An empirical method for determining the crystallinity of native cellulose was studied with an x-ray diffractometer using the focusing and transmission techniques. The influence of fluctuations in the primary radiation and in the counting and recording processes have been determined. The intensity of the 002 interference and the amor phous scatter at 2θ = 18° was measured. The percent crystalline material in the total cellulose was expressed by an x-ray "crystallinity index." This was done for cotton cellulose decrystallized with aqueous solutions containing from 70% to nominally 100% ethylamine. The x-ray "crystallinity index" was correlated with acid hydrolysis crys tallinity, moisture regain, density, leveling-off degree of polymerization values, and infrared absorbance values for each sample. The results indicate that the crystallinity index is a time-saving empirical measure of relative crystallinity. The precision of the crystallinity index in terms of the several crystallinity criteria is given. Based on over 40 samples for which acid hydrolysis crystallinity values were available, the standard error was 6.5%.

SynopsisA study is carried out to investigate the effects of spinning conditions on fiber formation in the wet-spinning process. The spinning conditions studied are free velocity (and hence free diameter), throughput rate, maximum take-up velocity, jet stretch (the ratio of take-up velocity to free velocity), and filament tension. The coagulating bath temperature and concentration are varied, and three spinnerette diameters are used. The spinning dope is an aqueous solution of polyacrylonitrile in sodium thiocyanate. The present study shows that the coagulating bath concentration influences the spinning tension and maximum take-up velocity. Two thread breakage mechanisms are postulated which take into account the rate of coagulation, spinning tension, and thread velocity. An attempt is made to predict the concentration profile of solvent in the moving filament by simultaneously solving the mass and force balance equations, in which the increase in elongational viscosity along the spinning way is assumed to be mainly due to the hardening process.

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On acid hydrolysis of cotton, the degree of polymerization (DP) of the insoluble residue falls rapidly to a low level (leveling off DP). Continued hydrolysis results in further losses in weight, but the DP, and the micelle dimensions, remain unchanged. Immergut and Rånby [6] suggest that individual micelles at the leveling off DP disap pear in entirety; i.e., further action of acid yields soluble fragments only. The present investigation was undertaken to compare the action of enzymes on the micelles with that of acids. The study was broadened by the inclusion of hydrocelluloses from cottons treated in various ways, and further extended to include the parent materials from which the hydrocelluloses were prepared.

Losses in tensile and tearing strengths and other physical properties of cotton fabric given durable-press finishes have been attributed to factors arising mainly from the crosslinking of the cellulose molecule. This conclusion was deduced from the results of textile testing of the treated fabrics. In order to define the sources of these strength losses, a study was made of cotton fabric treated with dimethylolethylene urea and a zinc nitrate catalyst in a commercial manner, but with varying times of cure. Heretofore unobtainable molecular parameters of durahle-press cotton fabric were established from solubilized samples. Correlations made between physical properties of the fabric and the fine-structural features of the fiber, both of which were measured, estahlished the fractions of losses arising from molecular degradation and from crosslink embrittlement as a function of the extent of cure. In the shorter cure times, the predominant strength loss came from crosslink embritttement, but this proportion dropped rapidty and molecular degradation became the major source. Changes in degree of polymerization suggest that the catalyzed crosslinking reaction produces a limited chain extension of the cellulose molecule which becomes evident after removal of the crosslinks.

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Beginning flight students from the University of Illinois flight training program were given two sessions of landing practice in a simulator with a computer-animated contact landing display before they commenced intensive landing practice in the aircraft. For each experimental student there was a control student, paired with the same instructor, who received no landing practice in the simulator. Experimental students required significantly fewer presolo landings in the airplane than did the paired controls, representing a potential saving of about 1.5 presolo flight hours per student. These data show that pretraining with a moderately detailed, yet relatively inexpensive, computer-animated landing display can offer worthwhile savings in flight time. Some students were provided adaptive visual augmentation during their simulator training, and there was evidence of incremental transfer attributable to this instructional feature.

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