Spun silk threads are soft, but they are
less lustrous than reeled silk and are not as strong or elastic. Spun silk
fabric tends to become fuzzy after wearing because the yarn is made of short
staple. Spun silk is less expensive than reeled silk. Although spun silk has
less strength and elasticity than reeled silk because of the shorter staple
used, it posses all the general characteristics of reeled silk. Silk fabric
made of spun silk yet gives good service when the quality of the fibre is
good. Spun silk is used for pile fabrics, dress trimmings and linings,
elastic webbing, sewing silk, summer wear silks, velvets, umbrella fabrics
In this article, geometrical properties of spun silk knitted fabric are
elaborately discussed. Spun silk yarn has been knitted in to three different
knit structures. The testing methods, the materials and knitting machine
details are given below:
Table 1. Yarn specifications
% of Count
% of Breaking elongation
% of Breaking force
% of Tenacity
% of Uster %
places /km (-50%)
% of Thin places /km
places /km (+50%)
% of Thick places/km
/ km (+200%)
% of Neps / km
% of Hairiness index
Table 2. Knitting machine
– 313 DJ
The following tests were carried out according to standard textile testing
Standard Yarn Stage
PREMIER i Q Quali
Ball bursting strength
ICI Pill box
Low stress mechanical
Geometrical properties of spun silk
The Table 3 shows the geometrical properties of single jersey, rib and
interlock silk knitted fabrics with three different stitch lengths, given by
SL1, SL2 and SL3 (in cm). The geometrical properties such as wales/cm,
courses/cm, are respectively designated as WPcm, CPcm, stitch density (cm 2)
as SD, loop shape factor as L and the tightness factor (Tex 0.5 cm -1) as TF,
dimensional constants for wales, courses, and stitch density are
respectively designated as Kw, Kc and Ks.
Stitch length or loop length is a parameter that mainly influences the
geometrical properties of a knitted fabric. When the stitch length
increases, the WPcm, CPcm, and SD decrease irrespective of the type of
structure. This is due to larger yarn loop area. If the yarn loop area
increases the wales and courses per unit length reduce. This has been
observed in cases of all the three structures.
Geometrical constants Kc, Kw and Ks values of single jersey, rib and
interlock knitted fabrics have been increasing with increased stitch length.
Kw value first increases and then decreases when increasing the stitch
length in the case of interlock silk knitted fabrics. Similarly, when stitch
length increases, Kc value first decreases and then increases in case of rib
knitted fabric. The reason may be due to higher tightness of spun silk
knitted fabrics. The same trend is reflected in the loop shape factor also.
(Because Kc / Kw is the Loop shape factor). Tightness factor reduces with
increasing stitch length in all the three structures because of the lower
stitch density of knitted fabrics.
Correlation coefficient between (1 / SL) stitch length and geometrical
properties of spun knitted fabrics are also tabulated below.
In general, there is a good positive correlation between stitch length and
geometrical properties of spun silk knitted fabrics like wales per cm,
courses per cm, stitch density, loop shape factor, tightness factor and good
negative correlation between stitch length and geometrical properties of
spun silk knitted fabrics like geometrical constants Kw, Kc, Ks values.
Physical and comfort properties of spun silk knitted fabrics
In this part, the mechanical and comfort properties of spun silk knitted
fabrics are discussed and the results are compared with relevant count of
cotton knitted fabrics. This research work does not focus on comparative
analysis of spun silk and cotton knitted fabric. Because type of material,
properties, method of production, yarn manufacturing process and
pre-treatments are different for silk material compared with cotton
material. So, the given comparison Table shows the level of performance of
silk knitted fabric compared with commercial cotton knitted fabric.
(relevant count of silk yarn)
The fabric samples were produced as mentioned in the materials and methods
(given in the Tables 1 & 2 ). The produced samples were tested for their
properties as mentioned. The average values of test results of knitted
fabric properties are tabulated below: [Table 5 and 6 ]
From these results, it can be observed that the spun silk knitted fabric
shows higher bursting strength value than the equivalent cotton knitted
fabric, irrespective of knit structure.
These results show that the spun silk knitted fabrics display higher
abrasion resistance than the equivalent cotton knitted fabrics, irrespective
of knit structure. This may be due to higher silk fibre tenacity.
From the above table, it can be observed that the spun silk knitted
fabric shows fuzziness and less pilling resistance than the filament silk
knitted fabric, irrespective of the knit structure. Pilling does not seem to
be a serious problem with spun silk and equivalent cotton knitted fabrics.
The drape results clearly show that the spun silk knitted fabrics give
lower drape coefficient values than the equivalent cotton knitted fabrics,
irrespective of structure. Unpredictable trend may occur due to the curly
nature of single jersey knitted fabric.
From the above table it can be seen that the spun silk knitted fabrics
have higher air permeability than the equivalent cotton knitted fabrics,
irrespective of structure.
The above values show that the spun silk knitted fabric is having a
higher wicking tendency than the equivalent cotton knitted fabric
irrespective of structure. The spun silk interlock knitted fabric shows
higher wicking values than the other knit structures, which may be due to
higher stitch density of interlock fabric.
Thermal insulation value
The thermal insulation results show that the values for spun silk
knitted fabrics are higher than the equivalent cotton knitted fabric
irrespective of knit structure, which may be due to lower thermal
conductivity of silk fibre. This may be the reason for higher thermal
insulation value in all the cases.
From the above table, it can be observed that the spun silk knitted
fabrics show relatively the same thickness as compared with the equivalent
cotton knitted fabrics irrespective of knit structure. Rib knitted fabric
shows higher thickness value than all the other knitted fabrics, and this
can be attributed to the bulkiness of rib knitted fabrics.
Weight [Gm per sq m]
From these observations it is clear that the weight of a knit structure
increases with stitch density irrespective of the knit structure and the
yarn. Spun silk and cotton rib knitted fabrics show higher weight values
than all the other knit structures because of the higher yarn density of
The results show that the percentage of area shrinkage is higher for the
spun silk knitted fabrics than the equivalent cotton knitted fabrics, which
may be due to the higher yarn tension (silk: 7-8 g, cotton: 4-5 g) during
Low stress mechanical properties
The above results show that the spun silk knitted fabric gives higher LT
and WT values than the corresponding cotton knitted fabrics irrespective of
knit structure. This may be due to the higher fibre tenacity and breaking
extension of silk. The spun silk knitted fabrics show lower RT values than
the equivalent cotton knitted fabric irrespective of knit structure, which
may be due to the good work recovery property of silk.
The above table shows that the spun silk knitted fabrics display higher
bending rigidity than the corresponding cotton knitted fabric irrespective
of knit structure. This may be due to the higher specific flexural rigidity
of silk fibre. (Silk: 0.6 mN mm2/tex2 and Cotton: 0.53 mN mm2/ tex2)
Spun silk knitted fabrics show lower hysteresis of bending moment than the
cotton knitted fabric irrespective of knit structure, a result that may be
due to the higher work recovery of silk fibre.
The above values show that the shear properties of G, 2HG, 2HG5 values
for spun silk knitted fabrics are higher than those of the equivalent cotton
knitted fabrics, which is mainly due to higher shear tenacity of silk fibre
than cotton. (Silk: 115.8 mN / tex and cotton: 84.4 mN / tex)
The compression test results show that the spun silk knitted fabrics
display lower LC and higher WC and RC values than the equivalent cotton
knitted fabrics in case of all three basic structures. Spun silk knitted
fabrics show higher RC values than the equivalent cotton knitted fabric,
which may be due to higher elongation and work recovery properties of silk.
Surface roughness and friction coefficient
From the above data, it can be observed that the spun silk and the
equivalent cotton knitted fabric show an unpredictable trend, which is
probably due to variation in the stitch density of knitted fabric.
Spun silk knitted fabrics have higher bursting strength, higher abrasion
resistance, higher air permeability, better wicking, higher Shrinkage and
lower drape as against the comparable cotton knitted fabrics, irrespective
of knit structure. Pilling does not seem to be a serious problem with spun
silk knitted fabrics.
Spun silk knitted fabrics have higher LT, WT value and lower RT value of
tensile properties, higher B, lower 2HB value of bending properties, higher
G, 2HG, 2HG5 value of shear properties, higher LC, WC and RC values of
compressional properties and higher MIU, MMD and SMD of surface roughness
properties than the respective cotton knitted fabrics irrespective of knit
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Note: For detailed version of this
article please refer the print version of The Indian Textile Journal April
Mr M Senthilkumar
Department of Textile Technology,
PSG Polytechnic College,
Prof B B Jambagi Department of Textile Technology,
DKTE Textile and Engineering Institute,