Textile Testing

Textile Testing

• Fabric testing plays a crucial role in gauging product quality, ensuring regulatory compliance and assessing the performance of textile materials.

• It provides information about the physical or structural, chemical and performance properties of the fabrics.

• Textile fabrics are manufactured for many different end uses, each of which has different performance requirements

The main reasons for testing of textiles

• control of product, • control of raw materials, • process control and • analytical information

Fabrics

Sewing Thread

Final Product – Shirt

Why Textile Testing is important ?

• Testing is important, mainly for customer satisfaction of the textile product

• as well as to ensure product quality for the market in which the textile manufacturer competes

• Testing is also important in order to control the manufacturing process and cost.

Two main Aspects of Quality Control

• Testing • Inspection • Testing should be accomplished by some

standard methods so that the test results can be compared.

• Inspection is visual examination with respect to the specifications

sources for standard test methods for textiles.

• American Society for Testing and Materials (ASTM)

• American Association for Textile Chemists and Colorists (AATCC)

• International Standards Organization (ISO)• Bureau of Indian Standards (BSI)

American Society for Testing and Materials (ASTM)

• The purpose of this organization is to develop standards on characteristics and performance of materials, products, systems and services.

• The standards developed by ASTM include – test methods, – specifications and – definitions and – usually deal with physical properties of materials.

Standards for Textiles

• For textiles, ASTM writes primarily physical-type tests such as methods for testing the – tensile strength – abrasion resistance, – twist determination, – fibre maturity, – denier and yarn count, among many others

American Association for Textile Chemists and Colorists (AATCC)

• AATCC was founded to promote greater knowledge of textile dyes and chemicals and therefore is concerned specifically with textile products.

• This organization works very closely with ASTM but writes chemical-type tests.

• AATCC sponsors scientific meetings and promotes textile education

International Standards Organization (ISO)

• The International Organization for standardization (ISO), based in Geneva, Switzerland is an organization that serves member organizations throughout the world– American National Standards Institute (ANSI)– Standards Council of Canada (SCC),– British Standards Institution (BSI),– Standards Australia (SAA), – the Bureau of Indian Standards (BIS), – China State Bureau of Technical Supervision (CSBTS).

Bureau of Indian Standards (BSI)

• The Bureau of Indian Standards (BIS), the national standards body of India, is involved in the development of technical standards (popularly known as Indian Standards), product quality and management system certifications and consumer affairs.

• It resolves to be the leader in all matters concerning standardization, certification and quality.

Precision and Accuracy of Test Methods

• Precision is the degree of agreement within a set of observations (or) test results obtained by using a test method. It is the measure of the scatter of the results when a test is repeated.

• Accuracy is defined as the degree of agreement between the true value of the property being tested and the average of many observations, made according to the best method.

Atmospheric Condition for Testing• In order that reliable comparisons be made

among different textile materials and products among different laboratories it is necessary to standardize the humidity and temperature.

• Conditions are – 65 + 2 % RH (Relative humidity),– 70 + 20F Temperature

• Before testing, samples (fabrics or garments) should be kept in conditioning room with the above atmospheric condition for minimum of 4 hours.

Fabric Testing• Fabric testing plays a crucial role in

gauging product quality, assuring regulatory compliance and assessing the performance of textile materials.

• It provides information about the physical or structural properties and the performance properties of the fabrics.

• Today more and more countries and markets have a stake in the treatment and testing of fabric. As consumers become more aware and more demanding of products, the number of tests required for textile fabrics has grown

Scope for fabric Testing

• The performance of a fabric is ultimately related to the end-use conditions of a material. The physical, chemical, physiological and biological influences on fabrics affect their end-use performance

Physical Testing

• The first broad classes of factors that affect the performance of fabrics are physical gents and influences.

• These may be further subdivided into mechanical deformation and degradation, tactile and associated visual properties of fabrics after their use and manufacture, and their response to heat, liquids and static charge.

• They include tensile behavior, compression, bending or flexing, shrinkage, abrasion resistance, frictional rubbing, torsion or twisting, and shear.

Chemical Testing

• Chemical and photochemical exposure of textiles may lead to yellowing or discoloration of un-dyed fabrics, to fading of dyed fabrics, and/or to degradation of dyed and un-dyed fabrics.

• Textile fabrics have varying degrees of resistance to chemical agents such as water and other solvents, to acids, bases and bleaches, to air pollutants and to the photochemical action of ultraviolet light.

Biological Testing

• Textile fabrics may be adversely affected by various microorganisms and insects.

• These tests would be useful for rapid screening of various modified and unmodified fabrics for their ability to withstand biological attack.

Visual Examination• Fabrics can be evaluated for a variety of attributes to

assess their performance by visual assessment either manually (subjective assessment) or by objective evaluation techniques.

• Visual examination of fabrics includes evaluating – the texture,– surface characteristics, – dye shade variations, – design details; – weave patterns, – construction particulars, – pilling assessment, etc.

Physiological testing• Fabric physiology deals with the physiological

characteristics of fabrics that are expressed in the well-being, performance and health of the wearer.

• It covers the areas of physics, chemistry, medicine, physiology, psychology and textile technology.

• Three important physical parameters that are instrumental in the physiological processes of fabrics are heat transmission, moisture transport and air permeability.

• The psychological properties include mainly the aesthetics of the fabric such as color, fashion, prejudice, suitability for an occasion, garment style, fabric finish etc.

Intelligence Testing

• In the last decade, research and development in smart/intelligent materials and structures have led to the birth of a wide range of novel smart products in aerospace, transportation, telecommunications, homes, buildings and infrastructures.

• The testing programmes must include the testing of these fabrics to meet the ever growing demand for hi-tech fabrics and garments.

Physical and Mechanical Testing of Fabrics

• Fabrics made from both natural and manufactured fibres have been extensively used for clothing, decoration and industrial applications.

• The physical and mechanical properties of these fabrics are affected by the fibre type, yarn construction and fabric structure, as well as any treatment that may have been applied to the materials.

Tests come under Physical and Mechanical Testing

• Weight and thickness• Tensile strength• Tear strength• Seam strength and seam slippage• Burst strength• Stretch properties• Abrasion resistance• Drape• Bending. • Shearing• Compression

Fabric Strength Tests

• The strength tests include – tensile, – tear, – seam and burst strength.

• These mechanical properties are important for all textile users including fabric processors, garment manufacturers, designers and customers.

Fabric Tensile Strength Testing • Measurement of tensile stress–strain

properties is the most common mechanical measurement on fabrics.

• Fabric samples are clamped in the jaws of a tensile tester and pulled apart until they break.

• Three samples are tested across the warp and three across the weft and the average breaking strength established is expressed in Newtons.

• BS 2543 states that tensile strength should be as follows for the different grades of intended duty.

The newton is the unit of force derived in the SI system; it is equal to the amount of net force required to accelerate a mass of one kilogram at a rate of one meter per second per second

Methods for testing tensile strength

• Three methods have been commonly used to measure tensile strength:

• Grab test• Modified grab test• Strip test

Grab test• In the grab test, the width of the jaws is less than the width of the

specimen. • An example would be for a 100 mm wide specimen where the centrally

mounted jaws are only 25 mm wide. • This method is used for woven high-density fabrics and those fabrics with

threads not easy to remove from the edges. • The grab method is used whenever it is desired to determine the

‘effective strength’ of the fabric in use.

Modified grab test.

• The mounting geometry is the same as for the grab test; however, lateral slits are made in the specimen to severe all yarns bordering the portion to be strength tested, reducing to a minimum the ‘fabric resistance’ inherent in the grab method.

• This method is desirable for high-strength fabrics.

Strip test.• There are two types of strip test:

– the raveled strip test and the cut strip test.

• In both tests the entire width of the specimen is gripped in both the upper and lower jaws.

• The raveled strip test is only used for woven fabric and specimens are prepared by removing threads from either side of the test piece until it is the correct width.

• The cut strip test is used for fabrics that cannot have threads removed from their sides such as knits, non-woven, felts and coated fabrics.

• The test specimens are prepared by accurately cutting to size.

Fabric Tear Strength Testing • Tearing of a fabric can occur in a wide range of products and is involved in fatigue

and abrasion processes as well as the catastrophic growth of a cut on application of a force.

• This test measures the force required to continue a tear which has already been started in the fabric.

• A cut is made in a rectangular sample to form two "tongues" and reference lines are marked to indicate the point the tear is to be continued to.

• One tongue is then placed in the upper jaw of a tensile tester, the other tongue in the lower jaw, and the two jaws opened to continue the tear to the reference line.

• The average tear strength is then calculated.

Again, BS 2543 specifies minimum tear strength for different uses: Occasional domestic/Light domestic = 15N, General domestic/Severe domestic = 20N, Severe contract = 25N

Fabric Bursting Strength Testing

• Burst strength testing is the application of a perpendicular force to a fabric until it ruptures.

• The force is normally applied using either a ball or a hydraulically expanded diaphragm.

• The fabric is clamped in place around the device that applies the force by a circular ring.

• The material is stressed in all directions at the same time regardless of the fabric construction. Ball burst testing is used as an alternative to tensile testing for materials that are not easily prepared for tensile testing or have poor reproducibility when tensile tested.

• These fabrics include knits, lace, non-woven and felts.

Hydraulic diaphragm method

• The hydraulic diaphragm test method uses a diaphragm inflated by hydraulic pressure to apply the perpendicular force to the fabric. The aperture size is normally different from that used for ball burst tests.

Fabric Appearance Testing• Fabric appearance is always considered to be one of the most important

aspects of fabric quality.• However, the definition of fabric appearance is quite complicated; it is a

general term including the visible properties of fabric material universally, which is related to many factors, such as – structure, – material properties, – surface morphology and – reflectance properties

• Usually, fabric appearance can be described separately in terms of different attributes:

• pilling, wrinkling, seam puckering, fuzziness, dimensional change and luster.

• These kinds of typical attributes are always happening and observed during the daily wearing or washing of fabric products.

Fabric Pilling Testing• Pilling is a phenomenon of fiber movement or slipping out of yarns, which

is usually happening on the fabric surface during abrasion and wear. The development of pilling could be divided into four stages: fuzz formation, entanglement, growth, and wear-off.

Visual assessment of pilling

Grade Description

5 No change

4 Slight surface fuzzing and/or partially formed pills

3 Moderate surface fuzzing and/or moderate pilling. Pills of varying size and density partially covering the specimen surface.

2 Distinct surface fuzzing and/or distinct pilling. Pills of varying size and density covering a large proportion of the specimen surface.

1 Dense surface fuzzing and/or severe pilling. Pills of varying size and density covering the whole of the specimen surface.

Fabric Pilling Standards

• Fabric pilling or related surface change is commonly tested in the laboratories simulated by the action of abrasive materials.

• Generally, the machines are supplied with a standard reference consisting of photographs of samples tory using specific machines by generating pilling on the fabric by simulating wear. S

• ample of the original fabric is fixed in the machine and wear with different degrees of pilling.

• The abraded fabric is then compared with standard photographs that have been developed by the standards institutions such as ASTM, AATCC, IWS, BIS, JIS, etc., and a degree of pilling is assigned accordingly.

Fabric pilling: instruments

• ICI pilling box tester:-. Specimens are mounted on the polyurethane tubes and tumbled randomly in a cork-lined box for a certain time.

• Martindale tester:-.Flat abrasion as specified in the ASTM D4970 pilling test. The instrument subjects specimens to a rubbing motion in a straight line that widens into an ellipse and gradually changes into a straight line in the opposite direction. This pattern of rubbing is repeated until fabric threads are broken or until a shade change occurs in the fabric being tested.

• Random tumble pilling tester:-. The specimen is placed in a cylindrical chamber and tumbled around within the chamber which is lined with mildly abrasive materials to brush the specimens to free fiber ends.

Fabric Abrasion Resistance Testing

• Both the fiber material and fabric geometry affect the abrasion resistance of a fabric. Some polymers are intrinsically better abrasion resistant than others. The twist level, yarn crimp and weave design affect the abrasion resistance of the fabric. The amount of fiber and yarn surface that is in contact with the abradant is important.

• Abrasion resistance of fabrics is measured in terms of visual appearance, number of cycles to open a hole in the fabric and residual strength of the fabric. There are several tests for abrasion resistance:– Inflated Diaphragm Test (ASTM D3886)– Flexing and Abrasion Method (ASTM D3885)– Oscillatory Cylinder Method (ASTM D4157)– Rotary Platform Double Head Method (ASTM D3884)– Uniform Abrasion Method (ASTM D4158)– The Accelerator (AATCC 93)– Martindale Abrasion Tester (ASTM D4966)– Special Webbing Abrader

Wrinkle Recovery & Crease Recovery Testing

• Wrinkles are three-dimensional versions of creases, and form when fabrics are forced to develop high levels of double curvature, which result in some degree of permanent in-plane and out-of-plane deformations.

• Most fabric will generate some wrinkles after laundering, dressing, and folding.

• These wrinkles seriously compromise the cloth’s acceptability.– For example, for most customers it is an unpleasant feeling to be

wearing a wrinkled shirt while attending some social activities.

The photographs in Figure show standard wrinkling images of fabrics from grade 1 to grade 5.

Crease Recovery

• The ability of textiles to recover from creases is determined by measurement of its creases recovery angle.

Drape and Hand

• Drape is the term used to describe the way a fabric hangs under its own weight.

• The draping qualities required from a fabric will garments made from them will tend to follow the body contours.

• Drape and hand are extremely important for apparel fabrics. Drape can be defined as the ability of a fabric to bend under its own weight to form folds. Hand or handle is a subjective property that can be related to the comfort perception of the fabric

WOVEN FABRIC IDENTIFICATION

• Determination of Warp Direction– If one set of yarns have ply in the fabric, it is usually the warp

yarns. – Warp yarn needs to be stronger than the filling yarn due to

heavy forces acting upon them. – In general, the warp density (ends/unit length) is more than the

filling density (fillings/unit length). – In the fabric, warp yarns are usually straighter than filling yarns

since filling yarns may have more tendencies for bow and skewness.

– The selvage of the fabric runs parallel to the warp direction. – Prominent stripes or marks are usually in the warp direction.

Reed marks also run in the warp direction.

Determination of face and back side• In general, the fabric design is more visible on the face. • For example, in a twill fabric, twill lines are more prominent

on the face. • Ribs are more visible on the face in a ribbed fabric. • Satins are smoother on the face than the back. • Slub yarn fabrics are more distinct on the face. • The face of the napped fabrics is fuzzier and softer. • The face is usually finer and more lustrous on double fabrics. • The face would have less reed marks than the back. • In finished fabrics, the face has better finish quality. • In printed fabrics, the prints on the face are clearer and the

colors predominate.

Determination of the Order of Interlacing (Weave)

• Order of interlacing can be determined with the naked eye for coarse fabrics or using a magnifying glass or a microscope for fine fabrics.

• It is important that an undistorted sample that is larger than the repeat unit (by estimation) is examined from the main body of the fabric for this purpose.

• Starting at a randomly selected point on the lower left side of the fabric, the interlacing pattern of the warp and filling yarns is determined until a repeat is found in both directions.

• Warp yarns are numbered from left to right and filling yarns are counted from bottom to top.

• The selvage design is determined in a similar way. However, it is usually drastically different than the rest of the fabric.

Determination of the Presence of Size and Finish

• Sometimes observation by the naked eye is enough to detect the size or finish on the fabric. The next step would be to determine the hand properties of fabrics such as stiffness, smoothness, etc. If necessary, the sample can be observed under a microscope.