Page 125 - Handbook of Properties of Textile and Technical Fibres

106 Handbook of Properties of Textile and Technical Fibres

known as dehairing, is a slow and expensive process that leads to fiber breakage and
limits yarn quality. Knowledge about the processing requirements of these fibers is
kept guarded as intellectual property.
Most of these rare animal fibers are produced in extensive grazing systems, usually
with traditional management and some are associated with nomadic lifestyles. During
the past 100 years more technology has been applied to animal husbandry, fiber qual-
ity, and other aspects of the animal production and marketing systems but to a far lesser
extent compared with Merino wool production. As a consequence, generally there is a
large variation in the physical properties of raw fiber and little appreciation of the in-
fluence that variations in fiber quality have on subsequent processing. This generaliza-
tion cannot be applied to newer production systems for mohair, cashmere, alpaca, and
angora, where technology has improved fiber quality and profitability of the
enterprises.
This chapter will follow the general structure of the previous chapter on wool.
Cashmere and mohair will be treated in more detail than other animal fibers given
the greater amount of published information on these fibers. Zahn (1990) provided
an overview of the role of mohair in keratin fiber research. Many of the chemical
composition studies of rare natural fibers have been hampered by their small sample
size, the use of processed samples that contain intermingled fiber from many animals
and possibly many sources, and the lack of statistical evidence to support their conclu-
sions. Sources for further information and references are provided.

4.2 Structure

4.2.1 Chemical

These animal fibers, like wool, are composed primarily of a-keratin proteins. These
proteins consist of 18 amino acids. Examples of the amino acid composition of a range
of rare animal fibers are shown in Table 4.1. Tucker et al. (1988) provide amino acid
values for camel, yak, and cashgora. Hunter (1993) summarizes the information on the
chemical composition of mohair and other rare fibers including analysis of the grease
in the raw fleeces. While there is a great similarity in the amino acid composition
amongst these fibers there also appears to be small differences between these fibers,
which is not surprising given they grow on very different animals in different environ-
ments. Differences in the amino acid composition of cashmere have been demon-
strated related to the country of origin and various aspects of the diet of the goats
(McGregor and Tucker, 2010; Table 4.1). This demonstrates that the chemical proper-
ties and therefore the reactivity of cashmere from different production systems can
differ. In this study, the color attributes of lightness and yellowness of cashmere
were affected by amino acid composition, nutrition treatment, and productivity of
the goats.
The chemical composition of wool and most probably these rare animal fibers is
typically: nitrogen 16%e17%; sulfur 3.2%e3.7%; ash 0.38%e0.42%, which includes
calcium 0.09%e0.12% and phosphorus 0.017%e0.023% and some undefined small