Crimp Percentage | Determination of Crimp Percentage

Experiment name: Determination of crimp percentage in warp and weft of a given fabric.

Introduction:
When warp and weft yarns interlace in fabric they follow a wavy or corrugated path. Crimp percentage is a measure of this waviness in yarns. Warp and weft crimp percentages are two of the eleven structural elements in fabric construction discussed by Peirce. The relationships between the geometry of a cloth structure and its physical behavior in use are complex. Although much pioneer work has been done there are many unresolved problems still to be investigated.

Objective:
To measure the crimp percentage in warp and weft of a given fabric.

Theory:
Percentage crimp is defined as the mean difference between the straightened thread length and the distance between the ends of the thread while in the cloth, expressed as a percentage. From the definition of crimp two values must be known, the cloth length from which the yarns is removed and the straightened length of the thread. In order to straighten the thread, tension must be applied, just sufficient to remove all the kinks without stretching the yarn. In practice it is seldom possible to remove all the crimp before the yarn itself begins to stretch. The standardized tensions recommended in the B.S. Handbook are given below:
 

From those two values we can calculate the crimp percentage with the following formula: 

  C=(l-p)/p*100%

where, c = crimp, l = uncrimped length and p = crimped length.

Five groups of threads selected for test are two warp way and three weft way groups. The mean crimp percentage is calculated warp way and weft way. Rectangular strips are carefully marked on the cloth and each strip cut into the form of a flap. From each strip ten threads will be removed. Removal of threads is as follows: the central part of the first thread is separated from the flap fringe by means of a dissecting needle, but the two extreme ends are left secured. One end is then removed and place in the grip of the tester, and the other end is removed and placed in the second grip. In this way the thread is transferred from the cloth to the crimp tester without loss of twist and with a minimum handling. Several crimp testers are available, Shirley crimp tester is one of them.

Atmosphere:
Temperature – 25oC and relative humidity – 67%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.

Apparatus:
1. Crimp tester
2. Fabric sample
3. Scissor
4. Scale

Sample:
Cotton woven fabric. Length = 10².

Procedure:
1. At first we have to select the warp or weft way of the fabric. Then we should select the test length of the yarn. Here it is 10².
2. According to test length we will cut the flap of fabric.
3. Now a single yarn is to remove from the flap of fabric carefully as discussed in theory.
4. One end of the yarn is gripped in the fixed gripper of the m/c and the other end is gripped in the other setting the test length.
5. Now the tension for the sample is found out from its count and it is set in the m/c.
6. After that we will apply tension along the yarn length with hand by taking away the other end of yarn far from the first end.
7. As soon as the white marl on the tension bar is on the same line of its both sides white mark, we will stop far away the other end.
8. The length of the yarn after applying tension is taken from the scale.
9. Now from this two lengths crimp percentage is calculated from the given formula.
10. In this way at least 10 crimp percentage for warp and 10 for weft is taken and average crimp percentage is calculated from them. 

Data:

S/n	Warp Yarn				Weft yarn
	Crimped length p	Uncrimped length l	Crimp percentage c	Mean	Crimped length p	Uncrimped length l	Crimp percentage c	Mean
1	10²	10.7²	7%	6.7%	10²	11.1²	11%	10.5%
2		10.9²	9%			11²	10%
3		10.8²	8%			11.2²	12%
4		10.4²	4%			11.1²	11%
5		10.6²	6%			10.9²	9%

Calculation:

Result:
Average warp crimp percentage 6.7%
and average weft crimp percentage 10.5%.

Remark:
We found that crimp percentage for warp is less than weft. It is because the warp yarns are kept in tension during weaving. Besides they are stronger and better yarn than weft. So they do not extend more. On the other hand weft yarns are kept in low tension and low in quality. So they can extend more. As a result their crimp percentage is more. We should notice that variation in crimp can give rise to faults in fabrics, e.g. reduction in strength, bright picks and diamond barring in rayons, strips in yarn dyed cloths and so on. So we should control it which is also necessary for design fabric to give required extensibility. Since crimp is related to length, it affects the amount of cloth as well as cost of production.

Lea Strength Tester | Determination of Cotton Yarn Strength and C.S.P.by Lea Strength Tester

Name of the Experiment: Determination of cotton yarn strength and C.S.P. by lea strength tester.

Theory:

Figure: The pendulum lever principle

C.S.P is the product of English count and strength of yarn in pound.

i.e. C.S.P = Strength of yarn in pound x Count in English system.
Again, english count is the no. of hanks in 840 yards length per 1 pound weight of yarn.
i.e. Count =( L*w)/(l*W)
Here, L = length of the sample & l = unit length of the system
W = wt. Of the sample & w = unit wt. of the system.
A lea strength tester measures the strength of one lea
yarn. One lea means 120 yards. Strength is a measure
of the steady force necessary to break a material and
is measured in pound. The m/c works in constant rate of
extension. Assuming the specimen to be extensible and an

absence of any dynamic effects, we get from the figure:
Fr = Mgr = MgRsinq  

As the value of MgR and r are constant, therefore
According to the applied force the m/c dial gives us the
strength in lb on the basis of this q.

Apparatus:
1.Cotton yarn
2.Wrap reel
3.Lea strength tester
4.Electrical balance

M/c specification:

1. The Lea Strength Tester
2. Goodbrand & Co. Ltd.
3. Capacity: 100lb

Testing atmosphere:
Temperature – 29oC and relative humidity – 76%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.

Sample:
Size - One lea cotton yarn (1 lea =120 yards).
No. of sample – 20.

Working procedure:
1.At first one lea cotton yarn is measured by wrap reel and in this way 20 samples are taken for testing.
2.Now, the first sample is fixed with the upper jaw J1 and the lower jaw J2.
3.The m/c is started and observed the dial until the sample is torn out.
4.When the sample is torn out the m/c is stopped and the reading is taken.
5.By this way the others’ reading are taken.
6.Then all the samples are weighted and counts are calculated.
7.C.S.P of the all samples are calculated.
8.At last average and CV% are calculated.

Data:

Reading	Yarn length (yds)	Yarn strength (lbs)	Sample Wt (gms)	Yarn Count (Ne)	C.S.P of the given sample	Avg C.S.P	SD%	CV%
1	120	86	2.6	24.9	2141.39	2397.16	99.9	4.16
2	120	93	2.63	24.64	2291.52
3	120	97.5	2.7	24	2340
4	120	95	2.62	24.73	2349.34
5	120	98.99	2.60	24.92	2466.83

Calculation:
Suppose for first sample, we find length = 120 yards and weight = 2.315gm.
Now we know, 1 lb = 453.6 gm.
Then Count = 24.9 » 25 Ne
And C.S.P = 24.9 X 86 = 2141.39
In this way others are calculated.
Here CV% = 4.16%

Result:
The strength of cotton yarn is 97 lb
and C.S.P is 2397.16
and the C.V% for C.S.P is 4.16%

Remark:
It is considered that fibres having C.S.P less than 1800 are bad or weak, between 1800-2200 are average and greater than 2200 are strong. From our experiment we see that our samples’ average C.S.P is 2397.16 which is greater than the std 2200 and CV% is 4.16. This is proved that there are many variations in this range but our supplied yarn has good strength. So finally we can say that these yarns have good strength fibres. But it may be vary because our testing atmosphere is not standard.

Determination of GSM (Gram per Square Meter) of Woven and KnittedFabrics

Name of the Experiment: Determination of GSM of woven and knitted fabrics.

Introduction:
The GSM of fabric is one kind of specification of fabric which is very important for a textile engineer for understanding and production of fabric. ‘GSM’ means ‘Gram per square meter’ that is the weight of fabric in gram per one square meter. By this we can compare the fabrics in unit area which is heavier and which is lighter. 

GSM Cutter

Objectives:

1. To determine the GSM of the given samples of fabric.
2. To compare the GSM of them.

Theory:
The weight of a fabric can be expressed in two ways, either as the ‘weight per unit area’ or the ‘weight per unit length’; the former is self explanatory but the latter requires a little explanation because the weight of a unit length of fabric will obviously be affected by its width. In woven fabric, the weight per unit length is usually referred to as the ‘weight per running yard’. It is necessary therefore to know the agreed standard width upon which the weight per running yard is based. Usually this width depends upon the width of loom. Before coming the term ‘GSM’ there was another term called ‘lb/100 yards’. This expression is used by British Standard. For measuring this there are a template and a quadrant balance. The template area is 1/100 square yards of which each arm is 1/10 yards in length. For measuring GSM, a GSM cutter is used to cut the fabric and weight is taken in balance. Both of these measurement and method is equally used for both woven and knitted fabrics.

Apparatus:

1. Template
2. Quadrant balance
3. Scissor
4. GSM cutter
5. Electric balance.

Sample:

1. Finished cotton woven fabric
2. Finished cotton knitted fabric.

Atmosphere:
Temperature – 25oC and relative humidity – 67%
Standard atmosphere: temperature – 20oC and relative humidity - 65%.

M/c specification:
Name: Quadrant balance
Brand: Good brand & Co. Ltd.
Scale: 100 yards for fabric.

Working Procedure:

1. For measuring with Quadrant balance, at first we should cut the fabric sample according to the template area. By this way we cut 10 woven samples and 10 knitted samples.
2. Now weigh these samples in pounds by quadrant balance according to 100 yards scale.
3. By this way we get the weight in pound per 100 square yards fabric.
4. For Measuring GSM, we should cut the fabric sample by GSM cutter. By this way cut 10 woven samples and 10 knitted samples.
5. Now weigh these samples by electric balance in grams.
6. By this way we get the weight in gram per one square meter fabric.
7. Now find out the average of these found weights.
8. For woven fabrics find out the weight per running yards assuming the loom width 48 inches.

Data: 

Type	Woven Fabric			Knitted fabric
Sl No.	lb/100 yd2	gm/meter2		lb/100 yd2	gm/meter2
1	20	107.64		38	144
2	19	107.64		37	144
3	19	104.75		35	149.67
4	19	102.86		38	143.81
5	18	102.86		36	148
Average	19.2	106.83		36.8	145.37

Calculation:
For measuring the weight of woven fabric in weight per running yards, form data table we get the weight of 100 yd2 fabric is 19.2 lbs. Now assume the width of loom is 48 inches. Therefore the area of the fabric will be 1.33 yd2. So,

Weight of 100 yd2 woven fabric = 19.2 lbs. 

Weight of 1.33 yd2 woven fabric =  0.255 lbs.

That is weight of fabric per running yard is 0.255lbs or 116 gms.

Result:

1. The weight of woven fabric is 19.2 lbs/100 yd2 or 106.83 GSM.
2. The weight of knitted fabric is 36.8 lbs/100 yd2 or 145.37 GSM.
3. The weight of woven fabric per running yard is 0.255lbs or 116 gms.

Remark:
This is a direct measuring tester. So the result should be accurate. But as the samples are of both cotton fabrics, so there are effects of moisture content on the weight of fabrics. Besides the knitted fabrics are very much extensible and proper relaxed state is quite different during cutting of sample with GSM cutter. Therefore there are variations among their weights. The effects of moisture content can be accounted for either by conditioning the specimen in the standard atmosphere or by taking the specimen to oven dry weight and adding the official regain.