ABSTRACTThe main goal of this study is to investigate the perfor-

mance behavior of hydroentangled nonwoven fabrics interms of input water jet energy and fabric structural parame-ters (basis weight and fiber orientation). The input jet energywas varied by altering jet pressure, number of passes, processspeed and fabric basis weight. To achieve the goal, two sets oftrials, which had different jet pressures, process speeds, basisweights and number of passes, were executed to reveal thesignificance of these parameters in achieving high fabric ten-sile strength. Image analysis was used to determine the fiberorientation of the hydroentangled nonwoven fabrics to aid inunderstanding fabric performance behavior.

KEY WORDSHydroentanglement, Fiber Orientation Distribution

Function (ODF), Specific Energy, Jet Pressure, Tensile Strength

INTRODUCTIONHydroentanglement is a process of entangling a web of

loose fibers on a porous forming surface (endless belt or per-forated drum) to form a sheet structure nonwoven fabric bysubjecting the fibers to multiple rows of fine jets of highlypressurized water. The fibers are pushed down by the waterjets from the top of the cross-over points (knuckles) to theinterstices of the forming wire, conformed to the formingwire, and these results in the rearrangement and intermin-gling of fibers. It is basically an energy transfer process thatstrengthens the array of loose fibers, imparting the desiredphysical, mechanical, texture and aesthetics properties.Hydroentangled fabrics rely primarily on fiber-to-fiber fric-

tion and fiber bending properties to achieve physical integri-ty and are characterized by relatively high strength, softness,drape and conformability.

Many factors may affect the ease of fiber entanglement. Thelevel of specific energy is a major parameter to the propertiesof the final product. Also, the process requires some specialfiber properties that fibers can bend easily around small radiiwhile possessing some degree of mobility. The importantproperties include those related to polymer composition andfiber properties, such as bending modulus, linear density,fiber length, fiber wettability, fiber cross-section shape [2] andfiber-to-fiber friction.

The forming surface provides several functions: (1) supportof the fiberweb, (2) increasing entangling efficiency, (3) creat-ing desired texture (non-aperture or aperture, for example).The constituents and the geometry of the forming surface,which is usually fine-mesh stainless steel, bronze, or poly-meric screen, must be fine enough to minimize fiber lossesand maximize water reflection back into the web to increaseentanglement while, at the same time, be open enough to ade-quately drain the water from the jets, and provide therequired fabric aesthetics.

Various steps are important in the hydroentanglementprocess. The steps for hydroentangled nonwoven fabricsinclude fiber selection, web formation, web entanglement,fabric drying and optional finishing treatments. While someof these steps are typical in a nonwoven process, some ofthem are unique to the process of hydroentanglement. Fiberselection is important to satisfy certain end use due to the roleof fiber properties in fabric formation and the fabric structurewhich determine the final fabric properties [2, 7].

The Impact of Input EnergyOn the Performance OfHydroentangledNonwoven FabricsBy Huabing Zheng, Abdelfattah M. Seyam, and Donald Shiffler, Nonwovens Cooperative ResearchCenter, College of Textiles, NC State University, Raleigh, NC, US

ORIGINAL PAPER/PEER-REVIEWED

34 INJ Summer 2003

Various web formation systems produce different fiber ori-entation. Cross-lapped web are characterized by their bi-modal fiber orientation (expressed in orientation distributionfunction or ODF) with significant fiber percentage oriented inthe cross machine direction (or CD) and low orientation inmachine direction (or MD). The two domain angles can becontrolled by the carding speed and the crosslapper conveyorbelt speed. The ODF of the final hydroentangled fabric is,however, the deciding factor in determining the fabric perfor-mance. The basis weight also has relationship with specificenergy needed to form hydroentangled fabrics.

The step of web entanglement is the major process costbecause of energy consumption in providing highly pressur-ized water jets. To achieve cost reduction, the energy transferfrom the high pressure water jet to the fabric need be under-stood and such transfer maximized. This includes: good jetorifice design forming uniform jet flow with minimum frictionloss, optimization of the energy distribution, and tailoring ofjet orifice and forming wire to the fabric application [5].

The principle of bonding fibrous webs with water energywas established back in 1968 by researchers at Du Pont [4].Since then, the hydroentanglement process has been a rapidlygrowing segment of the nonwoven technology complexbecause of its ability to achieve excellent fabric properties athigh processing speeds. While there are many articles pub-lished in trade journals that describe the process and products

of hydroentanglement, very few articles have been publishedin the scientific literature [1-6, 8-10] in the area of the impact ofprocessing and fiber parameters and their interactions on theaesthetics and performance of the spunlace fabrics. This maybe attributed to the fact that spunlace fabric producers consid-er the information highly proprietary.

OBJECTIVEThe objective of this paper is to study the performance

behavior of hydroentangled fabrics in terms of input water jetenergy and fabric structural parameters. The input jet energywas varied by altering jet pressure, number of passes, processspeed and fabric basis weight.

EXPERIMENTALMaterial and Fiberweb Formation

Polyester fibers of fineness of 1.63 dtex and 38 mm lengthwere provided in bale form. The fibers were processed in thecarding and crosslapping line at the College of Textiles, NCState University. This line is comprised of an opener, garnet,roller-top card, flat-top card, crosslapper, tacking, and fiber-web take-up. The fibers were passed through the opener, theflat-top card, tacking, and finally to the take-up to form therequired fiberwebs. Two fiberwebs with required quantities ofnominal weights of 50 g/m2 and 100 g/m2 were produced.

35 INJ Summer 2003

A SIMPLE SKETCH OF A HONEYCOMB HYDROENTANGLING SYSTEM

FilterTank

VacuumPump

Circulation

WaterJets

Belt Speed: 0-110 feet/min. (0-35 m/min)

Suction WaterWaterTank

Drain

Max pressure = 1500 psi (100 bar)

CityWater

Main Pump

Air Exhaust

Finefilter

HydroentanglementThe fiberwebs were entangled using a 50.8-cm (20-inch)

wide honeycomb model hydroentanglement machine with

three manifolds (see sketch on previous page). Fabric sampleswere produced using different energy levels by varying man-ifold pressure, number of passes, process speed and fiberwebbasis weight. The pressure of the first manifold was kept con-stant at 13.8 bar for the first pass only to prewet the samples.The fiberweb was placed manually on the forming wire. Aftereach pass the sample was removed manually and then thesample was fed again with its side reversed. This was repeat-ed until the required number of passes is achieved.

The hydroentanglement unit has several basic elements:Hydraulic Entanglement Stand: This stand provides support

to transport the web under the three entanglement headers soas to expose the web to a series of high pressure water jets thatwill entangle the fibers of web. Water and air are transportedfrom this stand to the air-water separator system.

High Pressure Water Pumping System: This regulates the vol-ume and pressure of the water delivered to the hydraulicentanglement stand.

Air-Water Separator System: This separates the water fromthe air so that the water may be reused for closed loop opera-tion or sent to drain for open loop operation.

Water Storage System: This system supplieswater in open loop operation that isemployed in our study.Water Filtration System: This system filtersunwanted particles from the city water.

Experimental Design Two sets of trials (referred at as Trial 1 andTrial 2 throughout the paper) were performedto achieve the purpose of the study. The vari-ables that were kept constant are summarizedin Table 1 and the independent variablesinvestigated are summarized in Table 2. Asshown in Table 2, the measured basis weightof the carded/crosslapped fiberwebs of Trials1 and 2 are different from the nominal. Tables3 and 4 show the levels of pressures for eachmanifold and pass of Trials 1 and 2 respec-tively. As mentioned before, the pressure ofthe first manifold was kept constant at 13.8bar for the first pass. Fabric sample 1 (Table 3),for example, was produced using two passes.The pressures of the manifolds were 13.8 bar,27.6 bar, and 27.6 bar respectively in the firstpass. The pressures of the three manifoldswere 27.6 bar, 27.6 bar, and 27.6 bar in the sec-ond pass. Fabric sample 7 (Table 3) wasprocessed using 6 passes. The pressures of themanifolds were 13.8 bar, 55.2 bar, and 55.2 barrespectively in the first pass. The pressures ofthe three manifolds were 55.2 bar, 55.2 bar,and 55.2 bar in the passes 2-6.

Testing and EvaluationFabric properties reported here are tensile strength, basis

weight and fiber orientation. The fabric tensile and basis

36 INJ Summer 2003

Table 1CONSTANT VARIABLES

Variable ValueJet Density, jets/cm 15.8Jet Diameter, mm 0.127Discharge Coefficient 0.7Number of Manifolds 3Mesh of Forming Screen 100

Table 2INDEPENDENT VARIABLES

Variable Trial 1 Trial 2Fiberweb Weight, g/m2 99.6 56.9Process Speed, m/min 4.57 9.14Jet Pressure, bar 27.6, 27.6,

55.2, 82.7 55.2, 82.7

* First manifold pressure was fixed at 13.8 bar for the first pass.

Table 3PRESSURE LEVELS AND NUMBER OF PASSES OF TRIAL 1

Fabric Passes Pressure, barManifold 1 Manifold 2 Manifold 3

1 1 13.8 27.6 27.61 27.6 27.6 27.6

2 1 13.8 27.6 27.63 27.6 27.6 27.6

3 1 13.8 27.6 27.65 27.6 27.6 27.6

4 1 13.8 27.6 27.67 27.6 27.6 27.6

5 1 13.8 55.2 55.21 55.2 55.2 55.2

6 1 13.8 55.2 55.23 55.2 55.2 55.2

7 1 13.8 55.2 55.25 55.2 55.2 55.2

8 1 13.8 55.2 55.27 55.2 55.2 55.2

9 1 13.8 82.7 82.71 82.7 82.7 82.7

10 1 13.8 82.7 82.73 82.7 82.7 82.7

11 1 13.8 82.7 82.75 82.7 82.7 82.7

12 1 13.8 82.7 82.77 82.7 82.7 82.7

weight testing and evaluation were performed according toASTM.

Tensile testing was performed on an MTS 30/G tensiletester using the ASTM D 5035-95 (strip method). Five samplesin the machine direction and five samples in the cross direc-tion were tested.

Fabric basis weight was determined using the ASTM D3776-96. Five samples were tested.

NCRC image capturing and processing (software and hard-ware) systems were used to measure fiber orientation of thecarded/crosslapped fiberwebs and hydroentangled fabrics[8].

RESULTS AND DISCUSSIONThe objective of trials 1 and 2 was to determine whether

energy delivered or jet force is more important indeveloping fabric properties. Additionally, the trialswere designed to reveal the nature of the specificenergy/fabric performance relationship when vary-ing basis weight and process speed. The two trialswere designed so that the throughput or mass perunit time (process speed multiplied by basis weight)is about constant.

As shown in Table 2 and 3, three different jet pres-sures (27.6 bar, 55.2 bar, and 82.7 bar) and four differ-ent numbers of passes (2, 4, 6 and 8) were used toprocess the hydroentangled fabrics of trial 1. Theresults are shown in Figure 1 (a)-(f). The mean tensilestrength shown in Figure 1 (d) is the average of tensilestrength in MD and CD. The specific energies (x-axis)were calculated using the formula shown in theAppendix.

The fabric basis weight {Figure 1 (a)} decreases withincreasing specific energy and number of passesbecause of fabric stretching caused by water jetsimpact and peeling the fabric from the forming wireafter each pass. The change of basis weight is signifi-cant so normalized tensile strength was calculatedand reported. The tensile strength results of Figure 1(b)-(d) show that tensile strength increases with spe-cific energy until a critical energy (threshold energy).After reaching the threshold energy, increasing ener-gy has no significant effect on hydroentangled fabrictensile strength. With the exception of one data point,the elongation at peak load in MD and CD {Figure 1(e) and 1(f)} decreases slightly with increasing specificenergy. Additionally, the results of Figure 1 show thatthe jet pressure has no or little effect on the hydroen-tangled fabric tensile strength and elongation.

The results of trial 2 are shown in Figure 2. Figure 2(a) shows that fabric basis weight decreases withincreasing specific energy and hence normalized ten-sile strength was used to nullify the effect of fabricweight. The weights reported in Table 2 were used asthe normalized weights. Tensile strength increases in

MD and decreases in CD with specific energy for all jet pres-sure levels used as it can be seen from Figures 2 (b) and 2 (c).For fabrics produced at jet pressure of 27.6 bar and 55.2 bar,the mean tensile strengths show clearly threshold energies{Figure 2 (d)}. For fabrics processed at 82.7 bar, however, spe-cific energy shows little effect on the mean tensile strengthand it is almost constant at all levels of specific energy {Figure2 (d)} indication of reaching the threshold at low specific ener-gy. The elongation at peak load decreases in MD and increas-es in CD with specific energy at all levels of jet pressures{Figure 2 (e) and (f)}. Contrary to the results of Figure 1, theresults of Figure 2 indicate that both specific energy and jetpressure play an important role in deciding fabric tensilestrength and elongation when dealing with lighter basisweight.

37 INJ Summer 2003

Table 4PRESSURE AND NUMBER OF PASSES OF TRIAL 2Fabric Passes Pressure, bar

Manifold 1 Manifold 2 Manifold 31 1 13.8 27.6 27.6

1 27.6 27.6 27.62 1 13.8 27.6 27.6

3 27.6 27.6 27.63 1 13.8 27.6 27.6

5 27.6 27.6 27.64 1 13.8 27.6 27.6

7 27.6 27.6 27.65 1 13.8 27.6 27.6

9 27.6 27.6 27.66 1 13.8 27.6 27.6

11 27.6 27.6 27.67 1 13.8 55.2 0

1 0 55.2 08 1 13.8 55.2 55.2

1 55.2 55.2 55.29 1 13.8 55.2 55.2

3 55.2 55.2 55.210 1 13.8 55.2 55.2

5 55.2 55.2 55.211 1 13.8 55.2 55.2

7 55.2 55.2 55.212 1 13.8 82.7 0

1 0 82.7 013 1 13.8 82.7 82.7

1 82.7 82.7 82.714 1 13.8 82.7 82.7

3 82.7 82.7 82.715 1 13.8 82.7 82.7

5 82.7 82.7 82.716 1 13.8 82.7 82.7

7 82.7 82.7 82.7

Results of Figures 1 and 2 show that: (i) lighter fabrics tensilestrength is reduced with jet pressure while heavier fabrics ten-sile strength did not get affected by jet pressure and (ii) the

MD tensile strength is higher than the CD tensile strength.The tensile behavior of fabrics in MD and CD with jet pressureand specific energy indicates that there must be changes in the

38 INJ Spring 2003

Figure 1EFFECT OF JET PRESSURE AND SPECIFIC ENERGY ON FABRIC PROPERTIES OF FABRICS OF

NORMALIZED WEIGHT OF 99.6 g/m2

Figure 1 (a) Fabric Weight

Figure 1 (c) Tensile Strength in CD

Figure 1 (e) Elongation at Peak Load in MD Figure 1 (f) Elongation at Peak Load in CD

Figure 1 (d) Mean Tensile Strength

Figure 1 (b) Tensile Strength in MD

Specfic Energy (x103 kJ/kg)

Specfic Energy (x103 kJ/kg)

Specfic Energy (x103 kJ/kg) Specfic Energy (x103 kJ/kg)

Specfic Energy (x103 kJ/kg)

Specfic Energy (x103 kJ/kg)

Fabr

ic B

asis

wei

ght (

g/m

2 )

Tens

ile S

tren

gth

in M

D (

N/

cm)

Tens

ile S

tren

gth

in C

D (

N/

cm)

Mea

n Te

nsile

str

engt

h (N

/cm

)

Stra

in a

t Pea

k L

oad

in M

D(%

)

Stra

in a

t Pea

k L

oad

in C

D(%

)

27.6 bar

55.2 bar

82.7 bar

27.6 bar

55.2 bar

82.7 bar

27.6 bar

55.2 bar

82.7 bar

27.6 bar

55.2 bar

82.7 bar

27.6 bar

55.2 bar

82.7 bar

27.6 bar

55.2 bar

82.7 bar

39 INJ Summer 2003

Figure 2EFFECT OF JET PRESSURE AND SPECIFIC ENERGY ON FABRIC PROPERTIES FABRICS

OF NORMALIZED WEIGHT OF 56.9 G/M2

fiber orientation and the structure of the resultant hydroen-tangled fabrics. To find out whether such change actually tookplace, fiber orientation was evaluated using image analysis todetermine the ODF (Fiber Orientation Distribution Function)of cross-lapped fiberwebs and hydroentangled fabrics.

Figures 3 (a)-(h) show the images of hydroentangled fabricsprocessed at different jet pressures and specific energies. The

effect of jet pressure on the texture of thehydroentangled fabric at constant numberof passes (two passes) can be noticed fromFigures 3 (a), (c) and (e). At 27.6 bar jet pres-sure the fabric exhibits only small holes.At 55.2 bar jet pressure the texture of thefabric shows clear streaks and mediumsize holes. The 82.7 bar jet pressure causedthe fabric to form the largest size roundholes and a clear streak pattern. Thisexplains why high jet pressure loweredthe tensile strength of lighter fabrics{Figure 2 (b) and (d)}. In such fabrics thereare fewer fibers in the fabric cross-sectionand the high jet pressure caused the fibersto be displaced apart and form largerholes or weak spots. The fiber displace-ment was not noticed at high pressure

when dealing with heavier fabrics {Figure 3 (g)} due to thehigh number of fibers in the fabric cross-section thus weakspots were not formed. This is the reason why the tensilestrength of heavier fabrics is not influenced by jet pressure{Figure 1 (b)-(d)}.

The effect of the number of passes on fabric structure at lowjet pressure of 27.6 bar can be seen by comparing Figures 3 (a)

40 INJ Summer 2003

(a) 27.6 bar, 2 passes, 56.9g/m2

(SE: 1.77x103kJ/kg)

(d) 55.2 bar, 6 passes, 56.9g/m2

(SE: 15.98x103kJ/kg)

(b) 27.6 bar, 12 passes, 56.9g/m2

(SE: 11.66x103kJ/kg)

e) 82.7 bar, 2 passes, 56.9g/ m2

(SE: 3.54x103kJ/kg)(f) 82.7 bar, 8 passes, 56.9g/m2

(SE: 39.53x103kJ/kg)

(g) 82.7 bar, 2 passes, 99.6g/ m2

(SE:9.92x103kJ/kg)(h) 82.7 bar, 8 passes, 99.6g/m2

(SE: 45.15x103kJ/kg)

(c) 55.2 bar, 2 passes, 56.9g/ m2

(SE: 1.98x103kJ/kg)

Figure 3IMAGES OF FABRICS WITH DIFFERENT PRESSURE, PASSES,

AND BASIS WEIGHT

and (b). Increasing the number of passes at such low pressurecaused the formation of large diameter holes in the fabric. Thenumber of passes at 55.2 bar jet pressure did not show similareffect {Figures 3 (c) and (d)}. The clear streaks of the fabric ofFigure 3 (c) disappeared and hole size is reduced by increasingthe number of passes to 6 {Figure 3 (d)}. For the fabricsprocessed at jet pressure of 82.7 bar, the streaks did not disap-pear when the number of passes is increased. Additionally,the texture was changed from round-shaped holes to ellipse-shape with the major diameter in the machine direction.

Figure 4 shows the ODF of the fiberweb. The bi-modal fiberorientation distribution of the crosslapped web is obvious.Figures 5 (a)-(d) show the ODF of hydroentangled fabricsprocessed at different jet pressures and specific energies. Theresults of Figures 5 (a) and (b) indicate that the fiber orientationincreases in MD with increasing the number of passes.Although fabrics processed with different jet pressures have

41 INJ Summer 2003

Figure 4ODF OF WEB

Figure 5ODF OF FABRICS WITH DIFFERENT PRESSURES AND NUMBER OF PASSES

Orientation Angle (degree)

Freq

uenc

y (%

)

Left

Central

Right

different fiber orientation {Figure 5 (c)}, the fiber orientationbecome quite similar at high number of passes regardless ofjet pressure level {Figure 5 (d)}.

The results of the ODF explain why the fabric tensile strength

in MD is higher than that of the fabric in CD {Figures 2 (b) and(c) and Figures 1 (b) and (c)}. The behavior of fabric elongation atpeak load of Figures 2 (e) and (f) can be also explained in termsof the ODF. With increase in fiber orientation in the MD the fab-

42 INJ Summer 2003

(a) Mean Tensile Strength (27.6 bar)

Specific Energy (x103kJ/kg)

Nor

mal

ized

Mea

n Te

nsile

Str

engt

h (N

/cm

)

(b) Mean Tensile Strength (55.2 bar)

Specific Energy (x103kJ/kg)

Nor

mal

ized

Mea

n Te

nsile

Str

engt

h (N

/cm

)

(c) Mean Tensile Strength (82.7 bar)

Specific Energy (x103kJ/kg)

Nor

mal

ized

Mea

n Te

nsile

Str

engt

h (N

/cm

)

(d) MD/CD Ratio of Tensile Strength (27.6 bar)

Specific Energy (x103kJ/kg)

MD

/C

DR

atio

of

Tens

ile S

tren

gth

(e) MD/CD Ratio of Tensile Strength (55.2bar)

Specific Energy (x103kJ/kg)

MD

/C

DR

atio

of

Tens

ile S

tren

gth

(f) MD/CD Ratio of Tensile Strength (82.7 bar)

Specific Energy (x103kJ/kg)

MD

/C

DR

atio

of

Tens

ile S

tren

gth

Figure 6EFFECT OF BASIS WEIGHT AND CONVEYOR SPEED ON MEAN TENSILE STRENGTH

AND MD/CD RATIO OF TENSILE STRENGTH

99.6 gsm

56.9 gsm

99.6 gsm

56.9 gsm

99.6 gsm

56.9 gsm

99.6 gsm

56.9 gsm

99.6 gsm

56.9 gsm

82.7 bar

26.6 bar 55.2 bar

27.6 bar

55.2 bar582.7 bar

99.6 gsm, 4.57 m/min

56.9 gsm, 9.14 m/min

ric strength in MD increases and in the CD decreases. Thisbehavior is reversed for the elongation at peak load. The resultsof load-strain of Figure 7 support this explanation.

As discussed above, the average tensile strength in MD andCD of fabrics processed at jet pressure of 82.7 bar did notchange significantly with increasing number of passes (specif-ic energy) as it can be seen from Figure 2 (d). It seems that thespecific energy of two passes spent to form the fabric was highenough to provide the maximum entanglement for the givenexperimental parameters employed. Further energy (or pass-es) did not cause significant change in the degree of entangle-ment. Additionally, the first two passes caused the fibers tototally conform to the forming surface. It seems that at low jetpressure of 27.6 bar, 2 passes were not enough to provide thehighest degree of fiber entanglement. This is why furtherpasses under such low pressure causes additional entangle-ment and produced higher strength fabric than those pro-duced at higher jet pressures. The increase in number of pass-es causes the tensile strength to increase the degree of entan-glement until the threshold is reached. Further increase innumber of passes beyond the threshold did not cause anyincrease in tensile strength of the fabric.

The tensile behavior of the fabrics of trial 1 is significantlydifferent from that of trial 2 as it can be seen from Figures 1 (b),(c), and (d) and Figures 2 (b), (c) and (d). The difference is morepronounced for those fabrics processed at high jet pressure of82.7 bar. Fabrics of trial 1 produced at jet pressure of 82.7 barexhibited tensile strength values comparable to those pro-duced at jet pressure of 27.6 bar and 55.2 bar {Figure 1 (d)}.Fabrics of trial 2 produced at jet pressure of 82.7 bar are sig-nificantly weaker as compared to those produced at jet pres-sure of 27.6 bar and 55.2 bar {Figure 2 (d)}. The reason behindsuch behavior in tensile can be understood by observing the

images of Figures 3 (e)-(h). It is obviousthat the jet pressure of 82.7 bar causedthe fibers in light weight fabric {Figures 3(e) and (f)} to disintegrate thus causinglarge holes and extremely localized lightweight areas with few fibers holding thestructure together. This is not the casefor fabrics of higher basis weight{Figures 3 (g) and (h)}. For fair compari-son of tensile strength data of fabrics oftrial 1 and trial 2, the values of mean ten-sile strength were normalized based onthe their basis weights and the resultsare shown in Figure 6 (a), (b) and (c).Fabric basis weight has significant effecton the fabric tensile strength. Further,there is a significant interaction of fabricweight and jet pressure on fabricstrength. For the fabrics produced at27.6 bar, fabrics with lower basis weightare stronger than fabrics of higher basisweight {Figure 6 (a)}. This is reversed forfabrics produced at jet pressures of 55.2bar and 82.7 bar {Figure 6 (b) and (c)}.

Figures 6 (d), (e), and (f) show the effect of fabric basis weightand specific energy on the MD/CD ratio of tensile strength.The increase in the MD/CD with specific energy is obviousdue to increase in fiber orientation in MD with specific energy.

CONCLUSIONS1) While crosslapped web has a bi-modal ODF, hydro-

entangled fabrics have a uni-modal ODF due to fiberrearrangement caused by peeling the fabrics, which causedfabric stretch in MD, after each pass and the jet pressure.Increasing the number of passes caused more fiber orientationin the machine direction.

2) There exists threshold energy, after which, increasingpressure and number of passes can’t improve the fabricstrength and may damage the fabric strength due to introduc-ing weak links.

3) Basis weight and specific energy affect MD/CD tensilestrength ratio. Higher specific energy causes higher MD/CDstrength ratio.

4) There is a significant effect of jet pressure and fabric basisweight interaction on fabric strength. Our results indicate thattensile behavior of lighter fabrics is influenced by jet pressureand specific energy. The tensile properties of heavier fabric,however, are significantly affected by specific energy with noor little jet pressure effect. At low jet pressure, fabrics withlower basis weight are stronger than fabrics of higher basisweight. This behavior is reversed for fabrics produced at high-er jet pressures. Determination of minimum jet pressure thatprovides the highest strength for a given basis weight and thecritical values of basis weight/jet pressure at which the reversetakes place would be beneficial to industry to minimize theenergy cost of producing hydroentangled nonwoven fabrics.

43 INJ Summer 2003

Strain (%)

2 passes, MD2 passes, CD8 passes, MD8 passes, CD

Loa

d (

N)

Figure 7LOAD-STRAIN CURVES OF FABRICS (82.7 BAR)

ACKNOWLEDGEMENTThis work was supported by a grant from the Nonwovens

Cooperative Research Center, NC State University. Their gen-erous support of this project is gratefully acknowledged.

REFERENCES1. Berkalp, O.B., Pourdeyhimi, B., and Seyam, A.M., Texture

Evolution in Hydroentanglement, International NonwovenJournal, Vol 12, No. 1, pp 28-35, 2003.

2. Bertram, D., Cellulosic Fibers in Hydroentanglement,INDA Journal of Nonwoven Research, Vol 5, No 2, pp 34-41, 1993.

3. Connolly, T., and Parent, L., Influence of Specific Energyon the Properties of Hydroentangled Nonwoven Fabrics,Tappi Journal, Vol 76, No 8, pp135-141, 1991.

4. Gilmore, T., Timble, N., and Morton, G., HydroentangledNonwovens Made from Unbleached Cotton, Tappi Journal, Vol80, No 3, pp179-183, 1997.

5. Ghassemieh, E., Acar, M., and Versteeg, H.K.,Improvement of the Efficiency of Energy Transfer in theHydroentanglement Process, Composites Science andTechnology, Vol 61, pp 1681-1694, 2001.

6. Hwo, C., and Shiffler, D., Nonwoven from Poly(trimeth-ylene-terephthalate) Staples, The proceedings of the 10thAnnual TANDEC Conference, November 2002.

7. Morton, W.E. and Hearle, J.W.S., “Physical Properties ofTextile Fibers”, John Wiley, New York, 1975.

8. Pourdeyhimi, B., Dent, R., and Davis, H., MeasuringFiber Orientation in Nonwovens, Part III: Fourier Transform,Textile Research Journal, 67, 143-151, 1997.

9. Timble N, and Gilmore, T, Spunlaced Fabric Performancefor Unbleached, Bleached and Low Micronaire UnbleachedCotton at Different Specific Energy Levels of Water, TheProceedings of INDA-TEC, Crystal City, Virginia, September1996.

10. Timble, N., and Allen, C., Hydroentangled FabricPerformance for Polyester/Unbleached Cotton Blends atVarious Specific Energy Levels, The Proceedings of INDA-TEC, Crystal City, Virginia, September, 1996.

APPENDIXCalculation of Input Energy

Specific energies required to form the fabrics of both trialswere calculated from:

Where C = coefficient of discharge, dimensionless d1= inlet diameter, mmPg = gauge pressure, barN = number of jets per inch of manifoldPasses = number of passes acted on fabricsW = basis weight, g/m2

S = line speed, m/min — INJ

44 INJ Summer 2003