Page 273 - Handbook of Properties of Textile and Technical Fibres

Tensile properties of cotton fibers: importance, research, and limitations 247

(a) 18

15
Regain (% dry basis) 12 9 6 Initially wet Initially dry

3

0
0 10 20 30 40 50 60 70 80 90 100
Relative humidity at 70 F
(b)
Initially wet sample

Regain (%) Equilibrium

Equilibrium

Initially dry sample

Time
Figure 7.8 Common moisture relationships of cotton fibers. (a) Moisture regainerelative
humidity relationship of cotton; (b) Moisture equilibrium of textile fibers.

at the equilibrium than the initially dry sample. This phenomenon is known as
“regainetime hysteresis.”
It follows from the abovementioned relationships that the cotton fiber is highly
sensitive to the ambient humidity and temperature. A change in moisture regain means
a consequent change in fiber dimensions (swelling and deswelling); this means that the
normalization of the parameters of tensile behavior with respect to the linear density
(tex or denier) discussed earlier will be directly affected by the level of moisture regain
in the fiber, and a comparison of the tensile behavior of two cotton fibers subjected to
two different ambient conditions will be invalid. For this reason, there is a standard
ASTM D1776 for the testing condition of cotton fibers prior to testing, which is

65 2% relative humidity and 21 1 C (70 2 F) of temperature. Normally, cotton