World Journal of World Journal of Engineering 9(5) (2012) 407-416 Engineering Effect of web formation on properties of hydroentangled nonwoven fabrics Paul Sawhney1*, Hiram Allen1, Michael Reynolds1, Ryan Slopek1, Brian Condon1, David Hui2 and Suhad Wojkowski1 1Southern Regional Research Center, Agricultural Research Center, U.S. Department of Agriculture, New Orleans, Louisiana 70124 2University of New Orleans, Department of Mechanical Engineering, New Orleans, LA 70148 *E-mail: [email protected] (Received 11 February 2012; accepted 23 July 2012) Abstract The aim of this study was to determine the effects of two popular web-forming technologies, viz., the Rando air-laid technology and the traditional carding and cross-laying technology, on properties of the hydroentangled nonwoven fabrics made therewith. A mill-like fiber processing study was conducted in a commercial-grade pilot plant using a variety of short staple fibers and their blends. The fibers used in the study were greige cotton, bleached cotton, cotton derivatives, and cut-staple polyester. The hydroentangled fabrics produced with the two systems were mainly evaluated for their physical and mechanical properties, absorbency, absorbency capacity, and whiteness. The study has shown that, with the exception of greige cotton linters, the greige cotton lint, greige cotton gin motes, and even greige cotton comber noils, either alone or in blend with the other fibers mentioned, can be mechanically processed into hydroentangled nonwoven fabric structures without any insurmountable difficulties. The drop test and sink time followed each other pretty closely, as the drop test time increased so did the sink times. The “whiteness” of fabric, which is significantly more dependent on the fabric’s constituent fiber content than on the fabric’s surface-based light reflection, obviously varied considerably. However, the whiteness index within the same fiber types and their blends shows no trend of significant difference between the fabric produced with carded fiber web and the fabric produced with random Rando fiber web. Incidentally, the Rando sample of bleached cotton was not available. Since the nonwoven fabrics of this discussion generally are disposable, the optional use of ‘brighteners’ to improve whiteness of certain whiteness-deficient fabrics may be considered as long as the brighteners do not easily bleed from the fabrics. Key words: Cotton fiber, Polyester fiber, Mechanical web-forming systems, Carding system, Rando system 1. Introduction generally bonded by mechanically twisting them Textile staple fibers can be “bonded” in several together to form a continuous, endless strand of yarn, ways to produce an integrated fabric structure. In which, in turn, is used to make woven and knitted traditional textile manufacturing, the fibers are fabrics. In the manufacturing of staple-based ISSN:1708-5284 408 Paul Sawhney et al./World Journal of Engineering 9(5) (2012) 407-416 nonwoven fabrics (where the fibrous webs are directly converted into fabrics without the yarn spinning), the fibers may be bonded in several different ways, such as by using chemical energy (via. resins and other chemicals), thermal energy (via. adhesives, low-melt fibers, ultrasonic’s, calendaring, microwaves, laser, etc.), and/or mechanical energy (via. needlepunching and/or hydroentangling systems). However, in each of the above different ways of bonding staple fibers into a nonwoven fabric structure, a reasonably manageable fibrous web or batt of certain density and integrity is required and hence must be produced. Although there are quite a few methods or technologies Fig. 1. SEM image of a carded web at a random location. The available to form a web of staple fibers, the most scale bar is equal to 200 M. predominantly used systems and their diverse sub- avenues today are based on carding and air-laid main cylinder wire clothing (Allen, 1990) Figure 1 technologies (Smith, 2008). shows a view of a typical web made on the roller-top, In the carding system, a fibrous batt or web is nonwovens card. The fibers in the web are well produced using a carding machine. A card individualized, although they, unlike in a typical basically opens up the randomly tufted feed-stock cotton card web, are not uni-directionally oriented fibers, uni-directionally individualizes and and parallel to each other, because the nonwovens parallelizes them in the machine direction by card used in this study also had a pair of means of a combing action of densely-wired card “randomizing rollers” to randomize the fiber clothing, and finally delivers the carded fibers in a orientation before the web exit at the end of the continuous (endless) web of light weight, for card (Fleissner, 2009). Nonwovens cards 2 example, 10 to 15 g/m . This fibrous web then generally have a pair of randomizing rolls to may either be assembled with other similar webs randomize fiber orientation to achieve more produced from several other cards in series or be uniform tensile and related properties in both the lapped/folded on a crosslapping machine to form a machine and cross directions of the end product web of desired weight density for the downstream (fabric). needlepunching and/or hydroentanglement system Figure 2 shows a typical web made on the air- for fabric formation. A “cotton card” typically has laid system. As seen, the fibers are very much revolving flats that are densely clothed with a wire randomized, compared to those of the carded web. similar to that of the main cylinder and set very In an air-laid system of preparing a fibrous web, close to the cylinder wire clothing. The flats traveling at a much slower linear speed of around only ~ 13 cm per minute (~5 inches per minute) against the main cylinder’s surface speed of about 2,000 m (78K inches) per minute (at the cylinder speed of 500 + RPM) achieve good “combing” of the fibers, while simultaneously removing any fine non-lint trash and any very short fibers still present in the feed material (Gordon and Hsieh, 2007; Condon, 2010). A “nonwovens card,” on the other hand, generally does not have the revolving flats, since it is normally used to mainly process clean and uniform manufactured fibers, such as polyester, polypropylene, rayon and others like this. Instead it has either a set of rollers or a set of fixed metallic plates, or a combination of rollers Fig. 2. SEM image of an air-laid web at a random location. and plates, which are set in close proximity to the The scale bar is equal to 500 M. Paul Sawhney et al./World Journal of Engineering 9(5) (2012) 407-416 409 the feed stock, after a thorough opening of its alone volumetric hopper to produce a rather more fibrous tufts, is pneumatically transported and uniform, intimately homogeneous fiber mix or piled into layers of fibers and ultimately formed blended for further processing to form carded as into a desired-weight web of randomized fiber well as rando webs, using the prevalent carding and orientation. Such a web may be desirable, if not Rando fiber preparatory systems and conditions, ideal, for producing a nonwoven fabric, but it may respectively. not be desirable in the traditional textile processing, viz., yarn spinning and weaving. For 2.1. Formation of carded webs the traditional textile processes and products, it is In this system, the various fibers and fiber blends generally required, if not imperative, to spin a yarn were separately fed into a meter-wide Rando fiber that has well oriented fibers in the machine opener, which further opened and blended the direction, in order to attain maximum yarn/fabric fibers. The output from the opener flows into a chute strength in the machine direction, while also feed system that, in turn, feeds its output material in attaining the desired uniformity and luster of the a mat form to a 20-inch wide Befama roller-top card end product (such as, a sewing thread, a knitted equipped with two fiber randomizing rolls at the fabric, or a woven fabric) (Sawhney et al., 2007). exit. The carded web thus produced feeds to a In case of the nonwoven fabrics, a randomized 20-inch wide befama crosslapper and is fiber orientation in the fibrous web attains the continuously lightly needled on a 20-inch wide desired, more uniform properties of the fabric in automax needlepunch machine, using a foster needle No. 15 ⊇18 ⊇32 ⊇ 3.5 RB F20 9-6NK and both machine and cross directions, although the 2 overall fabric strength (in any direction) and luster inserting 17 punches per m . The needlepunched may not be the maximum attainable with well output substrate, exiting from the machine, was oriented (crystalline) fibers. rolled in a continuous sheet of paper and taken to a Since staple fibers, particularly the natural fibers remote hydroentanglement system for producing a such as cotton and its derivative byproducts, can vary nonwoven fabric structure. It may be mentioned considerably in staple length and other properties, it here that the crosslapper was intentionally set to its was interesting to investigate the effects of the two lowest setting for the least number of laps, in order commonly adopted web-formation systems, to meet the desired low basis-weight of the various described above, on the properties of the nonwoven materials. Therefore, when the fiber properties (viz., fabrics made with different types of staple fibers and density, length, etc.) of the various materials their blends. Commercial-grade equipment and mill- changed, the resulting web densities also changed. like procedures and conditions were used to process 2.2. Formation of rando webs the fibers and standard test methods were chosen to In this system, the various fibers and fiber test and evaluate the various materials involved in blends were separately fed into a meter-wide the study.