The following test methods can be implemented by a hand-print manufacturer by having a small testing facility inhouse. Many of the following tests are required by
1. Colour fastness to Crocking resistance or rubbing
Purpose
To determine the resistance to transfer of colour from fabric to another surface by rubbing action
References
AATCC Test Method 8-2007
Apparatus27
Crockmeter
Dry test
The specimen to be tested should be rubbed with an un-starched, cotton cloth with a Crockmeter. On the Crockmeter, there is a white cloth, which is firmly attached to the flat end of a cylindrical “finger”, which is 5/8 inch (1.5 cm) in diameter. This finger presses on the dyed cloth with force. The finger is moved across the specimen ten times at the approximate rate of 1 second per stroke, each stroke about four inches (10 cm) long. The test is made with dry cloth and test piece.
Wet test
The wet crocking test is conducted in the same manner as dry crocking except that the crock cloth is saturated with distilled or deionized water and squeezed or wrung to remove excess water to a moisture pickup of 65% + 5% (AATCC method ) and 95% pick- up (ISO method) based on the weight of dry crock cloth. The crocking test is performed immediately thereafter.
Evaluating Scale
A sample of the original material is compared with the tested material as evaluated as per the following scale:
| Scale | Rating | Description |
|---|---|---|
| 5 | Excellent | No perceptible staining of the white crock cloth |
| 4 | Good | Slight staining of the white crock cloth |
| 3 | Fair | Appreciable, but not objectionable staining of the white crock cloth |
| 2 | Poor | Objectionable staining of the white crock cloth; |
| 1 | Very poor | Very objectionable staining of the white crock cloth |
2. Tearing strength using Elmendorf method
Purpose
To determine the resistance to further tearing after the material has been cut
References
ASTM D1424-09 – Standard Test Method for Tearing Strength of Fabrics by Falling- Pendulum Type (Elmendorf) Apparatus
Apparatus
Elmendorf Tester
Procedure
The tearing strength of a fabric may be determined by the falling pendulum method. The average force required to propagate tearing from a pre-cut specimen is measured using a precisely calibrated pendulum device known as the Elmendorf Tester.
The test apparatus should be checked for friction loss and calibrated as described in the referenced ASTM method.
Either before or after mounting the fabric in the test apparatus, a slit of 2.0 cm length should be made along the center line of the wide edge and in the direction of the specimen length.
With the pendulum in its raised position, the specimen is placed midway in the clamps so that its upper edge is parallel to the top of the clamps and the initial slit is at right angles to the top of the clamps.
Acting under gravity, the pendulum swings through an arc, tearing the specimen from the pre-cut slit. The specimen is held on one side of the slit by the pendulum and on the other side by a stationary member. The loss in energy of the pendulum is indicated by a pointer reading on a scale and is a function of the force required to tear the specimen. Specimens should be taken in a manner where two sets of five test specimens can be obtained. One set should have the long dimension parallel to the WARP direction and the other set should have the long dimension parallel to the WEFT direction.
When the specimen is torn, the scale should read between 20 and 80 percent of maximum reading. If the reading is over 90%, auxiliary weights should be employed to double or quadruple the capacity of the machine. If the tear deviates more than 3/8 inches (10 mm) from the line of the initial slit, the specimen should be rejected and a duplicate specimen tested.
Results are calculated as follows:
Grams to tear specimen: Directly or by calculating from scale reading. If additional weights are needed, the appropriate multiplier must be used. The average, maximum and minimum results for both the machine and cross machine directions shall be reported.
3. Tearing strength using Tongue method
References:ASTM D2261-07ae1 – Standard Test Method for Tearing Strength of Fabrics by the Tongue (Single Rip) Procedure (Constant-Rate-of-Extension Tensile Testing Machine)
Apparatus:
Testing machine consisting of straining mechanism, holding clamps and load recording mechanism
Procedure:
It should be made sure that the width of the jaws of the apparatus is greater than or equal to 2 inches (5 cm). The rate of separation of the jaws should be maintained at 12 + 0.5 inches (30 + 1 cm) per minute.
Testing speed can range from 2 + 0.1 inches per minute to as high as 12 + 0.5 inches per minute.
The specimen for the test should be 8 inches (20.0 cm) long by 3 inches (7.5 cm) wide. Two sets of five specimens each are required, with one set having the longer dimension parallel to the machine direction, and the other set having the longer dimension parallel to the cross-machine direction.
A longitudinal cut 3 inches (7.5 cm) in length is made lengthwise of the specimen starting in the center of one of the short edges.
The specimen should then be placed squarely in the machine with one of the tongues in each clamp. The load necessary to tear the fabric fluctuates and is recorded by means of a suitable autographic recording device on the testing machine.
The tearing strength of the specimen should be taken as the average of the five highest peak loads of resistance registered after 0.25 inches (6 mm) of separation of the tear.
It must be made sure that the machine capacity is neither in the lower 15% nor the upper 15% of the dial reading.
4. Tensile strength and elongation by Grab method
Purpose
To determine the pulling force required to rupture the fabric
References
ASTM D – Standard Test Methods for Fabrics
Apparatus
Testing machine consisting of straining mechanism, holding clamps and load recording mechanism
Procedure
The specimen for the test should be6 cm wide and greater than 15 cm in length. Two sets of five specimens each are required, one set for the WARP direction tensile strength having the long dimension parallel to the machine direction, and the other set for WEFT direction tensile strength having the long dimension parallel to the cross machine.
Unless otherwise specified, no specimen should be taken near the selvage less than 1/10th the width of the material.
The distance between the two pairs of jaws on the apparatus should be 3 inches (7.5 cm) at the start of the test. The rate of separation of the jaws should be 12 + 0.5 inches (30 + 1 cm) per minute. The jaws have smooth flat faces with edges slightly rounded to prevent cutting. The face of one jaw of each pair measures 1 x 1 inch (2.5 x 2.5 cm); that of the other jaw of each pair measures 1 x 2 or more inches (2.5. x 5 or more cm), the long dimension being perpendicular to the application of the load.
The specimen is placed symmetrically in the jaws of the machine with the long dimension parallel to and the short dimension at right angle to the direction of application of the load.
The tensile specimen at break is the numerical average of the results obtained by breaking five specimens separately and is expressed as force/unit width (e.g., lbs/in.).
If a specimen slips in the clamps, breaks in the clamps, breaks at the edge of the clamps, or for any reason attributable to faulty operation causes the results of a single specimen to fall markedly below the average for the set, the result is discarded, another specimen taken and the result of the break included in the average. No two specimens for WARP direction breakage shall contain the same yarns, or for the WEFT breaking strength.
It must be made sure that the machine capacity is neither in the lower 15% nor the upper 15% of the dial reading.
Unless otherwise specified, the elongation should be obtained at any stated force while the breaking strength is determined.
Elongation at break is calculated as follows:
Where α 1 = Distance between jaws at moment of rupture
α = Distance between jaws at start of test
5. Testing chemicals and auxiliaries
Larger facilities will have in-house labs that will also test the incoming chemicals and auxiliaries for the right consistency. The test methods for commonly used chemicals are as follows:
| Chemical | Method |
|---|---|
| Hydrochloric acid | Dilute 10g of sample, accurately weighed, with 1 liter of distilled water. Titrate 50 mL of this aliquot with 0.1 N sodium hydroxide using phenolphthalein indicator. 1 ml 0.1 N NaOH = 0.003647 g HCl |
| Sulfuric acid | Dissolve 5g of sample, accurately weighed, with distilled water to make it a 500 ml solution. Titrate 50 mL of this aliquot with 0.1 N sodium hydroxide using phenolphthalein indicator. 1 ml 0.1 N NaOH = 0.004904 g H2SO4 |
| Sodium carbonate (soda ash) | Dissolve 5g of sample, accurately weighed, with carbon dioxide free water to make it a 1 l solution. Titrate 50 ml of this aliquot with 0.1 N HCl using methyl orange indicator. 1 ml 0.1 N HCl = 0.0053 g Na2CO3 |
| Sodium hydroxide (caustic) | Dissolve 4g of sample, accurately weighed, with carbon dioxide free water to make it a 1 l solution. Titrate 50 mL of this aliquot with 0.1 N HCl, first in the presence of phenolphthalein till the pink color is discharged and then in the presence of methyl orange till an orange tint is produced. % of NaOH = (x-2Y) x Nof acid x 0.04x aliquot x 100/ weight of sample % of Na2CO3= 2y x N of acid x 0.053 x aliquot x 100 / weight of sample Where X = total volume of 0.1 N HCl used, Y = volume of acid used in second titration |
| Hydrogen Peroxide | Diluted 10g of sample, accurately weighed, with water to get a ONE volume solution. To 10 ml of this diluted peroxide, add 300 ml of water and 30 ml of 20% sulphuric acid. Titrate this mixture with 0.1 N potassium permanganate solution. 1 ml of 0.1 N KMnO4 = 0.001701 g H2O2 |
| Glycerine | Testing method is very complex so one can measure specific gravity of glycerine and calculate approximate purity. 1.253 specific gravity = 95% glycerine content |
| Sodium Nitrite | It converts slowly into Sodium Nitrate in air. Dissolve 2g of sample, accurately weighed, with water to make it a 500 ml solution. Slowly run 25 ml of this aliquot into a mixture of 50 ml of 0.1 N KMnO4, 300 ml water and 20 ml of 2 N H2SO4 with constant stirring. After 15 mins, add 3 g KI and titrate the liberated Iodine with 0.1 N sodium thiosulphate using starch as indicator. 1 ml of 0.1 N KMnO4=0.003451 g Sodium Nitrite |
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