34 Testing of Woven Fabrics – Surface Properties, Colour Fastness Properties

M. Saravanan

Introduction:

The module discusses on testing of woven fabric properties namely serviceability commonly referred to as durability of the material and their fastness properties. The serviceability of woven fabric mainly characterized on their surface response. The surface response here in this module covers about test methods used for pills, snag, abrasion, crease and drape tendency of woven fabric. The fastness properties mainly deal with loss in color of dyed/printed woven fabrics. Colored woven fabric against various factors such as light, sweat, wash, etc. and their test methods are discussed in this module.

Objective:

Module aims to discusses the following three points and elaborate them in detail inside the module.

Surface response of the woven fabric when they are subjected to abrasion, sharp point contact, crease.
Resistance to leaching of color for colored woven fabric against different parameters is touch upon in this module.
Test methods for pilling, snagging, abrasion, crease, fastness to color leaching are elaborated in this module.

Factors deciding serviceability:

A garment is considered to be serviceable when it is fit for its particular end use. Reduction in serviceable life is a complex phenomenon and can be brought about by any of the following factors:

Change in surface appearance of fabric
Wearing of parts of garment results frayed appearance
Tearing of fabric due to snagging by sharp object

Pilling:

Pilling is a condition that emerges in wear because of the formation of little ‘pills’ of clinging fibres sticking to the surface of fabric giving it an unattractive appearance. Pills are created by a rubbing activity on loose fibres which are available on the surface. Pilling was initially a blame discovered principally in wool fabric materials made from soft twisted yarns. The discovery of man-made filaments into apparel has aggravated its seriousness. The clarification for this is these strands are stronger than wool so the pills stay to the fabric surface as opposed to breaking away as like in wool fabric.

ICI pilling box

In this test method four specimens are cut with dimensions 125mm X 125mm each from the fabric. Seam allowances of 12mm are given for each sample. Equally, two of the samples marking made in seam parallel to the warp direction and in the other two parallel to the weft direction. Fabric samples are folded up face to face and a seam is sewn on the marked line. Two specimens with the seam parallel to the warp and two with the seam parallel to the weft are prepared for testing. Each specimen is turned inside out and 6mm cut off each end of it thus removing any sewing distortion. Fabric sleeves in tubular form are then mounted on rubber tubes so that the length of tube showing at each end is the same. Loose ends at end are taped with poly vinyl chloride tape so that 6 mm of the rubber tube is left exposed. Fabric sleeve specimens are then placed in pilling boxes, two on right and two on left side of the instrument. Samples are then tumbled together in a cork-lined box. The usual number of revolutions used in the test is 18,000 which take 5 hours. The specimens are removed from the tubes and viewed using oblique lighting in order to throw the pills into relief. The samples are then given a rating of between 1 and 5.

5 – no pilling

4 – slight pilling

3 – moderate pilling

2 – severe pilling

1 – very severe pilling

Snagging:

A snag is a loop of fibre that is pulled from a fabric when it is in contact with a rough object. Snags degrade the fabric appearance yet don’t decrease any of its different properties. Fabric produced using bulked continuous filament yarns are especially vulnerable to the formation of snags even woven structures with long floats can likewise experience the ill effects of this issue. The mace snagging test is a comparative test for the snagging propensity of knitted fabrics of textured polyester yarn originally developed by ICI to test Crimplene yarns. In the test a metal ball fitted with spikes bounces arbitrarily against a sleeve of the test fabric sample as it turns. The spikes just catch loops of thread that are lying in a particular orientation so that it is important to test both directions of a fabric. Four samples, each measuring 203mm x 330mm are tested; two with their long direction with the length of the fabric and two with their long direction lined up with the width of the fabric. A seam is marked on the back of the fabric 16mm from the shorter edge. The fabric samples are then folded and sewn along the seam to frame a tubular fabric. The tube is turned back to front with the goal that the face of fabric faces outside. It is then slid over the cylinder of the machine and secured at each end with an rubber ring. A mace is put on each of the four test samples so that the chain holding it passes around the guide rod. The machine is then set to keep running for 600 revolutions for 10 minutes. At end of the test, the surface appearance of the specimen is compared with a set of photographic standards and given a rating from 5 (no snagging) to 1 (severe snagging).

Abrasion Resistance:

The capacity of a fabric to oppose the action of abrasive forces is clearly one of the criteria to consider while evaluating durability. Abrasion may cause a decrease in appearances by affecting the surface of a fabric, and especially by causing pilling.

Type of abrasion

This may be plane, flex or edge abrasion or a combination of more than one of these factors.

Two approaches have been used to assess the effects of abrasion

Abrade the specimen until a required end-point, for example, a hole, and record the time or number of cycles to this.

Abrade for a set time or number of cycles and evaluate some part of the abraded sample, for example, change in appearance, loss of mass, strength loss, change in thickness or other significant property.

Martindale Abrasion Tester

Principle: In this test, circular fabric samples are subjected to abrasion under known pressure on an apparatus which gives a movement that is the resultant of two simple harmonic motions at right angles to each other. Resistance to abrasion is assessed by visual appearance or by loss in mass of the fabric specimen.

Method of sample mounting on sample holder:

Four samples each 38 mm in diameter across are cut utilizing the suitable cutter. They are then mounted in the sample holders with a circle of standard foam behind the fabric being tested. It is important that the mounting of the specimen is done with the samples put level against the mounting block.

The test sample holders are mounted on the machine with the fabric under test beside the abrade material. A spindle is inserted through the top plate and the right weight (more often than not of a size to give a weight of 12 kPa yet a lower weight of 9kPa might be utilized if indicated) is placed on top of it.

Assessment

The specimen is examined at suitable intervals without removing it from its holder to see whether two threads are broken.

Average rate of loss in mass

This is an alternative method of evaluating resistance to abrasion which requires eight samples for the test. Two of these are abraded to the endpoint as said above and other sets are rubbed to the halfway phases of 25%, 50%and 75% of the end point. The specimens are weighed to the closest 1 mg before and after the abrasion with the goal that a diagram can be plotted of weight reduction against the quantity of rubs. From the slope of this chart, in the event that it is a straight line, the average loss in mass measured in mg/1000 rubs can be estimated.

Crease recovery:

Creasing of a fabric on wear is not a change in appearance that is generally desired. The ability of a fabric to oppose crease is in the primary occurrence subject to the kind of fiber utilized as a part of its construction. Many fabrics have resin finishes in production with a specific end goal to enhance their crease resistance. This test was initially created to test the efficiency of such finishes. The magnitude of this crease recovery angle means that the ability of fabric to recover from incidental creasing. Few types of fabric, attributable to relaxation, thickness and propensity to twist, often lead to ill-defined crease recovery angles and in this manner loose estimations.

The test can be done in two atmospheres, either the standard one or at 90% RH and 35°C. Twenty rectangular samples are tested, each measuring 40 mm X 15 mm, half of the samples slice parallel to the warp and half parallel to the weft. In the test the samples are folded in two, the ends being held by tweezers. Half the specimens are folded face to face and half of them back to back. The samples are then set under an 1O N load for 5 minutes. They are then transferred immediately to the holder of the measuring instrument and one leg of the sample is embedded similar to the back stop. The instrument is balanced constantly to keep the free limb of the sample vertical. The crease recovery angle is measured, by reading the scale when the free limb is vertical, 5 minutes after the removal of the load.

Drape:

Drape is the ability of a fabric to assume a graceful appearance in use.
Drape is an important property of textile materials.
It is a result of the interaction between warp way and weft way characteristics.

Measurement of Drape

Drape ability of a fabric can be determined using the instrument Drape meter and is expressed in terms of drape co efficient. Measuring the following areas the drape co-efficient (F), can be calculated

a) The area of the specimen, AD

b) The area of the supporting disc, Ad

c) The actual projected area of the specimen, As Drape co efficient:

It is the ratio between the projected area of the draped specimen and its undraped area,

after the deduction of the area of the supporting disc.

F= As – Ad

AD -Ad

Colour Fastness:

Color stability and its fastness property are much valued in customer point of view. Fastness means ability of dyed fabric to have resistance against leaching of dyes against any hazards.
Resistance to color leaching is assessed in terms of light, wash, rubbing, perspiration, water, bleach, acid, alkali etc.

Color fastness tests

Color fastness against Washing
Color fastness against Rubbing
Color fastness against Sweat/Perspiration
Color fastness against Ironing
Color fastness against Light
Color fastness against Sunlight
Color fastness against frosting
Color fastness against burnt gas fumes

Color Fastness against Washing

Wash resistance determines the resistance of the colored textiles from all kinds of wash in water with soap and detergent. ISO standardized different test methods to check the color fastness to washing.

Apparatus and materials

Gyro wash m/c (Wash-wheel & Stainless steel container)
Stainless steel ball (diameter =0.6cm,wt. =1mg)
Multi-fiber fabric
Thermometer (0-100) ° C
Sewing m/c
Dryer
ISO type grey scale for changing shade
ISO type grey scale for staining
Color matching cabinet (light box).

Sample Preparation

Fabric specimen is cut in dimensions 10cm × 4 cm and also ensures all colors are included in it. Edges are sewn with the same size of multi fiber fabric. Composite test specimen thus formed is subjected to washing. The machine commonly used in industry is launder-ometer.

According to ISO 105 C03: The composite sample is dealt with in a wash wheel or an equal apparatus at 60 ± 2°C (140±3.6°F) for 30 mints utilizing the color fastness test cleansers 77(ISO Std cleanser) 5 g/l and 2 g/l soda ash to a given liquor ratio of 50:1. At the end we reduce the temperature and washed with chill water and dry them.

Evaluation

Compare the contrast between the treated and untreated sample with the changing grey scale and staining of color in the adjacent multi-fiber fabric with the staining grey scale.
This assessment is done in a color matching cabinet under standard lighting of D65 (Artificial day light).

Color Fastness against Rubbing

Principle

Test is designed to determine the degree of color which may be transferred from the surface of a colored fabric to a specify test cloth for rubbing (which could be dry and Wet). Crock meter is the instrument used, whereby the fabric specimen is subjected to rubbing with a sample of standard un-dyed cotton fabric in order to check for colour transfer.

Apparatus and materials

Crock Meter.
Cotton Rubbing Cotton.
Grey Scale
Stop Watch
Color Matching Cabinet.

To test, need to take 14 Cm × 5 Cm pieces of textile fabric sample (one warp direction/ wale direction and other weft/ course direction). Crocking is the transference of color by rubbing from one colored textile material to another.

Dark shades are more likely to crock than light colors because there is more dye in dark colors than light ones. Similarly, printed fabrics often will crock more easily than dyed fabrics because in printed fabrics the dye is on the surface than inside the fabric. Wet fabrics will crock more easily than dry ones because the moisture present assists in removing the dye.

Test Procedure

a) Lock the test specimen (textile sample) onto the base of the crock meter.

b) The arm is rotated back & forth causing the white crock test cloth to rub against the specimen.

c) Using the spinal clip, set 5 Cm × 5Cm of the white cotton fabric to the finger of the crock meter.

d) Lower the covered finger on the test sample

e) Turn hand crank at the rate of the one turn per second

f) Remove the white rubbing test cloth and e valuate with grey scale.

Evaluation

In this stage compare the contrast between the treated and untreated white rubbing cloth with grey scale and rated 1 to 5.

Color Fastness against Sweat / Perspiration

Principle

The garments 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.

Apparatus and materials

• Perspiration Tester

• Oven, maintained at 37±2ºC temperature

• Multifiber test fabric

• Grey Scale

• Color matching chamber

• Acidic and Alkaline solution

• Glass or Acrylic plate

• Weight etc

Test Procedure

Sample size used here is 10 cm * 4 cm
Wet-out the composite test sample in mentioned alkaline or acidic solution at room temperature. M:L ratio 1:50 and leave for 30 minutes.
Pour off excess solution and place the composite sample between two glass plate or acrylic plate under a pressure of 4.5 Kg and place in an oven for 4 hours at 37±2ºC temperature.
Remove the specimen and hang to dry in warm air not exceeding 60ºC. Evaluation is done by Grey Scale in a color matching cabinet and rated from 1 to 5.

Colorfastness against ironing (hot pressing)

Principle

Determination of the resistance of the color of dyed textiles to ironing and pressing on the hot cylinder

Apparatus and materials

Heating device that can put a pressure on the specimen of 4kpa.
A smooth asbestos sheet (3-6 mm thickness)
Wool flannel
A piece of undyed, bleached and mercerized cotton cloth
Grey scales
Standard color matching cabinet
Distilled water

Test Procedure

Cut 10cm x 4cm specimen from each fabric sample
Condition the sample in standard atmosphere of 21±1℃ and 65±2%RH before testing.

Then select the specified temperature as follow: 110 ±2 ℃,150 ±2 ℃, 200± 2 ℃

Dry pressing:

Place the dry specimen on top of the cotton cloth covering the wool flannel pad
Lower the top plate of the heating device and leave the test specimen for 15 sec at the recommended pressing temperature

Damp Pressing

A. The adjacent fabric in dimensions of 10 cm x 4 cm is immersed into the water and, squeezed as 100% pick up

B. Dry specimen is placed onto the undyed cotton fabric on the wool flannel pad 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.

Wet Pressing

A. Soak the test specimen and a piece of cotton adjacent fabric in distilled water and squeeze it to maintain 100% pick up.

B. 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 seconds.

Evaluation is done numerically; rate the color change immediately after testing and again 4 hours in standard atmosphere and standard light using the Grey Scale (1-5).

Color Fastness against light

• Here measures the resistance to fading of dyed textile when exposed to day-light. The test sample is exposed to light for a certain time(24 hrs, 36 hrs,48 hrs, 72 hrs, etc) or by customer demand and compare the change with original unexposed sample. The changes are assessed by Blue Scales (1-8).

Procedure

• The sample is cut and should be exposed (1/2 covered and 1/2 exposed) together with standard dyed wool samples (1-8).

• The standard and the specimen mounted in a frame. The composite sample must be protected from rain.

• Evaluation is made numerically by European/American blue Scale (1-8).

Colorfastness against Sunlight

Dyed fabrics when presented to daylight will in time blur or change shading. This property is called as color fastness to sunlight.
Many clothing are evaluated for 40 hours because certain fabrics need to oppose the blurring impact of the sun to a substantially more prominent way. Eg: men’s suit.
Drapery fabrics are generally evaluated for 8 hours while cover fabrics are 160 hours.
Instrument used is weather-ometer. It offers quick weathering and light fastness test for chemicals.
A mix of manufactured light, warm and dampness is utilized.

Color fastness against frosting

Device utilized is a surface Abrader.
Frosting is a routine colour change created by a generally serious, flat abrasion action. Eg: back pocket of a trousers.
Fabrics with poor color fixation will blur rapidly from the surface on wear due to abrasion, leaving a very light color on the dyed fabric.
Blended fabrics have color change if fibres are susceptible to abrasive actions.
In a dark grey fabric, the dark cotton will rub more rapidly than a white polyester fabric, result in light dim shading.

Colorfastness against burnt gas fumes

Finally color changes because of the nearness of nitrous oxide in the air.
Acetate is the most vulnerable material to this gas.
When disperse dye is consolidated with acetate material, serious shading changes take place.eg: blue which changes to purple.
Solution dyeing and inhibitors can be utilized to decrease or dispose of shading blurring.
The device used to carry out the test is gas fading chamber.
Source for burnt gas fumes is Bunsen burner found at the bottom of the instrument.

Conclusion:

The module concludes and summarizes the response behavior of woven fabric for surface damage they might expect in their usage namely wear properties of woven. The module concludes on color leaching and their resistance to color loss particularly to dyed woven fabric. The dyed fabric requires color resistance, if fails will result in unacceptable change in appearance for the woven fabric

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REFERENCES and URLs

B. P. Saville, Physical Testing of Textiles, Woodhead Publishing Limited, England, 1999
J. E. Booth, Principles of Textile Testing, CBS Publishers, India, 1996
Jinlian Hu, Fabric Testing, Woodhead Publishing Limited, England, 2008
V.K.Kothari, Testing and Quality Management, IAFL Publications, 1999.
Arindam Basu., Textile Testing (Fibre, Yarn and Fabric), SITRA, Coimbatore, 2001.
http://mytextilenotes.blogspot.com
http://www.textileschool.com/Home.aspx