I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
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VoI. 37, No. I2
with the more easily demonstrated birefringence of the fibers, shows that a considerable degree of orientation has been obtained.
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Figure 6.
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100 150 200 250 Elongotion in percent
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Relation of Tensile Strength of Fibers to Elongation 1. Fiber B after 4.5-hour precure
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Fiber B after 24-hour precure
3. Fiber B after 48-hour precure
mined at 70’ F. and 50% relative humidity on the Scott IP-2 Serigraph by the bundle method. The resulting strength test data (plotted in Figure 6) show a linear relation between elongation and strength. The plotted data show no indication of a change in the slope of the strength curves to correspond to the break in the load-elongation curves of Figure 5. The strongest fibers were obtained at the maximum stretch before breaking. The dried fibers, when immersed in water a t 45’ C., quickly returned to their original unstretched length. The load-elongation curves in Figure 5 are the same shape as the corresponding curves for wool and rubber given by Astbury ( I ) except that the Hooke law region, as described by him, is missing. A series of curves similar to those in Figure 5, but having in addition an initial linear part of high slope similar to Astbury’s, were recorded on the chart of a Scott IP-2 Serigraph. The recordings were made by using single wet tows of fiber B at about 21’ and 35’ C. The rate of loading was much greater than that described above. Astbury explains the 100% extensibility of wool (100% relative humidity) and the loadelongation curves by the transformation from the a- to the 8keratin structure. However, i t is difficult to explain the high extensibility and recoverability of wet zein fibers by the same theory. The elasticity of wet zein fibers is somewhat like that of rubber, and it may be explained by the tendency of the molecules to assume the most random distribution (E). If the break or change in slope of the load-elongation curve was due to plastic flow or to molecular slippage, tensile strength probably would not be a linear function of elongation. A detailed study of the x-ray diffraction diagrams of zein fibers has not been carried out at this laboratory, although sufficient evidence has been secured to indicate that some fibering occurs as evidenced by the arcing in the x-ray pattern of the more highly stretched fibers. Diffraction diagrams of the oriented fibers are similar t o the so-called @-pattern obtained from the stretching of hair and wool. The evidence from the x-ray studies, along
PROPERTIES OF ZEIN FIBERS
The process for the production of zein fibers is not yet fully developed. However, a preliminary survey of fiber properties is presented to indicate the excellent possibilities for the establishment of a commercial fiber from zein. Fibers obtained in the manner described above are high in wet and dry strengths. Dry strengths of 1.87 and wet strengths of 0.75 gram per denier have been obtained. I n comparison, the better known spun protein fibers have dry tensile strengths of 0.6 to 0.8 gram per denier and wet strengths of about one third the dry values; the dry tensile strength for a good grade of wool is about 1.3 grams per denier, The zein fibers have high resilience and are very flexible, although no plasticizer is used. Fibers finer than 0.6 denier ( 7 . 5 in ~ dimeter) have been produced by applying a high stretch in a heated coagulating bath. As stated earlier, the fibers prepared by the above method shrink to their precured length when immersed in hot water. This shrinkage can be greatly reduced by treating the fiber with strong formaldehyde while it is held under tension. Even so, there is some loss in strength from the maximum values, and the fibers from this “post cure” measure 1 to 1.25 grams per denier. Preliminary studies on dyeing the zein fibers showed that, after postcuring with strong formaldehyde, the fiber does not withstand the severe acid conditions normaIIy used in dyeing and processing wool. I n this respect zein fibers are similar to casein fibers, and like casein, the dyeing properties, in general, are greatly improved by acetylation. The work on acetylation will be reported in a future publication. It is sufficient to say here that acetyl contents above 2’% are necessary to give satisfactory resistance to acid-dye bath conditions. Acetylation followed by curing with formaldehyde has given a satisfactory control of shrinkage, and in some cases, the shrinkage has been lowered to 4% as determined by boiling for 15 minutes in water. From a study of the acid and alkaline peptization curves of zein, the fibers wc-xld be expected t o offer considerable resistance to the usual alkaline conditions encountered in the use of soaps and scouring powders. Acetylated and properly cured fibers have shown excellent resistance to boiling in buffered solutions of pH 8 to 9 and, in some cases, have shown no loss in strength upon boiling for 2 hours at this alkalinity. Fiber texture, feel, and appearance were not impaired by this boiling treatment. ACKNOWLEDGMENT
The authors acknowledge the assistance of N. Cyril Schieltz of this laboratory for the x-ray analysis of zein fibers. LITERATURE CITED
(1) Astbury, W. T.. “Fundamentals of Fibre Structure”, London, Oxford Univ. Press, 1933. (2) Guth, Eugene, “Surfaoe Chemistry”, p. 103, Lanoastar, Pa., Eoience Press Printing Go., 1943. (3) Harold, B.A., Am. Dyeatuff Reptr., 29, 53-7 (1940). (4) Meiga, F. M.,U.8.Patent 2,211,961(1940). (6) Ofelt, C.O., and Evans, C . D., in preparation. (6) S w d e n , L. C . , U. 8.Patent 2,166,929(1939).
Properties of Granular and Monocrystal-. line Ammonium Nitrate-Correction An unfortunate error has been foupd in this article by W. H. Ross, J. Y. Yee, and S. E. Hendncks in the November issue. On page l O q the pictures were inadveftently revemed. i n other words, as printed, Figure 1 is at the nght and Figure 2 is at the left.
