FIBER PRODUCTION & BLENDING

Most of you are at least generally familiar with the source and production of natural fibers. Therefore, the primary focus of this section is on the production of manufactured fibers. A discussion is also presented concerning the blending of both manufactured and natural fibers. It should be kept in mind that the process for developing each manufactured fiber has been carefully selected to produce a fiber with specific characteristics important to its use in fabrications for apparel, home fashion and other textile products.

Distinction Between Cellulosic andNon-Cellulosic Fibers
Regarding the production of manufactured fibers, a distinction should be made between cellulosic and non-cellulosic fibers. Four manufactured fibers, rayon, acetate, triacetate and lyocell, are cellulosic fibers. This means that one of the components used in their production is natural cellulose. Cellulose is wood pulp, generally obtained from trees. All of the remaining manufactured fibers are non-cellulosic, which means they are entirely chemically-based.

Production Chart for Acetate
To illustrate how man-made fibers are produced, below is a chart showing the production process for acetate fiber. Keep in mind that most manufactured fibers go through similar processes in their development. The production steps include:

• A chemical process, shown on the left side of the chart, which prepares and combines the components used.
• A spinning process, shown on the right, which produces the fiber.
• A twisting process, which twists the fiber into yarn.
• The twisted yarn is then packaged and sent to the textile mills to be either woven or knitted into fabric.

Discussion of the Fiber Production Process
It is not intended to go into all the technical details in this presentation. However, some of the key parts of manufactured fiber production are useful to understand in a little more detail---namely, the spinning process and the process for making filament and staple fibers. The difference between filament and staple fibers is important to understand when discussing the blending of one or more fibers together.

Initial Process
In their original state, the various components of manufactured fibers are solids. In order to be extruded into fibers, the fiber-forming substances must first be converted into a liquid state. To accomplish this they are dissolved in a solvent or melted. If they can't be dissolved or melted directly, they are chemically converted so they can be. The cellulosic fibers (rayon, acetate, triacetate and lyocell) come from purified wood pulp, which first must be shredded and then dissolved.

Spinning Process - The Spinneret
Before being formed into fibers, the fiber-producing substance for all manufactured fibers is in a thick liquid state. In the spinning process this liquid is forced through a spinneret, which resembles a large shower head. A spinneret can have from one to literally hundreds of tiny holes. The size of the holes varies according to the size and type of the fiber being produced.

Unlike natural fibers, manufactured fibers can be extruded in different thicknesses. This is called denier. Denier is a term you may have heard, and essentially relates to the fineness of the fiber filament. For example, a twelve (12)-denier monofilament is commonly used in sheer pantyhose, and a circular double-knit is about 140-denier.

Filament Fiber
As the thick liquid is forced through the spinneret, what comes out on the other side is a stringy liquid called filament. This stringy liquid is similar to airplane glue, which is a liquid acetate product. When the filament dries or solidifies, it forms what is called a continuous filament fiber. Strands of continuous filament fibers are then twisted together to form a continuous filament yarn, which is then woven or knit into fabric.

Staple Fibers and Blending
The long continuous filament fibers can't be used for blending because they're too long and too difficult to handle. Also, natural fibers, such as wool and cotton, with which many manufactured fibers are blended, are very short. Therefore, before blending, man-made fibers are first cut into short fibers, called staple fibers. The staple fibers can more easily be twisted with the shorter natural fibers, or with staple fibers of another manufactured fiber.

Staple fibers are created by extruding many continuous filaments of specific denier from the spinneret and collecting them in a large bundle called a "tow". A tow may contain over a million continuous filaments. The tow bundle is then crimped, in much the same way a curling iron is used to crimp a woman's hair, and is then mechanically cut into staple fibers, usually ranging in length from 1 to 6-1/2 inches, depending how they are to be used.

Purposes of Blending
Blending of different fibers is done to enhance the performance and improve the aesthetic qualities of fabric. Fibers are selected and blended in certain proportions so the fabric will retain the best characteristics of each fiber. Blending can be done with either natural or manufactured fibers, but is usually done using various combinations of manufactured fibers or manufactured and natural fibers.

For example, polyester is the most blended manufactured fiber. Polyester fiber is strong, resists shrinkage, stretching and wrinkles, is abrasion resistent and is easily washable. Blends of 50 to 65% polyester with cotton provides a minimum care fabric used in a variety of shirts, slacks, dresses, blouses, sportswear and many home fashion items A 50/50 polyester/acrylic blend is used for slacks, sportswear and dresses. And, blends of polyester (45 to 55%) and worsted wool creates a fabric which retains the beautiful drape and feel of 100% wool, while the polyester adds durability and resistance to wrinkles.

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