Influence of yarn count on knitted fabrics thickness and mass per unit area.

Kopitar, Dragana ; Vrljicak, Zlatko ; Skenderi, Zenun 等

Abstract: The influence of count of spun combed yarn on structure and properties of single jersey knitted fabric was investigated. The yarn counts were 14,3, 16,7, 20,0 and 25,0 tex with 14, 16, 18 and 20% of noil. The yarn were spun in the classical combed route with two drawing passage after combing. The fabrics were knitted at the circular knitting machine of fineness of E17 and diameter of 93 mm with input yarn tension of 0,15 and 0,40 cN/tex. Increasing the yarn count increases the mass per unit area and volume mass of fabric, whereas the surface and volume coefficient decreases.

Key words: spun yarn, knitted fabric, properties, input tension force.

1. INTRODUCTION

An influence of yarn count spun with different percent of noil on volume mass, linear, surface and volume loop coefficient were investigated.

Cotton single jersey knitted fabrics mostly are used for light underwear. These products are mostly manufactured by spun yarns of fineness of 12, 14, 17 and 20 tex, whereas the light cotton lingerie are manufactured by yarns of fineness of 14 and 17 tex with mass per unit area of 60 up to 100 g/[m.sup.2]. The weightier fabrics of mass per unit area up to 120 g/[m.sup.2] are manufactured by spun yarns of fineness of 20 tex. All parameters of fabric structure define the fabric mass per unit area. A mass per unit area is the main technological and economic parameter of knitted fabric design and its production planning. The mass per unit area of single jersey knitted fabric (m in g/[m.sup.2]) can be calculated using the following equation:

m = Dh x Dv x l x Tt x [10.sup.-2] g/[m.sup.2] (1)

where Dh is horizontal density in loop/cm, Dv is vertical density in loop/cm, l is length of loop thread in mm and Tt is the yarn fineness in tex.

Increasing the values of parameters to the equation (1) increases the square mass per unit area of knitted fabric. Knowing mass per unit area as well as thickness it can be determined the volume mass ([m.sub.z] in g/[cm.sup.3]) using the following equation:

[m.sub.z] = m/1000 x [d.sub.pl] g/[cm.sup.3] (2)

where dpl is thickness of knitted fabric in mm. The different yarn count can be used at the same knitting machine for the design of structure of knitted fabrics i.e. structure of the knitted fabrics is a function of the yarn count. The main technological parameters by which the mass per unit area determined are in certain relationship. The loop density firstly is the function of the machine gauges (needles per inch) as well as of yarn count. The vertical density depends on yarn count, the input tension force of the yarn, as well as take-down force of the knitted fabrics. The relationship between horizontal and vertical density (C=Dh/Dv) determines the loop length of thread. Nevertheless, the sinking depth in the more extends impacts to loop length of thread. When the sinking depth is higher the loop length of thread is higher as well, and because of that the structure of the knitted fabrics becomes more porous and vice versa. More porous knitted fabric structures are mostly used for lightly garment goods, whereas less porous structures are used for underwear (Vrljicak & Stahov 2005).

The basic parameters that describe the knitted fabric fullness are linear, surface as well as volume coefficient of loop. The linear coefficient of loop describes the relationship of loop length of thread as well as its thickness. It can be calculated using the following equation:

[delta] = l/d (3)

where [delta] is linear coefficient of loop and d is thickness of thread in mm.

An optimum field of usage of the linear coefficient for the single jersey knitted fabrics ranged from 18 to 23. Surface coefficient of loop describes the relationship between two surfaces of loop and that of thread. It is determined by the following equation:

[[delta].sub.p] = A x B/l x d(4)

where [[delta].sub.p] is surface coefficient of loop, A is width of loop in mm and B is height of loop in mm.

The surface coefficient is important with determination the air permeability of knitted fabrics and it is usually used to determination the usage properties of fabrics.

The volume coefficient ([[delta].sub.z]) describes the relationship between the loop volume and thread volume and can be determined according to the following equation:

[[delta].sub.z] = 4 x A x B x [d.sub.pl]/[d.sup.2] x l x [pi] (5)

In order to determine the volume coefficient it needs to know the thickness of knitted fabric. The volume coefficient is one of the more important parameters that is used with determine thermal properties of knitted fabrics as well (Vrljicak 2006).

2. RESULTS

The samples of knitted fabrics are manufactured at the circular knitting machine from the cotton single yarns of fineness of 14,3; 16,7; 20 and 25 tex. From everyone yarn count were knitted two fabric samples with different input yarn tension of 0,15 cN/tex and 0,40 cN/tex respectively.

[FIGURE 1 OMITTED]

The results of the mass per unit area in dependence of yarn count and input yarn tension are given in the Fig. 1.

The samples were made by yarn if fineness of 14,3 tex and input yarn tension if 0,15 cN/tex have the mass per unit area of 70 g/[m.sup.2] whereas the mass per unit area of samples made from courser yarns and the same input yarn tension ranged between 83 to 126 g/[m.sup.2]. It is obvious that by increasing the input yarn tension (from 0,15 to 0,4 cN/tex) increases the mass per unit area (form 2,7 to 18,7%). In this case it is obtained more compact fabric structure.

The measured and calculated parameters according to equations 2, 4 and 5 are given in Table 1.

The fabric thickness according to standard EN ISO 5084:1996 for these investigations was measured. Its values ranged from 0,6 to 0,9 mm.

The finest yarns provide the lowest volume (0,104 g/[cm.sup.3]). By decreasing the yarn fineness the volume mass of fabric increases. According to before mentioned the yarn of fineness of 25 tex has the volume mass of 0,150 g/[cm.sup.3] (Tab. 1). As the value of yarn volume mass ranged nearby 0,8 g/[cm.sup.3] and cotton volume mass is 1,53 do 1,55 g/[cm.sup.3], it is obvious that the knitted fabric volume mass is rather lower (Cunko & Andrassy 2005). Surface coefficient of loop is in fact surface coverage of loop from which the loop is made. Its values with all fabrics ranges from 0,81 do 1,41. From the obtained results it is perceived that the surface loop coverage is higher than 60%. When the surface coefficient of loop is lower of 1 it indicates that exists the considerable deformation of the yarn in knitting process. From the results obtained it is implied to the further investigation of intensity and reason of yarn deformation.

According to values of volume coefficient of loop it is seen that its values are 4 to 6 times higher than that of volume coefficient of thread. The loop made from finer yarns accomplish less space.

[FIGURE 2 OMITTED]

In the Figure 2 it is shown the influence of percent of noil on volume coefficient of loop with two input yarn tensions. It implies that the volume coefficient of loop is mostly lower with knitting by higher input yarn tension.

3. CONCLUSION

According to results obtained it can be concluded:

* Increasing the yarn fineness the mass per unit area as well volume mass decreases; single jersey knitted fabric made from cotton spun yarn of fineness of 14,3 tex has mass per unit area of 70 g/[m.sup.2] and volume mass of 0,10 g/[cm.sup.3]; with knitted fabric made of yarn of fineness of 25 tex has higher values of mass per unit area as well as volume mass (126 g/[m.sup.2] 0,15 g/[cm.sup.3] respectively).

* Surface coefficient of loop has mostly values higher than 1 (ranged from 0,99 to 1,41).

* Loop volume is 4 to 6 time higher than that of yarn volume.

4. REFERENCES

Cunko, R.; Andrassy, M. (2005). Fibres, Zrinski, 953-155-089-1, Cakovec

Fatkic, E.; Srdjak, M.; Skenderi, Z.; Vrljicak, Z. (2002). Dependence og the tightness of knitted fabric on structure density and yarn properties, Annals of DAAAM for 2002 & Proceedings of the 13th International DAAAM Symposium, Katalinic, B., Vienna, Austria, 23-26.10.2002.

Skenderi, Z.; Srdjak, M.; Kopitar, D. (2005). Impact of Combing Noil Percentage on Physical-mechanical Properties of Cotton Yarn, Fibrous materials XXI century, St. Petersburg, Russia, 23-28.05.2005

Vrljicak, Z.; Stahov, N. (2005). Design and Manufacture of Single Jersey Weft Knitted Fabrics of Different Density, Tekstil, Vol. 54, No. 9, 440-447

Vrljicak, Z. (2006). Maschenverschiebung in der Rechts / Links-Kulierbaumwollstrickware, XLIII Congress of the IFKT, Plovdiv, Bugarska, October, 2006.

Table 1 Knitted fabric parameters manufactured with input yarn
tension of 0,15 cN/tex knitted from cotton spun yarns of 14% of
noil

Yarn count m [m.sub.z]
(tex) (g/[m.sup.2]) (g/[cm.sup.3])

14,3 70 0,104
16,7 83 0,119
20,0 112 0,151
25,0 126 0,150

Yarn count
(tex) [[delta].sub.p] [[delta].sub.z]

14,3 1,41 6,28
16,7 1,26 5,52
20,0 1,08 4,43
25,0 0,99 4,14