Page 128 - Handbook of Properties of Textile and Technical Fibres

108 Handbook of Properties of Textile and Technical Fibres

amount of sodium. The remainder of the fiber is approximately oxygen 27%, carbon
47%, and hydrogen (Ward et al., 1955; Carr et al., 1986). Harris and Smith (1937)
found cashmere to have a nitrogen content of 16.4% and a sulfur content of 3.4%
and alpaca 4.2% sulfur. Onions (1962) reported Turkish mohair had a sulfur content
of 3.4% for fine mohair and 3.0% for coarse mohair. As with wool, the low-sulfur pro-
teins assemble into intermediate filaments (microfibrils). The microfibrils are
embedded into a matrix of high-sulfur proteins (see Chapter 3).
The large number of polar groups present in animal fibers mean that they have a
strong affinity for water. As discussed in the chapter on wool, many of the chemical
bonds between the different side groups are disrupted by water. As a result, these an-
imal fibers have properties that change with humidity and moisture content.
Satlow (1965) used chemical tests to distinguish between sheep’s wool, alpaca,
camel hair, cashmere, and mohair. He studied the cystine and cysteic acid contents;
alkali solubility; urea-bisulphite solubility; and the effect of acids, alkalis, and en-
zymes, concluding that the differences between the fibers were insignificant. Many
of the tests used are not very sensitive and the interpretation of many of them is often
difficult.

4.2.1.1 Cashmere
Roberts (1973) carried out a detailed analysis of 16.9 mm Mongolian cashmere and
17.3 mm South African lambswool by subjecting the fibers to the action of water,
steam, oxidising and reducing agents, acids, and alkalis. Prior to the extraction, the
tips of the wool fibers were removed, a standard practice for wool purification so
that photochemically degraded wool is not included in subsequent studies. Roberts
did not remove the tips from his cashmere because it was impossible given the physical
state of the cashmere. He also considered it not to be important “because undercoat is
unlikely to be subject to photochemical degradation.” However, recent research has
shown that cashmere fibers are weathered and that cashmere from different locations
is weathered to different extents (McGregor, 2016). These points highlight some of the
difficulties in comparing the limited data on rare animal fibers with each other and with
wool, and to what extent the fibers are weathered.
Using more modern analytical methods Tucker et al. (Tucker et al., 1985, 1988,
1989; Hudson, 1992; Hillbrick and Tucker, 1996) analyzed Chinese and Australian
produced cashmere, feral goat down, and cashgora. They found no correlation between
fiber diameter and any amino acid. They did find significant differences existed be-
tween the various samples for cystine in particular, as well as for serine, glutamic
acid, and proline. Such differences are common among wool samples. They found cys-
teic acid in the cashmere samples. Whilst the amounts were quite small (9e17 mmol/g)
it would appear that some photochemical degradation of the fiber has occurred during
growth.
Albertin et al. (1990) investigated the amino acid composition of 19.2 and 20.8 mm
cashgora from New Zealand and 15.9 mm Mongolian cashmere. No differences were
found between the amino-acid composition of the cashmere and cashgora. The high
cysteic acid of the finer cashgora could indicate an oxidative cystine cleavage as a