"Yarn Crimp: Understanding Its Role in Textile Performance"

Yarn Crimp refers to the waviness or curvature of a yarn as it follows the contour of the fabric structure, particularly in woven or knitted textiles. Crimp is introduced during the weaving or knitting process when the yarns interlace or interloop, causing them to bend and curve instead of remaining straight. It is an important property that affects the fabric's performance, appearance, and mechanical characteristics.

1. Yarn Crimp Dilshat Rubia Dola Lecturer Department of Textile Engineering   BGMEA UNIVERSITY OF FASHION AND TECHNOLOGY (BUFT)

2. Crimp

3. Crimp Inside the fabric, yarns form a wavy shape instead of straight yarn . As a result, actual length of the yarns is longer than the length of fabric width and length in fabric both in warp way and weft ways. The shortening of yarn length in fabric is known as crimp. Crimp of yarn is measured in crimp%.

4. Crimp% Crimp% is defined as the mean difference between the straightened thread length and curved thread length while in the cloth and is expressed as percentage. Crimp%= (Uncrimped length-Crimped length)/ Crimped length x100

5. Measurement of Crimp P ercentage To measure the yarn crimp two values are must be known, the cloth length from which yarn is removed and the straightened length of the thread. In order to straighten the yarn, some amount of tension must be applied just sufficient to remove all the crimps without stretching the yarn.

6. Measurement of Warp & Weft Crimp%  Take a fabric sample of 1 meter * 1 meter Pull out warp and weft yarns (of full length) from the fabric sample Remove crimp from yarns and straighten to its actual length  Measure the length of the straighten warp and wefts. Then calculate crimp% by using following formula. Yarn Crimp% = 100 X (Straighten Yarn length - Yarn length in fabric)/Fabric Length

7. Calculation of Warp & Weft Crimp%  Warp Crimp% = 100 X [(length of warps in straighten form - warp wise fabric sample length)/Warp wise fabric sample length] Weft Crimp% = 100 X [(length of weft in straighten form - weft wise fabric sample length)/Weft wise fabric sample length]

8. Calculation of Warp & Weft Crimp% 

9. Specimen Preparation Rectangular stripes are carefully marked on the cloth and each strip is cut in the form of a flap as shown in the fig. below. From each strip, 10 threads will be removed. Normally 3 strips in warp way and 3 strips in weft way are cut.

10. Removal of the Threads from the Flap The central part of the first thread is separated from the flap by means of a needle, but the two extreme ends are left secured. One end is then removed and placed in the clamp of the tester and the other end is removed and placed in the second clamp. By this method, there will be no loss in the twist of the yarn and also due to minimum handling, there will be no stretch in the yarn. Several crimp testers such as W.I.R.A., Shirley, and the M ANRA are available and here Shirley's crimp tester is taken for discussion.

11. Shirley Crimp Tester

12. Shirley Crimp Tester The standardized tensions as per British standard-

13. Shirley Crimp Tester

14. Shirley Crimp Tester

15. Shirley Crimp Tester

16. Shirley Crimp Tester

17. Shirley Crimp Tester

18. Calculation of Warp & Weft Crimp%  Assume that you got straighten length of warps are 1.05 meter and weft yarn length is 1.08 meter. From the above information Warp crimp% = ((1.05-1.00)/1.00) *100 = 5% Weft crimp%= ((1.08 -1.00)/1.00)* 100 = 8%

19. Mathematical Problems Problem-01 A cotton cloth is analyzed, and from a tested strip of 20 cm, the mean warp length is 21.2 cm. Determine the crimp percentage. We Know, Crimp % , C=(L-S)/S * 100% Where, L is warp length, S is cloth length Solution: Crimp Percentage: (21.2 – 20.0) / 20 = 6.0%

20. Mathematical Problems Problem-02 Calculate the length of warp required to weave 160 m of cloth if the warp crimp is 12%. We Know, Warp Length (L), L=(1+C)* S Where, C is crimp %, S is cloth length Solution: CW

21. Mathematical Problems Problem-03 What length of cloth can be woven from 800 m of warp if the warp crimp is 8% Cloth length (S), S=L/(1+C) Where, L is warp length, C is crimp % Solution: CW

22. Mathematical Problems Problem-04 To produce 5000 m of fabric with 3% warp crimp, how many yards of each warp yarn will require? We Know, Warp Length (L), L=(1+C)* S Where, C is crimp %, S is cloth length Solution: CW

23. Mathematical Problems Problem-05 Let you have 24 inch*20 cm dimension fabric sample. Calculate the warp crimp and weft crimp when length of yarn is 62 cm and 21.1 cm respectively. We Know, Crimp % , C=(L-S)/S * 100% Where, L is warp length, S is cloth length Solution: CW

24. Factors Affecting Crimp% of Yarn in the Cloth EPI- Higher the EPI, higher will be the weft crimp% PPI- Higher the PPI, higher will be the warp crimp% Warp linear density- Higher the coarseness of warp, higher will be the weft crimp% Weft linear density- Higher the coarseness of weft, higher will be the warp crimp% Yarn tension- Higher the warp tension, higher will be the weft crimp% Weave structure- Higher the interlacement no., higher will be the crimp% Yarn twist- Higher the twist in warp than weft, lower will be the weft crimp% Yarn extensibility- Higher the warp extensibility, lower will be the weft crimp% Calendaring finish- Higher calendaring results lower crimp% of yarn

25. Effects of Crimp of Yarn on Fabric Properties

26. Effects of Crimp of Yarn on Fabric Properties