Investigations were made concerning the effects of various salt solutions on the quality of wool fibres in treating them with permanganate, and it was found that 2 mol solution of (NH
4)
2SO
4 was most effective among the solutions for the treatment of shrinkproofing without such adverse effects as yellowing and poor handling.
The cation of the salt solution did not show any special tendency to give a shrink-proof quality to the fibres, but its SO
4= anion showed a tendency to improve the anti-felt treatment with permanganate.
With the increased concentration of the same salt solution, shrink-proof property of the treated yarn becomes better, its tensile strength larger, and its alkali solubility less. This may be attributable to the fact that the reaction occurres with the increased concentration, apt to be confined to the surface of the fibres mainly by their deswelling action and does not substantially hurt the fibres themselves.
Comparisons of physical properties between the wool fibres treated with KMnO
4/(NH
4)
2SO
4 solution and the ones treated with KMnO
4/H
2O solution revealed the following two facts. The static frictional coefficients between fibre-fibre as measured in their wet state by the Röder method showed an obvious difference from each other, at the same degree of concentration of KMnO
4 the former showed a smaller value of μ
2-μ
1 and a better shrink-proof effect than the latter.
Where the fibres were treated with KMnO
4/(NH
4)
2SO
4 solution, their values of both μ
1 and μ
2 became smaller up to 5% o. w. f. KMnO
4; but beyond that point those values tended to became larger.
This phenomenon could be seen from optical microscopic observations. The scale edges of the treated fibres tended to are collapse up to 5% o. w. f. KMnO
4; but beyond that point said edges are sunken, and only the central part of the scale remaines to be seen.
In the case of KMnO
4/H
20 solution, however, such a concave structure is hardly noticeable even if 30% o. w. f. KMnO
4 solution was used.
It was found that there is a linear correlation between the values of μ
2-μ
1 of the shrink-proofed wool fibres and the rates of its felting shrinkage.
Half scales of wool fibres were first abrased by a glass edge along the fibre axis, and then the fibres were treated with KMnO
4 solution in the presence and absence of (NH
4)
2SO
4. In both cases, it was found that MnO
2 is deposited on the abrased side (cortex) but rarely, if any, on the other side (coticle) before reduction. This clearly indicates that the cortex is more reactive than the cuticle.
View full abstract