –Range of density variation is much higher than knitted fabric. –Knitted fabric in general, is looser in structure.
Difference between woven and knitted fabrics 4) Thickness and Handle –Knitted fabric is much thicker and softer than woven fabric as it has a complicated 3-dimensional structure. –Knitted fabric seems to be softer because the knitted loops are more easily compress and extensible than straight yarn (warp and weft in woven fabric)
Difference between woven and knitted fabrics 5) Production Cost –Weaving requires expensive preparation processes like warping, sizing, draw-in; while knitting only requires yarn waxing. –The production rate of circular knitting is roughly FIVE times faster than modern weaving loom. and weft in woven fabric)
Difference between woven and knitted fabrics 6) Fabric Application –The popularity of sportswear, hosiery, underwear and high fashion knitwear make a strong demand on knitted fabric every year which cannot be replaced by woven fabric. –However, if fabric requires good dimensional stability, high tenacity like trousers, jackets, canvas, woven fabric is the right choice Tenacious: Holding together firmly
Single Knit Fabric
What is single knit fabric Single knit fabric or single jersey is a general term for knitted fabrics produced by the knitting machines using one set of needles only. The fabrics could be composed of different patterns, stitches, materials and different weight and thickness. Stitch:A mode of arranging the threads in sewing, knitting, or crocheting
General Characteristics of Single Knit Fabric 1)Fabric Elasticity The single knit fabrics are composed of loops linking with each other on the two sides as well as on the two ends. The shape of a loop can easily be changed by stretching the fabric in all directions. The elasticity of knitted fabrics makes them favorable for sports’ wear, casual wear and hosiery. This elasticity, however, will be deteriorate due to over stretching, washing or ageing and eventually, the loops cannot recover to its original shape. This change of shape is called distortion or poor dimensional stability hosiery
General Characteristics of Single Knit Fabric 1)Fabric ElasticityA loop is a very short length of yarn bent into a OMEGA shape as shown on the black area
General Characteristics of Single Knit Fabric 1)Fabric Elasticity The dimensional stability of single knitted fabrics can be improved by: Increase the fabric density, by using smaller loop length to give the fabric higher cover factor. Warp and weft insertion, by inserting straight yarns to the fabric and bind the loops together to reduce their freedom of movement Apply resin finishing, a resin chemical can set the fibres and loops on fabric. Use the thermal plastic yarns, man-made fiber like polyester or nylon can be set at high temperature and maintain the loop shape on knitted fabrics.
General Characteristics of Single Knit Fabric 2) Edge Curling –Almost all single knit fabrics will curl on the edges when cut. –It is the unbalanced loop structure and the yarn torque inside the fabric which tends to recover the original shape of the yarn. –It is the edges of a piece of fabric that is free for movement, therefore, the edges curl..
General Characteristics of Single Knit Fabric 2) Edge Curling The curling on the fabrics edges is one of the disadvantages of single knit fabircs. –It gives problems to the cutting, sewing and linking processes. –Edge curling can be reduced by the following : Wet finishing, high temperature treatment like sourcing, bleaching and dyeing can remove the torque in the yarn and fabric. Stentering or steam pressing, stentering is used on open width piece goods, and steam pressing for knitwear panel and garment..
General Characteristics of Single Knit Fabric 3) Laddering When a loop in the fabric is broken, the loop directly underneath it will slip off and become a short length of horizontal line instead of maintaining the OMEGA shape. If a vertical row of loops slip off from the fabric, it looks like ladder.
General Characteristics of Single Knit Fabric 3) Laddering Laddering is a fabric fault which affects the fabric appearance. Laddering will easily occur when: The fabric is loosely knitted; The yarn frictional index is low; The fabric is plain knit; There is a big knot in yarn during knitting; The needle head is broken.
General Characteristics of Single Knit Fabric 4) Fabric Appearance All single jersey fabrics have different appearance on two sides Looking on the face side, the fabric seems to be composed by thousands of “V” loops; while on the back side, the loops appear to be semi-circles.