In all cases, LCSP and single yarn strength decreased linearly as yarn numbers become finer, this is clear in both open end and ring spun yarns, for instance yarn tenacity of 25s open end and 30s ring yarns were significantly higher compared to 35s open end yarns and 40s ring yarns respectively.

In open-end yarns, the variation analysis, a statistical difference revealed between the tenacity values of 25s and 35 yarns. Therefore, the tenacity values of the 25s yarns were higher than those of the 35s yarns. On the other hand, the tenacity values of the 30s ring spun yarns were higher than those of the 40s yarns.

For a given cotton blend, the ring yarns were stronger than the open-end yarns. Comparing yarn strength of the different blends of Giza 85 with Greek and Sudanese cottons, cotton B produced the strongest yarns, followed by cotton C, D, G, H and then cotton I regardless the spinning system used. The same trend was found among the combinations of Giza 85 and Sudanese cottons, indicating that yarn strength increased as the percentage of Giza 85 increased in the blend with both Greek and Sudanese cottons.

The study of the effect of short fiber index on processing efficiency and yarn quality indicated that the increases in short fiber contents have a detrimental effect on spinning performance (end breakage) and product quality. Even though it is well known that the long fibered, stronger and more uniform (Giza 85) cotton has a definite advantage over short fibered (Greek and Acala cottons), the high price of the longer cotton prohibits its indiscriminate usage.

Since cottons of longer staple length usually have less short fiber content than the shorter ones. Short fibers are generally immature, and weak fibers, it would appear that blending long cotton with short ones would reduce the short fiber content, resulting in increased spinning performance.

Coarse and medium yarns produced from Egyptian cotton are not economical due to high cost of raw material used in such cases. Regarding to the data mentioned above, the spinning industry in Egypt should blend high and low quality cottons to reduce and control the cost, as well as to meet functional use requirements.

Regarding to yarn strength which is the most important yarn character and determines the yarn quality and price in all markets, the spinning mills or the yarn consumers can determine the yarn quality level which they need according to the Uster provisional yarn quality levels, consequently yarn strength of the different blends of Egyptian cotton and Upland cottons as shown in figures 1, 2, 3, 4,5,6,7 and 8 could be helpful to determine the required blend. Any spinning mill primarily thinking in input "raw material cost and price" / output "yarn quality and price" system. In this regard, the best input (raw material cost and quality) situation is achieved when quality is at is highest possible level and price is at its lowest possible level. On the other hand, the best output (yarn quality and price) is achieved when quality is at its highest possible level and price is correspondingly high (from a spinner viewpoint). This is the only way to accomplish profit in the spinning industry.

Unevenness and imperfections properties

Regarding yarn C.V. %, the obtained data indicated that the yarns produced from 100% Giza 85 are more uniform than those produced from Upland cottons. The different blends of Giza 85 and Upland Greek and Sudanese cottons produced more uniform yarns than 100% Upland cottons and less uniform yarns than Giza 85. Moreover, yarn C.V. % increased as the percentage of Upland cotton increased in the blend regardless the spinning system. On the other hand yarn C.V.% for the blends obtained from Sudanese cotton was lower (more uniform) than for the Greek cotton blends regardless yarn count and spinning system. However, the open end yarns were more uniform than the ring ones regardless the blend ratio and yarn count. The unevenness of the Upland yarns and their blends could be due to its high short fiber content and lower length uniformity. It is already known that short fibers are poorly controlled by roller drafting at ring spinning and tend to stay in aggregates, which results in defects in the yarn. Such defects can be responsible for breaks at spinning and contribute to yarn unevenness. Thus, the decrease in unevenness of both Open-End and Ring blended with regard to a ratio increase in Upland in Egyptian cotton in the blend can be emphasize this parameter.