About
  PDF
Full Text
(36 K)

Some Useful Tips for Carding Cotton in a Nonwovens Lab

Paul S. Sawhney and D. V. Parikh


 
ABSTRACT

Carding is a critical operation in processing cotton for both woven and nonwoven fabrics. Basically, a carding machine opens, cleans and aligns fibers, as far as cotton is concerned. However, there are many different types of cards and carding systems for processing different types and qualities of fibers. To achieve optimum carding performance and efficiency, it is therefore imperative to select a proper card and set it according to the input fiber quality involved and the output fiber quality desired. It is unwise to use the same card for all types and qualities of fibers that are typically investigated and processed in a nonwoven research laboratory. This paper reviews some useful technical tips for processing, especially carding, cotton in a nonwoven lab. Selection, settings and clothing of a card and manipulation of other factors that influence carding effectiveness are briefly discussed.

Today, there are numerous carding systems and their modifications for processing fibers for nonwovens. Selection of a particular system chiefly depends on the nature and quality of the fibers and end-product involved. No matter what system is adopted, the quality of the final product largely depends on thoroughness of the fiber mixing, opening, cleaning, bleaching (if involved), blending and, above all, carding. Carding of synthetic fibers and carding of cotton for the nonwovens are two somewhat different processes. Synthetic fibers generally are long, strong, uniform and clean, whereas raw cotton fibers are relatively short, weak, irregular, and dirty or trashy. A standard bale of raw, ginned cotton has billions of compressed fibers which vary in length, strength, fineness, and maturity. Different bales of cotton may vary in trash content, color and hence grade. However, we should still expect a cotton end product, whether woven or nonwoven, to be uniform and homogeneous in its properties, especially the appearance.

To achieve the desired “homogenity” of a cotton or a predominantly-cotton nonwoven, we must first prepare the stock accordingly. Preparation of fibers for a nonwoven application includes a thorough initial-mixing, opening and cleaning, any blending, and carding. These fiber preparatory processes can, in fact, make or break a nonwovens operation. Although systematic planning and execution of all of these fiber preparatory processes are critical, the carding is at the top.

The purpose of carding cotton for the nonwovens is four-fold:

1. to effectively open and clean (by removing contaminants, approximately 1/2%, such as coarse and fine/pepper trash, etc.) the fibrous stock with minimal fiber damage and waste/loss;
2. to partially individualize and parallelize the fibers;
3. to remove too short fibers, motes and neps; and
4. to condense the fibers to the desired form (batt) of uniform linear density.

Carding basically is accomplished by two layers or sets of card clothing (on rolls) mostly consisting of a saw-tooth wire (occasionally embedded pins). The two sets of wires rake or tease the fibers, hold them for a while, and then release them. For example, the coarse wires of the licker in(s) rake the fibers from the feed roll/plate; the fine wires of the cylinder tease fibers into a filmy layer, so that a thin web of fibers is formed on the cylinder. The doffer wires gather the web from the cylinder to form a batt for the subsequent operations of a nonwoven project.

There are a host of important factors that can make a considerable difference in the quality and cost effectiveness of the cotton web or batt produced in a nonwoven Lab. Some of them are briefly mentioned below:





Reprinted from Proceedings of the 2001 Beltwide Cotton Conferences pp. 731 - 732
©National Cotton Council, Memphis TN

[Main TOC] | [TOC] | [TOC by Section] | [Search] | [Help]
Previous Page [Previous] [Next] Next Page
 
Document last modified XXXXXX, XXX XX 2001