Electrical Properties of Textile Fiber

Md. Nazmul Ahshan Sawon
Department of Textile Engineering,
BGMEA University of Fashion and Technology
Email: n.a.sawon0007@gmail.com

Introduction:
Textile materials have the inherent ability to store electric charges. “Electrifiability” means the ability of a clothing to generate and retain an electrostatic field of significant strength for a relative long time. The interest for investigation of the electrical properties of the textile fiber was generated with the use of fibers as insulating materials. Later, the resistance and capacity methods were used in instruments to determine the moisture content and the irregularity of the fiber assemblies. Applications of conductive textiles are more and more numerous in technical areas and cater to functions such as heating, conduction, or EMI shielding, prevention of static charges build-up. Most of the textile and plastic materials are electrical insulators. They accumulate electrostatic charge, which causes problems such as severe shock, fire, dust accumulation, etc. during processing. The electrical conductivity is required to dissipate the charges and use of fibers blended with conductive type of fibers prevents such risk. Low and limiting electrical conduction is required in many practical applications such as electromagnetic shielding, electrostatic elimination, conveyor belts, aviation/space suits, dry filtration, carpets etc. For this purpose, various products having reasonably good electrical conductivity are required. This can be obtained by incorporating metal fillers or coating with some agent. The textile materials being flexible and easily workable are the most preferred one in such cases.

Textile Material
Resistivity is a feature of the raw material. It is known the electrical resistivity of a material is an intrinsic physical property, independent of the particular size or shape of the sample. Resistivity of flat textile material can be different. The electrical resistance of textile material depends on the arrangement of fibers and yarns in textiles makes them, in the majority of cases, not homogeneous and anisotropic products. It also depends on the geometrical dimensions of the sample and on its structure. Surface resistance required to determine the surface resistivity of textile material depends on measurement technique, in particular electrode arrangement on sample surface.

The fabric contains fibers with a coating such as nickel which is stable against corrosion and has a good shielding value. The woven fabric contains 15 g of pure nickel per square meter. The technology combines highly conductive and corrosive resistant nickel with woven fabric provides to good surface resistance. Moreover the manufactured electro conductive fabric is flexible and durable. The potential applications of the textile material are: filters, shielding rooms, antennas, gaskets and components to medicine applications. Microscopic image of woven fabric taken with Olympus microscope was captured at 7.5× magnification.

What is Fiber?
Fiber or fiber (from Latin: fibra) is a natural or man-made substance that is significantly longer than it is wide. It is defined as one of the delicate, hair portions of the tissues of a plant or animal or other substances that are very small in diameter in relation to their length. It is a material which is several hundred times as long as it’s thick.

Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate fibers, for example carbon fiber and ultra-high-molecular-weight polyethylene.

Synthetic fibers can often be produced very cheaply and in large amounts compared to natural fibers, but for clothing natural fibers can give some benefits, such as comfort, over their synthetic counterparts.

What is Textile Fiber?
Textile fiber has some characteristics which differ between fibers to Textile fiber. Textile fiber can be spun into a yarn or made into a fabric by various methods including weaving, knitting, and braiding, felting, and twisting. The essential requirements for fibers to be spun into yarn include a length of at least 5 millimeters, flexibility, cohesiveness, and sufficient strength. Other important properties include elasticity, fineness, uniformity, durability, and luster.

Types of Textile Fiber:
Generally two types of textile fiber:

Natural fiber.
Manmade fiber.

Fig: Types of Textile Fiber Flow Chart (Click on Image for large size)

Natural Fiber:
Natural fibers include those produced by plants, animals, and geological processes. They are biodegradable over time. They can be classified according to their origin.

A class name for various genera of fibers (including filaments) of:

Animal (i.e., silk fiber and wool fiber);
Mineral (i.e., asbestos fiber);
Vegetable origin (i.e., cotton fiber, flax fiber, hemp fiber, jute fiber, and ramie fiber).

You may also like: Difference between Natural Fiber and Man Made Fiber

Manmade Fiber:
It is also known as manufactured fiber. Synthetic or man made fibers generally come from synthetic materials such as petrochemicals. But some types of synthetic fibers are manufactured from natural cellulose; including rayon, modal, and the more recently developed Lyocell. A class name for various genera of fibers (including filaments) produced from fiber-forming substances which may be:

Polymers synthesized from chemical compounds, e.g., acrylic fiber, nylon fiber, polyester fiber, polyethylene fiber, polyurethane fiber, and polyvinyl fibers;
Modified or transformed natural polymers, e.g., alginic and cellulose- based fibers such as acetates fiber and rayon fiber; and
Minerals, e.g., glasses. The term manufactured usually refers to all chemically produced fibers to distinguish them from the truly natural fibers such as cotton, wool, silk, flax, etc.e.g: Glass fiber.

Properties of Textile Fiber:
We saw three types of properties according to the fiber properties for a textile fiber. There are a lot of characteristics in the textile fibers. But it is characterized as three basic characterizations.

They are:

Physical properties,
Chemical properties
Mechanical properties of textile fiber.

A. Physical Properties:

1. Fiber length:
In physical properties the most important is the fiber length on which the quality of yarns depends. For cotton if fiber length increases the quality of yarns will be good, but this is just opposite for wool. In jute the fiber length is too long that sometimes the fibers are cut into small pieces.

Fig: Fiber length (Different Staple Length )

If the fiber length is too small it is difficult to produce yarn. Yarn is impossible if the fiber length is less than 0.5 inch. Thin fibers produce thin yarn and coarse yarn is produced from coarse fibers.

There are two types of fiber on the basis of length:

Continuous / filament
Staple fiber

Continuous / filament
Long and continuous fibers are called filament. Filaments are continuous in length which can be used as such form or cut into shorter staple fiber form. These fibers are collected from both natural and artificial source. Any natural fiber can be made into a filament. When only one filament is used in a yarn then it is called mono filament. When more than one filament are used in yarn then it is called multi filament.

Mono filament → 1.5 holes in spinneret.
Multi filament → 10-100 holes.

Staple fiber
When the length of fiber is short then it is called staple fiber. Stable fibers are manly shorter in length and related to natural fiber. All-natural fibers without silk can be collected as staple fiber. Artificial fibers also collected as staple fiber.

Staple fibers are three types on the basis of length:

Short staple: Length is less than 2 inch.
Medium staple: Length is from 2-4 inch.
Long staple: Length is more than 4 inch.

2. Strength
The capacity of a fiber to support a load is known as fiber strength. The strength is described as tenacity. Tenacity = Strength/ linear density.

It is expressed as CN/Tex or N/Tex. The tensile strength is commonly described as the force required to reach break the increase in the length before breaking is known as extension.

3. Elasticity
It is the property to recover from deformation. The fiber may be elastic or plastic which depends upon fiber condition and surrounding environment.

4. Flexibility
Flexibility is that property to resist repeated bending and folding.

5. Cohesiveness
It is the ability of the fibers to cling together during spinning depends on crimp and twist. In natural fiber the property comes from nature but in artificial fiber this property is given by crimping.

6. Fineness
The term fineness describes the quality of a fiber. By this, we know how fine a fiber is. It is expressed by the terms count, tex, denier, tex per unit length etc.

1 Tex = 1 gm/1000m.
1 denier = wt. in gm/900m.

Fineness affects some fiber properties. Such as yarn count, yarn strength, yarn regularity etc.

7. Cross section
The cross section of a fiber determines the physical properties of fiber. It gives idea about strength, fineness that varies from fiber to fiber. The cross-section shape of a fiber is important because it contributes to the surface appearance of the fiber. It helps to give properties of luster, bulk and body of the fibers, yarn and fabrics. It has effect in twisting, bending or shunning.

8. Crimp
It refers to the waves or bends that take place along the length of a fiber. It increases cohesiveness and resilience, resistance to abortion and gives increased bulk or warmth to fabrics. It also helps fabrics to maintain their softness or thickness, increase absorbency and show contact comforts bid reduces luster. A fiber may have one of the three types of crimps. Namely – Mechanical crimp, natural crimp or Inherent crimp and Chemical crimp.

9. Resiliency
It is the property of a fiber, which enables it to recover from certain load or stretch over a period of time.

10. Toughness
The ability of a fiber to endure large permanent deformations without rupture is called toughness.

11. Work of rupture
The area below the stress –strain curves provides a measure of the work required to break the fiber. It is called work of rupture and it commonly expressed in CN/Tex.

12. Appearance
It is expressed by length, fineness, cross-section cleanness and luster of a fabric. Generally short fibers are bulky and loss lustrous.

13. Density
The density indicates the mass per unit volume. The specific gravity of a fiber indicates the density relative to that of water at 4 degree Celsius.

14. Elongation
It is the ability to be stretched, extended or lengthened. Elongation vary at different temperatures and when wet or dry.

B. Mechanical Properties:

Tensile Properties.
Flexural Properties.
Torsional Properties.
Fictional Properties
Electrical Properties

1. Tensile Properties
Tensile properties indicates how a material will react to the forces being applied in Tension. Fibers usually experience tensile loads whether they are used for apparel or technical structures. Their form, which is long and fine, makes them some of the strongest materials available as well as very flexible. This book provides a concise and authoritative overview of tensile behavior of a wide range of both natural and synthetic fibers used both in textiles and high performance materials.

2. Flexural Properties
Flexural properties is one of the mechanical properties of textile material. It is the property or behavior shown by the fiber or material when we bend it. The importance of Flexural properties is required when we wear cloth. The flexural test measures the force required to bend a beam under three point loading conditions. The data is often used to select materials for parts that will support loads without flexing. Flexural modulus is used as an indication of a material’s stiffness when flexed.

3. Torsional Properties
The behaviors which are shown by a textile material when it is subjected to a torsional force is called torsional property. It is the property of fiber or material when a Torsional force is applied on it. Here Torsional force is a twisting force that is applied on the two ends of the material in two opposite direction.

4. Fictional Properties
Frictional properties is due to the friction between the fibers. This properties are shown during processing. Too high friction and too low friction is not good for yarn. Therefore it is an important property when yarn manufacturing and processing.

5. Electrical Properties

Electrical conductivity or specific conductance is a measure of a material’s ability to conduct an electric current
Conductivity is the reciprocal (inverse) of electrical resistivity, ρ (Greek: rho), and has the SI units of Siemens per meter (S·m-1)
Resistance –Ohms (e.g. Resistance of Dynamo is > 1014 Ohm)

C. Chemical Properties:
Solubility in aqueous and organic solvent. Useful properties of another hind desired in a textile fiber are indicated below.

Behavior towards dyes.
Ability to moisture absorption
Resistance to deteriorating influence including; light, thermal stability, resistance to bacteria, mildew moth and other destructive insect, corrosive chemicals.

1. Water:
Hydrophobic and Hydrophilic are the two classification of fiber according to the interaction of fiber with water. The fiber which has no joint for water that means less absorbency is called hydrophobic.

2. Absorbency:
Absorbency means the ability of the fiber to retain the water which depends on the ratio of fiber’s amorphous and crystalline region because this ration determines the polarity of the polymers.

3. Acid:
Interaction of different fiber with acid variable. To avoid the harmful effect on fiber different acid should be chosen carefully which will not harm fiber but bring the required change during the manufacturing process.

4. Alkali:
Like acid interaction of fiber varies with the different alkalis. Such as mild alkali don’t have any harmful effect on wool but high concentration of caustic soda has harmful effect on wool.

Without above that properties, fiber has also

Thermal Properties
Torsional Properties

Electrical Properties of Textile Fiber:
The electrical properties (conduction, resistance, etc.) are used in numerous solid materials, which are for the most part metal or metal derivative. In the textile field these properties are more difficult to highlight or engineer due to the various other requirements in suppleness, handle and care properties of such materials.

The electrical properties of fibers are interrelated, for e.g. The liability of materials to develop static charges is directly related to its electrical resistance, which in turn mainly determined by the permittivity of the material.

Hence we will concern our discussion to the three major properties i.e.

Dielectric Properties
Electrical resistance
Static Properties.

The permittivity ε of a material may be defined either in terms of capacitance C, of a condenser with the material between parallel plates of area “A” and separation “d” or in terms of the force “F” between two charges Q1 and Q2 at a distance “r” in the material. Expressed in SI units, the relation contains no arbitrary numerical factors and is represented as:

C = εA/d—————– (1)

F = Q1Q2/4Пεr2 ——————–(2)

In vacuum the equation becomes: C = ε0 A/d ——————(3)

F = Q1Q2/4Пε0r2 ———————(4)

Here ε0 is the permittivity of a vacuum and has the value of 8.854 X 10-12 farad/meter For many purposes the term relative permittivity is used which is expressed as:

εr = ε/ ε0, and this quantity is called the dielectric constant.

Dielectric effects are caused due to the polarization in the medium and these results in a reverse field, which tends to reduce the potential difference between the charged plates of a condenser, which thus increases the capacitance which is generally calculated as the value of charge/potential difference. This polarization is due to:

The alignment of the permanent dipoles such as water molecules.
Due to the separation of charge forming induced dipoles

Factors affecting dielectric properties:

Frequency:
The frequency of the applied voltage has an important effect on the dielectric properties. At low frequencies the dipoles line up in the field, reverse direction when the field reverses and so contribute to a high permittivity. But owing to their inertia and due to the restraints in the structure, the dipoles take a certain time to reverse direction, and this is characterized as their relaxation time. With increase in frequency the field reversals becomes so rapid that the reversals of fields take place at intervals comparable to the relaxation time, and at that point the dipoles cease to follow the changes in the field completely and the permittivity will decrease. At further higher frequencies the dipoles will not follow the changes at all and there will be no contribution to the permittivity. The reversing of the dipoles in the electric field leads to loss of energy owing to internal friction. At low frequencies the time taken in reversing is only a small part of the whole cycle, and hence the energy loss and consequently the power factor are low. At very high frequencies the movement of the dipoles being negligible, the energy loss and power factor is again low, but near the frequencies corresponding to a relaxation time the dipoles are moving throughout the cycle and so corresponds to a high energy loss and power factor.

Moisture:
At higher frequencies the dielectric properties of the cellulosic fibers are consistent with the assumption that the water molecules are restrained in a manner similar to that in ice. For wool the permittivity is lower which indicates that the absorbed water molecules are more tightly held and cannot line up in the field and the behavior is marked at low moisture content and is consistent with the theory that the water first absorbed by wool is firmly bond to the hydrophilic groups in the side chains of the keratin molecule.

hydrophilic groups in the side chains of the keratin molecule — Fig: Hydrophilic groups in the side chains of the keratin molecule

The permittivity for wool at high frequencies has been explained by Shaw and Windle with a three-phase theory of moisture absorption. The components of the system were regarded as dry wool, with experimentally determined properties, localized absorbed water in which the molecules cannot rotate, intermediate absorbed water in which the molecules are very little restricted and mobile absorbed water in which the molecules are as free as in liquid water.

The non-absorbing fibers like Saran and Dacron show no variation in dielectric constant and only a small change in power factor between 0 and 65% RH.

The effect of temperature: Arise in temperature reduces the restraints on the dipoles causing an increase in the permittivity in solid materials. In case of liquids and gases where the intermolecular restraints are small an increase in temperature causes a greater disorganization, a less regular alignment of the dipoles and thus a lower permittivity.

Direction of applied current: In case of an anisotropic material such as fiber the permittivity varies with the direction in which the electric field is applied. For cotton fiber it was seen that the axial permittivity is about twice the transverse permittivity, while Shaw and Windle found that the relative permittivity of dry wool fibers was 3.88 +(-) 0.15 with the electric field parallel to the fiber axis and 4.41+(-) 0.11 with the electric field perpendicular to the fiber axis.

Presence of Impurities:
The presence of impurities have a considerable effect on the permittivity of the fibers, ionic impurities in particular would have considerable effect at low frequencies.

Electrical conductivity and resistivity
Electrical conductivity is the capacity of a material to allow the passage of an electrical current. Resistivity is the inverse of conductivity. One must distinguish the resistance (R) which characterizes a physical element and the resistivity which defines the intrinsic nature of the material constituting the element as two objects may be constituted of materials with different resistivity but share the same electrical resistance value in ohms.

Ohm’s law defines the resistance (R) as the relation of the potential difference (V) applied to this element on the current (I) traversing it:

R = V/I ——(5)

1. There are three types of resistivity according to whether the material is presented in a linear, surface or volume format.

The linear resistivity Rl of a uniform linear element is characterized by the measure of the resistance compared to its length and is expressed in ohm/centimeter (O/cm):

Rl = R/L ————(6)

With R = resistance in ohms, L = the length of the sample.

2. The surface resistivity Rs characterizes flat materials of little thickness such as fabrics, and it is expressed in ohm (O) or in ohm/Sq(O/¨Sq)

Rs = R x L/D ———-(7)

With R = the resistance in ohms, L = the length of the electrode, D = the distance between the electrodes.

3. The volume resistivity Rv characterizes the three dimensional materials by the measure of the resistance R compared to the surface S, and to the length L. It is expressed in ohm. centimeter (O.cm):

Rv = R x S/L ———-(8)

Here, R = resistance in ohms, S = the surface area of the electrodes, L = the length of the sample.

Factors affecting fiber resistance:

Moisture:
It is the most important factor which determines the resistance of textile materials and causes a variation over a range of at least 1010 times the difference in 10 and 90 % r.h. causes a million fold difference of resistance.

For most hygroscopic materials textile fibers between 30 and 90% r.h, relations of the following form hold:

Log Rs = -n Log M +Log K ——– (9)

Rs. Mn = K,

Here M = moisture content (%), and n and K are constants

At low moisture contents the following form fits:

Log Rs = -n’ Log M +Log K’ ———– (10)

Here n’ and K’ are constants

At a constant temperature the resistance has been found to be a single valued function of moisture content, with no hysteresis being detected.

Effect of Impurities:
The resistance of the hygroscopic fibers depend on their electrolyte content. The addition of a salt such as potassium chloride lowers the resistance. At low salt contents, the evidence indicates that the conductivity is approximately proportional to the electrolyte content, but, at high salt contents the resistance of the cellulose film at given moisture content was independent of the nature or amount of salt present.

Washing in distilled water increases the resistance and washing in calcium sulphate increases the resistance even further.

The calcium sulphate solution replaces the monovalent ions left behind after washing in distilled water and replaces it with less conducting bivalent ions. The residual ions associate with the remaining groups in the fiber molecule for example carboxyl groups present as impurities in cellulose molecules. It was found by church that when hydrogen ions were replaced by calcium ions in paper the resistance increased by six times.

Effect of Temperature:
The resistance of fibers decreases as the temperature increases, a rise of 10°C causes a fall of the order of five times.

For cotton, viscose rayon, and wool, Hearle found that the rate of change of log R with temperature varied separately with moisture content, M and temperature θC

-d (log R)
————– = a – bM – cθ
dθ

Here a, b, c are constant for a given material.

The value of ‘a’ gives the rate of change of log R with temperature under dry conditions at 0°C and the value of ‘b’ and ‘c’ give the change of d(log R)/dθ, with moisture content and temperature respectively.

Polarization and Related Effects:
If polarization occurs by electrolytic or due to electrostatic charges occur, it will cause back e.m.f.s which is detectable in three ways:

The resistance ill increase with time as the back e.m.f develops. The resistance will decrease with voltage
The back emf will be present and will die away as the applied voltage has been applied.
It was found by several researchers that there is a negligible variation of resistance with time, except at low and high humidity.

The first understanding of the nature of electricity came from the study of the phenomenon of static electricity in the eighteenth century. Later the increased amount of trouble caused in the textile industry due to the introduction of the new fibers renewed and revived interest in understanding of this phenomenon.

Similar charges repel one another. This causes difficulty in handling materials, the filaments in a charged warp will bow out away from one another, there will be ballooning of a bundle of slivers, cloth will not fold down neatly after coming out of a folding machine. Similarly, unlike charges attract one another. This phenomenon has caused difficulty in opening of parachutes. It will also cause two garments which are oppositely charged to stick to one another causing embarrassment to the wearer. Another consequence is the attraction to a charged material of oppositely charged particles of dirt and dust from the atmosphere. When the fabric is positively charged the soiling is worse owing to the preponderance of negatively charged dirt particles in the atmosphere. This fine dirt adheres so firmly that it is difficult to remove and causes serious soiling. This is the reason for fog marking which occurs on the portion of the cloth in a loom that is left exposed overnight.

Formation of static:
Most textile fibers do not conduct electricity efficiently and can be classified as dielectric material, demonstrating insulating properties when dry. Whenever two surfaces come into contact, electrons can flow from one to the other. Conducting materials allow this electron flow to be equalized instantly when the surfaces are separated. Insulating materials like textile fibers can retain the electrical charge difference for some time. It was initially opined that the two necessary conditions for a charge to appear are:

Difference between the nature of the surfaces
Rubbing between them

Pioneering work by different researchers has established that either of these conditions in itself is sufficient to generate charges. Rubbing though not necessary increases the amount of charge produced significantly. Triboelectrification is the term used for electrical charges generated by frictional forces. fibers can be ordered in a triboelectric series such that each fiber type becomes positively charged when rubbed with fibers below it in the series and vice-versa.

Owing to the slight differences in the surface or the asymmetry in the rubbing, charges may easily be generated by inter-fiber contact between apparently identical fibers.

Factors affecting static generation:

Conductivity: The increase in conductivity or the lowering of resistivity reduces the static charges generated in the fiber. The resistivity as discussed earlier is the resistance of the fiber to electrical flow. Increasing the conductivity produces a lower charge build up and a more rapid dissipation.

Frictional forces: Lowering of the frictional forces between the fibers by enhancing its lubricity helps to reduce static generation by decreasing the initial charge build up.

Moisture: As discussed earlier the presence of moisture in the fiber increases the conductivity and hence the dissipation of charges from the fiber is faster, resulting in lowering of the static charges.

Measuring the contact resistance between the electrode and the textile substrate:
The surface resistance of flat textile products is substitute resistance resulting from the yarns resistance and contact resistance occurring between the yarns forming a fibrous structure. Due to the new use of electrically conductive textiles, e.g. electrodes to muscle electrical stimulation, it is important to uniform distribution of the resistance measured between any points on the surface of the sample. The authors have proposed a new approach for measuring the resistance of the flat textile of electro conductive properties. The measurement method is based on multi- variant testing of the electro conductive properties using four cylindrical electrodes placed on the sample surface. At some scale the electrode contact area is never completely flat. There are non-conducting and conducting regions between contact area of an electrode and a sample. This is due to the porous structure of textile materials and pressure force of the electrode. The measuring electrodes were made of brass and silver plated. The electrode contact diameter is 8 mm. The mass of a single electrode is 24 g, which means that its pressure force equals to 0.24 N. The electrodes have a comparatively small contact area with the textile substrate relative to the sample surface. The contact area of the electrode was selected so that it covers the fabric repeat. It is very important to ensure that the all yarns are contacted during measurements.

In order to determine the contact resistance between the electrode and the textile sample measuring stand was built. The scheme of the stand is shown in Fig.

Fig: Measurement system for determination of a contact resistance

The contact resistance measurement was conducted using the indirect method. DC Power Supply Agilent E3644A meter as voltage source was used. The current I was forced between the upper end of the electrode and a point on the thin copper measurement probe introduced into the electrically conductive sample. The probe was located in the immediate vicinity of the electrode and does not touch with the electrode. Using an Agilent 34410A ammeter the current value was recorded. Using an Agilent 34410A voltmeter voltage drop between the upper end of the electrode and a point on the wire was measured.

Equivalent resistance scheme of measuring system is shown in Fig.

Equivalent resistance scheme:

I—the current;
U—the voltage source;
Uc —the voltage;
Re—the electrode resistance with the connecting wire;
Ue—the voltage drop in the electrode;
Rc—the contact resistance

The equation resulting from the above connections (Fig.) is given by the following formula:

U−ReI−RcI=0U−ReI−RcI=0 ——–(1)

Here:

U—the voltage source;
I—the current;
Re —the electrode resistance with the connecting wire;
Rc —the contact resistance.

The contact resistance is given by the formula:

Rc=UcIRc=UcI ——–(2)

Here:

Uc —the voltage source;
I—the current.

The measurements of the contact resistance were repeated five times. The average contact resistance value calculated from the formula (2) is equal to 0.049 Ω. Because the value is small so it is expected that the power loss under the electrode will be small. Therefore the contact resistance has no significant impact on surface resistance of the textile sample.

Measurements of surface resistance of textile sample
The purpose of the study was to determine the resistance R of the textile sample and comparison of the received measurements results. The qualitative model of the research object, the woven fabric sample, is shown in Fig.

Fig: Measurements of surface resistance of textile sample (Test Object)

The measurement model was defined as follows:

R=f(I,Um)=UmIR=f(I,Um)=UmI ———–(3)

Here:

I—the current flowing between one pair of electrodes;
Um —the voltage drop measured between the other pair of electrodes.

It is assumed the estimates of quantities I and Um are uncorrelated.

The measuring stand designed for conducting multi-variant study of the electro conductive properties of textile sample was built (Fig.). The measuring stand consists of the following elements:

Fig: The measuring stand for multi-variant textile resistance measurements

An Agilent 34410A multi-meter;

a DC Power Supply Agilent E3644A meter; a table (A) or, alternatively, table (B)

Table (B) for the square-shape arrangement of electrodes on a sample—top view

Full size image sets consisting of four cylindrical measuring electrodes.

Table (A) enables the resistance measurement by the four-electrode method. An identical spacing between electrode mounting holes are assumed. The distance between the two outermost holes corresponds to the longest square side that can be achieved when arranging the electrodes using table (B). This table allows electrodes to be arranged in the shape of a square with a side of 70, 50 and 30 mm, respectively. The drilled holes allow the electrode to fall freely under its weight onto the fibrous substrate, while retaining the perpendicular direction of the electrode relative to the substrate.

In the case of table (A) the two outermost electrodes are connected to a current source (the DC Power Supply Agilent E3644A meter). To measure the voltage drop, the two inner electrodes are connected to the Agilent 34410A mustimeters. In the case of using table (B), two adjacent electrodes are connected to a current source (the DC Power Supply Agilent E3644A meter). To measure the voltage drop, the two remaining electrodes are connected to the Agilent 34410A mustimeters. For determining the resistance of the woven fabric sample 10 variants of electrode arrangement on the sample surface were selected which were denoted as A1, A2, B1, B2, C1, C2, D1, D2, E1, E2. The manner of electrode arrangement together with electrical circuit of the resistance measurement are shown in Figs.

Fig: Arrangement of electrodes in the four corners of the electro conductive sample

Fig: Coaxial arrangement of electrodes on the surface of the electro conductive sample (variants: C, D and E).

For the coaxial electrode arrangement, table (A) was used. For arranging the electrodes in the corners, on the other hand, table (B) was used.

Conclusion:
From the above discussion it is clear that the electrical properties of textile fiber is dependent on the moisture content, relative humidity, frequency of the applied voltage and the intrinsic properties of the material itself.

A variety of mechanism can cause a transfer of charge to occur at the surfaces in contact. Large charges develop at the surface of contact but these leaks away through the air, or material and observed charges are much lower.

The limiting condition for high static charges, and hence the susceptibility to troubles in use, is dependent on the resistance of the material. Low resistance materials like cotton, viscose rarely give any static problem while high resistance material like wool and silk and synthetic fiber will cause a tremendous amount of static generation.

References:

Physical Properties of Textile Fibres by J. W. S. Hearle, W E Morton
https://www.academia.edu/19491963/Electrical_and_Electronic_Properties_of_Fibers
https://textilemerchandising.com/properties-of-textile-fibers/
https://www.technicaltextile.net/articles/electrical-properties-of-fibers-6699
Pacelli, G. Loriga, N. Taccini, R. Paradiso, in IEEE/EMBS International Summer School on Proceedings of International Summer School and Symposium on Medical Devices and Biosensors (ISSS-MBDS 2006), Boston, USA, 4–6 September 2006, pp. 1–4
V.K. Mukhopadhyay, J. Midha, J. Ind. Text. 37, 225 (2008)
S.L.P. Tang, Trans. Inst. Meas. Control 29, 283 (2007)
Karaguzel, C.R. Merritt, T. Kang, J.M. Wilson, H.T. Nagle, E. Grant, B. Pourdeyhimi, J. Text. Inst. 100, 1 (2009)

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Mazharul Islam Kiron

Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.