How to Identify Constituent Fibre Percentage in a Blend-1

Blend of Polyester/Cotton (viscose)

1. Take 0.5 to 1.0 gms of blend sample, carefully weighed, and put it in a flask.

2. Add 75% (w/w) Sulphuric Acid (M:L::1:200).

3. Put in a water bath for one hour at 50+-5 deg C.

4. Filter it, whatever is left is polyester.

5. Wash it thoroughly.

6. Neutralise it with Dilute solution of Ammonia

7. Dry at 110 deg C, cool and weigh to find the Percentage of Polyester and the other cellulosic component.

Blend of Cotton/Viscose

1. Take 0.5 to 1.0 gms carefully weighed sample and put it in 60% w/w Sulphuric Acid. Keep material to Liquor ratio as 1:100.

2. Stir this solution mechanically for 30 minutes. Viscose fibres will dissolve by this process and cotton fibres will be left.

3. Filter the cotton fibres and wash it in Sulphuric Acid.

4. Again wash it with water and neutralise it with a dilute solution of Ammonium Hydroxide.

5. Dry and Weigh. Note that cotton fibres lose weight by 5% in this process. Apply this correction factor in finding the blend percentage .

Blend of Polyester/Cotton/Viscose

1. Put the fibres in 60% w/w sulphuric acid (after weighing). Viscose will dissolve in 60% w/w sulphuric acid.


2. Dry and weigh carefully the rest of the fibres.

3. Put these fibres in 75% sulphuric acid. Cotton will dissolve.

4. The fibres left will be of polyester, which are weighed after thorough washing and drying.