Page 147 - Handbook of Properties of Textile and Technical Fibres

Physical, chemical, and tensile properties of cashmere, mohair, alpaca 125

4.3.2 Bundle tenacity

Tenacity is the textile term used for “filament strength.” Modelling by Yang et al.
(1996) showed that a 10% decrease in bundle tenacity of wool tops roughly doubled
the number of times the yarn breaks during spinning, and was equivalent to a decrease
of 9 mm in the mean length of fiber in the tops (Hauteur). On this basis, they concluded
that bundle tenacity was the third most important property in wool tops after MFD and
fiber length. McGregor and Postle (2004a, 2004b) surveyed the bundle tenacity of
dehaired cashmere and cashmere tops. Whilst the dehaired cashmere was finer, and fi-
ber length shorter, than the tops, there was little difference in bundle tenacity and
extension (Table 4.4). The tenacity of the tops was dependent on Hauteur, a finding
reported for wool (Yang et al., 1996) but the best prediction equation only explained
30% of the variance. The linear regression constants were: Tenacity (cN/tex) ¼
5.5 þ 0.12 (0.04) Hauteur (mm).
The bundle tenacity (cN/tex), bundle extension (%), and MFD (mm) of other fibers
from the same survey were respectively: alpaca tops 10.8e13.9, 39.7e43.3,
21.9e27.5 (n ¼ 8); dehaired camel 10.9e13.1, 44.8e50.7, 16.5e21.2 (n ¼ 4); and
depigmented yak tops 9.1e10.1, 42.2e43.2, 18.1e20.1 (n ¼ 3). Two samples of
dehaired bison wool (MFD 17.4e19.6 mm) had a mean bundle tenacity of 8.7 cN/
tex and bundle extension of 39.3% (McGregor, 2012).

Table 4.4 Mean and range for attributes of international dehaired
cashmere and cashmere tops
Dehaired (n [ 40) Tops (n [ 21)
Attribute Median Range Mean Range
MFD (mm) 16.4 13.5e19.3 17.3 15.2e19.3
Fiber diameter coefficient of variation (%) 21.7 19.8e29.0 21.3 19.8e23.8
% Fibers >30 mm 0.5 0.1e2.1 0.6 0.1e1.6
Fiber curvature (degrees/mm) 60.0 40.1e79.7 59.2 48.9e68.5
Incidence of medullated fiber (%w/w) 0.3 0.0e8.8 0.4 0.1e1.5
Length after carding or Hauteur (mm) 22.8 15e36 39.4 28e45
Bundle tenacity (cN/tex) 9.9 8.2e12.0 10.3 8.3e12.0
Bundle extension (%) 40.8 31.3e50.0 38.8 19.5e50.0

Adapted from McGregor BA, Postle R: Processing and quality of cashmere tops for ultra-fine wool worsted blend fabrics,
Int J Cloth Sci Techn 16:119e131, 2004a and McGregor BA, Postle R: Softness and other fibre attributes of commercial
cashmere textiles from China and other origins of production, In Proc. Text. Inst. 83rd World Conf., Shanghai, 2004b, pp.
372e375.