The objectives of this work were to develop a method to measure the tensile properties of individual cotton fibers and to use the data from the method to study the relationships between the tensile properties of individual fibers and fiber bundles. Mathematical models were developed to predict bundle strength from individual fiber tensile prop erties. The single fiber strength method gives information about the elongation and crimp of cotton fibers. For the set of samples used in this work, the average elongation was 11.8% and the average crimp was 4.8%. Analysis of the single fiber strength data suggests that the average single fiber breaking strength sets an upper limit for the fiber bundle strength. The correlations between fiber strength and yam strength were some what improved by using the average single fiber strength rather than the Stelometer or high volume instrument ( HVI ) bundle strength.

The content of gram-negative bacteria was determined for 109 samples of the 1978 crop of American upland raw cotton derived from seven grade divisions and five visual color groups. The populations of gram-negative bacteria entrained in these raw cottons varied from 1.5 X 1010 to 1.5 X 1014 for standard bale size (217.7 kg) lots. Raw cotton fiber parameters, including upper-half-mean length, length uniformity, strength, micronaire, maturity, and fineness, were all significantly and inversely correlated with the content of entrained gram-negative bacteria. The yellowness of raw cottons as measured by the cotton colorimeter was significantly and positively correlated with bacterial content. About half of the variability of gram-negative bacterial content in raw cotton samples of the 1978 American upland crop can be accounted for by variation in micronaire ( r2 = 0.504).

The content of endotoxin was determined for 255 samples of 1979 crop, American upland raw cotton derived from seven grade divisions and five color groups. A bale of raw cotton from the better white grades contained less than one gram ofendotoxin, whereas tinged and yellow stained cottons were found to have five or more grams of this microbial material. Fiber yellowness was significantly and positively correlated with endotoxin content of representative raw cottons from the Southwest. By contrast, the endotoxin content of representative cottons from all other major geographical regions was significantly and inversely correlated with fiber maturity. For the 1979 crop there was an absence of significant differences in endotoxin levels among representative sample groups from five major U.S.A. growing regions..

Determining cotton fiber tenacity with high volume instrumentation (HVI) requires an accurate measure of specimen linear density. Indirect measurements of linear density such as light attenuation, by which the Zellweger Uster Spinlab HVI system accom plishes this, require additional knowledge about fiber numbers or fiber fineness, usually by introducing a Micronaire correction factor. The effectiveness of this correction is less applicable than fiber fineness determinations obtained by direct weighing methods. Furthermore, fiber fineness distribution is not accounted for, and this factor may be important to enhanced HVI technology. For purposes of discussion, length-fineness distributions by number count and direct weighing methods have been determined for twenty cotton samples using Suter-Webb sorting techniques. Ramifications of fine ness distributions across length groups on cumulative fiber fineness distribution within a randomly prepared test specimen are presented in the context of breaking load normalization by a fiber fineness indicator.

Strict good ordinary grade cotton was mechanically cleaned and washed using treatments that ranged from water at 333 K (60°C) to a complete scour and bleach at 344 K (71°C). The micronaire of the cotton increased slightly when washed. The length of the fiber decreased slightly when higher washing temperatures were used, but the decrease was not statistically significant. The length-uniformity ratio was lowered about 1 unit by washing in hot water, and about 2 units by scouring. Washing increases the fiber bundle strength about 20 kN·m/kg (2 gf/tex). Washing in water at 333 K does not change the reflectance, but scouring causes a slight increase, and bleaching causes a large increase. The yellowness readings are significantly decreased by washing in water and decreased even further by scouring.