The Tootal-Broadhurst-Lee Company's method was improved as follows: A cloth is conditioned for 2 days at 25°C and 65% R. H., from which the test pieces of 2cm long and 1cm wide are cut by means of a cutter. A test piece is folded across the narrow dimension and placed between two glass plates and loaded with a 500gm weight for 1hour. It is then allowed to recover for 10min. while hung over a horizontal wire of 0.3mm diameter, and then the distance
l between the ends is read with a calipers. During the test the air is conditioned at 25±0.5°C and 65±1% R. H.
The long dimension of the test piece was shortened to 2cm, in order to obtain the value of
l,
l=2sinθ/2 where θ is the crease angle.
The process of crease recovery was followed in order to estimate the value
l at equilibrium from an exact value after 5 or 10min. recovery period. It is found that
l changes in the following relation for cloths. _??_ (1)
where
l_??_ is the value of
l at
t=o, a
1, a
2 and a
3 are the constants,
t the time of recovery, and λ
1, λ
2 and λ
3 are the relaxation times.
In the case of yarn two relaxation times λ
1, λ
2 are given for recovery, and one relaxation λ
1 for filament. The values of λ
1, λ
2 and λ
3 are 50_??_70, 10_??_20 and 1_??_2min. in the case of the viscose yarn used.
In the range of
t=3_??_20min., 160 samples of the cloths, which were woven variously by using the same viscose yarn, containing partly the resin-treated, are all indicated by the equation (1).
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