textile testing of finished goods
TRANSCRIPT
Textile testing of finished goods.
1. Physical Properties:
a. Appearance – color and uniformity of finished yarn or
fabric - visual assessment only.
b. Tensile strength of finished yarn
c. CSP of finished yarn
d. Tear strength of finished fabric
e. GSM of fabric of finished
f. Shrinkage Test of Woven fabric and Knit fabric .
2. Finished goods’ Qualities:
1. What is a Grey Scale and Staining Scale? How Fastness grading is done?
2. Fastness to Washing
3. Fastness to Crocking or Rubbing fastness
4. Fastness to water
5. Fastness to perspiration
6. Fastness to peroxide bleach
7. Fastness to Chlorine or Chlorinated Pool water fastness
8. Fastness to Mercerising
9. Fastness to Hydrolysis
10. Fastness to Dry-cleaning
11. Fastness to light
12. Pilling Tests13. What is whiteness Index
14. What is total color difference or DE
15. Method of Detecting Starch and PVA
16. Method of testing desizing efficiency
17. Measurement of Absorbency
18. Antimicrobial Tests
19. Flammability Test
20. Detection and estimation of Formaldehyde content in Textiles
b. Tensile strength of finished yarn-
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:
d. Tear strength of finished fabric
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
f. Shrinkage Test of Woven fabric and Knit fabric
Before doing any Shrinkage test, the sample should be conditioned in an atmosphere
of 65% R.H. and 24 to 27C for a minimum of 4 hours.
WOVEN FABRIC SHRINKAGE AATCC-135 Method (ISO 3759)
1. Sample size 50 cms X 50 cms
2. Marking area 35 cms X 35 cms
3. Samples weight should be 1.8kg +/- 0.1 kg
(If the sample weight is less than 1.8kg put the dummy cloth and maintain the weight of 1.8
kgs).
4.Liquour Ratio : 1:50
5.Suitable detergent (0.5%) on the weight of sample i.e 1.8kgs
6.At 400C for 60 minutes in Wash-cator.
7.Dry the sample at 600C to 650C using tumble dryer.
8.Press the sample in flat bed hot press at 1500 +/- 15°C with 30 gms/cm2 pressure.
9.Cool the sample and measure.
Shrinkage for Cotton Hosiery IS-3326
1.Liquor Ratio 1:50
2.Temperature : 30 to 35°C
3.Suitable Wetting agents (detergent) 0.5% on the weight of the hosiery sample.
4.Sample size 20 x 20 cms.
5.Marking area 14 x 15 cms (mark with marking scale).
6. Time 2 hours at 30 to 35°C
7.After that dry at room temperature.
8.Measure.
9.Shrinkage % = [100 x (a-b)]/a
where a = Distance between two ends before treatment
b = Distance between two ends after treatment.
21. What is a Grey Scale and Staining Scale? How Fastness grading is done?
Grey Scale for Assessing Change in Shade
EN ISO 105-A03 / IUF 132 / VESLIC C 1211
This Grey Scale is for assessing the degree of change in shade caused to a dyed Textile
fabric / yarn in color fastness tests. For example, the chnage of shade of wool and cotton fabrics
in the wash fastness, perspiration fastness, etc.
The scale consists of nine pairs of gray color chips each representing a visual difference and
contrast.
The fastness rating goes step-wise from:
Note 5 = no visual change (best rating) to Note 1 = a large visual change (worst rating).
The gray scale has the 9 possible values:
5, 4-5, 4, 3-4, 3, 2-3, 2, 1-2, 1.
It is now quite common to measure the Grey Scale change in color instrumentally. This is made
using a suitable reflectance spectrophotometer according to the test method procedure,
EN ISO 105-A05.
Grey Scale for Assessing StainingEN ISO 105-A03 / IUF 132 / VESLIC C 1211
This Grey Scale is for assessing the degree of staining caused by a dyed Textile / yarn in color
fastness tests. For example, the staining of wool and cotton fabrics in the wash fastness,
perspiration fastness, etc.
The scale consists of nine pairs of gray color chips each representing a visual difference and
contrast.
The fastness rating goes step-wise from:
Note 5 = no visual change (best rating) to Note 1 = a large visual change (worst rating).
The grey scale has the 9 possible values:
5, 4-5, 4, 3-4, 3, 2-3, 2, 1-2, 1.
It is now quite common to measure the Grey Scale for assessing staining instrumentally. This is
made using a suitable reflectance spectrophotometer according to the test method procedure, EN
ISO 105-A04.
Fastness to Washing
Color Fastness:
The resistance of a material to change in any of its color characteristics, when subjected to washing is called color fasntess to washing.
General Principle:
A specimen of the textile to be tested, with the adjacent fabric attached is subjected to washing under specifiend conditions. Te extent of any change in
color and that of the staining of the adjacent fabric are assessed and the rating is expressed in fastness numbers.
There are two types of adjacent fabrics; (1) single fibre fabric and multiple fibre fabric. In the case of multifiber fabric only one specimen is required and in the of single fiber fabric two adjacent faabric are required.
There are various colorfastness tests. Details of some of the tests are given below.
Fastness to washing:
In the test, change in color of the textile and also staining of color on the adjacent fabric are assessed. A 10 x 4 cm swatch of the coloured fabric is taken and is sandwitched between two adjacent fabric and stitched, The sample and the adjacent fabric are washed together. FIve different types of washing are specified as different washing mthods.
Fastness to Wash
Sr.No Method Washing severity Soap+Soda in grams/liter
Time in minutes
TemperatureSteel balls
1 IS:687:79Very mild like hand wash
5 30 40+/- 2 Nil
2 IS:3361:795 times severe than method 1
5 45 50+/- 2 Nil
3 IS:764:79 Mild washing 5 + 2 30 60+/-2 Nil
4 IS:765:79 Severe washing 5 + 2 30 95+/-2 10
5 IS:3417:79 Severe washing 5 + 2 4 hrs 95+/-2 10
The solution for washing should be prepared to the required temperature of washing. The liquor material ratio is 50:1 .
After soaping treatment, remove the speciment, rinse twice in cold water and then in running cold water under a tap. Squeeze it and air dry at a temperture not exceeding 60°C. The change in color and staining is evaluated with the help of grey scales.
22. Fastness to Crocking or Rubbing fastness
Rubbing/Crocking fastness
Reactive dyes being water soluble it is difficult to achieve the same level of wet rubbing ratings as
compared to insoluble dyestuff and also dry rubbing. With water soluble dyes, apart from the
bleeding of the dyestuff from the rubbed area, finely distributed substrate particles also rub off on
the surface of crockmeter cloth.
The problem is increasing with higher depths and fabrics like towels, corduroy etc. with rough
surface. While evaluating the rating it is necessary to 9gnore such rub-off particles appearing
on the crockmeter cloth and consider only the staining of the dye on the rubbed cloth.
Instrument used for checking is the standard crockmeter. However, test is quite sensitive and for
getting consistent result, it is necessary to use standard crockmeter cloth, maintain uniform
pressure for applying rubbing strokes and number of strokes. Besides, for wet rubbing, %
moisture on the crock-cloth has to be kept to uniform level. For ISO-105 x 12 test method,
rubbing cloth that has been wetted with water, has to be squeezed to contain its own weight of
water. For AATCC 116-1995 methods, wet pick up is to be maintained between 65 ± 5% by
squeezing the wet crockmeter cloth using a AATCC blotting paper. Any variation in the moisture
content can lead to deviation in the rating. With high amount of moisture i.e.., wet pick up, ratings
will be lower. Degree of staining is visually assessed using Grey scale for change of colour with
grade of 1-5 where rating of 5 signify negligible change and 1 maximum change.
In order to get maximum achievable wet rubbing rating, with reactive dyes, it is absolutely
necessary to remove all unfixed hydrolyzed dyes by proper soaping/washing of the sample before
evaluating the ratings. Extraction with pyridine can be done to check the removal of hydrolyzed
dyestuff.
1. Effect of depth of shade/selection of Dyes:
For reactive dyes with high solubility and good washing fastness properties, rating will be
relatively higher. However, in deep shades, even with dyes with good washing fastness, a
fastness rating of 2-3 on the grey scale is achievable and is considered satisfactory and
acceptable. The liquid introduced with the wet crocking cloth results in all cases in a deterioration
in rub fastness of up to 2 points in comparison to dry rubbing.
2. Effect of Mercerising
The colour transfer is relatively less, for the mercerised cotton and the rubbing fastness grade is
higher. Due to change in the fiber structure on mercerising, there is a 30% less extent of removal
of fiber particles, during wet rubbing and lesser amount of colour on the fibre for the same visual
depth of shade.
3. Effect of finishing treatments
Different types of finishing treatment viz. softness, polysiloxanes, Zr-compounds, fluorocarbon,
chitosan and cellulase enzymes etc. applied to dyes, fabrics do not show improvements in wet
rubbing ratings. With some of the cross linking agents, rubbing fastness grade is lowered by 1/2
to 1 unit. In one of the recent study it is claimed that for reactive dyed blacks and bordeaux
materials, with polyacrylate finishes there is some improvement in the wet rubbing fastness
rating.
Method of testing desizing efficiency
Desizing Efficiency Test:
Desizing efficiency is found in two ways conventional and TEGEWA method.
Conventional Method:
In this method we first take the weight of the sized fabric, let it be W1. Then desize the fabric, dry
& take the weight, let it be W2. After that the fabric is treated with 3gpl (35%) HCl at 700 C for 30
min. dry & take the weight of the fabric. Let it be W3.
Total size = W1-W3.
Residual size = W2-W3.
Desizing Efficiency = (Total size – Residual size)/Total size X 100.
TEGEWA RATING:
Reagent: potassium iodide (10 gm. Of KI (100%) in 100 ml water, add 0.6358 gm of iodine
(100%) stir and shake; iodine is completely dissolved. Fill up to 800 ml with water then complete
to 1000 ml with ethanol. (Shelf life approx 6 months only).
Method:
1. Spot drop wise solution onto fabric.
2. Rub in gently.
3. Assess change of color.
Note: the test must be carried on fabric cooled down to room temperature; residual alkalinity has
to be neutralities prior to the test.
Assessment:
Grey fabric:
No change of color = no starch size present.
Pale blue to bluish = presence of starch size or blend
Violet =of starch size with synthetic size
Desized fabric:
Pale blue to bluish violet = refer to violet scale TEGEWA This indicates residual Starch content.