2001 - Volume 2 - Journal of Engineered Fibers and Fabrics

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Figure 6 EFFECT OF MIXING PRESSURE ON DRAINAGE. (CONSISTENCY 0.012%, PAM 165 PPM, DISPERSANT 2 PPM, DEFOAMER 1 PPM, MIXING TIME 5 MIN.) Figure 8 DRAINAGE RATE VERSUS WHITE WATER VISCOSITY (CONSISTENCY 0.012%, PAM 165 PPM, DISPERSANT 2 PPM, DEFOAMER 1 PPM) Drainage index, as defined in Eqn. 1, is a calculated value [16, 17] that takes into account for both the structural parameters and air permeability of a forming fabric. Where, AP is the air permeability in cubic feet per minute (CFM) per square foot, Nc is the CD (cross or transverse direction) mesh count, and b, as defined in Eqn. 2, is the CD support factor on the sheet side. Although drainage index is usually believed to be a more (1) (2) Figure 7 EFFECT OF MIXING TIME ON DRAINAGE. (CONSISTENCY 0.012%, PAM 165 PPM, DISPERSANT 2PPM, DEFOAMER 1 PPM, MIXING PRESSURE 40PSI) cosity. The two wires A and B, again, responded similarly to the mixing effect. The results in Figure 8 indicated that the strong mixing (shearing) effect has broken the PAM molecular structures, resulting in a reduction in flow resistance. Forming Wire and Drainage As mentioned earlier, wet process drainage is a filtration process and depends on both the characteristics of white water chemistry and the structures of a forming fabric. In the paper industry, air permeability (AP) and drainage index (DI) are the two parameters that are believed closely related to the drainage performance of a forming fabric. Air permeability is an experimentally determined value that measures the air flow rate in cubic feet per minute (CFM) per square foot of fabric. accurate prediction for the drainage capability of a forming fabric on a paper mill, there have been only a few reports [16, 17] that correlated the rate of drainage to drainage index. On the other hand, there have been no known reports that addressed how drainage index and air permeability of a forming fabric affect the rate of drainage in a WFGM process. The following discussion would provide some interesting results. Air Permeability Figure 9 is a plot of drainage rate versus the wire air permeability under various experimental conditions. The results shown in Figure 9 included pure water, white waters with different PAM concentrations, and fiberglass slurries at various consistencies. The legend “water” stands for pure water; the “WW” for white water with the last three digits representing the PAM concentration in parts per million; and the “X-Y” for a fiberglass slurry in white water, in which the first number, X, represents the mat basis weight and the second number, Y, the PAM concentration in parts per million. For instance, the legend “WW033” represents a white water with a PAM concentration of 33 ppm, and the legend “1.60-165” stands for a 18 INJ Summer 2001
drained faster than pure water, and a white water of 33 ppm PAM drained faster than pure water with a coarse wire of air permeability above 600 CFM. This was due to the streamingline-forming characteristics of the polymer at very low concentrations [15,18], which facilitated the drainage process. Drainage Index Figure 10 shows the dependence of drainage rate on drainage index under various experimental conditions, and the legends used in the figure are exactly the same as those in Figure 9. Drainage index is usually believed to be a more accurate prediction for drainage in the paper industry, because it characterizes both the sheet support (the b and Nc) and the initial flow resistance (the AP) of a forming fabric. However, Figure 10 indicates that drainage index failed to predict the rate of drainage in the WFGM process. It was expected that for the three fabrics used in this investigation, the drainage rate would monotonically increase with the increase in drainage index. As shown in Figure 10, however, none of the drainage lines showed monotonic increase with drainage index. Some of the drainage lines decreased monotonically and the others increased first, but then decreased as the drainage index was increased. There are no known answers at this time why the drainage Figure 9 EFFECT OF WIRE AIR PERMEABILITY ON DRAINAGE Figure 10 EFFECT OF WIRE DRAINAGE INDEX ON DRAINAGE RATE fiberglass slurry that has a PAM concentration of 165 ppm and would form a mat of 1.60 pounds/CSF after being dewatered. Figure 9 indicates that for pure water and the white waters at various PAM concentrations, air permeability was a good prediction for the rate of drainage. The drainage line for pure water and the four lines for white waters (WW010, WW033, WW066, and WW165) all increased monotonically as air permeability was increased from 465 to 715 CFM, and drainage rate closely followed the air permeability of the forming fabrics. For fiberglass slurries, however, the drainage responses were more complex, and air permeability seemed unable to predict the drainage rate of a forming wire. As shown in Figure 9, the four drainage lines of 1.00-66, 1.60-66, 1.00- 165, and 1.60-165 increased monotonically with the increase in air permeability. However. the other two lines of 2.30-66 and 2.30-165 first increased, but then decreased as the air permeability was raised. Also, most drainage lines of the fiberglass slurries tended to flatten out from AP 630 to 715 CFM, though they increased sharply as the AP was increased from 465 to 630 CFM. It seems true that the higher the mat basis weight and the higher the PAM concentration, the more likely the air permeability would fail to predict the rate of drainage. It is also worth noting that in Figure 9 the entire line of WW010 and part of the line of WW033 are above the drainage line of pure water, meaning that a white water of 10 ppm PAM INJ Summer 2001 19
Page 1 and 2: Nonwovens INTERNATIONAL Journal A S
Page 3 and 4: Nonwovens Nonwovens INTERNATIONAL J
Page 5 and 6: GUEST EDITORIAL CONTINUE THE JOURNE
Page 7 and 8: RESEARCHER’S TOOLBOX materials an
Page 9 and 10: INJ DEPARTMENTS DIRECTOR’S CORNER
Page 11 and 12: DIRECTOR’S CORNER safety, acciden
Page 13 and 14: TECHNOLOGY WATCH biocides is for wa
Page 15 and 16: THE NONWOVEN WEB made and more are
Page 17 and 18: meters. Recently, a wet process mim
Page 19: Gravity drainage, in essence, is a
Page 23 and 24: ORIGINAL PAPER/PEER-REVIEWED Effect
Page 25 and 26: Cotton/PCA blend was examined, also
Page 27 and 28: No Water Water Dip-Nip 20% Acetone
Page 29 and 30: fibers the Hough transform of the i
Page 31 and 32: cessing has been modified to get th
Page 33 and 34: Figure 5a Figure 5b DISTRIBUTION OF
Page 35 and 36: a = 0.50 mm b = 1.01 mm c = 2.26 mm
Page 37 and 38: Bond Width Strain %) Bond Height St
Page 39 and 40: Figure 15 IMAGES CAPTURED AT 50% FA
Page 41 and 42: Figure 1 (A) WELDING SYSTEM; (B) A
Page 43 and 44: (7) (13) We need to know the initia
Page 45 and 46: diameter, density and web structure
Page 47 and 48: The origin of the domain coordinate
Page 49 and 50: Verification of the model and the e
Page 51 and 52: PATENT REVIEW sible; ensure that no
Page 53 and 54: PATENT REVIEW PATENT GUIDELINES Any
Page 55 and 56: INJ DEPARTMENTS WORLDWIDE ABSTRACTS
Page 57 and 58: NONWOVENS ABSTRACTS using small sam
Page 59 and 60: INJ DEPARTMENTS NONWOVENS CALENDAR

2001 - Volume 2 - Journal of Engineered Fibers and Fabrics

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