Preston E. Sasser

Interpretations of Single Fiber, Bundle, and Yarn Tenacity Data:

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.

Inorganic Content of Cotton Dusts, Trash, and Bracts

The exact etiological agents responsible for the biological effects of cotton dust are unidentified, but most investigators believe they are organic in nature. Inorganic compounds have not been considered as significant factors. However, cotton dusts, trash, and bracts have high inorganic contents (7–43% ash), as reported here; more importantly, aqueous extracts of the trash and bracts have inorganic contents as high as 65%, which means a significant amount (10–36%) of the inorganic compounds in trash or bract is water extractable. Elements present in the ash include: N2, Cl2, P, K, Ca, Mg, Mn, Cu, Zn, S, and O2. KCl and K2SO4 have been definitively identified. It is suggested that greater attention should be given to the inorganic nature of cotton dust in the etiology of byssinosis.

The Mathematical Basis of Fiber-Length Analysis from Fibrogram Data

Theoretical equations are developed which give the average length and the length distribution of the whole fiber popula tion from the scan of a fibrogram type specimen. The average fiber length is shown to be equal to twice the area under the fibrogram curve plus an offset which is dictated by the amount of fiber loss in the clamp. The length distribution, in terms of coefficient of variation, is shown to be the square root of three times the length at which the centroid of the fibrogram is located divided by the mean length minus 1. Data are presented for comparison of array data mean length and length distribution with mean length and length distribution by instrument using the derived equations. Linear correlation coefficients between the methods were 0.95 for length and 0.86 for distribution.

Chemical Composition of Cotton Dusts Part II : Analyses of Samples Collected in a Model Card Room

The ash and protein contents of Pneumafil (PN) trash samples collected in a model card room and of the aqueous extracts of these samples arc reported here. The average ash content of these samples is 12.5% (σ = 4.2%). The average ash content of the dried aqueous extracts of these samples is much higher than that of the raw samples (mean 36.9%, σ = 10.8%). The average protein content of these samples and their dried aqueous extracts are about the same (13.2 and 14.9%, respectively). Trash samples from cotton grown under dry, arid conditions tend to have relatively high inorganic contents. Steaming tends to reduce the inorganic fraction of both the raw samples and their dried aqueous extracts but has little effect on the protein content. Increasing the number of gin lint cleaning stages reduces the dust level in the card room but has little effect on the proximate chemical composition of the PN samples. The fraction of ash in the PN dust tends to increase as the grade of cotton improves. Respirable dust collected from an electrostatic precipitator and respirable dust separated from lint trash are shown to have very high inorganic contents (41.3 and 37.1%, respectively). The average ash content of five samples rollected on the vertical elutriator was 20.1%, a value close to the average ash content of leaf and bract samples.

Chemical Composition of Cotton Dusts Part I: Analyses of Cotton Plant Parts, Gin Trash, and Weed Samples

Cotton plant parts are thought to be a major source of dust generated during cotton processing. Their chemical composition is important with regards to identifying the causal agents of byssinosis. Reported here are the ash and protein contents of cotton bract, leaf, stem, burr, and gin trash samples and of their dried aqueous extracts. The average ash contents of the above samples are 18.0, 16.6, 7.2, 7.5, and 19.1%, respectively. Significantly, the average inorganic contents of dried aqueous extracts are from two to five times higher than those of the raw samples.. The average protein contents of the above samples are 12.5, 17.4, 8.6, 5.7, and 13.6%, respectively. The average protein contents of the dried aqueous extracts of bract, leaf, and gin trash samples are about the same as the raw samples. The protein of the dried aqueous extracts of stem and burr increases markedly compared to the raw samples (from 8.6 to 21.3% and 5.7 to 15.5%, respectively). Ash and protein contents of several weed samples have been analyzed, and their extracts are approximately the same as stem and burr samples. The fraction of each sample that is extractable by water is about the same (ca. 13%) for all plant parts, gin trash samples, and weed samples investigated in this study.

Gram-Negative Bacterial Content and Fiber Properties of Raw Cotton:

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).

Endotoxin Content and Fiber Properties of Raw Cotton

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 con trast, the endotoxin content of representative cottons from all other major geo graphical 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.

Evaluation of Cleaning and Washing Processes for Cotton Fiber Part I: Introduction and Cotton Properties 1

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-uni formity ratio was lowered about 1 unit by washing in hot water, and about 2 units by scouring. Wash ing 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.

Estimating Single Cotton Fiber Tensile Properties from the Load-Elongation Curves of Slack Bundles

A method has been developed to estimate single cotton fiber tensile properties from load-elongation curves of slack fiber bundles. The method is applied to bundle load- elongation curves from HVI tests to estimate the averages of fiber breaking strength, elongation, and crimp. The estimated values are compared with single fiber tensile properties obtained from a Mantis® single fiber tester.

TENSILE BEHAVIOR OF SLACK FIBER BUNDLES : THEORY AND APPLICATION TO HVI TESTING

A statistical model for the tensile behavior of a bundle of slack fibers is developed in terms of its constituent single fiber properties. A large amount of data on single fiber tensile properties is obtained by a Mantis® tester. Application of this theory to HVI tensile test results shows much better agreement than other models developed earlier for bundles of straight, equal length fibers.