THE EFFECT OF TREATMENT WITH SULPHURIC ACID ON THE BREAKING LOAD OF COTTON

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Abstract
The tendering effect of sulphuric acid solutions on single cotton hairs and yarns has been studied by making breaking load tests on a modified form of the O'Neill apparatus or a Baer single thread tester. The samples were soaked in the acid for two days at the room temperature, then washed thoroughly and dried in the air, and sufficient specimens were tested to give results with small probable errors. It is shown that treatment with 10% sulphuric acid already causes distinct tendering of cotton hairs or yarns and that complete disruption is caused by acid containing about 77 grms, H2SO4 per 100 cc. With single hairs, the tendering effect is directly proportional to the concentration of the acid. With yarns, the strength decreases slowly but proportionately to the concentration of acid until the latter reaches 20–30%, and thereafter it falls more rapidly but still in proportion. This is due to the effect of the structure of the yarn; during the first period, the yarn breaks mainly by slipping, but in the second the individual hairs are already so weakened that they snap without slipping. The effect of kier boiling on tendered yarn has also been tested. Although kier boiling itself weakens single cotton hairs, it strengthens raw yarns or yarns which have been treated with sulphuric acid of concentrations below 10%. This is ascribed to its causing the closer packing of the hairs in the yarn and thus hindering slipping. The beneficial effect of kiering disappears, however, with more tendered yarns, and these are actually still further weakened.

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