Page 150 - Handbook of Properties of Textile and Technical Fibres

128 Handbook of Properties of Textile and Technical Fibres

The tensile, elongation, and wear properties of pure and blended cashmere worsted
spun yarns and knitted fabrics, and the effect of blending with superfine wools (MFD
17.0 mm) of different fiber curvature (74 vs. 114 degrees/mm) have been investigated
(McGregor and Postle, 2007, 2008, 2009). They found that
1. Pure cashmere yarns had lower tenacity and elongation than pure wool yarns. Adding cash-
mere to wool reduced tenacity of the yarns.
2. Pure cashmere fabrics were softer and thinner than pure wool fabrics. Adding cashmere to
wool increased the softness (compression) and reduced the thickness of the fabric.
3. Pure cashmere fabrics had a lower bending rigidity than cashmere/wool blends and pure wool
fabrics. Adding cashmere to wool made the fabric more flexible by reducing both bending
rigidity and bending hysteresis in both directions of knitted fabric for all but loosely knitted
fabrics.
4. Pure cashmere knitted fabrics had lower shear rigidity and shear hysteresis than cashmere/
wool blends and pure wool fabrics. Overall, shear rigidity was reduced when cashmere
was blended with wool as there is less yarn to yarn contact and cashmere blend fabrics are
thinner than knitted wool fabrics.
5. The lower extensibility of cashmere and cashmere blend fabrics compared with the pure wool
fabrics was associated with the reduced fiber curvature of the cashmere, which reduces not
only the ability of the yarn to straighten or extend, but also the ability of the fabric to extend
relative to higher crimped wool fibers. The lower tensile linearity of pure cashmere fabric
relative to cashmere/wool blends means that pure cashmere fabrics were more supple and
springy than cashmere/wool blend fabrics or pure wool fabrics. Cashmere fabric was thinner
and more open, with relatively low inter-yarn friction, resulting in lower forces opposing
deformation and recovery of fabrics.
6. Increasing cashmere in blends with wool was associated with reduced pilling and appearance
change (i.e., an improvement) at all cover factors.
Fabric pilling is associated with fiber fatigue related to rubbing and abrasion. The
finding that adding cashmere to wool in worsted spun knitted fabric reduced pilling
and appearance change was associated with greater mass loss with cashmere and
different mass loss depending on the fiber curvature of the wool in the blend (McGre-
gor, 2006b). The assessment also depended on the test method. The ICI Pill
Box Method differentiated to a greater extent the effects of wool type and blend ratio
of cashmere and wool compared with the Random Tumble Method. When evaluating
the pilling of woollen spun pure Chinese cashmere knitwear (MFD 15.4 mm) Li and
Zhou (2004) reported that the ICI Pill Box Method was preferred over the Random
Tumble and Martindale abrasion tests that were regarded as being too severe, a finding
perhaps related to the woollen yarn structure.
Liu et al. (2005) found that alpaca fibers take longer to fatigue under abrasion than
do wool fibers of similar MFD, with the differences between these fibers increasing as
MFD increased above 20 mm. They provide images of fiber cracking, cuticle peeling,
rupture, splitting, and fibrillation.
Villarroel (1959) concluded that the greater scaliness of Huacaya fiber and the
greater elongation and strength will allow Huacaya fiber to spin better compared
with Suri fiber. Sanderson and Wilkinson (1990) discuss the characteristics; perfor-
mance; and end-use of red deer, crossbred goat, cattle, and horse fibers in 33% blends
with carpet wool. Yarn strength and extensibility of goat fiber blends were acceptable
but cattle, horse, and deer blend yarns were poor and more uneven.