Textile Testing Quality Control

Product Development and Research Checking Raw Materials The production cycle as far as testing is concerned starts with the delivery of raw material.. Product Development and Research I

Textile Testing:

The testing of textile products is an expensive business A laboratory has to be set up and furnished with a range

of test equipment Trained operatives have to be employed whose salaries have to be paid throughout the year, not just when results are required Moreover all these costs are nonproductive and therefore add to the final cost

of the product Therefore it is important that testing is not undertaken without adding some benefit to the final product There are a number of points in the production cycle where testing may be carried out to improve the product or to prevent sub-standard merchandise progressing further in the cycle

Reasons for Textile Testing

1 Checking Raw Materials

2 Monitoring Production

3 Assessing the Final Product

4 Investigation of Faulty Material

5 Product Development and Research

Checking Raw Materials

The production cycle as far as testing is concerned starts with the delivery of raw material If the material is incorrect or sub-standard then it is impossible to produce the required quality of final product The textile

industry consists of a number of separate processes such as natural fibre production, man-made fibre extrusion, wool scouring, yarn spinning, weaving, dyeing and finishing, knitting, garment manufacture and production of household and technical products These processes are very often carried out in separate establishments,

therefore what is considered to be a raw material depends on the stage in processing at which the testing takes place It can be either the raw fibre for a spinner, the yarn for a weaver or the finished fabric for a garment maker The incoming material is checked for the required properties so that unsuitable material can be rejected

or appropriate adjustments made to the production conditions The standards that the raw material has to meet must be set at a realistic level If the standards are set too high then material will be rejected that is good enough for the end use, and if they are set too low then large amounts of inferior material will go forward into

production

Monitoring Production

Production monitoring, which involves testing samples taken from the production line, is known as quality control Its aim is to maintain, within known tolerances, certain specified properties of the product at the level at which they have been set A quality product for these purposes is defined as one whose properties meets or exceeds the set specifications Besides the need to carry out the tests correctly, successful monitoring of

production also requires the careful design of appropriate sampling procedures and the use of statistical analysis

to make sense of the results

Assessing the Final Product

In this process the bulk production is examined before delivery to the customer to see if it meets the

specifications By its nature this takes place after the material has been produced It is therefore too late to alter the production conditions In some cases selected samples are tested and in other cases all the material is

checked and steps taken to rectify faults For instance some qualities of fabric are inspected for faulty places

which are then mended by skilled operatives; this is a normal part of the process and the material would be dispatched as first quality

Investigation of Faulty Material

If faulty material is discovered either at final inspection or through a customer complaint it is important that the cause is isolated This enables steps to be taken to eliminate faulty production in future and so provide a better quality product Investigations of faults can also involve the determination of which party is responsible for faulty material in the case of a dispute between a supplier and a user, especially where processes such as

finishing have been undertaken by outside companies Work of this nature is often contracted out to

independent laboratories who are then able to give an unbiased opinion

Product Development and Research

In the textile industry technology is changing all the time, bringing modified materials or different methods of production Before any modified product reaches the market place it is necessary to test the material to check that the properties have been improved or have not been degraded by faster production methods In this way an improved product or a lower-cost product with the same properties can be provided for the customer A large organisation will often have a separate department to carry out research and development; otherwise it is part of the normal duties of the testing department

Textile Testing & Quality Control (TTQC) is very important work or process in each department of export oriented industry Buyers want quality but not quantity In every department of textile industry quality

maintained of each material, Because one material‘s quality depend on another‘s quality For example, if

qualified fiber is inputted then output will be good yarn

Testing : Testing is the process or procedure to determines the quality of a product

Quality : The term quality refers the excellence of a product When we say the quality of a product is good

We mean that the product is good for the purpose for which it has been made

Control : To check or verify and hence to regulate

Quality Control: Quality control is the synthetic and regular control of the variable which affect the quality

Objects of Quality Control:

 To produce required quality product

 To fulfill the customer's demand

 To reduce the production cost

 To reduce wastage

 To earn maximum profit at minimum cost

Objective of Testing

Reasons for Textile Testing:

Checking the quality and suitability of raw material and selection of material

Monitoring of production i.e process control

Assessment of final product, whether the quality is acceptable or not, (how will be the yarn performance in

weaving? etc)

Investigation of faulty materials (analysis of customer complaint, identification of fault in machine etc.)

Product development and research

Specification testing: Specifications are formed and the materials are tested to prove whether they fall within the limits allowed in the specification (e.g specified by a customer)

Test Requirement for Export quality Textile Product

Standard Operating Procedure(SOP)

Major Chemical Test of Textile Product

Formaldehyde

 Volatile compound

 A gas at room temperature with a pungent smell

 Readily soluble in water to form formalin or formol

 Washing might reduce formaldehyde of fabrics

 Release from textile at body temperature

 Formaldehyde exposure can be in the form of gas –phase inhalation or liquid - phase skin absorption Exposure to high concentration formaldehyde can be fatal; it can cause skin allergy and mucous membrane irritations

 Long term exposure may cause respiratory difficulty, eczema and sensitization

It is classed as a human carcinogen and has been linked to nasal lung cancer, and with possible links to brain cancer and leukemia

Nickel Release

 Asthma and chronic bronchitis

 Allergic reactions such as skin rashes

 Heart disorders

Hexavalent Chromium (Cr VI)

Chemical element chromium (Cr) exists in three main forms:

1 Chromium metal

2 Trivalent chromium (Cr III)

- health effect: safe

- Cr III sulfate: tanning processes

3 Hexavalent chromium (Cr VI)

- inhalation exposure: lung cancer

- direct skin contact: cause skin irritation

WHO & EPA: Cr VI is human carcinogen WHO EP

Requirement is 3 mg/kg

Phthalates

Phthalates , or phthalate esters, are esters of phthalic acid and are mainly used as plasticizers (substances

added to plastics to increase their flexibility, transparency, durability, and longevity) Phthalates are

manufactured by reacting phthalic anhydride with alcohol(s) that range from methanol and ethanol (C1/C2) up

to tridecyl alcohol (C13), either as a straight chain or with some branching They are divided into two distinct groups, with very different applications, toxicological properties, and classification, based on the number of carbon atoms in their alcohol chain They are used primarily to soften polyvinyl chloride (PVC) Lower-

molecular-weight phthalates (3-6 carbon atoms in their backbone) are being gradually replaced in many

products in the United States, Canada, and European Union over health concerns They are replaced by molecular-weight phthalates (those with more than 6 carbons in their backbone, which gives them increased permanency and durability) In 2010, the market was still dominated by high-phthalate plasticizers; however, due to legal provisions and growing environmental awareness and perceptions, producers are increasingly forced to use non-phthalate plasticizers

high-Phthalates are used in a wide range of common products, and are easily released into the environment Although there is no covalent bond between the phthalates and plastics, they are physically bound into the plastic as a result of the heating process used to make PVC articles They can be removed only by exposure to severe heat

or using strong solvents However, people are exposed to phthalates, and most Americans tested by the Centers

for Disease Control and Prevention have metabolites of multiple phthalates in their urine Phthalate exposure may be through direct use or by indirect means through leaching and general environmental contamination Diet

is believed to be the main source of di(2-ethylhexyl) phthalate (DEHP) and other phthalates in the general population Fatty foods such as milk, butter, and meats are a major source In studies of rodents exposed to certain phthalates, high doses have been shown to change hormone levels and cause birth defects

Application

 As plasticizer in plastics (especially PVC)

 Increase softness and flexibility

 Advantage: flexibility, durability, longevity and low cost

 Synthetic organic colorants

 In theory, azo dyes can supply a complete rainbow of colours They have fair to good fastness properties

 The azo compound class accounts for 60-70% of all dyes

 These dyes may undergo in vivo reductive cleavage to aromatic amines and some of them are proven or supposed carcinogenic

Technical relevance of Azodyes

More than 3000 different azo colorants (dyes+pigments) are produced

Approximately 50 - 150 are banned azodyes 50-150

- banned amine components

> 50% of the dyes used nowadays are azodyes

Percent distribution of each chemical class between major application range

Pigme nt

Reac tive

Solve nt

Percent distribution of chemical classes in Reactive dye hue sectors/%

Chemical

class

Yello w

Oran ge

Red Violet Blue Green Brown Black % of all

reactive dyes

Oran ge

Red Violet Blue Green Brown Black % of all

disperse dyes

Listed of banned amines

 22 aromatic amines are forbidden in the EU Regulation 1907/2006 Annex XVII and item 43 (limit：30ppm) These 22 amines are known to be carcinogens or potential carcinogens

 2 additional aromatic amines (2,4-Xylidine & 2,6-Xylidine) that are forbidden for many retailers such as

Wortmann, Novi, Adidas, Deichmann …

 China also forbids the use of aromatic amines in the national standard GB 18401 with a limit of 20mg/kg

 Forbidden in EU over 20 years

APEO/NPEO/NP/LABSA/LAS:

Alkylphenol ethoxylates (APEOs – often called

alkyphenols or alkylphenyls) are surfactants which

have an emulsifying and dispersing action, so they

have good wetting, penetration, emulsification,

dispertion, solubilizing and washing characteristics

This makes them suitable for a very large variety of

applications: they‘ve been used for over 50 years in a

wide variety of products In the textile industry, they

are used in detergents and as a scouring, coating or waterproofing agents, in printing pastes and adhesives, and

in dyeing The most important APEO or alkylphenol ethoxylates for the textile industry are NPEO (nonylphenol ethoxylates) and OPEO (octylphenol ethoxylates) due to their detergent properties, but there are a big family About 90% of the produced APEO are in fact NPEO

PAHs(polycyclic aromatic hydrocardons)

Polycyclic aromatic hydrocarbons (PAHs, also polyaromatic hydrocarbons) are hydrocarbons—organic

compounds containing only carbon and hydrogen—that are composed of multiple aromatic rings (organic rings

in which the electrons are delocalized) Formally, the class is further defined as lacking further branching

substituents off of these ring structures Polynuclear aromatic hydrocarbons (PNAs) are a subset of PAHs that

have fused aromatic rings, that is, rings that share one or more sides.Though poly- in these cases literally means

"many", there is precedence in nomenclature for beginning this class and subclass with the two ring cases, where biphenyl and naphthalene would therefore be considered simple examples; beginning at three rings, examples include anthracene and phenanthrene

16 EPA PAH(Polycyclic aromatic hydrocarbons)

Found for example in tobacco smoke

One reason that tobacco smoke may cause cancer

Naphthalene Nap

 was used in moth balls

 gave moths balls its typical smell

Requirement:

Major Physical Tests for Textile product:

Dimensional Stability Test

Determination of the dimensional stability (shrinkage or growth) of woven and knit fabrics when subjected to Domestic washing and drying procedures - (ISO 5077, ISO 6330 & ISO 3759)

Significance

The test is to confirm that garments will perform to the user’s satisfaction if they are washing according to provided care instructions Any distortion like shrinkage or growth out of shape, etc., would affecting the comfort and appearance of garments

The specimen is conditioned in standard environment according to ISO 139 (20 ± 2°C, 65 ± 4% relative humidity)

Specimens are marked and measured with calibrated ruler, then washed and dried according to the provided care

instructions The washed specimen is re-conditioned in standard conditions before measurement of the dimensional change

Number of washing cycle: 1 (ISO requirement)

Fabrics: specimen size 500mm x 500mm,

bench mark distance 350mm

Control of shrinkage:

Origin of shrinkage in fabrics:

Fibers spun into yarn are under constant tension during the weaving process Such action will impose internal stresses in the fiber molecules Without permanent fixing, fibers tend to revert to their natural state, which causes shrinkage

In general, the factors in controlling shrinkage in fabrics are stability of the fiber and the construction of the fabric

Construction based on the type of weave, the amount of twist in the yarn, the fabric count, and the yarn count There are several ways to control and reduce shrinkage in fabrics

1 Compressive Shrinkage

2 Resin Treatment

3 stentering

Torque (Spirality)

Spirality is the measurement of twisting of fabrics after washing

The origin of spirality arises from molecule, yarn and fabric construction

The specimen is conditioned in standard environment according to ISO 139 (20 ± 2°C, 65 ± 4% relative humidity) A standard square marking is put on a specimens, then washed and dried according to the provided care instructions The washed specimen is re-conditioned in standard conditions before measurement of spirality

Spirality (Twisting)of Knitted Fabric

It is well known that weft knitted fabrics tend to undergo certain dimensional change that causes distortion in which there

is a tendency of the knitted loops to bend over, causing the Wales to be at diagonal instead of perpendicular to the courses

Angular relationship of course and Wales in a knitted structure

In other words, spirality occurs in knitted fabric because of asymmetric loops which turns in the wales and course of a

fabric into an angular relationship other than 90 degree This is a very common problem in single jersey knits and it may

exist in grey, washed or finished state and has an obvious influence on both the aesthetic and functional performance of

knitwear However, it does not appear in interlock and rib knits because the wale on the face is counter balanced by a

wale on the back

Course spirality is a very common inherent problem in plain knitted fabrics Some of the practical problems arising out of the loop spirality in knitted garments are: displacement or shifting of seams, mismatched patterns and sewing difficulties These problems are often corrected by finishing steps such as setting / treatment with resins, heat and steam, so that wale lines are perpendicular to the course lines Such setting is often not stable, and after repeated washing cycles, skewing of the wales normally re-occurs

Causes of generation (spirality ):

The residual torque in the component yarn caused due to bending and twisting is the most important phenomenon

contributing to spirality The residual torque is shown by its twist liveliness Hence the greater the twist liveliness, the greater is the spirality Twist liveliness of yarn is affected by the twist factor or twist multiple Besides the torque, spirality

is also governed by fibre parameters, cross-section, yarn formation system, yarn geometry, knit structure and fabric

finishing Machine parameters do contribute to spirality For instance, with multi-feeder circular knitting machines, course inclination will be more, thus exhibit spirality

Besides marking method, measurement of the spirality in garment samples can be based on side seam twisting Such measurement will include not only the fabric torque but also the effect from garment structure

Ways to reduce Spirality :

 Relaxation Finishing - This allows the individual loop structure to distort to relieve the internal stress

 Heat Setting - for thermoplastic man made fabrics The fabrics temperature is raised almost to the glass transition temperature† of the fibers in order to relieve the internal stress

 Resination - Stabilization of the fabric through application of resin Hand will be impaired, however softener can improve such adverse effect

† Glass transition temperature is the temperature of transition between rubbery stage and glassy stage

Appearance:

Evaluation of appearance of a product (distortion, pilling, hand feel, trim compatibility) after washing according to the provided care instructions

Specimens are visually evaluated before and after washing according to the provided care instructions Any visual

defects, such as rippling, puckering, trims damage, color loss, print loss, fabric rupture, differential shrinkage, etc., will be reported

The avgas force required to continue a tear previously started in a fabric is called the tensile strength

In other word tearing strength (force) is the resistance showed by fabric against tearing

Bursting strength

Busting is the resistance of a material to rupture when subjected to a pressure acting perpendicular to the plain

of the fabric The load is carried by both warp & waft thread

In tearing or breaking strength, the strength of fabric was tested by applied load is only one direction, But in case of bursting strength the direction resistance to rupture of a circular specimen in determined

Tensile Strength:

Determination of breaking force and elongation of textile fabrics - (ISO 13934-2)

Significance

It indicates the potential strength of woven fabric within a product in resistance to tension

This test method is not recommended for knitted fabrics and other textile fabrics which have high stretchability (more than 11%)

The fabric is conditioned in a standard environment of 20 ± 2°C and 65 ± 4% relative humidity for at least 24 hours The fabric is cut into specific specimen sizes 200mm x 100mm Both warpwise and weftwise directions are required Test specimens are mounted on a tensile tester along the long dimension and subjected to a constant rate of extension The loading force at point of rupture or break is recorded as tensile strength

General Note:

 Coarser yarn size gives a greater tensile strength

 High twist yarn gives a greater tensile strength

 Higher fabric count gives a greater tensile strength

 Different fiber possess different tensile properties

Tearing Strength:

Determination of the average force required to continue a tear from a slit in a woven fabric by means of falling pendulum (Elmendorf) apparatus - (ISO 13937-1)

Significance

It indicates the potential strength of woven fabric within a product in resistance to tearing action

The method is applicable to treated and untreated woven fabrics, including those heavily sized, coated or treated The test is not suitable for knit fabrics, felts or non-woven fabrics

resin-The fabric is conditioned in a standard environment of 20 ± 2°C and 65 ± 4% relative humidity for at least 4 hours Specimens, for both warpwsie and weftwise, of specific shape are die-cut from the sample fabric The specimens are mounted between two clamps, precut by a knife then torn through a fixed distance by the

swinging pendulum to generate the average tearing force in pounds for both the warp and weft directions

Sample size for Pendulum tear

Important Note:

 Coarser yarn size gives greater tearing strength

 Looser sett gives better tearing strength

 Different surface finishes on the fabric will affecting the tearing properties

Bursting Strength

Determination of bursting strength of textile fabrics using hydraulic method - (ISO 13938-1)

Significance

It indicates the potential strength of the knitted fabric within a product

The fabric is conditioned in a standard environment of 20 ± 2°C and 65 ± 4% relative humidity according to ISO 139 Test specimen is clamped over an expandable diaphragm The diaphragm is expanded by fluid pressure to the point of specimen rupture

Important Note:

 Coarser yarn size gives greater bursting strength

 Higher stitch density gives higher bursting strength

 Different surface finishes on the fabric will affecting the bursting properties

Seam slippage is the separation of seam due to slippage of filling yarns over warp yarns or warp yarns over filling yarns

In such slippage, the stitching thread is remain unbroken

The fabric alignment of adjacent patch of a seam may not be the same in a garment seam Direct measurement of seam slippage on garment seam provide a more accurate result

Remedies for preventing seam slippage:

1 Superimposed seam type

2 Lapped seam type with tape / interlining reinforcement

3 Anti-slip finish (resin treatment)

Colour fastness

The stability of color or it fastness is one of the most important requirement of valuable customers Color

fastness is the resistance of the color to fade or breed by these agencies These changes occur because of

decomposition of the molecules in the fiber or because of their removal into the external medium

Colour fastness to domestic and commercial laundering