Last updated on July 16th, 2023 at 10:36 am
Optical Brightening Agents (OBA) are colorless or very pale yellow colored organic compounds which when added to a substrate increase the apparent reflectance in the visible by converting ultra-violet radiation into visible light and thus increase the whiteness or brightness.
An OBA can be called a colorless dye which has some substractivity for the fibre on which is to be used.
Optical brightening agents can also be called:
- Fluorescent brightening agent
- Physical brightening agent
- Brighteners
- White dyes etc.
Fibre and Fabric
Fibre: 100% cotton
Fabric: Knit fabric
Method
Here, one of the exhaust methods is used.
Instruments and glass ware
- Beaker
- Glass rod
- Measuring cylinder
- Bowl
- Electric balance
- Scissor
- Sample dyeing
- Water shaking bath
- Tumble dryer
Instruments and materials needed for washing test
- SDC recommended multi-fibre fabric
- Water shaking bath
- Thermometer
- Dryer
- Color matching cabinet
- Sewing machine
- Grey scale
Reagent required for washing fastness test
- ISO reference detergent
- Sodium carbonate
- Distilled water
- Pipette
Recipe
Optical brightening agent: 3%
NaOH: 4gm/l
H2O2: 8gm/l
Wetting agent: 2gm/l
Stabilizer: 1gm/l
Sequestering agent: 1gm/l
Sample weight: 5gm/l
M : L: 1 : 20
Total liquor: 100 cc
Necessary Calculation
NaOH → Stock solution 4% = (10 X 100 X 100)/(1000 X 4) = 10 CC
H2O2 → Stock solution 8% = (8 X 100 X 100)/(1000 X 8) = 10 CC
Wetting agent → Stock solution 2% = (2% X 100 X 100)/(1000 X 2) = 10 CC
OBA → Stock solution 5% = (5 X 3%)/(5%) = 3 CC
Water required = { 100 – (10 + 10 + 10 + 3)} CC = 67 CC
Process Description
- The dye bath is set at 300C and add sample, wetting agent stabilizer.
- The temperature is raised at 600C and added NaOH and kept it for 5 minutes.
- Add H2O2 at 700C for 5 minutes.
- Raise the temperature 80 – 1000C by 1.50C/min for 60 minutes.
- Check the shade and cooling down at 500C.
- Drop down the bath and wash sample at running water and do not squeeze.
Neutralization
Necessary Calculation
Acetic Acid → 1% stock solution = (1 X 100 X 100)/(1000 X 1) = 10CC
Water requires = (100 – 10) CC = 90 CC
Procedure
Neutralization is at 600C temperature for 10 minutes
Precautions
- Stock solution should be made carefully.
- Time and temperature should be maintained carefully.
- Soda, OBA should be properly dosed.
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