Chapter Eight Pile Fabrics Introduction: Pile fabrics are characterized by the brush-like surface formed by tufts of warp or weft cut threads. Cutting the threads can be done either on the loom or on the machines of the fabric finishing department.

Pile fabrics can be divided into the following two groups: 1. Weft pile fabrics, which contains a weft cut pile produced by cutting the weft threads at the fabric finishing process by specially constructed knives. 2. Warp pile fabrics, having a pile produced on the loom from the threads of an extra warp called a pile warp.

8.1 Weft Pile Concept: 1) The piles are formed by weft threads 2) There are two systems of weft threads and one system of warp threads 3) The main representative products are corduroy and velveteen Sample of corduroy fabric:

8.1.1 Corduroy Introduction: Corduroy is a fantastic fabric which possess soft handle, clear stripes, lofty and full piles, good strength, and aesthetic properties, so they are widely used as apparel fabrics appealing to men and women, young and old.

1. The principles of constructing corduroy fabric.  The weave contains two pile picks a, b and two ground picks 1, 2. The ground picks 1, 2 interlace with warp forming the ground weave. Arrangement of ground pick and pile pick is 1:2. The pile pick floats over five warp threads which are convenient for cutting process. Pile root

The pile picks interlace with the warp threads 5, 6 for binding the piles where the intersections are called pile roots.  After weaving, the pile weft was cut by specially constructed knives between the warp threads 2 and 3 (where the arrow points in Fig. 8.1). Then, brushing it, the piles will be upright, forming a full bulky band corduroy.

The principles of the cutting are described in the Fig. 8.2:

The circular knife is placed on a mandril A indicated by the arrow. As the knives revolve, fabric advances towards in the direction indicated by an arrow F. A guide wire E is inserted in the fabric under the long weft floats. The guide wires have these functions: ① guiding the weft floats forming a loop-like: “race” to the knives, and tautening them when they are cut, and ② keeping the knives in the centre of each “race”. As the uncut fabric approaches, the knives guide wires are conveyed along by it, and consequently require to be pushed forward again intermittently. This is accomplished by a series of spirally arranged rotary cams. Show flash

2. The classification of corduroys According to the width of cord, the corduroys are classified as following: 1)Fine (needle) corduroy, more than 11 cords/25mm. 2)Mid-wale corduroy, 9-11 cords/25mm. 3)Wide-wale corduroy, 6-8 cords /25mm. 4)Spacious-wale cording, less than 6 cords/25mm.

According to the ways of finishing process, the corduroys are classified into : 1)Printed corduroy 2)Dyed corduroy According to the materials used, the corduroys are classified into : 1)Cotton corduroy 2)Blended corduroy

3. The weaves and setts ① Density : Suitable warp cover factor is 50-60%; a suitable weft cover factor is %; and the suitable ratio between warp cover factor and weft cover factor is 1/3. Notes: warp cover is defined as the fraction of the fabric covered by threads. It is common to mention warp cover and weft cover separately Say: e --- fabric cover; d --- diameter of thread; S --- space in warp/weft direction So: e o = d o /S o e y = d y /S y More details is coming up in chapter 11

② Ground weave The ground weave’s function is to hold the piles, the widely used weaves are as following: plain, 2/1 twill, 2/2 twill, 2/2 weft rib, 2/2 warp rib. Different ground weaves used can achieve different handle, fastness of the piles. ③ Selection of pile weaves Three aspects should be considered for selecting pile weave as the following a, b and c

a) The binding types See Fig. 8.3 (A) and (B). There are two types of binding, V- type and W-type. The advantage of V-type is easy to tighten, and the short-coming is that the piles are easily taken out. That of the W-type just reverse themselves.

b) The height of the piles The height of the piles is decided by the length of the pile floats. h (mm)= Where: C —the number of the pile floats Po —the warp density c) Distribution of pile roots The distributions of the pile roots decide the appearance of the fabric. Some examples are shown on the next page. Some of the roots disperse, and others are concentrated.

Various corduroy pile roots:

8.1.2 Velveteen  If the pile roots are dispersed, the fabric would be covered by even piles. Those fabrics are called velveteen. Velveteen is always raised during finishing instead of cutting.

Home works: 1. List the binding types of corduroy, and compare the difference of each type. 2. Construct the following corduroy weaves 1) base weave 2/1 ↗, ground pick : Pile pick =1:2, Ro=6, V-type binding. 2) Base weave 1/1 plain, ground pick : Pile pick = 1 : 2 ; Ro=8, W-type binding.