7.8. YARN QUALITY & OTHER PARAMETERS 1. Yarn Appearance: The Visual Effect obtained by viewing a sample of yarn wound with a designated traverse on a black board of designated size. ♦ Nep: a tightly tangled mass of unorganised fiber ♦ Slu b : an abruptly thickened place of yarn ♦ Thick place: a yarn defect where the diameter is greater than the adjoining segments and extending for 6 mm ♦ Thin Place: a yarn segment where the diameter is 25% lesser than the average diameter of yarn ♦ F u zz: Untangled fibers that protrude from the surface of the yarn ♦ Bunch: a yarn segment not over 6 mm in length that shows abrupt increase in diameter caused by more fibers matted in this particular place ♦ Me th o d : yarn wound on hylam black boards wound for fixed wraps per inch as per count compared with standard reference boards. ♦ Grades:

Above ‘A’ to below ‘D’ - The imperfections increase from Grade ‘A’ and the maximum in grade ‘D’. Average

index of five boards of five graders.

2. Yarn Evenness: ♦ Unevenness: Variation in the linear density of a continuous strand or of a portion of a strand. ♦ Apparatus: Uster–Evenness Tester ♦ Pr in c ip le :

Difference in the capacitance variation. Lower the Count lower the

Imperfections. One km of yarn is run through two capacitance plated

at specific speed (fixed as per the count). The capacitance variation

is integrated and expressed as % unevenness (U%). The

imperfections are counted and are reported per kilometer.

3. Linier Density of Yarn:

♦ Expression of thef in en ess of Yarn

♦ A number indicating the mass per unit Length or the length per unit mass of Yarn

♦ Direct system: Denier, Tex (Weight Of Unit Length)

♦ Indirect System (Units of Lengths) per (Units of weights)

4. Count Test – Apparatus

♦ Wrap reel

♦ Ba la n c e

♦ 120 yards of yarn / 100 meters of yarn wound in a wrap reel and weighed .

♦ From the weight, the count is calculated.

5. Single Thread Strength Testing

♦ Force Required to break a single strand of yarn of unit length

♦ Apparatus - Single thread Strength Tester

♦ R KM

♦ % Elo n g a tio n

6. Lea Stength Testing

♦ Lea Breaking Strength

♦ The Force required to break one lea

♦ Unit –pounds

♦ Count Strength Product

♦ Apparatus –Lea Tester

7. Principles Of Tensile Testing ♦ Constant Rate of Loading: The Rate of change of Load is constant – Uster Dynamat ♦ Constant rate of Traverse: The pulling clamp moves at a constant rate – Lea – Pendulum tester ♦ Constant rate of Extension:Rate Of change of Specimen length is constant – Statmat 8. Twist Testing ♦ Direction Twist ♦ S –Twist: When Held in vertical position, the spiral confirm in slope to the central position of the letter ‘S’ ♦ Z –Twist: When Held in vertical position, the spiral confirm in slope to the central position of the letter ‘Z’ ♦ No of Turns (Twists) per Unit length ♦ Single Twist

♦ Double Twist

♦ Twist Multiplier

♦ Apparatus: Twist Tester

♦ Direct Method

♦ Indirect Method

7.9. Analysis Of Cloth Sample: On analysing a sample of cloth made from cotton; rayon, silk or flax with view of its

reproduction produced thus: -

1. Record whether a fabric is in the grey or the finished state.

2. Determine which threads constitute warp and which weft.

3. If in grey, test for the presence of size material by staining with iodine, when the starch in the size warp turns deep blue in colour, the weft being unaffected.

4. Examine for direction of spinning twist in the yarns, and also if either set of threads is two-fold yarn. If crepe yarns

have been used it may be necessary to test for amount of twist present.

5. Count the ends and picks per inch in the fabric. If more than 2 warps or wefts are used, find the number per inch of each yarn type used.

6. Test the yarns for Regain i.e. how much longer they are out of the cloth than the length of the sample from which they

were abstracted. By this means we can estimate the length of warp required to give the length to cloth and from the

weft regain we can estimate the length in Reed or length of each pick of weft. In weaving ordinary classes 10% of

cotton goods warp regain between 4% and according to the structure, while the weft regain is usually about 5%.

These figures apply to grey cloths only. In finished goods, the regain will differ according to the nature of the

finished applied. Very often the length of the cloth is increased and its width reduced on finishing, hence the warp

regain may be as low as 1% to 4% while the weft regain may be 8% to 10 %. “Rigmel” finished and “Sanforising”

are finishing processes in which the fabric is pre-shrunk both in warp and weft directions, the advantage being that

the fabric, when made into a garment, will retain its shape: it will not shrink in the laundering. When analysing these

materials regains of 8% to 10% will probably be found in both warp and weft.

7. Test the yarns for counts of warp and weft (The count of the yarn is the number of length units required to weight on

gain). In a grey sample the warp will probably be sized yarn and the count recorded will be the sized count. This

should be corrected by making a second test after thoroughly washing the fabric to remove all size and

illing materials. If the sample is a bleached, dye, or printed cloth, the counts of warp and weft will be affected counts

test then made, allowing about 5% in bleached count = 20s grey count: 38s bleached = 36s grey count.

8. Analyse the sample for weave details i.e. whether plain, twill, satin, or some other weave, and proceed to develop the draft and peg plan when necessary.

9. When analysing the sample containing rayon yarns, it is important to test for type of rayon i.e. Viscose,

Cuprammonium or Cellulose Acetate, i.e. number of filaments comprising the rayon thread must be countered and

the yarn exactly matched to obtain true reproduction of the sample. If the fabric is a coloured woven material, such

as a poplin shirting or a zephyr check, the warp and weft patterns must be abstracted.

For the ordinary kinds of cotton fabrics the contraction during weaving makes the cloth stand about 4

ends per inch closer in the cloth than in the reed and there is a gain of about 2 picks per inch from the loom to the

warehouse table. Thus if a cloth is required to the following dimensions: 36 inch wide, 120 yards long, 72 ends / 66

picks per inch, 34s warp, 30s weft, plain weave – the making particulars would be : warp length 126 yards : ends per

inch in reed, 68 : pick wheel on loom, 64 : pure warp ends – 36 x 72 = 2592 plus selvedge allowance say 30 extra

ends = 2622 ends width in reed 38.2 in.

When estimating the grey or loom particulars to reproduce a given finished sample of cloth, experience in

the handling of that type of cloth, both in the grey and finished states, is necessary. No general rule can be laid down

to cover all classes of goods, careful measurement of regains will, in most cases, be of great assistance in this work.