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 processing study was conducted in a commercial-grade pilot plant using a variety of short staple and their blends. The fibers used in the study were greige cotton, bleached cotton, cotton derivatives, and cut-staple . 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 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 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 ), 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, 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 . 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. This manuscript basically describes the Rando fiber opener to further open and blend the properties of the fibers used, the metrics of the various fibers. The opened fibers from the opener were processes involved, and the properties of the fabrics directly fed into a 12-inch wide rando web former produced using the two different systems of web that formed an isotropic randomized web. The formation. rando web was rolled in paper for the downstream hydroentangling system referred earlier. Again, it 2. Materials and methods may be noted that the rando web former also was A commercial bale of post-gin, pre-cleaned greige set at its lowest web-weight formation and, as (raw) cotton lint was procured from wildwood gin in such, the web weights attained from the various mississippi. Quantities of bleached cotton lint, greige fibers and fiber blends varied to an extent, cotton gin motes and linters and greige cotton comber depending on the properties of the fibers involved. noils were obtained from the available sources. Dacron T 54 polyester, 1.5- inch staple and 1.5-denier 2.3. Hydroentanglement of webs into nonwoven fine was obtained from DAK (made in USA). fabric structures The proper amount of each fiber was separately The various fibrous webs described above were weighed and initially hand blended for preparing uniformly hydroentangled using a fleissner minijet specific blends for the study. These hand-blended system, Figure 3, equipped with one low water fibers of each blend were processed through a stand- pressure jet head for wetting out the feed material 410 Paul Sawhney et al./World Journal of Engineering 9(5) (2012) 407-416

High pressure water jets Pre-wetting Web-compacting water jet belt

Unbonded Fabric cotton web winder Bonded Gas dryer cotton web

Rotating drum with a fabric-forming wire mesh Web-supporting/ Water suction heads fabric-forming belt

Fig. 3. A schematic of the fleissner minijet system. and two high water pressure jet heads-the first one (1) ASTM D 6,242- Mass per Unit Area impacts the substrate material on its top face and (Weight) of Nonwoven Textile Fabrics the other on its bottom face (Fleissner, 2009). For (2) ATSM D 5,035- Breaking Force and all fabrics, the low water pressure head was set to Elongation of Textile Fabrics (Strip inject the water at 50 bar and the two high water Method) pressure heads were set at 125 bar. The fabric (3) AATCC 110- Whiteness of production speed was 5 meters per minute. The (4) AATCC 79- Absorbency of Textiles (Drop hydro-impacted/entangled material/fabric was Test) dried using a meter-wide, gas-fired fleissner (5) ASTM D 1,117 Section 5- Absorbency through-air drum dryer and finally wound on to a Time and Absorptive Capacity Nonwovens tube to form a compact roll of at least 50 meters of the fabric. Incidentally, the hydroentangling line was flushed and cleaned after each fabric 3. Results and discussion production trial. Table 1 shows the measured properties of the various fibers involved in the study. As seen and as 2.4. Fabric absorbency measurements expected, all the fibers vary considerably in all the The AATCC drop test measures the time it takes tested metrics. However, since all of the fibers, with for one drop of water applied to a fabric held in an the exception of linters as stated previously, embroidery hoop to be absorbed (when the sheen processed reasonably satisfactorily without disappears) The ATSM method uses a sample of encountering any serious problem, it may be fabric that 76 mm wide and cut to a length that equals documented that greige cotton lint, greige gin motes, 5.0 ± 0.1 grams. The sample is rolled in to a cylinder and greige comber noils, either alone or in blend with shape, upon itself and placed in a basket of other fibers, can be mechanically processed into standardized weight and size. The basket is dropped hydroentangled nonwoven fabric structures without from a height of 25 mm into a water bath and the any insurmountable difficulties. Now, from the end- time it takes the sample and basket to sink is use application standpoint, one could logically argue measured (Sink Time). After sinking the sample is that the neps, visible foreign matter, and/or trash then allowed to remain submerged in the water for content of especially the gin motes and comber noils 10 seconds. The basket is removed and allowed to could be perceived a consumer concern. Well, let us drain 10 seconds and the sample is weighed. The make this concern a bit consoling by stating that even weight of the water is reported as the absorptive the (costly) bleached cotton (which is partly, but capacity (grams of water held by one gram of fabric). most often, used in the existing nonwoven products 2.5. Test methods such as wipes) may actually have even more neps The test methods used to obtain the reported and perhaps even more foreign particles than the results were (ASTM Standards, 2008): greige cotton lint and/or its various derivatives Paul Sawhney et al./World Journal of Engineering 9(5) (2012) 407-416 411

Table 1. Properties of the various cotton fibers, using the AFIS Instrument

Upper Mean Short-fiber Visible Trash quartile length- length- cm content Neps foreign content Fiber cm (by wt.) (by wt.) (%) (#/g) matter (%) (count/g) Ultraclean 2.87 2.34 10.8 178 1.14 1 greige cotton Gin motes 2.74 2.11 20.2 224 2.06 84 Comber noils 1.50 1.19 81.4 456 0.22 14

investigated in this study. The only difference is that noils, and gin motes) than when fibers are blended the bleaching process of cotton also bleaches greige and carded. Also, the standard deviation in the CD cotton’s foreign contaminants white, as well. Since is significantly higher than that observed in the the existing wipes and other similar disposable MD of carded samples. The standard deviation in products are invariably white in appearance, this the MD and CD tensile strengths of the air-laid whiteness-induced perception of consumer somehow samples are lower and there is less of a difference hides the referenced contaminants and thus befools between the CD and MD values. This likely has to the consumer by way of her/his inability to recognize do with the fact that the air-laid web is more the underlying said concern. As far as the main random than the carded web. Increasing the functional performance, i.e., the absorbency blending amount of cotton fiber with polyester characteristics, of these products is concerned, we does not appear to have a significant effect on the shall later see that some hydroentangled nonwoven strength of the final nonwoven fabrics made with fabrics, which are optimally made with greige cotton either web forming system. For instance, 60/40 and/or its blends with the greige cotton derivatives and 40/60 cotton/polyester blends have similar (gin mote and comber noils) and polyester, could be strengths. However, the absorbency difference nearly comparable with the equivalent fabrics made with respect to the sink time (140 v/s 240 in favor with bleached cotton. of cotton-rich blend) between the two blends, as Tables 2 and 3 below show the properties of the seen from the Table 4, is significant. hydroentangled fabrics made with the different Table 4 shows the absorbency attributes of the fibers and fiber blends, using the carded and cross- various fabrics made from the two different types of laid systems of web formations, respectively. As fibrous webs. As expected, the addition of seen, the air-laid webs, when compared to carded synthetics increase sink times of the fabric in the webs, consistently have a considerably higher case of both carded and Rando web forming tensile strength in the machine direction, but there systems. The drop test and sink time followed each doesn’t seem to be much of a difference in the other pretty closely, as the drop test time increased cross direction. This is expected since the card so did the sink times. However, there are a few cases web was crosslapped (multi-folded), which where this trend was not rigidly followed and that redirected the fiber orientation from the machine possibly could be due to any non-uniformity in the direction (MD) to the cross direction (CD). If the fabric. Another observation from the data in Table card web was not crosslapped, the MD strength III is that the sink time (whether fast or slow) does would have been much higher and the CD strength not seem to affect the capacity. In other words, once obviously would have been much lower of an the fabrics took on the water they held it about the equivalent basis-weight web. And even a greater same capacity. However, there is one anomaly difference between the two strengths, e.g., MD where the Rando 40% UC and 60% PES did not sink and CD, would have been observed had the at all. randomizing rolls on the card were not present. Looking at the absorbency data for the same fiber The standard deviation of the MD and CD blends, the drop test and the capacity were very tensile strengths appear to be higher when using similar for both the card and Rando webs. However, 100% natural fiber (viz., 100% cotton, comber looking at the sink time, the fabrics produced from 412 Paul Sawhney et al./World Journal of Engineering 9(5) (2012) 407-416

Table 2. Mechanical properties of the various hydroentangled nonwoven fabrics made with the carded webs

Fabric ID Tensile Elongation Tensile Elongation Tensile Tensile and fiber Weight MD MD CD CD Normalizing MD CD content g/m2 N /1” % N /1” % Factor N /1” N /1” 100% 54.6 60.63 34.53 44.30 51.60 1.28 77.70 56.78 UltraClean Cotton std. dev. 4.13 1.57 9.93 6.83 100% Gin 51.9 56.41 41.27 48.30 51.86 1.35 76.11 65.17 Motes std. dev. 3.39 3.33 8.22 3.45 100% Comber 73.9 57.60 28.80 100.44 52.67 0.95 54.58 95.16 Noils std. dev. 10.25 5.08 23.32 6.22 100% Polyester 68.6 156.18 70.13 169.61 73.47 1.02 159.47 173.18 std. dev. 15.07 4.57 19.69 3.18 60% UltraClean 60.1 60.09 26.13 44.20 51.13 1.16 69.96 51.46 40% Comber Noils std. dev. 3.84 2.65 5.91 2.29 40% UltraClean 74.8 81.65 37.40 84.21 48.33 0.94 76.43 78.83 60% Comber Noils std. dev. 3.72 3.28 11.33 4.24 60% UltraClean 66.5 84.74 35.07 70.67 60.13 1.05 89.21 74.39 40% Gin Motes std. dev. 10.41 3.84 10.25 2.78 40% UltraClean 59.5 65.00 29.07 62.85 59.40 1.18 76.53 74.00 60% Gin Motes std. dev. 6.20 2.56 5.64 5.00 60% UltraClean 75.4 128.72 51.87 125.27 78.67 0.93 119.55 116.34 40% Polyester std. dev. 12.15 5.62 11.14 2.72 40% UltraClean 66.6 104.55 52.47 123.77 77.60 1.05 109.81 130.00 60% Polyester std. dev. 33.41 8.47 17.26 5.66 Scoured and 103.4 133.29 36.53 181.93 32.80 0.68 90.64 123.71 Bleached Cotton std. dev. 7.20 1.45 10.10 2.06 the Rando webs were significantly lower (fast) in all well known for its optical whiteness, considerably fiber types and blends, except the 100% GM blend. improves whiteness of the fabric when blended This observation and finding indeed could be a with greige cotton. In fact, the 40 % greige cotton significant factor and useful in a real world scenario, 60 % polyester blend exhibited a whiteness where the end-use products require fast absorbency index~73-approaching the whiteness of the times (sink-time). bleached cotton fabric (included only for the Table 5 shows the whiteness of the fabrics made carded web and as a benchmark, since a Rando with the several different fibers and fiber sample of bleached cotton was not available). For blends. As seen and as expected, the whiteness of other blends, where the whiteness may need to be fabrics, depending on their fiber content, varies improved, the use of optional, relatively much less considerably. The 100% greige cotton lint fabric’s expensive optical brighteners may be considered, whiteness index of ~35; however polyester fiber, since the nonwoven fabrics of this discussion Paul Sawhney et al./World Journal of Engineering 9(5) (2012) 407-416 413

Table 3. Mechanical properties of the various hydroentangled nonwoven fabrics made with the air-laid webs

Tensile Elongation Tensile Elongation Normali- Tensile Tensile Fabric ID and Weight MD MD CD CD zing MD CD fiber content g/m2 N /1” % N /1” % Factor N /1” N /1” Fabric ID 79.0 154.56 41.87 110.66 48.87 0.89 136.87 98.00 and fiber content 100% UltraClean Cotton std. dev. 13.39 1.52 10.37 4.01 100% Gin Motes 54.3 69.63 32.13 46.35 56.20 1.29 89.72 59.72 std. dev. 15.73 4.12 3.55 2.85 100% Comber 74.9 107.49 29.13 101.16 46.74 0.93 100.43 94.51 Noils std. dev. 16.63 3.30 15.57 4.06 100% Polyester 103.9 266.76 54.20 198.87 73.40 0.67 179.77 134.02 std. dev. 24.80 4.19 23.74 5.46 40% UltraClean 85.6 128.46 33.27 103.20 53.33 0.82 105.03 84.37 60% Comber Noils std. dev. 12.75 1.34 10.65 1.85 60% UltraClean 79.0 131.01 29.60 122.65 51.13 0.89 116.06 108.66 40% Comber Noils std. dev. 11.42 3.97 8.19 3.08 40% UltraClean 60.9 116.13 34.73 68.78 49.53 1.15 133.39 79.00 60% Gin Motes std. dev. 9.31 2.33 6.74 2.91 60% UltraClean 65.0 94.82 30.47 70.80 49.33 1.08 102.10 76.23 40% Gin Motes std. dev. 8.91 4.26 10.19 3.15 40% UltraClean 60.9 141.11 47.40 113.23 74.13 1.15 162.28 130.21 60% Polyester std. dev. 16.73 5.94 23.25 4.04 60% UltraClean 55.5 136.39 44.87 93.28 66.80 1.26 172.11 117.71 40% Polyester std. dev. 18.40 5.78 9.14 4.18 40% UltraClean 60.9 116.13 34.73 68.78 49.53 1.15 133.39 79.00 60% Gin Motes std. dev. 9.31 2.33 6.74 2.91 60% UltraClean 65.0 94.82 30.47 70.80 49.33 1.08 102.10 76.23 40% Gin Motes std. dev. 8.91 4.26 10.19 3.15

Fiber Codes: UC = UltraClean, GM = Pre-Cleaned Gin Motes, CB = Comber Noils, PES = Polyester Staple, BC = Bleached Cotton. generally are disposable, anyway. So, as long as measured by reflectance of light from the fabric the brighteners do not easily bleed from the fabrics, surface and since the fabric surface/texture of they may be considered as a viable option to hydroentangled fabrics is influenced by the improve whiteness of whiteness-deficient fabrics. impacting water jets and the forming belt of the The data in Table 5 also show that the whiteness hydroentanglement system, it is possible that index, within the same fiber types and blends, the likely differences in the surface geometry of shows no trend of significant difference between the two different web configurations have some the fabric produced with carded fiber web and the influence on the final texture of the fabrics made fabric produced with random Rando fiber web. thereof. And that may be a possible explanation for However, since the whiteness index basically is some insignificant differences observed in the 414 Paul Sawhney et al./World Journal of Engineering 9(5) (2012) 407-416

Table 4. Absorbency characteristics of the various hydroentangled fabrics produced

Carded Carded Rando Rando Carded ASTM ASTM Rando ASTM ASTM AATCC 1,117 Absorbency AATCC 1,117 Absorbency Carded Drop Sink Capacity- Rando Drop Sink Capacity- Fiber/Fiber WT. Test Time- (g. H2O per WT. Test Time- (g. H2O per Blend (g/m2) (sec.) (sec) g. of fabric) (g/m2) (sec) (sec) g. of fabric) 100% UC 54.6 <1 40.8 4.97 79.0 <1 9.7 6.54 100% GM 51.9 2.4 32.1 6.88 54.3 <1 15.4 8.17 100% CB 73.9 6.6 45.0 6.71 74.9 3.6 20.0 6.07 100% PES 68.6 >60 >300 0.14 103.9 >60 >300 0.11 60%UC/ 60.1 <1 69.4 6.87 79.0 4.8 26.5 5.99 40%CB 40%UC/ 74.8 <1 79.0 6.12 85.6 <1 15.6 6.34 60%CB 60%UC/ 66.5 5.4 26.4 7.25 65.0 <1 8.2 7.63 40%GM 40%UC/ 59.5 <1 40.2 7.13 60.9 <1 33.8 7.01 60%GM 60%UC/ 75.4 >60 113.8 7.05 55.5 >60 68.5 9.57 40%PES 40%UC/ 66.6 >60 241.0 7.97 60.9 >60 >300 0.34 60%PESS 100% BC 103.6 <1 2.25 6.46 N/A N/A N/A N/A

Fiber Codes: UC = UltraClean, GM = Pre-Cleaned Gin Motes, CB = Comber Noils, PES = Polyester Staple, BC = Bleached cotton (It may be noticed here in Table 3 that the rando sample of bleached cotton (as a bench mark) was not available).

Table 5. Whiteness of the various fabrics (Measured by AATCC Method 110)

Whiteness Index Whiteness Index Fiber or fiber (of the fabrics made via (of the fabrics made via the Blend the carding principle) Rando principle) 100% UC 33.64 35.91 100% GM 24.91 25.09 100% CB 20.08 24.82 100% PES 110.59 107.69 60%UC/ 40%CB 33.98 33.15 40%UC/ 60%CB 34.19 33.10 60%UC/ 40%GM 30.84 28.68 40%UC/ 60%GM 28.47 27.97 60%UC/ 40%PES 68.79 68.54 40%UC/ 60%PES 72.42 73.24 100 % BC 84.99 N/A

Fiber Codes: UC = UltraClean, GM = Pre-Cleaned Gin Motes, CB = Comber Noils, PES = Polyester Staple, BC = Bleached Cotton. whiteness index of the fabrics made with the same the fabrics of same fiber content, whether produced types of fibers and fiber blends using the two from carded or Rando webs appear to be similar in different methods of web preparation. At any rate, whiteness when viewed by the naked eye. Paul Sawhney et al./World Journal of Engineering 9(5) (2012) 407-416 415

4. Conclusions greige cotton lint fabric in either case was ∼35. A fiber processing study conducted to determine However the polyester fiber, well known for its the effect of web formation on performance of the optical whiteness, when blended with greige cotton hydroentangled nonwoven fabric made thereof has considerably improves whiteness of the resulting shown that, with the exception of greige cotton linters, blend fabric. In fact, the 40 % greige cotton and 60 % the greige cotton lint, greige cotton gin motes, and polyester blend exhibited a whiteness index of 73 greige cotton comber noils, either alone or in blend which almost approaches the whiteness of the with other fibers, can be mechanically processed into bleached cotton fabric made only with the carded web hydroentangled nonwoven fabric structures without (since the Rando sample of bleached cotton was not any insurmountable difficulties. Further, the air-laid available). For other blends, where the whiteness, webs, when compared to the carded webs, especially when viewed by the naked eye, may need consistently have a significantly higher tensile to be improved, the use of optional, relatively much strength in the machine direction (MD), but there less expensive optical brighteners may be considered. doesn’t seem to be much of a difference in the cross Since the nonwoven fabrics of this discussion direction (CD). The standard deviation of the MD and generally are disposable, the brighteners, as long as CD tensile strengths appear to be higher when using they do not easily bleed from the fabrics, may indeed 100% natural fiber (viz., 100% cotton, comber noils, be considered as a viable option to improve whiteness and gin motes) than when fibers are blended and of certain whiteness-deficient fabrics. carded. Also, the standard deviation in the CD is significantly higher than that observed in the MD of Acknowledgements carded samples. The standard deviation in the MD and The authors would like to thank the agricultural CD tensile strengths of the air-laid samples are lower research service of the US department of agriculture and there is less of a difference between the CD and for providing all the necessary funding and resources MD values. to conduct and report this research. They also Regarding the fabric absorbency, the drop test and express their gratitude to lucien duplessis, adrian the capacity were very similar for both the card and mejia, pablo salame and farrell screen for their Rando webs. However, the addition of synthetic fibers outstanding “hands-on” assistance in conducting the increase sink times of the fabric in the case of both various processes involved in the study. carded and Rando web forming systems. The drop test and sink time followed each other pretty closely, as References the drop test time increased so did the sink times. Allen H. C. Jr., 1990. The cotton fiber process and fiber However, there are a few cases where this trend was characteristics. Cotton Incorporated publication. not rigidly followed and that possibly could be due to ASTM Standards, Section 7, 2008. Textiles and technical any non-uniformity in the fabric. Also, the sink time manual of the American Association of Textile Chemists and (whether fast or slow) does not seem to affect the Colorists. capacity. In other words, once the fabrics took on the Condon B., Gary L., Sawhney P., Reynolds M., Slopek R.P., water they generally held it at about the same capacity. Delhom C. and Hui D., 2010. Properties of nonwoven fabrics The fabrics produced from the Rando webs were made with Ultra Clean cotton. World Journal of considerably lower (fast) in all fiber types and blends, Engineering 7(2), 180–184. except the 100% gin motes blend. This unique Fleissner G.H, 2009. Nonwovens: nonwovens technology. finding indeed could be a significant factor and useful Trützschler Group. in a real world scenario, where the end-use products Gordon S. and Hsieh Y.L., 2007. Cotton: science and require fast absorbency times (sink time). technology. Woodhead Publishing and CRC Press. The whiteness of fabrics, depending on their Sawhney Paul S., Brian Condon and Kumar V. Singh, 2007. constituent fiber content, varies considerably. Textiles, testing. John Wiley and Sons, Inc. However, the whiteness index, within the same fiber Smith Johnson, 2008. Cotton opportunities in nonwovens and types and blends, shows no trend of significant the US nonwoven industry: a consulting study on cotton difference between the fabric produced with carded nonwovens for the U.S. Agricultural Research Service, fiber web and the fabric produced with random Southern Regional Research Center, New Orleans, Rando fiber web. The whiteness index of the 100% Louisiana.