PL232097B1 - Method for obtaining electrically conductive textile materials, preferably for application in clothing products - Google Patents

Description

Description of the invention

The subject of the invention is a method of obtaining electrically conductive textiles, especially for use in clothing products.

The industry of the so-called intelligent textiles, also known as active, interactive or adaptive (smart and intelligent textiles and clothing) (Bartkowiak 2010, Mattila et al. 2006, Bendkowska 2002), which, when used in clothing products, create intelligent clothing.

Smart textile products can be divided into two groups:

• changing their properties under the influence of specific stimuli • electrically conductive and integrated with electronics.

The first group consists of textile products which change their physical properties under the influence of external stimuli (temperature, humidity, electric and magnetic fields, ultraviolet radiation - UV, infrared IR, pressure, pressure, stress). It can be, for example, a change in geometry, state of aggregation, emission of electromagnetic radiation, change in electrical resistance, change in stresses. Intelligent textiles use solutions in the form of fibers, yarns or electrically conductive coatings. The production of intelligent textiles consists in incorporating specific, active materials into a fiber material or modifying the surface of textile products in order to provide the textile products with the intended properties. Significant technologies in this group include, among others, phase change materials (PCM) available in the form of microcapsules, fibers, deposition (Bartkowiak 2012), shape memory materials available in the form of metal alloy wire, polymer deposition, gels (Wei Z, G et al. 2002., Chang CY 2001 et al., Gall K. et al. 2004, Hayashi S. et al. 2004) that can respond to changes in temperature values, electric, magnetic, pH and electroactive polymers responsive to the electric field. Another example are laminates or applications on textiles that emit light and change color depending on the outside temperature.

The second group are electrically conductive materials designed to transmit electrical signals in clothing, and the so-called e-textiles, the task of which is to give textiles an electrical or electronic function, including sensory, executive and signaling functions (Leśniowski 2013, Mattila 2010, Michalak et al. 2006). In Poland, this field was called textronics. The essence of textronics is the integration of sensors, energy sources, electronics, signal processing and communication within textiles and clothing to give it additional functions. In textronics, such areas of knowledge as chemistry, textiles, electronics, information technology and automation are used (Tęsiorowski et al. 2008, Michalak 2006). In their research, the authors focus on introducing electrically conductive elements into fibrous structures, including electrical circuits, piezoelectric elements in such a way that the obtained products do not differ visually from the currently used products without electronic properties (Skrzetuska 2014, Bendkowska 2002). However, not all electrical components can be made in a textile form (e.g. electrical converters, processors, MP3 players), which is why the so-called wearable electronics, where commercially available miniature electronic devices are used and placed in clothing. These are both mobile phones, players, computers, and specialized equipment for measuring environmental or user parameters (Skrzetuska 2014). Textronic components can be used to create wireless networks and systems for monitoring human physiological signals (Coyle 2009). Textronic elements of clothing can be used to monitor physical parameters and vital functions, such as: sub-clothing temperature, heart rate, respiratory rate (pneumography), without reducing the comfort of use and body performance (Walter et al. 2011, Coyle 2009, Scilingo et al. . 2005, Krucińska 2012). The respiratory rate is measured by recording the chest deformation, i.e. by measuring mechanical signals (Scilingo et al. 2005). Chest strains generate low-frequency signals that are measured using strain gauges and piezoelectric sensors.

Textronics is used not only for intelligent clothing, but also, for example, in car upholstery (Walter et al. 2011), equipped with sensors enabling the identification of the number of passengers in the car or monitoring the ECG parameters of the driver, especially monitoring the elderly. The fabric is made of, inter alia, electrically conductive carbon fibers (trade name Detect), used in the upholstery of the seats, it acts as a pressure sensor and signal transmitter

PL 232 097 B1 telling the car steering system how many people are in the car. This allows the on-board computer to adjust the suspension to the load. A similar material arrangement is used to create soft, flexible Qwerty keyboards (Bartkowiak 2010).

The above solutions, apart from being used in accessories and sportswear, to monitor the user or in everyday situations, to provide him with entertainment functions (iPod), also play a role in protecting people and improving their safety in the work environment. This applies especially to positions where high physical activity is required, where there is stress and the risk of dangerous factors, e.g. thermal factors. In such conditions, miniaturization and integration of electronics with clothing can eliminate difficulties in performing activities related to the use of traditional electronics, e.g. in the form of large, uncomfortable measuring devices. Intelligent textiles are used in specialized protective products, including protective clothing. In the last ten years, projects aimed at the development of smart clothing monitoring the user or the environment, including protective clothing, have been carried out under national programs and in the European framework programs.

The following projects can be mentioned as an example of research work:

• l-protect “Intelligent PPE system for personnel in high-risk and complex environments, which aimed to develop advanced personal protective equipment (PPE) to provide information and support to workers operating in high-risk environments including firefighters, chemical rescuers and mine rescuers. The project involved the integration of chemical sensors with clothing, and the use of heart rate sensors with the use of optical fibers, • PROETEX E-Protective Textiles - systems made of textile micro and nanostructures for use in disaster conditions' - the project incorporates miniature sensors (temperature, respiratory rate, heart rate) in clothing products, • WearlT @ work, in which the computer system is built into the clothing product, • My Heart - the project uses sensors to monitor the heart rate and is connected to the monitoring system and integrated with the clothing product in in the form of a T-shirt, • BioTex - biochemical sensors were used to analyze and monitor body fluids and placed in clothing, • Stella - Stretchable Electronics for Large Area Applications - the project uses sensors to monitor the heart rate, blood saturation, temperature, • Context - in the project was used in b sensors for recording electromechanical changes in muscles (myography) and sensors for monitoring the frequency of heart contractions successfully in clothing, • Ofseth - an attempt was made to develop sensors made of polymer optical fibers to monitor the heart rate and respiration rate as part of the fabric.

In the Polish project carried out by the Lodz University of Technology, TUL and CIOP-PIB, clothing for emergency services, e.g. firefighting units, with implemented electronic microcircuits enabling the monitoring of the physiological parameters of the clothing user and the level of threats was developed (Owczarek 2007). The purpose of this garment was to control the physiological condition of the firefighter, taking into account the environmental conditions and the degree of effort during work (energy expenditure and the resulting load on the body). In another project carried out by TUL, which was a continuation of the work, a safe firefighter's outfit was developed, equipped with a network of functional sensors monitoring the physiological condition of the firefighter. The produced T-shirt is equipped with sensors for measuring the heart rate, respiratory rate and temperature at the skin. The respiratory frequency was measured with a piezoresistive textile sensor consisting of 5 sensors located together with a temperature sensor in the waist at the level of the chest.

The aim of the works described above was to increase the safety of people in everyday life and in the work environment. This applies in particular to changing conditions and unknown hazards of the work environment, where according to Directive 89/656 / EEC [Directive] on the minimum safety and health requirements for the use of personal protective equipment by workers at work, workers should use personal protective equipment. Unfortunately, all the developed technologies are not mature enough to be put into production. In the mentioned projects, where traditional sensors are used, commercially available or developed textronic sensors, there is a problem of connecting them with each other, as well as with the power source,

PL 232 097 B1 with a measurement and control system or a communication module. In projects, traditional sensors were connected with traditional wires (laminated in waterproof foil) or with electrically conductive yarns woven into the fabric structure or embroidery made with electrically conductive threads.

Techniques of imparting electrically conductive properties to textiles

In order to develop intelligent materials, various techniques are used to give textiles an electrically conductive function in terms of connecting elements such as sensors, actuators (actuators - materials that change one form of energy into another, usually mechanical), transistors, and a current source. On the one hand, the technique of integrating or combining existing electrical or electronic devices with textiles is being used, and on the other hand, new technologies are being developed to develop textile-based electrical or electronic devices. The basis for the creation of such structures is the development of textile electrical circuits. It is not easy due to numerous technological limitations, especially in the field of combining electronic and textile components. The following is an overview of developments in the development of electrically conductive textiles, including flexible electrical circuits. Application of electrically conductive materials to non-textile materials.

Conventional printed circuits are multi-layer structures that form an array of conductive conductors on a non-conductive substrate. The most commonly used printed circuit boards are glass-reinforced phenolic or epoxy resins with a copper layer. Plates are etched by photolithography or by means of an electron beam. These traditionally printed circuits are rigid. In the last decade, a technology has been developed to produce flexible electronic circuits and circuits, made with the use of commonly known printing methods such as screen printing, offset or inkjet printing. It offers the possibility of cheap and easy printing of electrical circuits as an alternative to commonly used etching or semiconductor circuits. Using techniques used in the printing industry, it is possible to produce electronic circuits on flexible substrates, including foils. Using these techniques, it is possible to create not only printed circuits in the form of electrically conductive tracks, but also circuits with electronic passive elements (e.g. resistors).

Various coatings are used to impart electrically conductive properties to the films. These can be electrically conductive polymers such as: polyacetylene, polyphenylene, polyphenylene vinyl, polypyrrole, polythiophene, polyaniline (Kinal 1998, Oh 1999, Mattila 2010). In the polymers mentioned, chains containing TT double bonds ensure high mobility of electrons inside the molecule and easy removal or delivery of an additional electron, i.e. the formation of a charge carrier. Unfortunately, the above-mentioned polymers are characterized by low electrical conductivity, having values of the order of 10 ^-6 -10 ^-9 S / cm in the dark. Doping them with such substances as, for example, AsF5, SbF3, AlCh, ZrCl4, MoCI5 causes an increase in their conductivity by several orders of value, reaching the level characteristic for metals in some cases. As a result of doping, complexes with a portable electric charge are formed, which show the independence of conductivity from temperature or an increase in conductivity with a decrease in temperature (Leszkowski 2010).

Nanoparticle additives are also incorporated into non-conductive polymers to render them electrically conductive. The most common are:

• metals (silver, copper) and metal compounds;

• carbon particles: fullerenes, carbon nanotubes (single, double or polyhedral), graphite.

In this way, polymer nanocomposites are created, i.e. dispersions of solid particles with sizes in the order of nanometers in a polymer matrix. Due to the size of nanoadditives and their extremely developed surface, effects are created that are not observed in traditional composites. Even a small addition of nanofiller, in the amount of 3 wt.%. up to 5 wt.% it is often sufficient to change the electrical properties as well as mechanical (increased tensile strength), thermal (increased thermal resistance) and optical properties.

A new form of carbon that has been obtained on a larger scale and used as a nanoadditive to the polymer is graphene. In the last five years, a method of producing graphene has been developed, including monatomic, diatomic or several-atom layers of epitaxial graphene on smooth substrates and graphene in the form of flakes by chemical methods (Park 2009) or ultrasound from graphite. The development of methods for the production of graphene by chemical methods on a larger scale created the possibility of its wider application. Graphene is characterized by unique properties, i.e. high value

Electrical conductivity, for graphene flakes: Rs = 0.081 Ω / m ^2, and thermal conductivity (Gallego et al. 2011). Therefore, it is considered an electronic material that can replace silicon. It is also used in the construction of supercapacitor covers (Linh et al. 2011, Stoller 2008) and Fet transistors (Kang et al. 2011). Moreover, graphene as an element of composites gives the composites increased mechanical resistance. Depending on the effects you want to achieve, graphene flakes, graphene oxide or graphene oxide enriched with carboxyl groups are used. In order to make polymers electrically conductive, the best results are obtained when graphene flakes are incorporated into the polymer (Jakubowska 2012).

Worldwide, work is underway on applying electrically conductive graphene layers on foil in order to produce transparent electrically conductive foils that can combine the functions of electronics and a display (e.g. a tablet in the form of a foil) (Jakubowska 2010).

Polymer composites containing carbon fillers have proven their worth in flexible sensors made, inter alia, by printing techniques (Jakubowska 2013, Moon 2008).

At the Department of Thick Film Materials at the Institute of Electronic Materials Technology (ITME), preliminary work was carried out to develop pastes containing carbon nanomaterials to be applied to the material by screen printing (Jakubowska 2010, 2011, 2012).

Pastes with the content of multiwall carbon nanotubes (MCWNT-multiwall carbon nanotubes) and graphene nanoflakes (GNP) were developed (Janczak et al. 2013). Carbon nanotubes with a diameter of 10-160 nm and a length of 0.5-5 μm and graphene flakes with an average size of 15 μm and thickness up to 10 nm were used. The nanomaterials suspended in toluene with the addition of dispersants were subjected to the sonication process in order to break the agglomerates, and after evaporating the toluene, the filler material was added to a solution of polymethyl methacrylate (PMMA) or polyvinylidene fluoride (PVDF) in butyl carbitol acetate (OKB).

The process of preparing a paste consisting of a composition of nanoflakes or nanotubes with a polymer carrier was aimed at breaking the agglomerates of carbon filler, homogenizing the distribution of nanomaterials in the matrix, ensuring repeatability of the mechanical and electrical properties of the layers applied by screen printing technology. After premixing in a mortar, the paste was rolled twice on a three-roll mill with silicon carbide rolls. The paste was printed on a polymer film and then cured at the temperature of 120 ° C for 30 minutes. Pastes were produced with different contents of multi-wall carbon nanotubes: 0.25% wt, 0.5% wt, 1% wt, 2% wt MCWNT and graphene nanoflakes: (1.5 - 2) according to% GNP. The average thickness for all printed resistive layers was 10 µm. The measurements showed a decrease in surface resistance with an increase in the percentage of carbon filler in the polymer composite. At the same time, it was found that the PMMA support allows obtaining layers with a lower surface resistance than PVDF for pastes with a comparable filler content. Layers with a resistance of approx. 120 kΩ / □ were obtained for pastes 1.5 by% GNP / PMMA, 2 by% GNP / PVDF, 0.5 by% CNT / PVDF. After carrying out mechanical fatigue tests on the resistive layers, excellent adhesion of the printed surfaces to the polymer film and minimal changes in the surface resistance not exceeding 5% were found.

In other studies of resistive layers containing multi-wall carbon nanotubes (MWCNTs) in a PMMA polymer matrix and using butyl carbitol acetate (OKB) as a solvent, the authors drew similar conclusions. The resistance of the paste deposition on the polyester film decreased with the increase of MWCNT share. The obtained resistances were in the range of 2.1 (ki2 / m ² ) for 2 wt% MWCNT to 44.7 (ki2 / m ² ) for 0.25 wt% MWCNT (Janczak 2013, Słoma et al. 2013).

After the bending resistance tests of the material, the minimal change of the surface resistance from 11.87 Ω / ο for new material to 11.93 Ω / ο after 61500 bending cycles was demonstrated.

In other studies, as part of the cooperation between ITME and the Warsaw University of Technology, the following three conductive inks were developed to be sprayed onto the material (Słoma 2012): ink with carbon nanotubes, ink with graphene flakes (GNP), paste-based ink with silver particles.

Ink containing carbon nanotubes

Double-walled carbon nanotubes (DWCNT) from Cheap Tubes Inc. were used to develop the ink. with a purity of 60 wt.%, dimensions 2 to 4 nm and a length of less than 50 μm. As a solvent, butyl carbitol acetate was used. The carrier, which was polymethyl methacrylate, was gradually added to the mixture of carbon nanotubes with solvent until an ink was obtained which did not sediment for 72 hours. The carbon nanotube ink finally developed had the following

The composition is: 0.308% DWCNT (double-walled carbon nanotubes), 0.025% PMM (polymethyl methacrylate), 99.667% OKB (butyl carbitol acetate). The ink layers were applied to a polyester film substrate with an airbrush feed pressure of 0.2 MPa and a spray distance of about 100 mm. The layers were then dried at 120 ° C for 1 h.

Graphene Flake Ink (GNP)

The graphene flake ink is based on graphene nanoflakes commercially acquired from Cheap Tubes Inc. The layers of graphene can agglomerate by joining together, one layer on top of the other. Graphene nanoflakes may consist of multiple graphene layers (Yasmin 2004, Serena 2012). In the development of the carcass to spray application is used nanopłatków graphene type C (GNPC) having an average thickness of 10 nm, an average size of 15 pm and a surface area of about 100 m ² / g. The layers of the developed ink were applied at a pressure of 0.5 MPa at a distance of 100 mm from the substrate, and then cured at 120 ° C for 20 minutes. It was found that the uneven distribution of graphene flakes in the polymer matrix and the lack of a preserved bond between the flakes resulted in lower electrical conductivity of the polymer.

Paste-based ink with silver particles

Another material used in the development of the spray inks was the PALMIX I silver particle paste, which contained silver nanopowders obtained at the Institute of Electronic Materials Technology by thermal decomposition of silver salts of fatty acids. The dimensions of the nanopowders ranged from 15 to 20 nm. The nanosilver ink consisted of 1 g of PALMIX I silver particle paste (200 ° C, 1h 30 ') and 1.4 g of butyl carbitol acetate. The silver ink was sprayed (pressure 0.5 MPa, distance 100 mm) onto the substrate, and then dried at 120 ° C for 1 hour. After drying, the samples were fired at 300 ° C for 1 hour.

The produced layers with silver particles showed a sheet resistance between 0.7 and 0.8 kΩ / m ² . The layers containing carbon nanotubes had a surface resistance in the range of 2 to 7 kO / π, while the layers of graphene nanoflakes had a surface resistance in the range of 35-52 kO / π. The developed inks were used on a foil base, they were not used on textile bases, because their purpose was to impart electrically conductive properties to the transparent foil. This type of deposition can be used on membranes laminated with a textile material or directly on textile materials.

The spray application method can be used when there is a need for layers with a thickness smaller than those made by screen printing.

Applying electrically conductive layers to textiles

In order to give textiles an electrically conductive function, especially to form electrically conductive paths, conductive or non-conductive polymers are applied to the textiles, followed by removal (etching, reduction or physical removal of conductive materials from selected regions. Another method is the method of applying electrically conductive polymers using a mask. that an electrically conductive pattern is produced on the textile, similar to printing on flexible film (de Angelis et al. 1995, Kuhn et al. 1987, Slade et al. 2002).

De Angelis developed a method of applying a non-conductive polymer to a non-woven or knitted fabric and then applying an electrically conductive polymer to this substrate using a mask (de Angelis et al. 1995). In this way, he obtained designed electrically conductive fragments on a flexible textile substrate.

Instead of applying electrically conductive polymers to the substrate, they can be synthesized directly on the material or fiber (Kuhn et al. 1987). In Kuhn's work, the material or fiber was immersed in a liquid polymer solution and a coating of electrically conductive polymer was formed on the surface of the material in the presence of an oxidizing agent. This process can be used to form electrically conductive circuits on fabrics.

Adams and colleagues described yet another technique for making an electrically conductive material. They applied a thin layer of electrically conductive polymer to the fabric and then removed the polymer from selected places with a high pressure water jet (Adams 1990). A more precise method was used by Gregory et al. (Gregory 1990). A layer of doped electrically conductive polymer (polypyrole) was applied to the fabric and then a reducing agent was applied to selected areas of the fabric. A change has been achieved in places where a reducer is used

The conductivity of the material. The reducing agent was used in selected places at different concentration values, at different times and at different temperature values. In this way, a material with inhomogeneous electrical conductivity was obtained.

Another technique for the production of electrically conductive textiles is the technique of applying an electrically conductive material to the fibers from which the yarn is made and then the fabric. Akbarov and his team used nickel deposition on PAN (polyacrylonitrile) fibers. The fibers were soaked in NiCl2 and COCl2 and then dried for 20 min in 413K. (Akbarov 2005). Tsukada and his team used a similar method. An electroconductive polyelectrolyte, poly (3,4-ethylenedioxythiophene) poly (styrene sulfonate) (PEDOT-PSS) was electrochemically bonded to the silk yarn. After adding glycerol, an additional increase in electrical conductivity was obtained from 0.00117 S / cm (resistance 2.62 Mohm / cm) to 0.102 S / cm (20.6 kohm / cm) (Tsukada 2012).

Guo Ronghui in his doctoral dissertation developed a method of applying copper and nickel layers to polyester fabric. The fabric was chemically nickel plated (electroless electroplating) in NiSO4 (Ronghui 2010). A similar method was used by Schwarz and his colleagues who covered para-aramid fibers with copper in their research. Copper shows good adhesion to polypyrole, therefore a layer of polypyrole was applied to the fiber and then a layer of copper. As the time of application increased, the thickness of the copper layer increased and the resistance of the fibers exponentially decreased (Schwarz 2012). Other works also used the application of polypyrrole to textile fabrics followed by metal particles (Dall'Acqua et al. 2004, Kim 2004, Boutrois 1997).

In order to develop electrically conductive materials for intelligent textiles, work is also undertaken on the application of electrically conductive materials to textile substrates using the method of magnetron sputtering [Ziaja 2008, Nowak et al.].

In the work, Nowak et al. Created copper electrically conductive tracks using the magnetron sputtering technique on a substrate made of a spun-bounded polypropylene nonwoven fabric with an area weight of 50 g / m ² and a thickness of 0.5 mm. The authors were not able to obtain an electrically conductive path with a resistivity of less than 50 Qm / m and a width of less than 4 mm. Moreover, it has been found that the metal layer is not as flexible as the textile substrate, so it is damaged by slight movements of the substrate. As shown in the literature (Parka et al. 2007), the use of copper deposition on textiles is at risk, as copper is thermodynamically unstable under atmospheric conditions.

The literature review shows that in the research, electrically conductive materials were also applied by screen printing. In the work of Kazani et al. [Kazani 2012], pastes with silver particles (Electrodag PF 410 by Acheson and 5025 by DuPont) were applied on fabrics with different raw material composition (cotton, viscose, polyamide, polyester, cotton / polyester blends and viscose / polyester). The authors found that the resistance of the obtained deposition depended on the textile substrate. For one type of paste, different resistances were obtained on different substrates. It was also found that each of the pastes had a different distribution on the materials. Moreover, it was found that the resistance / π of the paste on the fabric is much higher than that declared by the manufacturer, which may be due to the fact that the paste penetrates the fabric structure and the value given by the manufacturer relates to measurements on a flat and smooth substrate. The authors also investigated the resistance / π of deposition after simulation of use, i.e. after abrasion and washing. After the cycles of abrasion with woolen fabric, a relative change in resistance / π was found from 14% to 579%. After the washing cycles, a significant increase in the resistance / π was also found. In order to protect the application against damage due to abrasion or washing, the authors used a coating of thermoplastic polyurethane with a thickness of 80 μm, which allowed to obtain for two out of eight materials no change in resistance after washing.

The literature reports presented above show how much work was carried out to develop electrically conductive textiles for use in intelligent clothing. However, to assess their suitability for use in textronic systems, it is necessary to perform not only resistance or resistance / π tests, but also to check these deposition in practical application in the form of electrically conductive paths in an electric or electronic system, depending on their purpose and current load.

Transmission lines

With regard to the use of electrically conductive paths, their electrical parameters are very important. The requirements for lines intended for constant or slowly changing currents are different, e.g. for power supply lines, and other requirements for lines transmitting high-frequency signals, e.g.

PL 232 097 Β1 computer data buses, high-frequency signal lines to textile antennas. (Krucińska et al. 2008), lines transmitting signals in the USB 3.0 standard. (Leśniowski 2013).

In the case of DC lines or slow-changing signals, when designing such a line, its electrical resistance and electrical loadability are important, expressed as the maximum current that can be transmitted through the line without the risk of damaging it due to the generated heat. This is related to the maximum allowable current that can be sent through the power line. Lines with high thermal load capacity can be used in clothing with textile heating systems (Kurczewska et al. 2008, Leśniowski 2013) in the form of flat textile products made of electrically conductive resistance yarn or electroconductive resistance coatings.

For a line transmitting high-frequency signals, one of the basic parameters of a signal line is its wave impedance (characteristic). For a lossless line, it is expressed as:

where:

L - unit line inductance,

C - unit line capacity.

In the real signal line, there are losses in series resistance of electrically conductive elements, losses in series resistance of conductive elements and dielectric losses due to the existence of a conductance G of less than infinity. For such a line, the impedance is expressed by the formula:

Z _c ¹ R + jcoL

G + jcoC where:

R-series unit resistance of the conducting part of the line,

G - unit dielectric conductance, ω - pulsation in rad / s.

The electrical parameters (R, L, G, C) of the designed transmission line are influenced by the electrical properties of the materials and the geometric configuration. Changes in these quantities along the length of the line affect its wave impedance and cause the appearance of uneven wave impedance along the signal line. This has a major impact on the quality of the electrical signal transmission over the line. The unevenness of the wave impedance leads to reflection of the transmitted wave and overlapping with the traveling wave and this may cause a strong distortion of the transmitted information and even the inability to transmit it.

An important parameter characterizing the transmission properties of the line is the propagation constant y.

y = -J (R + jaL) (G + jaC) = a + pj

The actual value of the propagation constant is the factor a, (attenuation factor), the value of which determines the attenuation of the signal transmitted over the line. The greater the value of a and the longer the signal line, the greater the variation in the amplitude of the transmitted wave after passing through the line.

As a standard, a characteristic impedance of 50 Ω is assumed for transmission lines. Measurements of the electrical parameters of textronic signal lines for various designs of these lines are described in the literature. Cottet and colleagues (Cottet 2003) tested various transmission lines made of copper wire fabric covered with polyesterimide insulation and twisted with polyester yarn. The developed lines differed in the number of ground paths (from 1 to 2) and signal paths (from 1 to 3). After measuring the wave impedance for a textile line 15 cm long, a significant difference was found between the measured value and the reference value Z _c = 50 Ω. Results ranging from 120 Ω to 320 Ω were obtained. Moreover, it has been found that the value of the wave impedance decreases with increasing the number of signal paths. This causes significant signal attenuation. This was confirmed by the conducted tests of attenuation depending on the signal frequency. The line frequency response in (-3 dB) shall not exceed 1 GHz. In order to prevent distortion you should then

The use of matching circuits between the signal line and the source, and between the signal line and the receiver of the transmitted signal, makes the design of the signal system very difficult.

In turn, in the research of Pourdeyhimia and colleagues, three types of electrically conductive pastes were applied to the surface of the nonwoven fabric by screen printing (Pourdeyhimii 2006). The pastes from different manufacturers Creative Materials, Du Pont 50025 and DuPont 509, differed in viscosity and surface tension. The pastes characterized by higher viscosity showed greater stability of line impedance over time, but also greater susceptibility to damage. The impedance value of the developed lines was also well above the intended value of Zc = 50 Ω. It was also found that depending on the type of paste, different accuracy of the line paths execution is obtained, and this affects the value of its impedance.

The literature review presented above shows that despite the conducted many studies in the field of the development of electrically conductive textiles and attempts to make transmission lines, there are still many unsolved problems of applying the developed solutions in practice in intelligent clothing.

The biggest problem is connecting electronic components with electrically conductive textiles. It is very difficult to obtain permanent connections with appropriate resistance, resistant to mechanical effects (Stęplewski 2013). The most commonly used methods are the use of metal naps or stitching elements with electrically conductive threads. At the Lodz University of Technology, a project was implemented in which electrically conductive adhesive tapes were developed for use in textronic systems (Zięba et al. 2012), but they are not available in the commercial offer. Moreover, they can be used in specially designed systems.

Another problem is the precision of applying electrically conductive paths. When applying the methods of applying electrically conductive layers to the entire material and then removing selected electrically conductive parts, it is difficult to achieve the precision of applying electrically conductive tracks. It is also very difficult to obtain the resistance of the textile transmission line to maintenance cycles and mechanical operations, especially when applying metal particles to the textiles by the magnetron method. The results are inflexible and very little resistant to mechanical effects. Moreover, as it results from the literature, limitations in the width of the electrically conductive paths were observed with this method of applying the electrically conductive material. Good results in terms of low resistivity of the material after abrasion and washing were obtained when applying electroconductive pastes by screen printing and securing them with another layer of thermoplastic polyurethane. Unfortunately, the authors made plots on a large plane and did not make electrically conductive paths. Therefore, their current-carrying capacity has not been assessed, which, with low resistances in combination with cotton, viscose and polyester substrates, does not seem to predict high resistance to current flow. The literature review also shows that the application of one variant of the application on various textile substrates with different weaves, weft and warp densities brings results in the form of different / π resistances and resistance to use, and the effect cannot be predicted without testing.

The method of obtaining electrically conductive textiles, especially for use in clothing products, consists in plasticizing the ethylene-octene copolymer by mixing, and then adding the filler in the form of electrically conductive carbon black with a grain size of 10-210 nm in the amount of 15-30 parts. by weight per 100 parts by weight of rubber or silver particles with a size of 1.5-5 µm in an amount of 25-50 parts. by weight per 100 parts by weight of rubber and mixing is continued, and then optionally one ionic liquid selected from the group: 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium chloride in an amount from 2 pg. wt. up to 3 pcs. wt. for 100 parts by weight of rubber and re-mixed until a homogeneous mixture is obtained. The mixture thus obtained is rolled and formed into sheets. In the case of mixtures containing no ionic liquid, they are extruded after the rolling process to form the desired sheets in the extruder head. The sheets obtained are cut into strips, laid on the fabric in the desired pattern and vulcanized with the fabric.

P r z k ł a d

Materials used

The aim of the attempts to use this polymer was to obtain flexible composites mechanically resistant, primarily to bending and abrasion, so that they could be used in products

PL 232 097 Β1 for clothing. The fillers described below were used to impart electrically conductive properties to the polymers. The materials described below were used.

Polymer

The following were used as the polymer:

• ethylene-octene copolymer (EOR) - without cross-linker, trade name: Engage 8150, degree of crystallinity: 27%, viscosity acc. To Mooney (ML (1 + 4) 121 ° C): 16, manufacturer: The Dow Chemical Company, USA

Fillers

The following fillers were used, i.e. electrically conductive particles:

• electrically conductive carbon black, • silver particles,

Table 1 shows the designations and characteristics of the fillers used.

Table 1

Designations of the electrically conductive fillers used

Ident. The filler Type of filler Particle size and Electrically conductive carbon black (Printex) (10 - 210) nm c Silver particles (Silver flake AX20L) (1.5-5) pm (mean 2.5 pm)

IONIC LIQUIDS:

> ionic liquid 1 (hydrophobic) 1-hexyl-3-methylimidazolium hexafluorophosphate [PF6] [hmim] manufacturer: Sigma Aldrich> ionic liquid 2 (hydrophilic) 1-butyl-3-methylimidazolium hexafluorophosphate [PF6] [bmim] manufacturer: > ionic liquid 3 (hydrophilic) 1-butyl-3-methylimidazolium chloride [Cl] [bmim] manufacturer: Sigma Aldrich

TEXTILE MATERIALS

Fabric was used as a textile material

The compositions of the developed polymer films for vulcanization with textile materials

In order to make polymer films for vulcanization with textiles, two series of polymer blends, differing in the type of fillers, were developed. Done:

• in the first series, polymers with the addition of electrically conductive carbon black; • in the second series, polymers with the addition of silver particles

20 variants of mixtures with the addition of carbon black and 8 mixtures with the addition of silver were made. Within each group, different blend compositions were used: i.e. different filler content, additives in the form of ionic liquids. Alternatively, the method of extrusion of the polymer was used.

The compositions of the blends are given below.

MIXTURES WITH THE ADDITION OF ELECTROCONDUCTIVE SOOT

Table 2 shows the composition of polymer blends with the addition of electrically conductive carbon black.

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Table 2

Composition of polymer blends from ethylene-octene copolymer without crosslinking unit with the addition of electrically conductive carbon black, ionic liquids and with the use of the extrusion process

Designation of the mixture EOR [phr] PRINTEX [phr] DCP [phr] Ionic liquid 100 15-30 0 No ionic liquid 100 15-30 0 Liquid 1 100 15-30 0 Liquid 2 100 15-30 0 Liquid 3 100 15-30 0 No ionic liquid, extrusion process

MIXTURES WITH ADDED SILVER PARTICLES

Table 3 shows the composition of the polymer blends with the addition of silver particles.

Table 3

Composition of polymer blends from ethylene-octene copolymer without cross-linker with the addition of silver, ionic liquids and using the extrusion process

EOR [phrl Silver [phr] DCP [phrl Ionic liquid 100 25 - 50 0 No reference ionic liquid 100 50 0 Liquid 1 100 50 0 Liquid 2 100 50 0 Liquid 3 100 50 0 No ionic liquid, extrusion process

Technology of producing electrically conductive polymers, polymer films and vulcanizates Below is a description of the preparation of polymer blends

Level 1

The polymer blends were prepared with the use of a laboratory mixer by Brabender GmbH & Co. KG.

First, the polymer itself was plasticized for about 5 minutes, then an appropriate amount of filler was added and mixing was continued for another 5 minutes. The last step was adding the ionic liquid where applicable and further mixing for a further 5 minutes to homogenize the mixture.

Mixer parameters:

Chamber volume: V = 80 [cm ³ ];

Torque measuring range: 0-200 [Nm];

Rotor Rotation Ratio: 2: 3;

Heating medium: paraffin oil;

Sample weight: 70-80 [g];

Temperature: 333 [K];

Time of mixing: 10 [min.];

Time for making the mixture - 15 minutes.

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Stage 2

The polymer blends prepared with method 1 were then standardized and formed into sheets with a thickness of approx. 3 mm using a laboratory rolling mill.

Rolling mill parameters:

> rollers length L = 450 [mm];

> roll diameter D = 200 [mm];

> width of the gap between the rolls: 1.5-3.0 [mm];

> rotational speed of the front roller: Vp = 16 [rpm];

> friction: 1.0 - 1.2;

> average temperature of rolls: 300 [K];

Mixing time - 15 minutes.

Stage 3 optional when there is no ionic liquid

Extrusion of selected polymer blends

After the rolling process, selected polymer mixtures were extruded on a Lab-Station Plasti-Corder N50 laboratory micro-extruder by Brabender GmbH & Co. KG. The extrusion process consisted in plasticizing the mixture with screws, and then the mixture was directed to the extrusion head, forming the desired shape of the extrudate under pressure. A characteristic feature of this process is the possibility of obtaining pomace with an oriented structure.

Thin strips were cut from the rolled mixtures. The feed to the extruder with raw material was carried out as evenly as possible. After extrusion of one blend was completed, pure polymer was placed in the feed port and the next blend was extrusion. A head with a rectangular mouthpiece was used. During the extrusion of the mixtures, the rotation speed was adjusted in the range of 25:45 rpm in such a way that the pressure and temperature inside the head did not exceed the limits indicated below. The extrudates were made in accordance with the ASTM D 2233 standard

Extruder parameters:

• screw diameter: 19 mm;

• screw length: 190 mm;

• ratio of the length of the screw to its diameter (L / D): 10;

• maximum torque: 150 Nm;

• maximum working temperature: 300 ° C;

• maximum mass pressure: 700 bar;

• production capacity 0.5: 5 kg / h;

Vulcanization of mixtures - preparation of polymer-fabric composites

Vulcanization

Preparation of polymer-fabric composites was made in a rectangular form placed between electrically heated shelves of the PW-1 Hydraulic Press, with dimensions of heating plates - approx. 200 x 150 mm, clearance between heating plates - approx. 100 mm, number of ironing shelves - 2 pcs.

Conditions of the conducted process:

> temperature of heating plates: 160 ° C;

> pressure between the plates (in the mold) - 100 - 130 Bar;

> time spent in the form: 30 minutes;

Electrical properties test results

Methodology of measuring surface resistance

The four-point measurement method was used to measure the surface resistance of electrically conductive tracks / materials. Four electrodes were used in the measurements, placed in one axis at equal distances from each other.

The current was supplied by two external electrodes, while the two internal ones were used to measure the voltage. This allowed to eliminate the resistance of the wires between the meter and the electrode.

Each of the electrodes was embedded in a cylindrical plastic and contained a spring in its structure to ensure even pressure to the substrate.

In order to eliminate the influence of the pressure and the angle of electrode application to the substrate on the measurement result, a structure stabilizing the position of the electrodes was made. In a sheet of acrylic glass, using a laser plotter, four holes with a diameter of 7 mm (adjusted to the diameter of the measuring electrodes) were cut at a distance of 9 mm.

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There are electrodes in the holes, to which the wires for connecting the multimeter are soldered. The whole thing was secured with one more layer of acrylic glass and screwed together, which allowed to place a weight on it in order to ensure constant pressure on the electrodes.

During the measurement, a constant pressure was applied using a weight of 1.25 kg. Measurements were made with two Keithley sourcemeter2420 multimeters in a climate of 25 ° C, 45% relative humidity.

The results of the surface resistance tests

Table 4 below shows the results of measurements of the surface resistance of the obtained polymer coatings.

Table 4

The results of the surface resistance tests of the elaborated electroconductive coatings.

Sample determination The composition of the polymer mixture Resistance value Rs EOR / carbon black-Printex / llq 1 15 4.5 kO 2 15 / [PF6] [hmim] 2.5 kO 3 15 / [PF ₆ ] [bmim] 6.4 kO 4 15 / [CI] [bmim] 3.4 kO 5 15 embossing 6.1 kD 6 twenty 2.3 kO 7 20 / [PF6] [hmim] 1.5 kO 8 20 / [PFe] [bmim] 2.0 kO 9 20 / [CI] [bmim] 1.2 kO 10 20 embossing 3.1 kO 11 25 1.7 kO 12 25 / [PF6] [hmim] 1.2 kO 13 25 / [PF ₆ ] [bmim] 1.3 kO 14 25 / [CI] [bm and m] 1.0 kQ 15 25 extrusion 2.8 kO 16 thirty 1.5 kO 17 30 / [PF6] [hmim] 692 ohms 18 30 / [PF ₆ ] [bmim] 1.2 kO 19 30 / [CI] [bmim] 962 Ω twenty 30 extrusion 1.7 kO EOR / Ag / llq 21 25 / [PF6] [hmim] 23 GO 22 25 / [PF ₆ ] [bmim] 26 GO 23 25 / [CI] [bmim] 24 GO 24 50 1.2 ΜΩ 25 50 / [PF _e ] [hmim] 1.4 kO 26 50 / [PF _e ] [bmim] 50 kQ 27 50 / [CI] [bmim] 19GQ 28 50 embossing 110 ΚΩ

Mark:

EOR - ethylene-octene rubber PRINTEX - conductive carbon black Ag - silver llq - ionic liguid / ionic liquid

Claims (1)

Patent claim 1. The method of obtaining electrically conductive textiles, especially for use in clothing products, characterized in that the ethylene-octene copolymer is plasticized by mixing, then the filler in the form of electrically conductive carbon black with a grain size of 10-210 nm is added in the amount of 15-30 parts. by weight per 100 parts by weight of rubber or silver particles with a size of 1.5-5 μm in the amount of 25-50 parts. by weight per 100 parts by weight of rubber and mixing is continued, and then optionally one ionic liquid selected from the group: 1-hexyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium chloride in an amount from 2 pg. wt. up to 3 pcs. wt. for 100 parts by weight of rubber and remixed until a homogeneous mixture is obtained, then the mixture obtained in this way is rolled and formed into sheets, and in the case of mixtures without ionic liquid, they are extruded after the rolling process, forming the desired sheets in the extruder head, the resulting sheets are cut into strips , it is arranged on the fabric in the desired pattern and vulcanized with the fabric.