Saturday, 5 January 2019

Technical Parameters of a PolyCot Saree



About Tearing Strength of Fabrics



Tear strength is more important in the assessment of "serviceability" of the fabric. In order to tear a cloth, the threads are broken singly. It is therefore a frequent mode of fabric failure.

The factors which contribute to the resistance to the tear is :

a. Strength of the yarn normal to the tear.Suppose you are trying to tear the weft yarns. Then those yarns need to be stronger.

b. Freedom of movement of the yarn in the direction of the tear. As in a. The freedom of movement in the warp yarns should be there, which can be done by reducing the EPI.

There are two types of Tear strength measurement come into play. First is Initial Tear Strength: It is when the load is applied on the fabric to tear it. This load is always higher than the average tear strength. It is because of the fact that up to this load, yarn crimp removal and sliding takes place. But once this point is reached the load is instantly transferred to the successive yarns and the tear strength obtained is known as average tear strength. 

These are ways that the tear strength in a fabric can be affected:

1. By reducing the thread count in the direction opposite to the direction of test, the tearing strength can be increased. So if you are tearing warpways-means you are tearing weft yarn- reduce the thread count of warp yarn-means reduce EPI.

2. Use yarns with the high breaking load in the direction of test to increase tearing strength. Means take stronger yarns in weft, as in example in point 1. This is the most important factor.

3. Decrease friction between yarns to increase tearing testing strength. This allows threads to group closer together under the tearing force, so instead of the successive breakage of individual threads, the action becomes more of a strength test on plied yarns. Decreased friction allows this grouping.

4. Related to 3, is the effect of the weave. Thus a twill or 2/2 matt structure allows the threads to group better than a plain weave. So Twill or 2/2 exhibit better resistance to tearing than plain weave.

5. Related to the point 1, high sett fabrics preclude thread movement hence the assistance by thread group is reduced.

6. Special Finishes such as drip dry or crease resistance finishes may reduce tearing strengths.




Source: 1 , Textile Testing by Booth, 3,

Video below gives the tearing testing procedure:






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Thursday, 15 November 2018

Can Wet Rubbing Fastness Greater than Dry Rubbing Fastness



Usually, Wet rubbing fastness ratings are lower than those of dry rubbing. However, there may be cases when it is reversed. As per Texanlab manual:

"This is sometimes observed in polyester fabrics. In these cases, the friction coefficient in wet crocking is lower than  dry crocking. Thus, in contrast to cotton, the colorfastness to wet crocking for polyester is higher than its colorfastness to dry crocking."

Other Resources:

1

How a Rubbing Fastness Tester Works. Watch this video:



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Saturday, 3 November 2018

Jaipur Printing- Jajam Print



Textile with Jajam prints used to play a great role in the social life of Rajasthan. These textiles used to get spread out on special occasion. It used to be printed in the region of Chittor, where it is spread for playing chaupad, an Indian version of Chess.

An amazing account of this craft is found here.  Anokhi Museum Blog talks a lot about it.


This video is posted by Mr. Brij Ballabh Udaiwal on Facebook:




Reference

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