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Electrical resistance of jute needle-punched non-woven fabric – effect of punch density, needlepenetration and area densitySurajit Sengupta a & Anindita Sengupta ba Mechanical Processing Division, National Institute of Research on Jute & Allied FibreTechnology , Kolkata , Indiab Department of Electrical Engineering , Bengal Engineering and Science University ,Shibpur , IndiaPublished online: 05 Jul 2012.

To cite this article: Surajit Sengupta & Anindita Sengupta (2013) Electrical resistance of jute needle-punched non-wovenfabric – effect of punch density, needle penetration and area density, The Journal of The Textile Institute, 104:2, 132-139,DOI: 10.1080/00405000.2012.699940

To link to this article: http://dx.doi.org/10.1080/00405000.2012.699940

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Electrical resistance of jute needle-punched non-woven fabric – effect of punch density,needle penetration and area density

Surajit Senguptaa* and Anindita Senguptab

aMechanical Processing Division, National Institute of Research on Jute & Allied Fibre Technology, Kolkata, India;bDepartment of Electrical Engineering, Bengal Engineering and Science University, Shibpur, India

(Received 28 June 2011; final version received 31 May 2012)

The electrical resistance of jute needle-punched non-woven fabric has been studied. Statistical model using centralcomposite rotatable experimental design is developed for electrical resistance depending on the three importantparameters of needled non-woven fabric, i.e. punch density, depth of needle penetration and mass per unit area.From this model and its contour diagrams, the effects of different parameters can be understood on electrical resis-tance of those fabrics. Prediction of electrical resistance can be made knowing the values of independent parame-ters. The correlation coefficients between observed and predicted values are found to be significant in all thecases. As depth of needle penetration increases for a particular punch density, electrical resistance increases andafter reaching to maximum, it decreases having optimum at about 140 punches/cm2 and 12mm depth of needlepenetration. With the increase of area density, resistance decreases. As punch density increases for a particular areadensity, resistance increases for high needle penetration.

Keywords: central composite rotatable experimental design; electrical resistance; jute; needle-punched non-wovenfabric

Introduction

The electrical resistance of an object is a measure ofits opposition to the passage of a steady electrical cur-rent. The resistance of an object determines theamount of current through the object for a givenpotential difference across the object. In accordancewith Ohm’s law, I =V/R where R= resistance in ohm,V= potential difference across the object in volts andI= current in ampere.

For a long time, different textile materials are usedas insulator. From the ancient age, the conductive wireis wrapped with cotton or silk yarns for insulation(Priestley, 1777). The use of textile material has beenreduced with the extensive use of synthetic polymersand also with the reduction in the cost of insulation.But there is enough scope of using textile material asinsulator, where heat is generated in the conductor as itcan melt the polymer insulator. Specially designed tex-tile material can also be used as gloves, jackets (apron)for electrical work or as floor covering in the roomwhere high voltage electrical appliances are kept.

The measurement and understanding of electricalresistance of textile material is complex in nature. Forthe textile material, (i) uniform cross-section is not

achievable and impractical, (ii) it can absorb or des-orbs moisture in the atmosphere and (iii) its structureis not uniform and depends on the processing parame-ters. Hence, it is expected that the electrical resistanceof the textile material vary with raw material and itsconstruction parameters.

Some electro-physical properties of textile sampleshaving different forms and raw material compositionswere studied by Asanovic, Mihajlidi, Milosavljevic,Cerovic, and Dojcilovic (2007). For determining theelectric resistance, a measuring device, based on themeasurement of direct current through textile samples,was developed. The dielectric loss tangents and relativedielectric permeability were measured for some of thetextile samples tested. The dielectric properties weremeasured using specially designed capacitance cells.Hains, Fris, and Gordos (2003) tested electrostaticproperties of polyurethane coated textiles used for pro-tective clothing. Gonzalez, Rizvi, and Crown (1997)proposed mathematical modelling of electrostatic pro-pensity of protective clothing systems. Ghosh and Dha-wan (2006) and Dhawan, Ghosh, Seyam, and Muth(2004) reported the developments in the field of elec-tronic textiles, focusing on the current state-of-the-art

*Corresponding author. Email: ssg_42@rediffmail.com

The Journal of The Textile Institute, 2013Vol. 104, No. 2, 132–139, http://dx.doi.org/10.1080/00405000.2012.699940

Copyright � 2013 The Textile Institute

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of electro-textile products and the research being car-ried out in this field.

Jute dominated the world market as packagingmaterial, carpet backing and industrial textiles till thesynthetic material came into competition. In search ofdiversified uses of this fibre, successful attempts havebeen made to use this natural and ecofriendlytechnical fibre in the field of geotextile, floor covering,filtration, etc. (Ganguly & Samajpati, 1996).

Mechanically entangled needle-punched non-woven fabric, produced by penetrating barbedneedles into an open fibrous mat, is essentially athree-dimensional network of fibres enclosing smallair pockets. The needle-punched non-woven fabricmade of jute may be used as floor covering,underfelt, air filtration medium, geotextile, thermalinsulation medium, etc. Punch density (i.e. numberof needle punches per unit area), depth of needlepenetration (i.e. the distance of the needle pointpasses through the fibre assembly) and mass perunit area of jute needle-punched non-woven fabricare the parameters which have significant effect ondifferent properties (Ganguly et al., 1997, 1999;Sengupta et al., 1999, 2005) of fabric. No work isavailable so far regarding the effect of these param-eters on electrical behaviour of jute needle-punchednon-woven fabric.

In this study, an attempt has been made to measurethe electrical resistance of different jute needle-punched non-woven fabrics to understand the effect ofpunch density, depth of needle penetration and areadensity on the electrical resistance of fabric using cen-tral composite rotatable experimental design. It willhelp to design technical textiles out of jute needle-punched non-woven fabric, where electrical resistanceproperty is required.

Materials and methods

Materials

Tossa jute of grade TD3 (Indian Standards Specifica-tions [IS 271], 1975) was used to prepare needle-punched non-woven fabric, having the fibre propertiessuch as linear density, 2.08 tex; tenacity, 32.30 cN/texand extension at break, 1.60%.

Methods

Selection of the useful limits of the variables

The significant independent variables of jute needle-punched non-woven fabric with respect to differentproperties, namely punch density, depth of needle pen-etration and mass per unit area, were identified. Theuseful limits of the three variables stated above wereselected based on the information available in litera-tures (Ganguly et al., 1997, 1999; Sengupta et al.,1999) and also by conducting a number of preliminaryexperiments. The limits and the actual and coded val-ues of different factors are given in Table 1.

Developing the design matrix

To determine the effects of factors (variables) on theresponse parameter, it was decided to use the statisti-cal technique called central composite surface designto develop the design matrix. The matrix so developedwas a 20 point central composite design which con-sists of a full factorial design 23 (8) plus six centrepoints and six star points. The 20 experimental runsthus allowed the estimation of the linear, quadraticand two-way interactive effects of the various factorson fibre properties. The design matrix so developedwith coded values of the factors is given in Table 2.

Fabric preparation

Jute reed (in this form jute is extracted after rettingand supplied to industry) was subjected to softeningtreatment with 2% jute batching oil-in-water emulsionand then processed in a breaker card. To make juteneedle-punched non-woven fabric, the breaker cardsliver was fed to Dilo non-woven plant comprising aroller and clearer card, a camel back cross-lapper andneedle punching machine (model number OD II/6).Twenty samples as per the design matrix (Table 2)were prepared using five levels of punch density,depth of needle penetration and mass per unit area.

Measurement of electrical resistance

A circuit for measuring current–voltage characteristicsof textile material has been setup according to

Table 1. Actual and coded values of different factors.

Symbol

Code

Factor �1.682 �1 0 +1 +1.682

Punch density (punches/cm2) X1 80 114.5 165 215.5 250Depth of needle penetration (mm) X2 8.6 10 12 14 15.4Mass per unit area (g/cm2) X3 309.6 437.5 625 812.5 940.4

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Figure 1. It consists of sample holder (S), variac (B),rectifier unit (D), Ammeter (A), Voltmeter (V) and10MΩ discrete resistance (R). Two bulldog clips areused between which sample is kept (Figure 2) withgauge lengths 1, 2.54, 5.08 and 10.16 cm. The sampleis in series with a known resistance (10MΩ) and isconnected to a DC power supply. The voltage is var-ied from 80 to 220V in five steps and correspondingcurrent through the sample is measured after 10s tocalculate the resistance. The measurement is done in27 °C and 65% relative humidity. Five sets ofvoltage–current readings are taken for plotting V–Icharacteristic curves. The slope (voltage/current) foreach V–I characteristic is determined.

Development of statistical model

Proposed polynomial. To correlate the effects of fac-tors and the response, the following second-order stan-dard polynomial was considered (Devies, 1978)

y ¼ b0 þ b1x1 þ b2x2 þ b3x3 þ b11x21 þ b22x

22 þ b33x

23

þ b12x1x2 þ b13x1x3 þ b23x2x3;

where y represents the response and b0, b1, b2, …and b23 are the coefficients of the model.

Figure 2. Sample and its holders.

Figure 1. Set-up for measurement of resistance.

Table 2. Constructional details of experimental fabrics.

SampleNo.

Experimentalrun order

Needling density(punches/cm2)

Depth of needlepenetration (mm)

Mass per unitarea (g/m2)

Resistance at230V (mega-ohm)

Resistance at 80V(mega-ohm)

1 4 1 1 1 1200 16002 11 �1 1 1 308 3643 9 1 �1 1 1200 16004 15 �1 �1 1 274 2865 2 1 1 �1 950 11436 10 –1 1 �1 438 5717 3 1 �1 �1 1754 26678 7 �1 �1 �1 1200 13339 17 1.682 0 0 912 114310 1 �1.682 0 0 814 88811 16 0 1.682 0 356 44412 19 0 �1.682 0 877 133313 13 0 0 1.682 1629 160014 20 0 0 �1.682 543 80015 5 0 0 0 1060 133316 18 0 0 0 1036 123117 6 0 0 0 970 114318 14 0 0 0 991 106719 12 0 0 0 894 100020 8 0 0 0 829 1000

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Evaluation of coefficients of model. The coefficientsof main and interaction effects were determined byusing the standard method (Cochran & Cox, 1963).The regression coefficients of the proposed model fordifferent parameters can be calculated.

Correlation between observed and calculated value.The correlation coefficients between the observed val-ues and the predicted values by proposed model areshown. It illustrates a very good correlation.

Checking and adequacy of models. The analysis ofvariance (ANOVA) technique was used to check theadequacy of the developed models. Accordingly,F-ratios of the developed models were calculated for95% level of confidence and then compared with thecorresponding tabulated values. If the calculated val-ues of F-ratio do not exceed the corresponding tabu-lated value, then the models are considered adequate.The tabulated value of F-ratio at 95% confidence levelis found to be 5.05. For this purpose, the F-ratio isdefined as follows:

F-ratio = Lack of fit (mean square)/Error (meansquare)

Table 3 shows the ANOVA of the proposed model.

Results and discussion

Table 2 shows the values of dependable parameters,i.e. resistance in mega-ohm obtained from the testingat 230 and 80V. To establish the relationshipsbetween the independent and the dependent vari-ables, regression analysis was done. The regressioncoefficients (Table 4) were used in the quadraticproposed polynomial for the determination of pre-dicted response values. The correlation coefficientsbetween the observed values and the predicted val-ues by proposed model illustrate a very good corre-lation (Table 5). The values of the calculatedcorrelation coefficient are much higher in all thecases than the standard value of correlation coeffi-cient (i.e. 0.444) at 5% level and 18 degree of free-dom (Chambers, 1958). It indicates that observed

values of needle-punched non-woven fabric has areal degree of association with the predicted valuesof the fabric.

The significance of the effect of the variables wastested by F-ratios (Table 3). These quadratic equationswere also used to arrive at possible combinations foreach assessment and the respective response usingthese values. The contour diagrams were plotted tostudy the effect of variables on the responses (Figures3–5).

The regression coefficients (Table 4) have a valueeither positive or negative and accordingly, have aneffect on the experimental results. For a variable tohave a significant effect, its coefficient must be greaterthan twice the standard error and marked in bold dig-its. However, the non-significant coefficients shouldnot be eliminated altogether.

The effects of variables or interaction of variableson resistance in mega-ohm at 230 and 80V can effec-tively be interpreted and explained by regression coef-ficients and contour plots. The information availablefrom contour diagrams regarding the interactions ofparameters on electrical resistance is very much usefulto design a jute needle-punched non-woven fabric forvarious applications.

Effect of depth of needle penetration

Figures 3(a) and 3(b) show the contour diagrams ofresistance at 230 and 80V with respect to area den-sity and depth of needle penetration for punch den-

Table 3. ANOVA results.

Parameter 1st order term 2nd order term Lack of fit Error F-ratio p

d.f. 3 6 5 5 – –Resistance at 230V SS 2,152,436 614,581 154,723 38,409 4.03 .076212

MS 2,152,436 614,581 30,945 7682Resistance at 80V SS 3,619,061 926,983 350,706 89,466 3.92 .077156

MS 3,619,061 926,983 70,140 17,893

Note: df, degree of freedom; SS, sum square and MS, mean square.

Table 4. Regression coefficients of the model.

Coefficients 230V 80V

b0 961.423 1123.563b1 87.514 105.220b2 176.295 271.126b3 �344.775 �424.758b11 �21.361 �4.964b22 �108.531 �49.772b33 57.330 60.224b12 199.849 295.455b13 93.979 80.738b23 �9.464 �104.978

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sity 200 punches/cm2. As depth of needle penetrationincreases for any particular area density, electricalresistance increases. Literatures [8–11] show thathigher the depth of needle penetration, higher is thecompactness (bulk density) of fabric due to strongfibre peg formation as more number of fibres arearranged vertically. Furthermore, as density increases,chance of fibre breakage increases especially for rigidand inextensible jute fibre. Therefore, higher vertical

rearrangement of fibres (as fibre orientation has agreat effect on resistance observed from machine andcross direction of fabric, Sengupta & Sengupta,2012) and higher discontinuity (breakage) of fibresare responsible for increase of resistance. Figure 3(a)and 3(b) show that the resistance value for 80V isalways higher than 230V for any particular combina-tion of area density and needle penetration. Forohmic material, resistance remains constant with the

Figure 3. (a) Effect of needle penetration and area density on electrical resistance for 200 punches/sq cm with 230V and (b)200 punches/sq cm with 80V.

Table 5. Correlation coefficients between the observed values and the predicted values by proposed model.

Parameter Calculated correlation coefficientCorrelation coefficient at 5% level and

18 degree of freedom Remark

Resistance at 230V 0.967 0.444 SignificantResistance at 80V 0.914 0.444 Significant

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increase of voltage as current also increases propor-tionately with voltage. But with jute non-wovenfabric, current is not increasing proportionately andhence resistance decreases.

Figure 5(a) and 5(b) show the contour diagram ofresistance at 230 and 80V with respect to punch den-sity and needle penetration for area density 500 g/m2.As depth of needle penetration increases for a particu-lar punch density, resistance initially increases andafter reaching to maximum it decreases. The optimumreaches at about 140 punches/cm2 and 12mm needlepenetration. The increase in resistance is due to highervertical rearrangement and breakage of fibres whereasin high depth of needle penetration, all the fibres arearranged and inter-linked in such a way that their dis-crete nature does not exist due to strong inter-fibrecontacts in consideration with electrical behaviour and

most of the fibres are contributing towards electricalconduction. Hence, resistance decreases. Figure 5(b)shows the higher value of resistance and the optimumreaches at about 100 punches/cm2 and 12mm needlepenetration.

Effect of area density

Figure 3 shows the contour diagram of resistance at230 and 80V with respect to area density and needlepenetration for punch density 200 punches/cm2. Asarea density increases for a particular needle penetra-tion, resistance decreases. This is due to increase inthe amount of jute fibre in the fabric cross-sectionwhich increases the conductivity. Figure 4(a) and 4(b)also show the similar effect of area density on resis-tance for fixed punch density.

Figure 4. (a) Effect of punch density and area density on electrical resistance for 13mm needle penetration with 230V and(b) with 80V.

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Effect of punch density

With increase of punch density for a particular areadensity, resistance increases (Figure 4). According toFigure 5, as punch density increases for particular nee-dle penetration, resistance decreases for low needlepenetration, but it increases for high needle penetra-tion. Literatures [8–11] show that higher the punchdensity, higher is the bulk density of fabric due tohigher number of fibre peg formation (verticalarrangement of fibres). As density increases, chance offibre breakage increases for jute fibre. These are

responsible for increase of resistance. In low needlepenetration, the fibre web density is very low andhence, the increase in punch density increases theinter-fibre contacts resulting in decrease in resistance.The optimum resistance is appeared at 140 punches/cm2 for 230V and 100 punches/cm2 for 80V.

Confirmation of model

A needle-punched non-woven fabric of 500 g/m2 hasbeen prepared separately with 220 punches/cm2,

Table 6. Predicted and tested values of test sample.

Predicted value Tested value Accuracy, %

Resistance at 230V, mega-ohm 1221.6 1189 +97.26Resistance at 80V, mega-ohm 1465.5 1490 �98.36

Figure 5. (a) Effect of punch density and needle penetration on electrical resistance for 500 g/m2 with 230Vand (b) with 80V.

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12mm depth of needle penetration using the sameset-up and parameters of machines. Then the testedand predicted (using proposed model) values ofresistances at 230 and 80V (Table 6) show a goodagreement. This confirms that the proposed model isacceptable.

Conclusion

(1) Second-order polynomials have been proposedwith a good correlation for electrical resistanceof jute needle-punched, cross–laid, non-wovenfabric with respect to punch density, depth ofneedle penetration and mass/unit area. Fromthis model, one can understand the effects ofdifferent parameters on electrical resistanceand can also predict the resistance approxi-mately knowing the values of factors orparameters.

(2) The information available from contour dia-grams regarding the interactions of parameterson resistance is very much useful to design ajute needle-punched non-woven fabric insulatorfor electrical applications.

(3) As depth of needle penetration increases forany particular area density, electrical resistanceincreases.

(4) With the increase in depth of needle penetrationfor a particular punch density, resistance ini-tially increases and after reaching to maximum,it decreases. The optimum reaches at about140 punches/cm2 and 12mm depth of needlepenetration for 230V.

(5) The resistance value for 80V is always higherthan 230V for any particular combination of areadensity, needle penetration and punch density.

(6) As area density increases for a particular needlepenetration or punch density, resistancedecreases.

(7) With the increase in punch density for a partic-ular area density, resistance increases.

(8) As punch density increases for particular needlepenetration, resistance decreases for low needlepenetration but it is reversed in case of highneedle penetration.

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