tricot knitfiberglassknitting

Image Credit: Pacor Inc. | Apex Mills

 

Industrial fabrics are designed and engineered to be used in products, processes, or services where functional requirement trump the aesthetic form commonly considered the realm of textiles. They are used by non-apparel industry professionals for challenging and high-performance applications. Industrial fabrics can be a component part of another product in order to alter the strength, performance and other properties of that product. They can also be used in product manufacturing or used alone to perform one or several specific functions. Industrial fabrics differ from textile (apparel) fabrics in several ways.  Industrial fabrics are made of higher performance fibers, yarns, and chemicals to prevent failures which could have dangerous consequences. Functionality is the most important feature because the fabric must be able to handle the environmental factors and structural requirements of the application. Manufacturing industrial fabrics is more difficult because higher value fibers and materials can be more difficult to manipulate due to the intrinsic performance specifications. For example, glass fibers are very abrasive. Regular and thorough testing using highly accurate and reliable tests lead to an increase in the life expectancy of the fabrics.

 

 

Fiber vs. Fabric

A fiber is a natural or synthetic substance with a very high aspect ratio (length to width) that can be processed by various means into a fabric. Properties of fibers include length, size and surface contour. Fibers are available in two lengths, staple or filament. A staple fiber has limited or finite length. The length of the fiber is measured in inches or centimeters and the length can vary within a fiber of the same source. Short fibers may be twisted together to make yarn or used in their staple form to produce non-woven fabrics. A filament is a fiber with an unlimited or seemingly infinite length. The long continuous filament fibers are measured in yards or meters. If a filament is bundled and cut it is called a tow.

Staple vs filament fibers

Image Credit: Textile School 

  

A fabric is created by fibers which have been spun into yarns and then bonded together.  It is a planar assembly of fibers, yarns, or both. Due to the many methods of fabric manufacturing, there is a great variety of characteristics and structures.

 

Natural vs. Synthetic

Natural fibers are made of cellulose which is the primary structural component of plants and bacterial cell walls. Animal fibers are also considered natural fibers because they are composed of protein. Natural fibers are structurally strong and resistant to chemical attacks because the molecule contains many polar hydroxyl groups that interact with adjacent molecules. Natural fibers, such as cotton, can be chemically modified to form regenerated fibers known as rayon and acetate. 

Advantages

Disadvantages

·         Producible with low investment at low cost.

·         Thermal recycling is possible.

·         Low specific weight, which results in a higher specific strength and stiffness than glass. This is a benefit especially in parts designed for bending stiffness

·         It is a renewable resource, the production requires little energy, CO2 is used while oxygen is given back to the environment.

·         Price can fluctuate by harvest results or agricultural politics.

·         Lower durability, fibre treatments can improve this considerably.

·         Moisture absorption, which causes swelling of the fibers.

·         Lower strength properties, particularly its impact strength.

Chart adapted from textileschool.com

 

Inorganic materials consist of glass, metals, and ceramics. A good example of this is fiberglass, which is made of spun glass and mixed with epoxy resins to create reinforcing components for cars and boats. Steel fibers are used in steel wool pads, or ropes. Carbon fibers are created by treating carbon at a high temperature and then converted to graphite ribbons which are packed together to form fibers. The fibers are light and strong, making them more expensive. They are being considered in golf clubs, bicycles, and cars. Gold and silver can also be used as fibers and fabrics

 

Synthetic fibers are made of polymers. The polymers are put through a chemical reaction described below. Synthetic fibers are strong, resistant to most chemicals, and can be manipulated to have a variety of performance characteristics. To make a synthetic fiber, a liquid chemical composition is forced through spinnerets, hardened, and produced into a continuous strand of any length.

 

Advantages

Disadvantages

·         Greater strength

·         Greater durability

·         Less expensive production

·         Low maintenance

·         Weather resistant

·         Easy to clean

·         Cannot absorb water (This is an advantage or disadvantage depending on the application)

·         Produced using fossil fuels (petroleum)

·         Use chemical which could harm humans and the environment

·         Melt when hot

·         Burn easily

·         Get electrically charged in dry weather

·         Non-biodegradable

 

Identification Techniques

It is important to know what type of fabric is being used for an application to ensure that it will meet the desired specifications. Identifying the material in a fabric can be difficult, if not impossible to do just by the look or feel.  

 

Identification Tests

There are several tests that can be used to identify the material in a fabric. These include the burn test and observation under a microscope. Generally, synthetic fibers need to go to a laboratory for observation under a microscope. Synthetic materials based on petroleum (polyester, nylon, acrylic) will untwist, and unravel into fibers of even length and thickness. Burning these fabrics produces a black smoke after it quickly melts. Burn tests are a somewhat subjective but simple test used to identify fibers. If the fiber or fabric is blended than the results may be inconclusive.

 

The following questions should be considered when preforming the burn test:

  • Do the fibers melt and/or burn?
  • Do the fibers shrink from the flame?
  • What type of odor do the fumes have?
  • What are the characteristics of any smoke?
  • What does the residue of the burn fibers look like? 

This video demonstrates what happens to several different fiber types when exposed to a flame.

 

 Video Credit: chemixish

 

Shape

Fibers come in many shapes depending on the material used. Their shape can be viewed under a microscope. This image can be used to identify that type of fiber used in the industrial fabric.

 

Image Credit: Textileschool.com

Thread Size/Numbering

Threads are several single strands twisted or plied together. A numbering system exists to identify what type of thread is being used or needed for an application. There are two numbers in a thread sizing: the count is related to the thickness of a single strand and the second number, the ply, is the number of strands (count/ply). The count is not the thickness directly. It's related to the length per unit weight. For example, in the Nel system of thread measurement, one count equals 300 yards per pounds. Thus a 30/2 thread Nel is a two-ply thread, and each single strand measures 30 X 300 yards/pound.

 

How Industrial Fabrics are Made

Fabric is made when fibers are combined. The process is different for manufacturing natural fibers and synthetic fibers into fabrics.

 

Fibers

Natural- Most natural fibers are considered "readymade." This means they do not need to go through the processing used to create fabric. Cotton must go through a process called ginning in order to be used as a fiber. Ginning separates the seeds from the cotton fibers. There are three types of ginning: Knife roller, Mscarthy roller, and saw gin. The saw gin is used for American, West African and Pakistani cotton.

 

Once the material is collected (fibers running from 5 to 20cm), it is pulled as a filament and aligned into a continuous yarn or thread. The filaments are held together using Van der Wals type forces and spun together using a spinning machine. This technique tends to produce natural fibers with filament branches, which increases bulk and porosity of the fiber, and makes the fibers curly.

 

Synthetic- Synthetic fabrics consist of bulk fibers, yarns, woven cloth, or other textile products manufactured from polymer-based materials such as polyamide (nylon), polyester, aramid, or other spun thermoplastics. Most synthetic fibers go through a similar production process which includes three steps: chemical, spinning, and twisting. For more information on how fibers are made please see the Fibers and Filaments Selection Guide.  

 

Fabric

After the fibers are created and aligned together to form a yarn or thread, they are used to form the fabric. An important distinction in fabrics is whether they are woven or non-woven. Woven fabrics have an orientation associated with them.

 

General overview of fabric construction

Video Credit: LZXpress

 

Weaving

Weaving is a very popular method of creating fabrics. Simply, it is the interlacing of a lengthwise yarn system with a width-wise yarn system at 90 degrees to each other. Along with braiding, weaving is considered an interlacing process. There are several types of weaving including satin weave, twill, basket, and basket weave, but the plain weave is the most common. Plain weave is simple and is formed by alternatively lifting and lowering one warp thread across one weft thread. A more complete description of how weaving creates fabric can be seen on this video.

 

weaving fabric

Image Credit: Wikipedia

 

The yarns do not lie flat because they have to go under and over one another as they are interfaced. The features of the woven cloth will depend on the type of fiber used. Factors such as using a monofilament yarn, a multifilament yarn, and whether the fiber is synthetic or natural will affect the stiffness of the fabric.  

 

Tufting

Tufting is the process of sewing a surface yarn system. Hundreds of needles on a special machine form loops. The loops are stitched in the primary backing fabric into vertical columns (rows) and horizontal lines (switches) forming cut and/or uncut loops (piles). The fabric comes out of the machine and is back-coated to secure tufted loops. The backing supports the fiber, provides strength, and stability. The backing is held in place with a latex adhesive which secures the tufts and laminates the primary and secondary backing. This technique is commonly used in making carpets. A more complete description of how tufting create carpets can be seen on this video.

 

tufting

Image Credit

 

 

Knitting

Knitting is the interlooping of one yarn system into vertical columns and horizontal rows of loops. The loops are called wales and courses, respectively. There are two main types of knitting, warp and weft. In warp knitting, the loops made from each warp are made sequentially along the length of the fabric so that each warp thread is fed in line with the direction of fabric production. Warp knitting is the fast method of converting yarn into fabric. Weft knitting has the loops made by each weft thread made sequentially across the width of the fabric. The thread is fed at right angles to the direction of production. This technique can use one to 144 needles on one machine and is the most versatile in terms of range of products produced and the types of yarns that can be used.

 

Image Credit: Handbook of Technical Textile

 

Non-Wovens

Non-wovens are sheets or web structures which are bonded together by entangling fiber or filaments. This is done using a mechanical, thermal or chemical process. Non-woven fabrics do not have a preferred fiber orientation and they do not need fiber to be converted to yarn. The engineered fabric is produced fast and inexpensive enough to be used for limited life or single-use applications. They are durable and can be designed with such properties as stretch ability, flame retardancy, strength, softness, liquid repellency, and sterility. The properties can combined to make fabrics for specific jobs by selecting and mixing the raw material and applying a finish. Non-woven synthetic fabrics are 'glued' together. Non-wovens are manufactured in three stages: web formation, web bonding, and a finishing treatment. They have many applications and are used in a variety of industries including personal care, healthcare, automotive, industrial, and in construction. Many types of fibers can be used to produce non-woven fabrics; the selection is based on the required profile and the cost effectiveness to produce non-woven bonded fabrics.

 

Selection Criteria

GlobalSpec allows industrial buyer to select industrial fabric based on several specifications including, the end-type product, material, fabric properties, and fabric features.

 

End-Type Product

The end-type product is the state or condition the buyer will purchase the fiber or fabric. The end-type needed depends on the application and ability to further manufacture the material.

  • Fibers and monofilaments- Single fibers are called filaments and a monofilament is when a single continuous filament is rolled on a spool. A filament bunch is called a strand or end. Bulk chopped fibers or thin, continuous fiber filaments are used typically in composite reinforcement applications, flow-able insulation, or as the key component in woven fabrics, braids, knits, rope roving, or other specialty fabrics.
  • Roving- Roving is made of parallel filaments. Graphite rovings are referred to as tows. Rovings are marked by the number of filaments they contain. Tows are marked by the number of filaments with the most common graphite tows being 3K, 6K, and 12K.
  • industrial yarnYarn-Yarn is made of continuous, often plied strands of natural or man-made fibers or filaments. The filament is then twisted to hold fibers together. Yarn is often created with filament branches that add bulk and porosity to the fabric. To create a yarn without any filament branches, the yarn should be made by bringing the filaments together as they are created. However, to increase the similarity between natural and man-made fibers, the filaments are usually chopped into staples before making the yarn. Image Credit
  • Carded and needle punched, non-woven- Carded yarn has been through the card machine but has not been combed. Because they contain a range of fiber lengths they are low strength, low density, and low cost.
  • Braided products- Braided fabrics are made by crossing a number of strands diagonally so each strand passes alternating over or under one or more of the other strands. These products are used for tubular composite structures, thermal insulation, and in other applications. Image Credit
  • Rope and cordage- Cord is formed by twisting together two or more plied yarns. It can also be defined as a rib on the surface of a fabric. Rope is a heavier and stronger cord. It is made from either natural or synthetic fibers and is available in a wide range of diameters. Rope is made in a two-step process; first the yarns are twisted together to form strands and then the strands are twisted together in the opposite direction to form the rope. The alternating direction of the twist at different stages of the rope assembly makes the rope twist stable and resistance to kinks.
  • Webbing- Webbing is strong, narrow fabric that has been closely woven. They are available in a variety of weaves and often found in straps that have to withstand strain (belt, seat belts, suspenders, etc.) Webbing includes ribbons, strapping, and tape. Image Credit
  • Blankets or batts-Blankets or batts (batting) are made of thick layers of woven and/or non-woven fabric sheets. Battings are webs of loose fibers that have usually been carded. Battings are sold in sheets or rolls and used for warm linings and comforter stuffings.
  • Sleeves or wraps- Sleeves or wraps (sleeving) are flexible, fibrous-refractory products for insulating pipes, tubes, ducts, and other process components. Image Credit
  • Thread- Synthetic thread includes both monofilaments and multi-fiber filament; a slender, strong strand or cord. Most threads are made by plying and twisting yarns. There is a large variety of yarns available for many different industrial applications.   

Material

Industrial fabrics are made of natural, synthetic, or inorganic materials. For more information on the fibers available in any of these categories please click the links below.

Blended Fiber Structure

Blended fibers are manufactured from a mixture of two or more different type of fibers. Mixing fibers allows manufactures to form new textile yarns with distinct advantages. Each fiber retains its separate set of physical and aesthetic characteristics inherent in its design but the fabric acquires new characteristics depending on the type and percent of fibers used. Blends utilize the advantages of all the fibers to counteract the disadvantages of a single fiber. Synthetic fibers can be blended with natural fibers to create a material that is stronger, but more comfortable.

 

Coated or Sized Fabric

Coated fibers are a tightly woven or knit-based fabric that is coated on one or both sides with a synthetic or natural elastomer.  The selection of fiber and fabric for coating depends on the application. Coating is used to enhance the strength, abrasion resistance, stiffness, thermal stability, water repellency, and air permeability of the fabric. This technique is often seen in applications such as in life rafts and diving suits. Woven, knit, tufted, and non-woven fabrics are used in coating. There are many materials that can be used for the coating and there are several options available for applying the coating.

 

 

Image Credit

 

Sized fibers have been treated to reduce the hairiness around the fiber. It is part of a slashing process and reduces the hairiness that would interfere with the weaving process. This protects the yarn from yarn-to-yarn and yarn-to-loom abrasion as well as increasing the strength of the yarn so it can make it through the loom without breaking. If the process is done incorrectly, the long hair fibers around the yarn will be glued to the adjacent yarns and the strands will be damaged when they are put through the loom. Proper sizing requires the size film, which can be a variety of polymers, to coat the yarn surface without excessive penetration into the body of the yarn bundle. 

 

Image Credit: Wellington Sears Handbook of Industrial Textile 

Fabric Properties

GlobalSpec allows industrial buyers to search for the right fabric by properties.

 

Overall Thickness

The thickness of a fabric is defined by the distance between the face and backside of the fabric. It is measured at a specific pressure using a fabric thickness gauge. Fabric thickness is measured in thousandths of an inch and is an average of the thickness reading a several different spots on the fabric. The gauge is a set of platforms  in the shape of a 'C'. The fabric should be tested at standard atmosphere by placing the fabric on the top of the gauge (anvil) and raising the bottom (pressure foot) to touch the fabric. The thickness is read and recorded and then the measurement is repeated in the same spot. This procedure occurs at several places along the fabric and the recordings are averaged. Thickness is important if the fabric needs to be sewn or cut by a manufacturer.

 

Overall Width/OD

The width of the fabric must be measured under standard conditions and is expressed in centimeters. Many factors can cause variation in the width measurement including moisture, tension, and contractions during finishing. If the cloth's width changes, other parameters, such as area density and threads per centimeter, will be affected.

 

Overall Length

The length of the fabric can vary from one yard to in excess of one mile. Fabrics sold in roll form and the length needed should be specified when making a purchase.  

 

Fabric Weight

Fabric weight is important for international selling and buying. It is the relative weight of the fabric, not the absolute weight. The measurement is usually expressed as grams per square meter (GSM), ounce per square yard, or yards per pound.  The measurement is taken using a cutter with four blades that cut a sample specimen which is 100th of a meter. That sample is weighed, and in the cause of GSM, the weight in grams is multiplied by 100 to give the GSM of the fabric.

 

The weight measurement is only a small sample of the fabric while the density can be measured continuously for more complete data. Area density can either be loomstate or finished. If it is loomstate, the density will depend on the weaving specifications such as yarn spacing and sizing. Finished clothes are often altered by tension or chemical treatments that will affect the density. The density is measured in grams per square meter. Density of the fabric can be calculated by placing the fabric on a smooth surface and placing a densimeter of the fabric parallel to the warps. A densimeter is an acrylic sheet with lines printed on it. The device comes with sheets that should be placed under the fabric. As the densimeter is rotated (maintain contact with the cloth) a family of parabolic curves can be seen through the device. The apex of the curve is the ends per inch and if the procedure is repeated with the densimeter parallel to the wefts of the fabric, the picks per inch can be obtained. Fabric weight and density are related linearly as seen in the graph below.

 

Image Credit: Automation Partners Inc.

 

Thermal Characteristics

Fibers and fabrics have unique responses in the presence of heat. Heat can hurt or help the fiber or fabric, but when used correctly, heat can help fiber soften, melt, or decompose. Heat can also give fiber the ability to heat set, function properly at elevated temperatures, and function at room temperature after exposure to high temperatures.

 

Thermal Conductivity- Thermal conductivity is the linear heat transfer per unit area through a material for a given applied temperature gradient. Heat flux (h) = [thermal conductivity (k)] x [temperature gradient (Δ T)]

 

Strength

Fabric strength is the load per inch-width that a fabric can withstand before breaking. 

 

Break Load (Rope/Fiber)- Breaking strength is the maximum tensile load or force that a rope, cord, webbing, or fabric will hold before breaking. Breaking strength is multiplied by a safety factor to determine the actual operating or working load of the rope or textile product.  

 

Electrical Resistivity

Resistivity is the longitudinal electrical resistance (ohm-cm) of a uniform rod of unit length and unit cross-sectional area. Resistivity is the inverse of conductivity.  

 

Elasticity

The ability of a strained material to recover to its original size and shape immediately after removal of the stress that causes deformation.  

 

Fiber Resiliency

Resiliency is the ability of a fabric to return to its original shape after being manipulated. The resiliency of a fiber can be determined by observing if the fiber was able to regain a smooth appearance after being twisted or plushness after being compressed.

 

Abrasion Resistance

The ability of a fiber or fabric to withstand surface wear and rubbing. A high abrasion resistance is especially important for cords and ropes that will be rubbing along a support or hold.   

 

Industrial Fabric Features

In terms of structural features, some industrial fabrics include:

 

·     Chemical/fuel resistant- Materials are designed to resist damage caused by acids, alkalis, general chemicals, fuel and oils. These materials are used to seal fuel or oil tanks.

·     Electrically conductive- Textiles or fabrics include fibers with high electrical conductivity or low electrical resistivity. Often, conductive filler is added to increase conductivity. Products are used in electronic, anti-static or electrostatic discharge (ESD) applications.

·     Electrical insulation/dielectric- Dielectric fibers, fabrics, and textiles are electrically insulating. Dielectric materials are used to form a barrier or isolator between electrical or electronic components.

·     Flame retardant fabrics- Flame retardant products reduce the spread of flames or resist ignition when exposed to high temperature, or insulate the substrate and delay damage. A UL 94 rating indicates that the material is flame retardant in accordance with Underwriters Laboratories, Inc.(UL) Flame Class 94V-0 or other equivalent ISO standards.

·     Hydrophilic/absorbent- The surfaces of hydrophilic materials absorb water. They are often used when high absorbency (many times the basis weight of the material) is important.

·     Sound proofing/insulation- Sound proofing or acoustic insulation materials are used to form a barrier or isolator between components and sources of noise or vibration. This category includes foam material products used for diffusing sound without causing a large degree of attenuation.

·     Thermal insulation/fireproofing- Thermal insulation materials provide a barrier between a component and a heat source.

·     UL approved/listed- Materials meet applicable standards from Underwriters Laboratories, Inc. (UL).

·     Hydrophobic/waterproof- Waterproof materials do not dissolve or degrade when exposed to water. The fabric may still absorb water if the product is hydrophilic and has open porosity.

·     Weather/UV resistant- Plastic or elastomer foams are resistant to ultraviolet (UV) light or sunlight. Some non-UV resistant foam will crack, yellow, or degrade on exposure to UV light. Weather resistant materials can withstand exposure to the elements, such as wind, rain, snow, dust, humidity, heat, cold, and other weather conditions.  

 

Applications

Industrial fabrics are used in a variety of industries and applications, including: aerospace, apparel or clothing, architecture and construction, automotive and transportation, chemical processing, electrical, electronic, filtration, marine, and medical. Specialized products can also be used to control electrostatic discharge (ESD) and provide shielding from electromagnetic interference (EMI) and radio frequency interference (RFI).

 

protective fabricgeotextilearchitectural fabric

Image Credit: cfs.sa.gov.au | Geo Options, Inc. | Taconic

 

Fabrics can be specialized for applications including reflective fabric for security in lifejackets and some apparel, and in the street as reflectors and alerts, narrow fabrics which are thicker and used for tapes or laces, and laminated fabric to protect the product for dust and other particles.

 

Standards

The Industrial Fabrics Association International (IFAI) has a standards committee who disseminates information regarding the specifications, standards, and test methods pertinent to specialty fabrics and their end products.

 

There are several committees, including the National Fire Protection Agency (NFPA) which oversees the use and safety features in flame-retardant fabrics.  

 

Resources

Quality testing of fabrics - A must for survival and growth

Textileshool.com

Fibers 

Horrocks, A. Richard., and Subhash Anand. Handbook of Technical Textiles. Boca Raton, FL: CRC/Woodhead Pub., 2000. Print. 

Adanur, Sabit. Wellington Sears Handbook of Industrial Textiles. Lancaster, PA: Technomic Pub., 1995. Print.

Fabric University

Synthetic Fiber Manufacturing

About Nonwovens Textiles


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