How to measure cotton degardation during bleaching and other processing?

It has been seen that during bleaching process the cotton (or cellulose) undergo oxidative degradation and form oxycellulose. Such degradation not only reduce the cellulose molecular chains or other word lower the degree of polymerization (DP) but also introduces new functional groups such as aldehydes, ketones and carbonyls.

The oxycellulose that form during degradation is of two types:

i) Reducing oxycellulose

ii) Acidic Oxycellulose

To measure the above two types of oxycellulose followoing two methods are adopted:

i) Copper number for reducing oxycellulose

ii) Methylene blue absorption test for acidic oxycellulose

The reducing oxycellulose, which act as reducing agent and copper number is the grams of copper which are reduced from cupric to the cuprous state by 100 grams of cellulose when boiled with fehling's solution.

Pure cellulose has no affinity for methylene blue, but the formation of acidic oxycellulose is generally accompanied by the appearance of carboxyl group which confer an affinity.

These tests are also helpful in distiguishing between oxycellulose from acid oxidation (low values of methylene blue absoption) and those from alkaline oxidation (high methylene blue absorption).