The amount of liquor taken up by the fabric
is often described as the mangle expression though more correctly it
should be called pick up. The two terms are used interchangeably.
It is the difference in dry to wet weight expressed as percentage of dry
weight. Thus
Example: 200 kg of cotton
poplin weighs 360 kgs after padding. What is the expression or pick up?
Calculation of pick up = (360
- 200)x 100/200 = 80%
Example: 800 kg of cotton
poplin are padded with a mangle expression of 75%. How much liquor has the
fabric taken up or how much must be added to the trough to maintain a certain
volume?
Calculation: Wet Weight - dry
weight = Weight of water taken up.
= (Dry weight X % pick up) / 100
= 800 x 75/100 = 600 kg or approximately 600 liters.
Example: A cotton fabric is to
be padded with 3% peroxide (50%) o.w.f. at 90% expression. What is the
concentration of the pad liquor in g/l ?
Calculation: At 90%
expression, 100 g will hold 90 ml of water. For 3% peroxide(50%) 100 gram
fabric will pick up 3 gram peroxide 50% w/w. Chemical concnetration must
therefore be 3 gram per 90 m, in one liter.
Concentration = 3 x 1000 / 90
= 32.3 gram/liter of 50% hydrogen peroxide w/w.
= % o.w.f. X 1000 / % pick up. |
