Woven-pile fabrics are material with a raised hairlike or furlike surface. Two well-known fabrics with such a sur-face are velvet and terry cloth. The surface is produced with an extra set of yarns (warp or filling) known as pile yarns. Thus, pile fabrics have the regular warp yarns and filling yarns (called ground yarns) that are common to
Figure 5.17
Leno weave. Notice how each pair of warp yarns twists to hold the filling yarns.
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a uniform effect. Velvet, a cut-pile warp fabric is espe-cially sensitive to crushing and must be stored so that the pile is not flattened.1 Also, special care must be exer-cised in cleaning and refinishing velvet apparel.
Pile construction affects the fabric wearability. The short lengths of cut-pile yarn may have a V shape or a W shape. The W-shape pile is more firmly held in place because it interlaces with three yarns, and the V-shape interlaces with only one yarn. Thus, the W-shape pile yarn is held more securely, preventing a bald spot from developing.
The W-shape pile, however, is not as dense as the V-shape pile because the latter has two pile ends for each interlacing, and the W-shape pile has two pile ends for every three interlacings. (See Figure 5.20.) To obtain the same pile density for a W-shape pile as for a V-shape pile, woven beyond the rod, the rod is removed and the knife
at the end of the rod cuts all warp yarns that pass over the rod. The cut yarns stand up to form the pile. The weaving continues with the insertion of the rod after weaving a few additional filling yarns and the removal of the rod after weaving a few more filling yarns.
With filling cut-pile fabrics, there is no raising of yarns by wires. The pile-filling yarns are woven to float over a group of warp yarns. The pile yarns are then cut at the center of the float. The ends of the cut yarns pro-duce the cut-pile effect. The floats in corduroy fabric are placed in lengthwise rows, and the floats in velveteen are randomly spaced. Thus, when corduroy fabric is cut, the characteristic wale or hill-and-valley effect is pro-duced. The thickness of the wales can be varied, from narrow (used for apparel) to very wide (used for furni- ture fabric). When velveteen fabric is cut, an overall cut-pile surface is produced. Decorative patterns and effects can be created by cutting floats selectively.
Cut-pile weave fabrics are made with different heights of pile. For example, velvet has a low pile height, velour has a higher pile, and plush has still higher pile.
The face of cut-pile fabrics has an up-and-down direction (top and bottom) because of the position of the pile. A garment made with the pile fabric facing downward offers a smoother surface for light and so appears more lustrous. If the pile is up, the color is richer because more of the interior of the fabric (and color) is visible. However, the fabric is less durable because the pile fibers are more exposed to rubbing forces.
In cutting fabric for a garment, the pile of all pieces in the garment must lie in the same direction to produce
Figure 5.19
These velvet jackets are of a warp-pile weave fabric.
1. Yard goods of velvet are shipped and stored on special bolts that keep the layers separate to avoid crushing.
Figure 5.18
Filling-pile weave fabric: ground filling (purple and dark blue), ground warp (brown), and pile filling (light blue).
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end for one ground end, two pile ends for two ground ends, or some other simple arrangement.
Two warp beams are used for weaving terry. On one beam, the warp yarn is tight, and on the other, the yarn is quite loose. The extra length in the loose warp yarn forms the loops in the fabric. A pile warp yarn may be almost four times longer than a ground warp yarn from the same cloth.
Frieze fabric, a thick pile fabric with patterns made from its loop surface, used for upholstery, is an example of an uncut-pile weave fabric.
As in cut-pile weave fabrics, a strong ground fab-ric with a large number of yarns per inch and a dense pile makes a durable uncut-pile material. High loops and thick, low-twist pile yarns make a more absorbent, but less durable, fabric. Towels rented at the beach frequently are scratchy and have poor absorption, but are usually very durable because of the high-twist pile yarns.
more yarns per inch would have to be used. A denser pile can better resist crushing, gives better cover, and stands more erect, but also is more costly.
At times combinations of V-shape and W-shape pile are used in the same fabric. The V-shape adds depth to the pile and the W-shape adds stability. This alterna-tive is often utilized in the construction of wide wale corduroy.
Different ground weaves are used for cut-pile fab-rics. Usually the body of corduroy and velveteen fabrics are made with either a plain, rib, or twill weave. The base construction will add to the durability of the fabric.
A rib or twill weave will lock in the pile more securely.
A twill weave can result in a stronger fabric (more yarns per inch are possible; see p. 100), thus the twill-back pile fabrics are usually more durable than those with a plain weave ground.
Uncut-Pile Fabrics
Terry cloth is an example of a fabric with an uncut-pile weave (Figure 5.21). The fabric consists of ground warp and filling yarns plus an extra set of warp yarns for the pile, in the form of loops on the surface of the cloth.
The loops are formed by having the extra warp yarns (pile yarns) raised by a wire inserted across the loom.
The wire is then removed until the next set of loops is to be formed.
The warp direction of terry is readily determined because the extra yarn that forms the pile is length-wise. The weave varies so that there may be one pile knife
a b c d e Figure 5.20
Double cloth pile weaving. Knife cuts pile warp yarns to make two velvet fabrics: V pile formation (top) and W pile formation (bottom) with (a) ground warp (top); (b) ground filling (top); (c) pile warp; (d) ground warp (light blue) (bottom); and (e) ground filling (bottom).
Figure 5.21
Terry cloth is an example of a pile fabric, often used for towels.
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designs exceed the capacity of harness looms, a special loom must be used. This loom usually has no harnesses, and the ends are controlled by a jacquard head located at the top of the loom. The loom is referred to as a jac-quard loom because the control device was perfected in 1805 by Joseph-Marie Charles Jacquard.
The jacquard head uses a computer tape to control the warp yarns, in the same way that a punched paper roller controls the keys in a player piano. The position of the holes in the tape determines the sequence in which the warp yarns are moved. Hooks and needles are used to raise and lower the warp yarns by control-ling a cord attached to each heddle. Because there are no harnesses, any combination of yarns can be raised or lowered to produce the design.
The jacquard loom operates more slowly than do the other, simpler looms, so the fabrics produced on this loom are more expensive. Damask, tapestry, and bro-cade are several fabrics commonly made with jacquard designs.
Sometimes the pile loops are cut in a terry cloth for decorative effect. This is then considered a cut-pile fabric.