Technical Textiles

 

What is Technical Textiles?

A technical textile is a textile product manufactured for non-aesthetic purposes, where function or performance is the primary criterion.

Categories:

Protech Textiles:

´  Main target

´  Life Vest Jacket

´  Cut resistant (gloves, glass industry)

´  High temperatures (insulating, firefighters)

´  Burns (flame, convective and radiant heat, firefighters, ATEX area)

´  Electric arc flash discharge (plasma explosion, Electric companies)

´  Molten metal impacts (foundries)

´  Metal sparks (welding)

´  Acid environment (petrochemical, gas, refineries, chemical)

´  Bullet impact (military, security)

´  Astronaut's suits

´  Left over food packets

Life Vest Jackets:

Ø  Life jacket is a device that is used to safeguard the life of the person.

Ø  It is used in water while playing, fishing, boating, and swimming or in other water activities.

Ø   It is also known as PFD (Personal Flotation Device).

    

  What is Water Proof Fabric?

´  Waterproof fabric and waterproof material fabric is a generalized term for any materials which are resistant, either fully or partially, to penetration by water.

´  Waterproof fabric is usually a textile which is compound with polymer waterproof, breathable materials.

           

Raw Material:

´  Waterproof fabric completely prevents the penetration and absorption of liquid water, in contrast to water-repellent fabric, which only delays the penetration of water.

´  Nylon 

´  Polyester

´  Polypropylene

´  Cotton

´  Silk

Melt spinning:

´  In melt spinning, the fiber-forming substance is melted for extrusion through the spinneret and then directly solidified by cooling into continuous filaments and then drawn out of the chamber twisted and processed further and subsequently wound onto spools.

´  Melt the polymer to a viscosity suitable for the extrusion through the spinneret.

´ Polyester, Nylon, Polypropylene, Olefin, saran, and glass fibers etc. are produced via melt spinning process.

Requirements of Melt Spinning Process

´  Polymer should not be volatile

´  It should not decompose in the molten state and the melting point

´  It should be 30 degree centigrade less than its decomposition temp

´  Special Features of Melt Spinning:

´  Non Toxic

´  No environment pollution

´  No solvent required

Advantages of Melt Spinning:

´  Can be used for both staple and continuous filament

´  Direct and simple process.

´  High production speed (275 to 1500 yds/min) Low investment cost

Disadvantages of Melt Spinning:

´  Required more proper maintained of machine.

´  Heat of input is high.

How is it manufactured?

´  Naturally water proof material:

´  Waterproof coatings, such as oilcloth, some are laminated with thin, waterproof films.

´  There are different types of waterproof, breathable fabrics which are manufactured slightly differently:

´  Tightly Woven Fabrics: An Egyptian cotton, woven very tightly, when it gets wet the cotton swells and makes the weave even tighter.

´  Hydrophilic Coating:

    (Normally a mix of PU and PEO)

Life Vest Manufacturing Process

´  Creating Marker ( CAD & CAM)

´  Preparing Nylon

´  Cutting the Pattern

´  Cutting Foam

´  Assembling Pattern piece

´  Sewing

´  Finishing

 

Testing

Coated Fabrics Waterproofness    

 

 

Cutting Gloves:

Ø  Cut-resistant gloves are those designed to protect the wearer's hands from cuts while working with sharp tools.

Ø   They can be divided into metal mesh gloves, cut-and-sewn, and seamless knitted gloves.

Ø   Metal mesh gloves are a form of chainmail, and are made of rings of stainless steel.

Raw Material:

The cutting gloves completely covers the hand and prevents them from cutting with knife or other things.

Ø  Dyneema

Dyneema:

Ø  Dyneema is a super-strong fiber. Available in white and as Black Dyneema,

Ø   It is made from Ultra High Molecular Weight Polyethylene (UHMWPE) and offers maximum strength with minimum weight.

Ø   Ultra-high-molecular-weight polyethylene (UHMWPE) is synthesized from its monomer ethylene, which is bonded together to form the base polyethylene product.

Wet spinning:

Wet spinning is required for polymers that require dissolving in a solvent to be spun. It is named wet spinning because the fibres are extruded directly into a liquid bath. Being extruded into a liquid provides a greater drag force on the Filament? than those extruded directly into air, therefore the speeds at which this occurs is reduced from that of melt and dry spinning. Once evaporated these fibres then have to be drawn or stretched in order to orient the polymers to give the fibre its strength.

 

The fibre solution is extruded into a liquid that will draw out the solvent, leaving behind only the polymer. The rate at which this occurs is crucial, as if it occurs too quickly the bath liquid can create micro-voids in the fibre which will be a weak points.

Wet spinning is based on precipitation, where a polymer is drawn through a spinneret into a non-solvent. The prepared spinning dope is extruded into the non-solvent and precipitation or coagulation occurs.

Fibres spun using this process include Acrylic, Rayon, Aramid, and Spandex.

Manufacturing process of Cutting Gloves:

Weaving

The process of producing a fabric by interlacing warp and weft yarns is known as weaving. The machine used for interlacement of yarns is known as loom or weaving machine .

Warp and weft are the two basic components used in weaving to turn thread or yarn into fabric:

Warp:

The lengthwise or longitudinal warp yarns are held stationary in tension on a frame or loom.

Weft: Pick

The transverse weft (sometimes woof) is drawn through and inserted over-and-under the warp.

 

A single thread of the weft crossing the warp is called a pick.

Warp End:

Each individual warp thread in a fabric is called a warp end or end.

Here is a flow chart for yarn manufacturing:

Winding:

Winding is a process in which yarn from bobbins, which is the end product of ring spinning, are converted into suitable form of package. This transfer of yarn from one type of package to another package, more suitable for the subsequent process is also called winding. Main objectives of winding process are to increase the package size, clear yarn defects and produce a package suitable for subsequent process (size and shape).

 

Warping:

In warping process, the yarns are transferred from a number of supply packages (cones) to the warp beam in the form of a sheet. The main objective of warping is to get the required number of ends as per requirement.

The three main types of warping are high speed / direct warping, sectional / indirect warping and ball warping:

·         In direct warping, the yarns are withdrawn from the single-end yarn packages (cone) on the creel and directly wound on a beam.

·         The indirect / sectional warping process completes in two steps, i. e. warping and beaming.

·         Ball warping is the process in which warping is performed in rope form on to wooden ball.

 

   

Direct Warping                           Sectional Warping                             Ball Warping

 

 

Sizing/Slashing:

The weaving process requires the warp yarn to be strong, smooth and elastic or extensible to a certain degree. To achieve these properties on warp yarns, a protective coating of polymeric film forming agent (size) is applied on the warp yarns prior to weaving; this process is called slashing or sizing.

The Purposes of sizing:

·         To reduce the yarn hairiness that would interfere with the weaving process

·         To protect the yarn from yarn-to-yarn and yarn-to-loom abrasion

·         To increase the strength of the yarn.

Drawing-In:

After sizing, the sized warp beam is prepared to be placed on the weaving machine and for this purpose drawing-in is done. It is the entering of yarns from a new warp beam into the weaving elements of a machine, namely drop wires, heddles (healed wire) and reed, when starting up a new fabric style.

Drop Wire                                       Healed Wire                                           Reed

 

Weaving:

The length wise yarns which run from the back to the front of the loom, which forms the basic structure of the fabric and are called the warp. Warp yarns are yarns that are parallel to the selvedge which run through the length of the fabric.

WEFT/Fill:

Crosswise yarns that run across the loom are called the weft / filling yarns. Weft yarns are yarns that are perpendicular to the selvedge which run through the width of the fabric.

Basic operations of weaving:

The conversion of warp sheet into fabric by interlacing with weft yarn requires the basic operations to be carried out on loom in a specific order.

It involves the primary motions, secondary motions and the stop motions:

Primary Motions:

Shedding: the separation of the warp sheet into two layers to form a tunnel known as the shed.

Picking: insertion of weft yarn, across the warp sheet width, through the shed.

Beat-up: pushing the newly inserted length of weft (pick) to the fell of cloth.

Secondary Motions:

The secondary motions facilitate the weaving of fabric in a continuous way. These include:

Let off: this motion provides warp sheet to the weaving area at the required rate and under constant tension by unwinding it from weaver’s beam.

Take-up: this motion draws fabric from the weaving area at a uniform rate to produce the required pick spacing and wind it onto a roller.

Stop Motions:

·         These motions are used in the interest of quality and productivity; stopping the loom immediately in case of some problem.

·         The warp stop motion will stop the loom in case any warp yarn breaks, avoiding excessive damage to the warp threads.

·         Similarly, weft stop motion will come into action in the absence of weft yarn, and stop the loom.

 

Classification of Weaving Machines / Basic types of picking mechanism:

Weaving machines are classified according to their filling insertion mechanism. The classification is as follows:

·         Shuttle

·         Shuttle-less

·         Projectile

·         Rapier

·         Air-Jet

·         Water-Jet

 

Basic construction of Woven Fabric (Basic Weaves):

 

·         Plain

·         Twill

·         Satin

 

Knitting

Knitting is a process of manufacturing a fabric by inter- looping of yarns. Knitting is the second most important method of fabric formation. It can be defined as a needle technique of fabric formation, in which, with the help of knitting needles, loops are formed to make a fabric or garment. Fabric can be formed by hand or knitting machine but the basic principle remains exactly the same i.e. pulling a new loop through the old loop. Knitted Fabric are popular for their shape fitting property, soft handle, bulkier nature and high extension at low tension.

 

Types of Knits:

Knitted fabrics

Knitting

Warp knitting

Tricot

Raschel

Single jersey

Purl

Rib

k

 

 

Classification of Knitting:

Knitting is primarily classified as weft knitting and warp knitting. This classification is based on the direction of movement of yarn with respect to the direction of fabric formation.

Warp Knitting:

·         In case the yarns run in length direction, i.e. the direction of fabric formation during knitting, the process is called warp knitting.

·         The yarns inside the knitted fabrics are just like the warp yarns in woven fabrics. Such knitted fabrics are called warp knitted fabrics, and the machine which produces such fabric is known as warp knitting machine.

Weft Knitting:

·        
If the yarns run in the width or crosswise direction with reference to the direction of fabric formation during knitting, then the process of knitting is called weft knitting.

Applications of Knitted Fabrics:

·         Sportswear (conformity, flexibility)

·         Casual wear (comfort)

·         Dress wear

·         Technical textiles application

Compact Technical front and back

The side of the knitted fabric having all of face of Knit loop is called Technical face of the fabric.

 

Technical Back:

The side of knitted fabric consist of back loops is called technical back of the fabric.

 

Needle loop:

It is the basic unit of knitted structure consists of a head (H) and two side limbs or legs (L). At the base of each leg is a foot (F), which meshes through the head of the loop formed at the previous knitting cycle.

Wales:

A wale is a vertical column of loops produced by the same needle knitting at successive knitting cycles. The number of Wales determine the width of the fabric and they are measured in units of Wales per centimeter.

Courses:

Courses are rows of loops across the width of the fabric produced by adjacent needles during the same knitting cycle and are measured in units of courses per centimeter. The courses determine the length of the fabrics.

Stitch Length:

The stitch length is one of the most important factors controlling the properties of knitted fabrics. The stitch length, measured in millimeter is the length of the yarn in the knitted loop. Generally, longer the stitch length, the more open and lighter the fabric.

Stitch density:

Stitch density is a term frequently used in knitting and represents the total number of needles loop in a given area. Stitch density is the product of Courses and Wales per unit length and is measured in units of loops per square centimeter.

                                                        Textile Processing

Textile materials in different forms, such as fiber, yarn, woven fabric, knitted fabric or garment may be subjected to different textile processing operations. An additional heat-setting process may be required for fabrics containing synthetic fibers. Some processes may be combined, for example scouring and bleaching may be combined in one operation; similarly dyeing may be combined with some chemical finishes or finishing may be done directly after bleaching.

 

                                                            A general textile processing flowchart

 

 

Singeing:

Singeing is a process of passing an open-width fabric over a hot surface or a gas flame at such a distance and speed that it burns only the protruding fibers but does not damage the main fabric.

The main objective of the singeing process is to produce a clean fabric surface and reduce fabric pilling tendency by removing the protruding fibers from the fabric surface.

The singeing is done by three ways:

1.   Plate singeing machine

It consists of one or two brass plates. These plates are heated until red hot. Fabric is passed at the speed of 125---200 m/min depends on quality. The one side of fabric is singed. This is the oldest method.

2.   Roller Singeing Machine

The only difference between plate singeing and roller singeing is that here we use brass rollers instead of brass plates. The only advantage of the roller singeing is that fabric is heated very smoothly.

3.   Gas Singeing Machine

The advantage of gas singeing is that the fabric is singed from both sides.

 

 

Desizing:

Desizing is a process of removing sizing agents from the fabrics, which are usually applied on the warp yarns before weaving. Sizing agents mostly comprise macromolecular film-forming and fiber-bonding substances such as starch, PVA and polyacrylates.

Methods of desizing are:

·         Hot water Desizing

·         Desizing with hot alkali treatment

·         Desizing with hot detergent solutions

·         Oxidative Desizing

·         Acid Desizing

·         Enzymatic Desizing

(Singeing and Desizing)

Scouring:

Scouring is a process for removing natural and acquired impurities from fabrics to make them more absorbent Scouring removes all the oils, waxes, fats and dirt/dust so that it becomes water absorbent.

Cotton fabrics are usually scoured by using liquors containing strong alkali such as caustic soda and detergents at boiling temperature.

 

Bleaching:

 

Bleaching means the removal of the all color impurities. Bleaching is done by different methods such as:

 

·         Chlorite Bleaching

·         Per Acetic Acid Bleaching

·         Per Oxide Bleaching

 

Some common bleaching agents are:

Sodium hypochlorite (NaOCl), calcium hypochlorite Ca(OCl)2, hydrogen peroxide, optical brightening agents etc.

Mercerizing:

Mercerizing is a chemical process to improve the luster and increase strength. In this process the fabric is treated with specific concentration of alkali (NaOH) under tension. This will lead the cotton fibers to be swollen and increased strength. Also, this will improve dye absorption of the fibers. Mercerization process is only done for

those fabrics which are made from 100 % cotton or contain substantial amount of cotton in case of a blend. Mercerization is not done for purely synthetic fabrics such as those made from polyester or nylon.

 

 

Dyes and Pigments:

There are two main types of colorants:

·         Dyes

·         Pigments

Dyes are either soluble in the dyeing medium (e. g. water) or can dissolve into the textile substrate.

Pigments are neither soluble in the dyeing medium nor can dissolve into the substrate.

Both pigments and dyes can be natural or synthetic.

Dye:

Dye is a substance made from plants or chemicals which is mixed into a liquid and used to change the colour of something such as cloth or hair.

Pigment:

Pigment is a substance that imparts color to other materials especially; a powdered substance that is mixed with a liquid in which it is relatively insoluble and used specially to impart color to coating materials (such as paints) or to inks, plastics, and rubber.

Dyeing:

Dyeing is the process of coloring textile materials by immersing in an aqueous solution of dye called dye liquor. Generally the dye liquor consists of dye, water and other such materials which increase the effect of dyeing. Heat is usually applied to the liquor.

Textile materials can be dyed in fiber, yarn, fabric or garment form.

Ø  Dyeing of fibers is known as ‘stock dyeing’.

Ø  Dyeing of yarns in the form of wound packages, skeins or beams is known as ‘package dyeing’, ‘skein dyeing’ or ‘beam dyeing’ respectively.

Ø  Fabric dyeing is also known as ‘piece dyeing’.

 

 

Some specific dyeing materials are mentioned for some fiber materials:

 

Different dyeing materials are used for different fiber materials. Various dyeing materials exits, as the fiber possess different reactive groups due to their chemical structure

Cellulose:

 

•          Direct Dyes

 

•          Vat Dyes

 

•          Reactive Dyes

 

•          Sulfur dyes

 

Wool:

 

•          Acid Dyes

 

•          Chrome Developed dyes

 

Polyester:

 

•          Disperse dyes

 

 

Dyeing Methods:

Dyeing methods can be classified into two main types:

·         Exhaust dyeing

·         Pad dyeing.

Exhaust dyeing:

In exhaust dyeing, textile materials (in the form of fibers, yarn or fabric) are placed in the dye liquor and remains in its contact throughout the dyeing time, during which the dye molecules gradually move (or exhaust) from the liquor toward the fabric, for absorption and fixation in the textile material.

 

(Winch Dyeing machine for Exhaust Methods)

 

 

Pad dyeing:

In pad dyeing method, a continuous batch of fabric in open width, passes through an impregnator (or padding trough) containing dye liquor, followed by a passage between a pair of squeeze rollers. The pressure of the squeeze rollers can be adjusted to obtain a desired wet pick-up. For example, a wet pick-up of 100 % would result in fabric twice its original dry weight, after the impregnation and squeezing.

(Anti Deflection Padder Machine)

Printing:

Printing is actually a type of dyeing. The main difference between printing and dyeing is that in dyeing the fabric is given one color only by dipping in the solution of dye, whereas in printing different colors are applied according to the requirement of design.

 

PRINTING MACHINE

 

For printing usually four types of machines are used:

·         Roller printing machine

·         Multi roller printing machine

·         Flat belt printing machine

·         Rotary printing machine

Finishing department:

In finishing department final process is done. The fabric is brought to finishing department after bleaching, dyeing or printing. Many qualities are produced in fabric during finishing.

The Finishing process is divided into two major portions:

1- Mechanical Finishing:

This is surface treatment of textile by means of special mechanical processing machine. This process is used to developed the special fabric characteristics e.g. Shearing, Gigging, Calendaring.

2- Thermal Finishing:

 

Thermal Finishing includes finishing process that requires warmth, coating of chemical finishes and drying processes are belong to this group.