Analysis of Textile Filament Yarn and the Yarn Size System

What is filament yarn:
Textile filament yarn consists of very long continuous fibers either twisted together or only grouped together. Filament yarn are two types: mono filament yarn and multi-filament yarn. Mono filament yarn is a single strand of filament form yarn and multi filament yarns are composed of two or more filament strands twisted, plied or yarns twisted together to form one yarn. Thicker mono filaments are generally used for industrial purposes rather than fabric production or decoration. Filament yarn can be natural, non-synthetic, and synthetic. This type of yarn has excellent uniformity; excellent strength; can be very fine; fair handle; poor covering power.
Textile filament yarn
Fig: Textile filament yarn
Characteristics of textile filament yarns:
  1. Composed of long continuous fibers.
  2. Made from natural silk fibers.
  3. Made from man-made fibers.
  4. Fine and smooth.
  5. More uniform in diameter than spun yarn.
  6. Equal number of filaments throughout.
  7. Provides lustrous, shiny or gossamer-sheen appearance.
  8. Softer and more pliable than spun yarns.
  9. Thick to thin diameters.
  10. Light to heavy weight.
  11. Loosely twisted.
  12. Do not fall apart when untwisted and can be counted.
  13. Stronger than spun yarn of the same diameter.
  14. Poor covering power.
  15. Produce high seam and yarn slippage.
  16. Snagging depends on fiber content.
  17. May be bundled into a ‘tow’ which will be cut into staple size.
Analysis of Textile Filament Yarn and the Yarn Size System:
Unlike spun yarn, we use a very different system to control the size. The big number is the thick size, small number, the small size. Filament yarn usually comes in 70 denier and 140 denier (or 160 denier). 140 denier is twice as thick as 70 denier. In the trade, we usually say 70d and 140d to stand for 70 denier and 140 denier. In theory, we can make filament yarn of any size. A piece of filament yarn consists of a bundle of filament, not spun (untwisted.)

Nylon or other synthetic filament is made from a process called extrusion by which you can make the filament thick or thin. At present, the sizes of filament commonly produced are about the following:

  • 4 denier per filament
  • 3 denier per filament
  • 2 denier per filament
  • 1 denier per filament
Therefore for 70d yarn, you can use 17 pieces of 4 denier filament to form the yarn, or 24 pieces of 3 denier or 34 pieces of 2 denier, or 68 pieces of 1 denier to form one piece of 70d yarn with the size and weight almost identical.

For the popular fabrics such as taffeta, or flight sateen, we usually use 3 or 4 denier filament for cost saving, but for finer fabrics which have to be soft and drapable, we would use 2 denier filament. Filament of one denier or finer that one denier is weight wise, 10,000 yards of 70d filament yarn is 70 gram.

Calculation of fabric weight made of filament yarn:
10,000 yards of 70d filament yarn weight 70 gram or we can say one yard of 70d is 0.oo7 gram. Now with this knowledge, we can figure out the weight of any fabric made of filament yarn. Let us use 210 T nylon taffeta as n example to figure weight of it per square yard as follows:

The construction of 210 T nylon taffeta is       : (Warp)         (Weft)
Number of yarn per inch                                : 120         x      90
Size of yarn                                                  : 70d         x     70d

The above means, in one square inch, there are 120 pcs of warp threads and 90 pcs of wefy threads both of which are of 70 denier thickness. In one square yard, you have 36” x 36”. Therefore 36” x 120 pcs of warp threads =4320 yards of 70d yard. 36” x90 pcs of weft threads =3240 yards of 70d yarn.

When you add up the above, you have 7560 yards of 70denier yarn from 1 square yard of this fabric.

7560 yards of 70d yarn x 0.007 gram = 52.9 gram (1 gram=0.0352 oz)

52.9 gram x 0.0352 oz =1.862 oz per square yd.

This is calculated weight which does not include:

   A. Shrinkage caused by weaving (about 5%)
   B. Shrinkage caused by dyeing (about 3%)

We should allow 5% for weaving shrinkage are 3% for dyeing shrinkage a total of 8%. 1.862 x 1.08 = about 2 oz per square yard. This is the net weight of the fabric.

However, if the fabric has some kind of finish on it, such as water repellence or water proof finish, the weight is increased slightly. This should all be taken into consideration when you try to determine the weight of the fabric.

Here is a short cut formula to do the same weight calculation:

A convert all yarn sizes to 70d and adjust the warp and weft thread numbers accordingly.

B add up the number of warp and weft.

C divide the total by 105 (this is a constant used in the formula regardless of weight or construction of the fabric) to get weight of the fabric per square yard in oz.

Let us try it on the following fabric                     : (warp)  x   (weft)
Number of threads per inch                               : 120      x     90
Size of yarn                                                      : 70d     x    70d

A. There is no need to convert the yarn size to 70d as they are already 70d.
B. Add up 120 and 90 you get 210.
C. Drive 210 by 105 =2.0 oz (weight per sq yard)

Let us try it again on the following fabric which is more complicated:

                                                   (warp)         (waft)
Thread number per inch                : 120      x     70
Size of yarn                                  : 70d     x    140d

When you convert the yarn size of heavier than 70 denier to 70 denier, you should divide they are size by 70 and then multiply the number of yarn by that figure. In the following example you should divided 140 by 70 and get 2 and then multiply the warp thread number by 2 and get the following:


(Warp)     x         (weft)       (Warp) x  (weft)
120          x          70           120    x    140
--------------------------------- = ---------------------------------
70d         x         140d         70d    x    70d

Divided by 70d = 2                    B. 120 +140 =260

And divide 140d by =2              C. 260 divided by 150 = 2.48 oz per square yard

Fabrics made of filament yarn are usually shinier and smoother than of spun yarn because you do not have the ends of fiber on the fabric, there is no nap at all.