Daniela Negru, Cozmin-Toma Buda, Electrical Conductivity of Woven Fabrics Dorin Avram Coated with Black Particles

Gheorghe Asachi, Abstract Technical University of Iasi The aim of this work was to develop a fabric with electrical conductivity. This fabric Department of Technology was made from coated with a solution based on carbon black. This paper re- and Design of Textile Products ports the results of preparing different recipes using a number of quantities of carbon black Bd. D. Mangeron nr. 67, 700050 Iasi, Romania particles and other components of the coating mixture, which were tested in order to obtain E-mail: [email protected] the best results regarding electrical conductivity. The optimal concentration of conductive particles of carbon black was studied.

Key words: conductive fabric, carbon black, conductive yarns, electrical conductivity.

carbon black preserve the flexibility and filler in a coating solution is that the con- elasticity of the textile material to a great ductivity of the layer is in direct relation extent, which make them ideal for appli- with the quantity of carbon black from cation in electronic . Conductive the solution, thus the carbon black per- polymers/materials have interesting elec- centage determines the final destination trical properties and can be a replacement of the conductive textile fabric obtained. for inorganic materials [6]. The coating Conductive textile obtained using con- techniques are attractive due to their ductive materials can be used in heating process simplicity and easy handling. applications where parts of the body can The textiles produced not only gain elec- be heated, as well as in health care and trical properties but also maintain their military applications. excellent physical properties, such as mechanical strength and flexibility [7]. n Coating conductive materials on a textile Materials substrate can be made through chemical Coating solution materials oxidative polymerisation (polypyrrole), The conductive particles were in the electrospining (polyaniline) and the form of highly structured carbon black manual deposition of a solution (carbon powder, Printex L6, supplied by Degussa black). The choice of conductive material Corp. The characteristics given by the n Introduction is primarily determined by the final des- supplier are presented in Table 1. tination of the product obtained, by the Recently electrically conductive textiles textile substrate used, etc. The properties Disperbyk is an additive from BYK Ad- have been of increasing research interest of carbon nanotubes are very good elec- ditive, a member of ALTANA. DISPER- due to their numerous possibilities for trical and thermal conductivity, strength, BYK®-110, a copolymer with acidic application in various fields of activity. stiffness, toughness, and a low frictional groups, is a wetting and dispersing ad- Conductive fabrics represent potential coefficient. Due their unique properties, ditive for solvent-based coatings to im- application in clothing as well as in the CNTs are used as flexible strain sen- prove pigment wetting, reduce the time medical and military fields, as sensors, ac- sors and electromagnetic shields [7, 8]. required for the grinding process, and tuators, electromagnetic shields etc. Elec- Shields made of electrically conductive stabilise the pigment dispersion. The ad- troconductive textile fabrics for different textiles are light and have a considerably ditive reduces viscosity and improves the applications have been obtained through low cost in comparison with those made several methods, such as chemical coat- of metal sheets and wire . Howev- Table 1. Main characteristics of carbon ing, metallisation, electroless deposition, er, even though CNTs have outstanding black filler particles. the insertion of metallic yarns, and the electrical, mechanical, electromechanical deposition of thin layers containing con- and chemical properties, they are very Mean particle diameter, nm 18 ductive fillers such as carbon nanotubes expensive. As a solution, carbon black Structure (DBPA number) 122 Specific area, m²/g 250 (CNT) and carbon black particles (CB) particles were used to obtain conductive Volatiles, % <1 [1, 5]. The conductive materials used in fabrics, being less expensive and hav- order to obtain electroconductive fabrics ing good properties regarding electrical are conductive polymers like polypyr- and mechanical characteristics. Carbon Table 2. Main characteristics of Disperbyk. role, polyaniline, polytiophene, etc, as black particles have good electrical and Solution of a copolymer with Composition well as metal particles, carbon nanotubes thermal properties and may be used for acidic groups and carbon black particles. From an elec- coating a textile surface, the purpose be- Methoxpropylacetate / Solvents tric point of view, conductive polymers ing to obtain a heating fabric. The meth- alkylbenzene 1 / 1 exhibit properties similar to those of ods used for coating carbon black onto a Recommended 5 - 10% upon inorganic levels (additive pigments conducting metals, and coating a textile textile substrate can be coating, screen- as supplied) 2 - 4% upon dioxide Typical substrate with a conducting polymer by printing, hand painting, etc. The main Non-volatile matter: 52% polymerisation or applying a thin layer of issue using carbon black particles as the properties

Negru, D.; Buda, C.-T.; Avram, D. Electrical Conductivity of Woven Fabrics Coated with Carbon Black Particles. 53 FIBRES & TEXTILES in Eastern Europe 2012, 20, 1(90) 53-56. Table 3. Main characteristics of Kraton diameter. The fabrics were made using a IR0401 BU Latex machine.

Solids content, % 63 min Along with the cotton yarns, stainless pH 9.5 – 12 steel yarns (SS) were interlaced as weft Brookfield viscosity, cPs 150 max yarns and warp yarns, following a specif- Median particle size, μm 1.8 max ic pattern, which can be observed in Fig- T.A.M.C at drumming, CFU/ml 1000 max Odor neutral ure 1. Since an electroconductive can be considered as a combina- tion of parallel resistor connections that gloss and leveling of the coatings. The correspond to the resistivity of the characteristics given by the supplier are themselves and to the resistance between Figure 1. Cotton fabric with presented in Table 2. fibers [8], the pattern designed for SS was yarns in the structure. intended to decrease the electrical resist- ance by creating these parallel electrical Kraton IR0401 BU Latex is a water- one side of the fabric along its width in connections. sufficient quantity, and a metallic cylin- based emulsion of anionically polymer- der was positioned in front of the fabric, ized polyisoprene. The emulsion also n Experimental which means in front of the coating so- contains a non-staining antioxidant and a lution. When the device is on, the cylin- surfactant. It offers high tensile strength, In the first part of the experiment, a der advances with a certain pressure and low cohesive strength, high elasticity, coating solution was prepared using the covers the fabric with a thin layer. The solvent process, with the solution based durability, and softness, in addition to samples obtained were left to dry for on water. First a quantity of water was 24 hours at room temperature. which it is non-allergic and has specific introduced into a Berzelius glass along advantages such as light colour, consist- with the dispersant, Kraton was then Surface resistivity measurements were ency and low levels of impurities. The added drop by drop, and finally carbon performed using two electrodes placed characteristics given by the supplier are black particles, The mixture was stirred on the surface of the sample, The electri- presented in Table 3. continuously, and the time required for cal resistance (R) was measured using a this was around 30 min. The solution ob- multimeter (1906 computing multimeter, tained was left to rest for approximately TTI); the distance between the electrodes n Textile materials 2 hours at room temperature, and then it was 3 cm, and the width of the sample was applied onto a textile substrate using Cotton yarns with a fineness of 31.25 tex was also 3 cm. The measurements were a printing device. The covering principle performed according to the AATCC Test were used in a woven fabric of plain is as follows: the textile substrate was Method 76-1995. weave. The stainless steel yarns were laid on a magnetic table with the pattern 90.9/2 tex, 275×2 filaments of 12 μm above, the mixture was then applied on n Results and discussions Table 4. Electrical resistivity of fabrics coated with CB solutions. The experiments performed on fabrics from 100% cotton yarns with different Composition of the coating solution Electrical resistivity, σ (standard deviation), recipes of CB, Kraton, Disperbyk and CB, Kraton, Disperbyk, Water, CB, kΩ/sq kΩ/sq g g g g % water show the influence of the concen- 6.25 10.41 12.00 0.2087 tration of these components on electrical 7.50 25.00 12.5 12.50 10.50 0.1202 resistivity (Table 4). 8.75 14.58 8.00 0.100 16.25 22.00 13.65 4.25 0.0240 The results obtained show mainly the 18.75 25.0 14.28 2.75 0.0359 influence of the CB particle concentra- 12.50 13.56 1.25 0.0271 tion on the conductivity of the fabric. 11.00 18.18 2.00 0.1354 14.0 The values of electrical resistivity were 9.40 18.73 1.80 0.0517 high, and it was necessary to insert SS 14.20 20.0 17.79 1.60 0.0200 10 11.86 12.0 18.57 1.20 0.0160 yarns in the fabric in order to lower the 10.60 19.01 1.40 0.0180 electrical resistance and bring about an 13.40 16.27 2.10 0.0447 increase in electrical conductivity. The 13.0 20.40 14.62 4.80 0.0249 concentration of carbon black particles 12.57 25.0 15.98 2.40 0.0283 is very important for the completion of a 16.28 15.0 15.09 2.00 0.0726 conductive fabric, hence different recipes 19.16 14.46 3.40 0.0309 were tried and studied using a statistical program in order to obtain an optimum

Table 5. Numerical encoding of variables x1 and x2. coating solution.

Real Encoded -1.414 -1 0 1 1.414 The experimental data were obtained us- % CB X1 10.41 11.33 13.65 15.96 16.88 ing a program for the statistical process- % Dispersant X2 27.55 29.43 34.13 38.83 40.71 ing of data, TEXPRO 2, developed by a

54 FIBRES & TEXTILES in Eastern Europe 2012, Vol. 20, No. 1 (90) research team from the Textile Faculty of Table 6. Experimental matrix for the two variables x1 and x2. Iasi, Romania. The program TEXPRO x x 2 allows to obtain a statistical-mathe- No. of the 1 2 Y1 measured, Y2 measured, experiment KΩ/sq KΩ/sq matical model [10]. In this program we Real, % Encoded Real, % Encoded 1 15.96 +1 38.83 +1 1.25 0.019 consider the carbon black particles con- 2 11.33 -1 38.83 +1 8.5 0.250 centration and the concentration of the 3 15.96 +1 29.43 -1 3.2 0.018 rest of the components as independent 4 11.93 -1 29.43 -1 6.5 0.200 variables and the electrical resistivity as 5 10.41 -1.414 34.13 0 10.5 0.280 a dependent variables. Y1 is the electri- 6 16.88 +1.414 34.13 0 1.7 0.016 cal resistivity of a sample coated directly 7 13.65 0 27.55 -1.414 4.25 0.020 with carbon black solution and Y2 - the 8 13.65 0 40.71 +1.414 4.1 0.030 electrical resistivity of a sample with 9 13.65 0 34.13 0 4.25 0.025 stainless steel yarns inserted in the struc- 10 13.65 0 34.13 0 4.2 0.028 ture coated with a solution based on car- 11 13.65 0 34.13 0 4.15 0.025 bon black particles. For the two cases of 12 13.65 0 34.13 0 4.5 0.027 samples made from cotton yarns and cot- 13 13.65 0 34.13 0 4.35 0.035 ton yarns plus SS yarns, values of the en- coding variables are presented in Table 5. evolutions indicate that the influence of with CB solution and stainless steel yarns x1 is far greater than that of the x2 pa- in the structure, respectively. The experimental matrix and values of rameter on electrical resistivity. Actually the dependent variable obtained are pre- the influence of the 2x parameter on the The influence of the concentration of CB sented in Table 6. Y variable is minimal; the conclusion be- particles on electrical resistivity for dif- ing that the CB particle concentration is ferent values of the x2 variable for the Using the program TEXPRO 2, after test- decisive in order to obtain the decrease of two types of samples is presented in Fig- ing the significance of coefficients, two the electrical resistivity. ures 2 & 3, respectively. The values from regression equations were found: the diagrams are encoded , and the real of The linear part of the model has negative which can be found using Table 5. It has Y = 4.291 - 2.874·x - 0.02·x + 1 1 2 (1) regression terms, which indicates a de- to be mentioned that from the diagrams + 0.835·x 2 - 0.127·x 2 - 0.986·x ·x obtained only the values situated in the 1 2 1 2 crease in electrical resistivity values with interval were taken into account [-1.414; an increase in parameters x1 and x2. The Y2 = 0.027 - 0.098·x1 + 0.008·x2 + 1.414], with the outside values being (2) x1·x2 coefficient is the interaction factor + 0.069·x12 + 0.008·x22 - 0.012·x1·x2 theoretical ones assessed by the program and its value is small, which indicates in which the experimental values were From the study of the regression equa- that the interaction of the two factors x1 processed; some values of the electrical tions, some conclusions can be drawn: and x2 is not significant regarding the in- resistance are negative, probably due to the influence of the two independent pa- fluence on electrical resistivity (Y). Coef- regression equation errors. 2 2 rameters (x1 - the concentration of CB ficients 1x , x2 reinforce the conclusion particles and x2 - the concentration of that x1, x2 are parameters that have an in- According to the diagrams obtained, it other components) is different. The co- fluence on electrical resistivity. The mini- can be observed that the concentration of efficients of the linear term are 2.874(1) mal value of electrical resistivity (Y) for CB particles has the biggest influence on and 0.098(2), which are bigger in the the measurement made on textiles coated the electrical resistivity, which decreases absolute value than those of the linear directly with CB solution was 1.25 kΩ/sq with an increase in the CB particle con- terms which correspond to x2. These and 0.016 kΩ/sq for the textile coated centration. However, by studying the two

Figure 2. Variation in the electrical resistance of the sample coated Figure 3. Variation in the electrical resistance of the samples co- with carbon black particles. ated with carbon black particles with SS yarns in the structure.

FIBRES & TEXTILES in Eastern Europe 2012, Vol. 20, No. 1 (90) 55 graphs, we can see that the minimal value decrease in electrical resistivity; the con- of electrical resistance is 1.25 kΩ/sq for centration of the other components of the Technical University 15.96% The CB particle concentration coating material have less of an influence for the material coated with CB solution of Lodz on the electrical properties of the conduc- Faculty of Material is 0.016 kΩ/sq for 16.88% CB particle tive fabric obtained. concentration for the material coated Technologies with CB solution with SS yarns in the and woven fabric. An increase in CB particle Acknowledgments concentration up to these values does not The authors would like to thank to researcher Department cause a decrease in electrical resistivity. staff from Laboratoire de Génie et Matériaux Textiles (GEMTEX), Roubaix, France, whe- of Man-Made Fibres n Conclusions re the experimental part of this paper was carried out. The results show that both the fabric Research: coated with carbon black and that coat- The Department of Man-Made Fibres ed with CB with SS yarns inserted have References has more than 50 years of history electrical conductivity. 1. Kim, B.; Koncar, V.; Dufour, C. Poly- and experience in man-made fibres aniline-Coated PET Conductive Yarns: The main scientific interest of the De- The electrical properties of these con- Study of Electrical, Mechanical and partment can be divided into several ductive materials are influenced by dif- Electro-Mechanical Properties, Journal fields: ferent factors such as the carbon black of Applied Polymer Science, 2006, 5 Au- n composite interactive cellulose fi- gust, 101, 3, 1252–1256. concentration, and the insertion of con- bres based on NMMO, 2. Xue, P.; Park, K. H.; Tao, X.M.; Chen, n nanofibres from biodegradable ductive yarns in the fabric. The electri- X.Y.; Cheng, X.Y. Electrically conductive polymers, cal resistivity (kΩ/sq) decreases in the yarns based on PVA/carbon nanotubes, n advanced materials based on bio- interval [10.41, 15.96] increases in the Composite Structures, 2007, April, 78, 2, 271-277. degradable polymers for medical interval [15.96, 16.88] for the textile ma- and technical applications, terial coated with CB solution only, and 3. Dall Aqua, L.; Tonin, C.; Peila, R.; Fer- rero, F.; Catellani, M. Performances and n special fibres based on advanced decrease in the interval [10.41, 16.88] properties of intrinsic conductive cellu- polymers. for the textile material with SS yarns lose-polypyrolle textiles, Synthetic Met- The Department is equipped with ad- coated with CB solution. An increase in als, 2004, 20 October, 146, 2,, 213-221. vanced devices for spinning solution CB particle concentration from 10.41% 4. Yoshiyuki Show, Hironori Itabashi, Elec- preparation and fabrication of fibres to 15.96% causes a decrease in electrical trically conductive material made from and nanofibres by different methods CNT and PTFE, Diamond & Related resistivity from 10.5 kΩ/sq to 1.25 Ω/sq (melt state, dry-wet, wet spinning). Materials, 2008, 17, 602–605. in the first case and from 0.28 kΩ/sq to 5. Gasana, E.; Westbroek, P.; Hakuzi- 0.016 kΩ/sq in the second case (from mana, J.; De Clerck, K.; Priniotakis, G.; 10.41% to 16.88% CB particle concen- Kiekens, P.; Tseles, D. Electroconduc- Cooperation: tration). The results show the influence of tive textile structures trough electroless The Department is currently looking for partners from academia or industry. CB particles and other components of the deposition of polypyrolle and at solution on resistivity and set conditions polyaramide surfaces, Surface & Coat- ings Technology, 2006, 201, 3547-3551. in order to obtain a minimal electrical re- 6. Bohvon, K.; Koncar, V.; Devaux, E. Elec- sistivity, which causes an increase in the trical properties of conductive polymers: We offer: sample temperature. For a 15.96% con- PET-nanocomposites fibers, AUTEX The Department is equipped with var- centration of carbon black particles on Research Journal, 2004, March, 4, 1. ious devices for the determination of fabrics made from cotton yarns and for 7. Cochrane, C.; Koncar, V.; Lewandowski, the properties of fibres and polymers: M.; Dufour, C. Design and Development 16.88% concentration of carbon black n thermal analysis (TGA and DSC), of a Strain Sensor for Textile Structures n particles on fabrics made from cotton rheometers and devices to deter- Based on a Conductive Polymer Com- mine the melt flow rate, yarns with SS yarns in the structure, the posite, Sensors, doi: 10.339/7040473, n devices for determining the me- electrical resistivity was minimal. Taking 2007, 7(4), 473-492. chanical properties of fibres (e.g. 8. Aniooczyc, H.; Koprowska, J.; Mamrot, into account the values of electrical re- tensile tester), sistance of the samples, one of the appli- P.; Lichawska, J. Application of Electri- cally Conductive Textiles as Electromag- n spectrometers (FTIR, UV-vis), cations can be using them as detachable netic Shields in Phisyotherapy, FIBRES n optical microscopes. heating fabrics which can be embedded & TEXTILES in Eastern Europe, Octo- into clothing like jackets, gloves, etc. ber / December, 2004, 12 4 (48). These heating elements can be removed 9. Banaszczyk, J.; De Mey, G.; Schwarz, in the process of washing, which can be A.; Van Langenhove, l. Current Distribu- For more information please contact: an important factor regarding the stabili- tion Modelling in Electroconductive Fab- rics1), FIBRES & TEXTILES in Eastern ty of the electrical resistance; for keeping Department of Man-Made Fibres Europe, 2009, 17, 2 (73), 28-33. Technical Universiy of Lodz the elasticity and preventing the abrasion 10. Serbulescu, L.; Ciocoiu, M. Optimizarea ul. Zeromskiego 116, 90-924 Łódź, Poland of the conductive layer, on top of which Tehnologiilor de Prelucrare a Firelor Tip tel.: (48) 42-631-33-59 a protective layer from latex can be laid. Bumbac, Ed. Performantica Iasi, 2002, e-mail: [email protected] 89-110. web site: http://www.k41.p.lodz.pl/ In the end, we can say that increasing the CB particle concentration causes a Received 29.06.2010 Reviewed 20.04.2011

56 FIBRES & TEXTILES in Eastern Europe 2012, Vol. 20, No. 1 (90)