Cotton Quality and Fiber Properties

Several years ago Hall and Elting pointed out that certain raw cottons which had been subjected to the action of fungi in the field or immediately after harvesting suffered a deteriora tion in cotton quality characteristics upon storage in bale form. Such cotton was termed by them to be "cavitomic." This deterioration was most manifest in a reduction of processing efficiency and a lowering of yarn quality. Certain chemical tests (pH and reducible sugars) were established as methods to detect cavitomic cotton. Because there seemed to be consider able lack of information regarding the nature and primary causes of quality deterioration at tributable to cavitomic cotton, the study presented in this paper was undertaken to determine what changes in fiber properties resulting from the "cavitoma" might be responsible for the effects noted previously. The opportunity for this study was presented when it was found that 3 of 12 bales of a homogeneous lot of Deltapine 15 cotton obtained for another investigation gave positive evidence of being cavitomic. These 3 bales were set aside, stored for a year, and then made into fabric. A similar fabric was simultaneously made from a blend of the remaining 9 bales in a processing comparison. Samples at all stages of processing were taken from both cottons and carefully compared in an extensive laboratory testing program. It was found that the cavitomic cotton did, in fact, produce more processing waste; less even slivers, rovings, and yarns; 45 % more end breakage in spinning; and yarns as much as 10% weaker than the normal cotton. In the laboratory study it was found that the cavitomic sample exhibited lower flat-bundle strength at a 5-mm. clamp spacing, a lower fiber crimp, and a shorter fiber length than the normal sample. Although the length difference was barely detectable by conventional methods it was clearly established from number-length distributions based on single-fiber length measurements. It is concluded from this study that some of the fibers are subjected to a localized weakening as a result of the microbial action, either directly or as a result of enzymatic action during storage. These fibers break more easily in processing than fibers in the normal cotton, giving rise to a length distribution biased in the direction of short fibers. This difference in fiber- length distribution is believed to be responsible for the reduction in cotton quality characteristics observed in this and the previous work by Hall and Elting. These results emphasize the importance of fiber-length uniformity as a factor in raw-cotton quality and the need for more sensitive methods of evaluating this factor than are presently available.