What is the true spiral angle in cotton? Does solvent exchange alter it?

✍ Scribed by P. Bhama Iyer; K. R. Krishna Iyer; N. B. Patil

• Publisher: John Wiley and Sons
• Year: 1993
• Tongue: English
• Weight: 198 KB
• Volume: 50
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1993.070500721

✦ Synopsis

What Is the True Spiral Angle in Cotton? Does Solvent Exchange Alter It?

In a recent communication, Moharir' used the data reported by Iyer et al.* on Hermans' orientation factor f (Ref. 3) and convolution angle (0) on air-dried and solvent-dried cotton fibers to calculate the average crystallite orientation angle a, using the relationship

The convolution angle was then subtracted from a, such that (a, -0 ) could be regarded as the true spiral angle of the fibrils in cotton. On computing (a, -0) and ( a h -e'), respectively, for the air-dried and solvent-exchanged fibers, the author found that the latter is generally higher. Based on this observation, he pointed out that the convolution angle in the solvent-dried fiber could have been underestimated or that the solvent-exchange process could have altered the spiral structure. This interpretation appears to be rather simplistic. To understand why (a:, -0') was, in general, higher than (a, -8 ) , a closer look at the spiral structure seems to be necessary. The present communication intends to accomplish this. The author's observation' that (a, -0 ) works out to be lower than ( a h -0') is not a revelation following from the use of a, in place of the 50% X-ray angle (4). An examination of the values in columns 3 and 6 in Table I will show that in 18 cases out of 21 ( $ -0 ) is found to be lower than ($' -19'). Thus, the anomaly in the spirality of solvent-dried and air-dried fibers was already evident from our original data. However, we did not proceed to highlight this aspect for two reasons: First, our interest was only to demonstrate that the range of the true spiral angle in different varieties is lower for the solvent-dried fibers than for the air-dried. The actual values of the spiral angle were not intended to be discussed and the range, indeed, reduced from 7.71' to 4.77' (see Table I). This is equally true for a, and a(,, where the range reduced from 6.69" to 2.95". In other words, physical removal of convolutions reduces the spread in the mean orientation angle among varieties in a remarkable way. Second, it appeared inappropriate to compare the nett spiral angle in solventdried and air-dried cotton as air-drying would produce geometrical and structural changes in the fiber. In accordance with the constant pitch model' of cotton fiber, a