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Determination of Twist Per Inch (T.P.I) of Cotton Yarn by Ordinary Twist Tester | Textile Study Center
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Determination of Twist Per Inch (T.P.I) of Cotton Yarn by Ordinary Twist Tester

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Determination of Twist Per Inch (T.P.I) of Cotton Yarn by Ordinary Twist Tester

Theory:  “Twist is the measure of the spiral turns given to a yarn in order to hold the constituent fibres or threads together”. (Shinkle)

“Twist is the spiral disposition of the component of a yarn, which is result of relative rotation of the extenemities of the yarn. Twist per inch is the number to term per unit length of yarn”.

Twist mainly two types. They are-   

  1. Z- twist
  2. S- twist

Z-twist : 

The yarn has Z twist if the fibres inclined to the axis of the yarn conform in direction of slope to the central portion of the letter Z.

S-twist :

A single yarn has S twist if, when it is held in the vertical position, the fibres inclined to the axis of the yarn conform in direction of slope to the central portion of the letter S.

Sample: One inch cotton yarn.

Apparatus: 

  1. Twist tester.
  2. Niddle
  3. Seizer

Atmospheric condition : 

  1. Wet condition: -26 ° c.
  2. Dry condition: -30° c.
  3. Difference between wet and dry bulb = 30° c-26 ° c.  = 4° c
  4. So, relative humidity (RH) = 70 %

Procedure : 

The straightened fibre principle is still used for the actual measurement of the twist and it is the method of yarn control which is the main feature of this instrument. The yarn passes from the sample package, through a guide, through the non-rotating jaw, through the rotating jaw, and is wound on to a clockwork-driven drum. Assuming that a 1 inch length of yarn is gripped between the jaws, the twist is taken out and the number of turns noted. The handle is then turned until the counter reading is again zero; i.e. all the twist has been put back. The spring-loaded jaws of the rotating clamp are opened and the clamp moved 1 inch. forward, to touch the fixed clamp. The latter is then opened and, under the tension of a light spring, the rotating clamp is pulled back to its working position and in so doing pulls a new 1 inch sample into the test zone.

Experimental Data :

RESULT :

Hence the twist per inch of cotton yarn is = 16.7

Conclusion :

By this method we can easily defined the twist of the yarn. Without twist a strand of fibres has very little strength, and in the first instance a yarn must have sufficient tensile strength to withstand the stresses of preparation.

These ideas are only the beginning of a highly complex but fascinating subject, but in the present volume we can only touch upon some of the many effects of twist and fibre properties on the yarn and on the fabrics made from the yarn.

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