Statistical Quality Control(S.Q.C) | Function of Statistical QualityControl(S.Q.C) | The Significance of Statistical Quality Control(S.Q.C)in the Textile Industry

Statistical Quality Control(S.Q.C)
It is the application of statistical tools in the manufacturing process for the purpose of quality control. In SQC technique attempt is made to seek out systematic causes of variation as soon as they occur so that the actual variation may be supposed to be due to the guranted random causes.

Statistical quality control refers to the use of statistical methods in the monitoring and maintaining of the quality of products and services. 

Basic Categories of Statistical Quality Control(S.Q.C):

All the tools of SQC are helpful in evaluating the quality of services. SQC uses different tools to analyze quality problem.

1) Descriptive Statistics
2) Statistical Process Control (SPC)
3) Acceptance Sampling

1. Descriptive Statistics:

Descriptive Statistics involves describing quality characteristics and relationships.

2. Statistical process control (SPC):
The application of statistical techniques to determine whether a process is functioning as desired

3. Acceptance Sampling: 

The application of statistical techniques to determine whether a population of items should be accepted or rejected based on inspection of a sample of those items.

Variations of Statistical Quality Control(S.Q.C):

1. Allowable or cause variation
2. Assignable or preventable variation

Function of Statistical Quality Control(S.Q.C):

1. Evaluation of quality standards of incomeing material, product process and finished goods.
2. Judging the conformity of the process to establish standards taking suitable action , when deviation are noted.
3. Evaluation of optimum quality, obtainable under given condition.
4. Improvement of quality and productivity by process control and experimentation.

Main purpose of Statistical Quality Control(S.Q.C):

The main purpose of Statistical Quality Control(S.Q.C) is to divide statistical method for separating allowable variation from preventable variation. 

The Significance of Statistical Quality Control(S.Q.C) in the Textile Industry:

1. The expected quality of product can be produced and hence customers satisfaction can be achieved which brings higher profit.
2. It is very easy to separate allowable variation from the preventable variation by this.
3. It ensures an early detection of faults in process and hence minimum wastage.
4. With its help one can easily defect the impact of chance in production process in the change in quality.
5. It ensures overall co-ordination.
6. It can be use in the interpretation control chart.

Microscopic Test for Natural Fiber | Microscopic Test for Manmade Fiber| Chemical Test for Textile Fiber

There are certain technical tests performedfor identifying various fibers. These tests require high technology laboratory equipment and are much more reliable than the non technical fibre tests.Technicals tests require high skilled personnel and technical know how of handling chemicals and their accurate analysis. These tests are very valuable for those fabrics that are a blend of different yarns and also have certain special properties including flame retardance etc.  

TYPES OF TECHNICAL TEST

1.  Microscopic test 
2. Chemical test

MICROSCOPIC TEST 

1.  Microscopic test is a technical test that involves identifying the fabric with the help of a microscope with a magnification of minimum 100 power.
2.  The test can easily distinguish between fibers.
3. The test identifies the natural fibers more easily as compared to man made ones.
4. Synthetic fibers are very similar in appearance and the increase in the number of varieties, makes it a little tough to distinguish the fibers even under a microscope.

MICROSCOPIC TEST FOR NATURAL FIBERS

COTTON:

• It is a single elongated cell. Under the microscope, it resembles a collapsed, spirally twisted tube with a rough surface.
•  The thin cell wall of the fiber has from 200 to 400 convolutions per inch.

LINEN:

• Under the microscope, the hair like flax fiber shows several sided cylindrical filaments with fine pointed ends.
•  The fiber somewhat resembles a straight, smooth

WOOL:

• Under the microscope , wool’s cross section shows three layers- epidermis, cortex and the medulla.

SILK:

• It appears somewhat elliptical and triangular in cross section when we see under the microscope.
• It is composed of fibroin, consisting of two filaments, called brin which is held together by sericin.

MICROSCOPIC TEST FOR MANMADE FIBERS

RAYONS:

• Rayon fibers have a glasslike luster under the microscope and appear to have a uniform diameter when viewed longitudinally.

ACETATE:

•  The cross sectional view has a bulbous or multilobal appearance with indentations.
•  These indentations appear as occasional markings or

NYLON:

•  The basic microscopic appearance is generally fine ,round, smooth, andtranslucent.
•  It is also produced in multilobal cross-sectional types.

POLYESTERS:

•  Generally, polyester fibers are smooth and straight and the cross-section is round.
•  This general characteristics may be altered to achieve certain characteristics, such

ACRYLICS: The methods of manufacturing of the acrylic fibres differ, the appearances vary accordingly.

•  ACRILAN ACRYLIC: It has a bean-shaped cross section, its longitudinal appearance is straight and smooth.
•  ORLON ACRYLIC: It has a flat, nut-shaped cross section.
•  CRESLAN ACRYLIC: It has an almost round cross section.
•  MOD ACRYLICS: it is of two types verel modacrylic and SEF modacrylic

SPANDEX: Spandex fibers are unique in appearance, they appear to be groups of fibersfused together.

GLASS: The fiber is smooth, round, translucent, highly lustrous, and quite flexible.

CHEMICAL TESTS

•  Chemical tests are another technical means of identifying fibers. But chemical tests are not intended for the general consumers.
•  Different types of chemical tests are undertaken to establish the identity of the fibers used.
•  These tests give accurate and precise analysis.
•  The tests are conducted in research laboratories.

TYPES OF CHEMICAL TEST

Stain Test:
Also known as the Double Barrel Fibre Identification (DBFI), the test is based on the theory that each fibre has its own distinct two- colour reaction when treated with stain.

A fibre will turn to a particular colour in the presence of dilute acetic acid and to some other specific colour when stained in the presence of a mild alkali.

Solvent Test:
The test involves treating the fibres in certain solvents for identifying them. The technical test is becoming difficult to conduct as most of the manufactured fibres and their blends are chemically similar. There is no individual chemical or solvent test for separating or identifying the fibres in combinations

This technical fibre identification test has the following advantages and limitations

Advantages
• More reliable than the non technical tests.
• Used for both man made fibres and natural fibres.
• Easily conducted.

Limitations
• Certain manufacturing and finishing processes like mercerizing, affects the appearance of the fibres under the microscope.
• Very dark coloured fabrics cannot be identified under microscope.
• Dye stuffs must be removed from fabrics.

Water Repellency Test | Bundesmann Water Repellency Test

Bundesmann Water Repellency Test

The Bundesmann test aims to produce the effect of a rainstorm on a fabric in the laboratory. Water repellency test is done by Bundesmann test.   In the test shown in Fig. the fabric is subjected to a shower of water from a head fitted with a large number of standard nozzles. During the shower the back of the fabric is rubbed by a special mechanism which is intended to simulate the flexing effect which takes place when the fabric is worn. 

The Bundesmann shower test.

The method is not currently a British standard because considerable variation has been found between different machines, although when tests are carried out on the same machine the variability can be reduced to acceptable levels. 

In the test four specimens are mounted over cups in which a spring loaded wiper rubs the back of the cloth while the whole cup assembly slowly rotates. They are subjected for l0 min to a heavy shower whose rate has been adjusted so as to deliver 65ml of water per minute to each cup. The water flow is maintained at 2O0C and between pH 6 and 8. Because of the large amount of water consumed the equipment has to be connected to the mains water supply which leads to difficulties in keeping the water temperature constant. The shower is calculated to have a kinetic energy 5.8 times that of a cloudburst, 90 times that for heavy rain, 480 times that for moderate rain and 21,000 times that for light rain.

Two fabric parameters are determined from the test:
1 Penetration of water through the fabric: the water collected in the cups is measured to the nearest ml.
2 Absorption of water by the fabric: in order to do this the specimen is weighed before the test and then after the shower. To remove excess water the fabric is shaken ten times using a mechanical shaker and then weighed in an airtight container: 

In each case the mean of four values is calculated.

Importance of Textile Testing | Reasons for Testing of Textile

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.

What is Serviceability? | Factors of Serviceability

Serviceability
Serviceability is a relative term which is serviceable of performing useful service.A garment is considered to be serviceable when it is fit for its particular end use. After being used for a certain length of time the garment ceases to be serviceable when it can no longer fill its intended purpose in the way that it did when it was new. The particular factors that reduce the service life of a garment are heavily dependent on its end use. For instance overalls worn to protect clothing at work would be required to withstand a good deal of hard usage during their lifetime but their appearance would not be considered important. However, garments worn purely for their fashionable appearance are not required to be hard wearing but would be speedily discarded if their appearance changed noticeably. An exception to this generalisation is found in the case of denim where a worn appearance is deliberately strived for.

Factors of Serviceability:

If asked, many people would equate the ability of a fabric to ‘wear well’ with its abrasion resistance, but ‘wear’, that is the reduction in serviceable life, is a complex phenomenon and can be brought about by any of the following factors:

1. Changes in fashion which mean that the garment is no longer worn whatever its physical state.
2. Shrinkage or other dimensional changes of such a magnitude that the garment will no longer fit.
3. Changes in the surface appearance of the fabric which include: the formation of shiny areas by rubbing, the formation of pills or surface fuzz, the pulling out of threads in the form of snags.
4. Fading of the colour of the garment through washing or exposure to light. The bleeding of the colour from one area to another.
5. Failure of the seams of the garment by breaking of the sewing thread or by seam slippage.
6. Wearing of the fabric into holes or wearing away of the surface finish or pile to leave the fabric threadbare. Wearing of the edges of cuffs, collars and other folded edges to give a frayed appearance.
7. Tearing of the fabric through being snagged by a sharp object.

Burning Test of Textile Fiber | Flammability Test of Textile Fiber |Fiber Identification Through Burning Test

Fabric Identification is done with a simple fabric burn test or fiber burn test. Flammability testing, Flammability Test is best to know the identification of fabric.

To recognize the composition of fabrics by the burning test ,the sample of fibre, yarn of fabric should be moved slowly towards a small flame and the reaction to heat carefully observed .One end of the sample should be put directly into flame to determine its burning rate and characteristics. The burning odour should be noted and the characteristics of the ash such as amount ,form, hardness and colour should be examined.

To identify fabric that is unknown, a simple burn test can be done to determine if the fabric is a natural fiber, man made fiber, or a blend of natural and man made fibers. The burn test is used by many fabric stores and designers and takes practice to determine the exact fiber content. However, an inexperienced person can still determine the difference between many fibers to “narrow” the choices down to natural or man made fibers. This elimination process will give information necessary to decide the care of the fabric.

Warning
All fibers will burn! Asbestos treated fibers are, for the most part fire proof. The burning test should be done with caution. Use a small piece of fabric only. Hold the fabric with tweezers, not your fingers. Burn over a metal dish with soda in the bottom or even water in the bottom of the dish. Some fabrics will ignite and melt. The result is burning drips which can adhere to fabric or skin and cause a serious burn.

Identification of Fibers Through  Burning Test:

Cotton
When ignited it burns with a steady flame and smells like burning leaves. The ash left is easily crumbled. Small samples of burning cotton can be blown out as you would a candle.

Linen
Linen takes longer to ignite. The fabric closest to the ash is very brittle. Linen is easily extinguished by blowing on it as you would a candle.

Silk
It is a protein fibre and usually burns readily, not necessarily with a steady flame, and smells like burning hair. The ash is easily crumbled. Silk samples are not as easily extinguished as cotton or linen.

Wool
It is also a protein fibre but is harder to ignite than silk as the individual “hair” fibres are shorter than silk and the weave of the fabrics is generally looser than with silk. The flame is steady but more difficult to keep burning. The smell of burning wool is like burning hair.

Man Made Fibres

Acetate
Acetate burns readily with a flickering flame that cannot be easily extinguished. The burning cellulose drips and leaves a hard ash. The smell is similar to burning wood chips.

Acrylic
Acrylics burn readily due to the fibre content and the lofty, air filled pockets. A match dropped on an acrylic blanket can ignite the fabric which will burn rapidly unless extinguished. The ash is hard. The smell is acrid or harsh.

Nylon
Nylon melts and then burns rapidly if the flame remains on the melted fibre. If you can keep the flame on the melting nylon, it smells like burning plastic.

Polyester
Polyester melts and burns at the same time, the melting, burning ash can bond quickly to any surface it drips on including skin. The smoke from polyester is black with a sweetish smell. The extinguished ash is hard.

Rayon
It is a regenerated cellulose fibre which is almost pure cellulose. Rayon burns rapidly and leaves only a slight ash. The burning smell is close to burning leaves.

Limitation of Burning Test:
It is apparent that many fibers have similar burning reactions that might cause doubt and occasional confusion.

Introduction of Pressing Fastness Test | Color Fastness to Pressing

Color Fastness to Pressing:
Pressing fastness test of dyed and printed textile products is performed to determine of resistance of textiles to ironing and to processing on cylinders. Different tests are performed according to when the textile is dry, when it is wet, and when it is damp. 

Purpose and Scope:
This method is used for determining the resistance of the colour of textile of all kinds and in all forms to ironing and processing on hot cylinders. Tests are given for hot pressing when the textiles are wet, when it is damp, and when it is dry.

Apparatus and Reagent  

• Hand iron of proper weight to give a pressure of approximately 30g/sq.cm at the temperature indicated in the following ;

1. Cotton & Linen 190-200C˚
2. Wool, Silk & Viscose 140-160C˚
3. Cellulose acetate & Polyamide 115-120C˚

• White bleached cotton cloth weighting approximately 125g/sq.meter. Five pieces not less than 14×4 cm are required. 
• Gray scale by assessing change in colour and staining.(ISO scale)  
• The size of the specimen is 10×4cm

Working Procedure
Specimen preparation
Specimen of materials, which has been subjected to any heat or drying treatment, must be allowed to condition at 65% RH, temp. 20±2C˚, before they tested.

Dry Pressing
Place the specimen on the piece of dry cotton cloth on a smooth horizontal surface. Place the iron on the specimen and leave it for 15 Sec.

Damp Pressing: 

The adjacent fabric in dimensions of 100 mm x 40 mm is immersed into the water and, squeezed as 100% pick up. Dry specimen is placed onto the undyed cotton fabric on the filler and, the wet adjacent fabric is placed onto them. The top layer of the device is pulled down and, dry specimen is pressed for 15 seconds at the determined temperature. The change in color of the specimen is evaluated in two different ways according to grey scale.

a) Soon after the end of the test
b) After conditioning for 4 hours under standard atmospheric circumstances.
The staining to undyed fabrics is evaluated by grey scale.

Wet Pressing
Soak the specimen and cotton cloth in distilled water and squeeze or extract them to contain their own weight of water. Place the wet specimen on a piece of the dry cotton cloth and place the wet cotton cloth on the specimen, press by moving the iron to and fro over the wet cloth (without additional pressure) for 15 sec.

Assessment
Assess the change in colour of the specimen with appropriate grey scale.

Standard
Dry Pressing 4
Wet Pressing 3-4 

Introduction of Perspiration Test | Color Fastness to Perspiration

The color fastness to perspiration (acid and alkaline) shall be at least level 3-4 (color change and staining). This criterion does not apply to white products, to products that are neither dyed nor printed, to furniture fabrics, curtains or similar textiles intended for interior decoration. A level of 3 is nevertheless allowed when fabrics are both light colored (standard depth

Color Fastness to Perspiration
The garments a\which come into contact with the body where perspiration is heavy may suffer serious local discoloration. This test is intended to determine the resistance of color of dyed textile to the action of acidic and alkaline perspiration. Before knowing about the Color Fastness to perspiration you must have to know about Color Fastness to Wash and Color Fastness to Rubbing.

Perspirometer

Well, in today’s class you will know about the perspiration matters which affects on Color fastness.

Purpose and Scope
This method is used to determine the resistance of the colour of textile of all kinds and in all forms to perspiration.

Equipment For Fastness Measurement

1. Perspiration tester
2. Oven, Maintained at 37+-2 Degree centigrade
3. Multifiber test fabric
4. Grey scale
5. Color matching chamber
6. Acidic and Alkaline solution
7. Glass or Acrylic plat
8. Weight.

Reagent for Perspiration Test

1. Solution freshly prepared, containing 0.5g 1-histidine mono-hydrochloride mono-hydrate, 5g sodium chloride, and 2.5g disodium hydrogen ortho phosphate per litre brought to PH 8.0 with 0.1N sodium hydroxide.
2. Solution freshly prepared, containing 0.5g 1-histidine mono-hydrochloride mono-hydrate, 5g sodium chloride, and 2.2g sodium dihydrogen ortho phosphate per litre brought to PH 5.5 with 0.1N sodium hydroxide.
3. Two undyed cloths for each specimen each 6×6cm of the same kind of fibre as the sample. Place the specimen between the two pieces of white cloth and sew along one side to form a composite sample.

Working Procedure :
Thoroughly wet one composite sample in a solution of PH8.0 at the liquor ratio of 20:1 and allow it to remain in this solution at room temperature for 30min. pour off the solution and place the composite sample between two glasses plates measuring about 7.5×6.5cm under a force of about 4.5kg.

1. Treat the other sample in the same way but with the solution at PH 5.5.
2. Place the apparatus containing the samples in the oven for 4 hour at 37±2C˚
3. Separate the sample from the white cloth and dry them apart in air at the temperature not exceeding 60C˚
4. Assess the change in colour of the specimen and the staining of the white cloth with the greigh scale.

What is Pilling Formation on Fabric? | Pilling Resistance Test |Working Procedure of Pilling Resistance Test

Pilling
Pilling is a condition that arises in wear due to the formation of little ‘pills’ of entangled fibre clinging to the fabric surface giving it an unsightly appearance. Pills are formed by a rubbing action on loose fibres which are present on the fabric surface. Pilling was originally a fault found mainly in knitted woollen goods made from soft twisted yarns. The introduction of man-made fibres into clothing has aggravated its seriousness. The explanation for this is that these fibres are stronger than wool so that the pills remain attached to the fabric surface rather than breaking away as would be the case with wool. Figure 7.3 shows a pill on a cotton/polyester fabric.

The initial effect of abrasion on the surface of a fabric is the formation of fuzz as the result of two processes, the brushing up of free fibre ends not enclosed within the yarn structure and the conversion of fibre loops into free fibre ends by the pulling out of one of the two ends of the loop. Gintis and Mead consider that the fuzz formation must reach a critical height, which is dependent on fibre characteristics, before pill formation can occur.

Pilling Resistance Test:
Purpose and Scope:
This method is intended for the determination of the resistance of textiles of all kinds in all forms to the action of an applied resistive force. This causes pilling in the tested fabrics

Apparatus:
· Pilling tester
· Metal plates 4 inch diameter and 1 inch thick
· Standard for assessing the pilling grade

Working Procedure:
A piece of fabric measuring 10×10 inch is sewn to a firm fit when placed round a rubber tube. The out end of the fabrics is covered by cellophane tape and metal plates are placed on the tester .Run the tester for 300 cycles. Remove the sample and compare the sample with standard scale. 

Standard
Pilling Standard:              3-4 gray scale matching 

What is Air Permeability | Air Permeability Test

Air Permeability

The air permeability of a fabric is a measure of how well it allows the passage of air through it. The ease or otherwise of passage of air is of importance for a number of fabric end uses such as industrial filters, tents, sailcloths, parachutes, raincoat materials, shirtings, downproof fabrics and airbags.

Air permeability is defined as the volume of air in millilitres which is passed in one second through 10Os mm2 of the fabric at a pressure difference of 10mm head of water.

In the British Standard test the airflow through a given area of fabric is measured at a constant pressure drop across the fabric of 10mm head of water. The specimen is clamped over the air inlet of the apparatus with the use of rubber gaskets and air is sucked through it by means of a pump as shown in Fig.A. The air valve is adjusted to give a pressure drop across the fabric of 10mm head of water and the air flow is then measured using a flow meter.

Five specimens are used each with a test area of 508mm2 (25.4mm diameter) and the mean air flow in ml per second is calculated from the five results. From this the air permeability can be calculated in ml per 100mm2 per second.

The reciprocal of air permeability, air resistance, can be defined as the time in seconds for ImI of air to pass through 100s mm2 of fabric under a pressure head of 10mm of water. The advantage of using air resistance instead of air permeability to characterize a fabric is that in an assembly of a number of fabrics, the total air resistance is then the sum of the individual air resistances. 

 

Fig(A) : The air permeability test

To obtain accurate results in the test, edge leakage around the specimen has to be prevented by using a guard ring or similar device (for example, efficient clamping). The pressure drop across the guard ring is measured by a separate pressure gauge. Air that is drawn through the guard ring does not pass through the flowmeter. The pressure drops across the guard ring and test area are equalised in order that no air can pass either way through the edge of the specimen. A guard ring of three times the size of the test area is considered sufficient.

What is Drape? | Cusick Drape Test

Drape

Drape is the term used to describe the way a fabric hangs under its own weight. It has an important bearing on how good a garment looks in use. The draping qualities required from a fabric will differ completely depending on its end use, therefore a given value for drape cannot be classified as either good or bad. Knitted fabrics are relatively floppy and garments made from them will tend to follow the body contours. Woven fabrics are relatively stiff when compared with knitted fabrics so that they are used in tailored clothing where the fabric hangs away from the body and disguises its contours. Measurement of a fabric s drape is meant to assess its ability to do this and also its ability to hang in graceful curves.

Cusick Drape Test
In the drape test the specimen deforms with multi-directional curvature and consequently the results are dependent to a certain amount upon the shear properties of the fabric. The results are mainly dependent, however, on the bending stiffness of the fabric.

Drape Test

In the test a circular specimen is held concentrically between two smaller horizontal discs and is allowed to drape into folds under its own weight. A light is shone from underneath the specimen as shown in Fig. 10.4 and the shadow that the fabric casts, shown in Fig. A, is traced onto an annular piece of paper the same size as the unsupported part of the fabric specimen.

The stiffer a fabric is, the larger is the area of its shadow compared with the unsupported area of the fabric. To measure the areas involved, the whole paper ring is weighed and then the shadow part of the ring is cut away and weighed. The paper is assumed to have constant mass per unit area so that the measured mass is proportional to area. The drape coefficient can then be calculated using the following equation:

The higher the drape coefficient the stiffer is the fabric. At least two specimens should be used, the fabric being tested both ways up so that a total of six measurements are made on the same specimen. There are three diameters of specimen that can be used:

• A 24cm for limp fabrics; drape coefficient below 30% with the 30cm sample;
• B 30cm for medium fabrics;
• C 36cm for stiff fabrics; drape coefficient above 85% with the 30cm sample. 

Drape test top view of draped fabric

It is intended that a fabric should be tested initially with a 30cm size specimen in order to see which of the above categories it falls into. When test specimens of different diameter are used, the drape coefficients measured from them are not directly comparable with one another. Figure B shows a drape tester fitted with a video camera and computer for instantaneous measurement of the drape coefficient.

Bursting Strength Test | Diaphragm of Bursting Test

Bursting Strength

Tensile strength tests are generally used for woven fabrics where there are definite warp and weft directions in which the strength can be measured. However, certain fabrics such as knitted materials, lace or non-wovens do not have such distinct directions where the strength is at a maximum. Bursting strength is an alternative method of measuring strength in which the material is stressed in all directions at the same time and is therefore more suitable for such materials. There are also fabrics which are simultaneously stressed in all directions during service, such as parachute fabrics, filters, sacks and nets, where it may be important to stress them in a realistic manner. A fabric is more likely to fail by bursting in service than it is to break by a straight tensile fracture as this is the type of stress that is present at the elbows and knees of clothing.

When a fabric fails during a bursting strength test it does so across the direction which has the lowest breaking extension. This is because when stressed in this way all the directions in the fabric undergo the same extension so that the fabric direction with the lowest extension at break is theone that will fail first. This is not necessarily the direction with the lowest strength.

Diaphragm of Bursting Test
The British Standard describes a test in which the fabric to be tested is clamped over a rubber diaphragm by means of an annular clamping ring and an increasing fluid pressure is applied to the underside of the diaphragm until the specimen bursts. The operating fluid may be a liquid or a gas.

Two sizes of specimen are in use, the area of the specimen under stress being either 30mm diameter or 113mm in diameter. The specimens with the larger diameter fail at lower pressures (approximately one-fifth of the 30mm diameter value). However, there is no direct comparison of the results obtained from the different sizes. The standard requires ten specimens to be tested.

Bursting Strength Test

In the test the fabric sample is clamped over the rubber diaphragm and the pressure in the fluid increased at such a rate that the specimen bursts within 20 ± 3 s. The extension of the diaphragm is recorded and another test is carried out without a specimen present. The pressure to do this is noted and then deducted from the earlier reading.

The following measurements are reported:

• Mean bursting strength kN/m2 
• Mean bursting distension mm
• Liquid
• Piston
• Rubber
• diaphragm
• Specimen
• Clamp

The US Standard is similar using an aperture of 1.22 ± 0.3 in (31 ± 0.75mm) the design of equipment being such that the pressure to inflate the diaphragm alone is obtained by removing the specimen after bursting. The test requires ten samples if the variability of the bursting strength is not known.

The disadvantage of the diaphragm type bursting test is the limit to the extension that can be given to the sample owing to the fact that the rubber diaphragm has to stretch to the same amount. Knitted fabrics, for which the method is intended, often have a very high extension. 

Fiber Fineness is Measured by the Airflow Method

Principle:
In this method, fiber fineness is measured by air flow. If large amount of air is blown, the fiber will be coarse and if small amount of air is blown, the fiber will be fine. The method based on this principle.

This is an indirect method of measuring fibre fineness which is based on the fact that the airflow at a given pressure difference through a uniformly distributed mass of fibres is determined by the total surface area of the fibres . 

(a)

(b)

Fig: Fiber Fineness is Measured by the Airflow Method

The surface area of a fibre (length X circumference) is proportional to its diameter but for a given weight of sample the number of fibres increases with the fibre fineness so that the specific surface area (area per unit weight) is inversely proportional to fibre diameter; Fig. shows this diagrammatically. Because the airflow varies with pressure difference it is the ratio of airflow to differential pressure that is determined by the fibre diameter. Therefore the method can be used to measure either the airflow at constant pressure or the pressure drop at constant airflow.

The measurement of airflow at constant pressure is the more usual form of apparatus with wool. For fibres of approximately circular cross-section and constant overall density such as unmedullated wool, the estimate of fineness corresponds to the average fibre diameter as determined by the projection microscope with a good degree of accuracy.

What is Sampling? | Zoning Sampling Technique

Sampling:

It is not possible or desirable to test all the raw material or all the final output from a production process because of time and cost constraints. Also many tests are destructive so that there would not be any material left after it had been tested. Because of this, representative samples of the material are tested. 

The amount of material that is actually tested can represent a very small proportion of the total output. It is therefore important that this small sample should be truly representative of the whole of the material. For instance if the test for cotton fibre length is considered, this requires a 20 mg sample which may have been taken from a bale weighing 250kg. The sample represents only about one eleven-millionth of the bulk but the quality of the whole bale is judged on the results from it. 

The aim of sampling is to produce an unbiased sample in which the proportions of, for instance, the different fibre lengths in the sample are the same as those in the bulk. Or to put it another way, each fibre in the bale should have an equal chance of being chosen for the sample.

There are several techniques for sampling fiber. Here is given the most popular sampling method.

Zoning Sampling Technique:
Zoning is a popular testing method of fiber that is used for selecting samples from raw cotton or wool or other loose fibre where the properties may vary considerably from place to place. A handful of fibres is taken at random from each of at least 40 widely spaced places (zones) throughout the bulk of the consignment and is treated as follows. 

Each handful is divided into two parts and one half of it is discarded at random; the retained half is again divided into two and half of that discarded. This process is repeated until about nix fibres remain in the handful (where n is the total number of fibres required in the sample and x is the number of original handfuls). Each handful is treated in a similar manner and the fibres that remain are placed together to give a correctly sized test sample containing n fibres. The method is shown diagrammatically in fig. It is important that the whole of the final sample is tested. 

 Sample from each zone

Zoning Sampling Technique

Textile Testing | Objects of Textile Testing | Different Types ofTextile Testing | Fiber Test/Yarn Test/Fabric Test

Testing:

The process to determine the properties of different kinds of substance is called testing.

Types of Testing:
1. Routine process testing
2. Quality record testing

Objects of Testing:
1. Research
2. Selection of raw material
3. Process control
4. Product control
5. Process development
6. Product development
7. Specification test

The necessary Test of different Textiles:

Fiber Test:
1. Identification of fiber
2. Grading
3. Fiber length
4. Strength and elongation ;tensile properties
5. Fineness or linear density test
6. Maturity test
7. Trash, neps test etc.

Yarn Test:
1. Yarn count or linear density
2. Twist per unit length
3. Strength and elongation i.e. tensile properties
4. Appearance
5. Evenness and regularity
6. Hairiness

Fabric Test:
1. Strength and elongation test i.e. tensile properties
2. Width
3. Thickness
4. Number of ends and picks per unit length
5. The count of yarn used
6. Fabric weight per unit length
7. Design and construction of the cloth
8. Air permeability
9. Thermal properties
10. Stiffness, handle, drape
11. Crease resistance and recovery
12. Abrasion
13. Pilling
14. Shrinkage
15. Water absorbency or resistance etc. 

Water Resistance, Water Resistancy | Determination of Water Resistanceby Shirley Hydrostatic Head Tester

Name of the Experiment: Determination of water resistance by Shirley Hydrostatic Head tester.

Introduction:
The merit of a fabric intended for rainwear, wagon covers or tents is judged, amongst other properties, by its ability to keep water out; conversely, when intended for hose pipes or canvas buckets, to keep water in. In another direction, some fabrics must exhibit the ability to absorb water rapidly, toweling being an obvious example. So there is a relation between water and textile materials which is very necessary for their end use.
 
Objective:
To measure the water resistance of the given fabric.
 
Theory:
Water resistance is the force or pressure of water which it applied on textile material to keep out though it and the determination of this required pressure or force is very important for particular use of a fabric. Shirley Hydrostatic Head tester is used to determine this pressure of water. In this instrument the specimen holder consists a double-chambered cell; the internal diameter of the inner chamber is 5 cm. Circular specimens are clamped between rubber gaskets over the orifice. Compressed air enters the outer chamber through a tube B and displaced the distilled water contained in the chamber through communicating passages into the inner chamber, thereby forcing water up against the specimen. The clamp is provided with a skirt which prevents air from leaking continuously across the test specimen from inner to outer chamber or to the atmosphere. The tube is connected to a manometer and the pressure of water against the fabric is, for all practical purposes, the pressure shown on the adjustable scale mounted on one arm of the manometer tube. The air supply for the test is drawn from a reservoir of about 3 l capacity which is itself fed through a flow control device from a source which may vary between 4 and 20 in/lb2. The flow control device is so designed that once it has been set to give the required rate of increase of pressure of 10 cm of water per minute, the rate of loading will be within the specified limits of 10+/-0.5 cm/min up to the limit of the instrument. The maximum head attainable is 150 cm of water.

Spray tester

Apparatus:

1. Crease recovery tester
2. Water
3. Template
4. Canvas fabric.

Sample:
Spherical canvas fabric.
Size:       6 cm diameter.
 
Atmosphere:
Temperature – 25oC and relative humidity – 67%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.
 
M/c specification:
Name: Shirley Hydrostatic Head tester
Brand: NEGRETTI & ZAMBRA, made in England. 

Capacity: 0-150 cm.  

Working Procedure:

1. Circular specimens of 6 cm diameter are cut very carefully with as little handling of the fabric as possible.
2. The test cell is rinsed with distilled water and filled up to approximately 0.3 cm of the top.
3. The inner rubber gasket is thoroughly dried by wiping with a clean absorbent cloth and a test specimen is laid over the orifice.
4. The dried clamp is placed in position and screwed down.
5. The switch is turned to ‘Head’ position to start the compressor and then turned to ‘Test’ position.
6. The pressure under the specimen is increased at a specified rate and until water appears minimum at the three places on the fabric, the switch will not be turned to ‘Head’ position.
7. As soon as three drops of water appear on the fabric the reading is taken from the dial.
8. In this way at least 10 readings are taken from 10 specimens and average pressure is then calculated.

Data:

S/n	Pressure in cm	Average pressure
1	28	30.8
2	30
3	34
4	29
5	33

Table: Pressures found from the test.

Result:
The water resistance of the sample fabric is 30.8 cm water pressure. As a result fabric will be water repellent.

Remark:
According to the type of fabric the resistance of fabric varies between 0 -150 cm. The sample of the fabric is a canvas cloth and its water resistance is 30.8 cm. So it may say that the fabrics resistant to water is enough for its end uses.

Water Repellency, Water Repellent | Determination of Water Repellencyby Spray Tester

Name of the Experiment: Determination of water repellency by Spray tester.

Introduction:
The merit of a fabric intended for rainwear, wagon covers or tents is judged, amongst other properties, by its ability to keep water out; conversely, when intended for hose pipes or canvas buckets, to keep water in. In another direction, some fabrics must exhibit the ability to absorb water rapidly, toweling being an obvious example. So there is a relation between water and textile materials which is very necessary for their end use.

Objective:
To measure water repellency of a given fabric.

Theory:
Water repellent is a state characterized by the non-spreading of water globules on a textile material. This term is not normally applied to a water-repellent finish impervious to air. This is generally referred to as water proof. It is generally done by treated fabric with fat, wax, rubber etc. This addition may be in form of physical film or coating or physical combination. The feature of a waterproof fabric is the low degree of air permeability. Spray tester is such an instrument which measures the water repellency of a fabric. In this test a small amount of shower is produced by pouring water through a spray nozzle. The water falls on to the specimen which is mounted over a 6 in. diameter embroidery hoop and fixed at an angle of 45 degrees. To carry out the test, 250 cm3 of water at 70oF are poured steadily into the funnel. The American Association of Textile Chemists and Colorists recommend the use of a chart of photographs against which the actual fabric appearance is compared. 

The ratings are as follows:

Rating                Description
100                     No sticking or wetting of the upper surface.
90                       Slight random sticking or wetting of the upper surface.
80                       Wetting of upper surface at spray points.
70                       Partial wetting of whole of upper surface.
50                       Complete wetting of whole of upper surface.
0                        Complete wetting of whole of upper and lower surfaces.

Apparatus:
1. Spray tester
2. Water
3. Fabric

Sample:
100% cotton, polyester, umbrella, parachute cloth.

Atmosphere:
Temperature – 25oC and relative humidity – 67%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.

M/c specification:
Name: Spray tester
Brand: DAIEI KAGAKUSEHCI SEISAKUSHO LTD., Kyoto Japan.
Template: 50 cm circumference.

Working Procedure:
1. The sample fabric is mounted on the embroidery hoop and fixed on the instrument at 45o.
2. Now the beaker is filled with 250 cc water and poured on the funnel.
3. The water is showered through spray nozzle on the fabric.
4.After spraying has finished the sample holder is removed and the surplus water removed by tapping the frame 6 times against a solid object, with the face of the sample facing the solid object.
5. The water repellency is assessed from the spray rating chart.
6. 5 tests should be made and the nearest rating assigned to each, since no interpolation is allowed, i.e. a rating for a specimen cannot be 75.
7. The mean of the 5 ratings is taken as the result.

Data:

S/n	Type of fabric	Spray rating
1	100% cotton	0
2	Polyester	0
3	Umbrella	70
4	Parachute	100

Table: Ratings found for different fabrics.

Result:
Water repellency of a 100% cotton fabric is 0.
Water repellency of a polyester fabric is 0.
Water repellency of a umbrella fabric is 70.
Water repellency of a parachute fabric is 100.

Remark:
According to the type of fabric water repellency varies from 0-100. From the experiment we can understand this. It is mainly selected depending on the end use of fabrics.