I
IVAN A. WOLFF Northern Utilization Research and Development Division, U. S. Department of Agriculture, Peoria, 111.
Corn Amylose and Amylose Triacetate Fibers
CORN
AMYLOSE (7, 6), separated from commercial cornstarch by the butanol precipitation procedure (Z), was triacetylated using pyridine and acetic anhydride a t 100' C. The amylose triacetate, in 25 to 29 weight 7 0 concentration in filtered chloroform solution, was extruded a t 300 to 500 p.s.i. through spinnerets having orifices 0.003 to 0.005 inch in diameter into a vertical column with countercurrent flow of heated air. The filaments produced were collected on a reel. The spinning was a t a rate of 250 to 450 feet per minute. Amylopectin triacetate fibers were prepared similarly. Oriented amylose acetate fibers were prepared batchwise by stretching 1-inch long sections of fiber bundles in a glycerol bath heated at 140' to 170' C. After stretching, the fibers were washed with water, then dried at 110' C. and conditioned to 5070 relative humidity before tests. Fibers were also oriented by stretching in hot air and in steam. Amylose fibers were prepared from the triacetate by a number of alkaline saponification procedures-Le., varying alkali concentration, time of treatment, type of alkali, temperature, and solvent. T h e deacetylation procedure preferred was 0.25N potassium hydroxide in absolute ethyl alcohol for 2 to 3 days a t room temperature, under nitrogen. The regenerated amylose fibers were given five washes with absolute ethyl alcohol; the third contained a small amount of glacial acetic acid. Although deacetylation was complete, the fibers retained about 0.7% alkali by weight, calculated as sodium hydroxide. Properties of the fibers were measured either on a Scott IP-2 inclined plane serigraph or on a n electronically controlled single-fiber balance. Condition-
Table 1.
ing prior to test was a t 5OY0 relative humidity and 72" F. unless otherwise indicated. Although the strength of amylose triacetate fibers as originally obtained is rather low, this value can be approximately tripled by stretching for suitable orientation of fiber molecules. Not only is the strength, tested dry, improved ; but the wet strength of stretched fibers is also increased. Unstretched amylose triacetate fibers, soaked in water for l/z to 1 hour and tested wet, lost 35 to 40% of their breaking strength, whereas corresponding fibers, stretched 400 and GOO%, lost only 17 and 7%, respectively. Amylose triacetate fibers as originally spun are amorphous. These stretched fibers show typical (4,5 ) crystalline x-ray diffraction patterns. Amylopectin triacetate can be converted to fibers but, as anticipated from the branched nature of the macromolecules, they are weaker and more brittle. Amylose fibers, regenerated by deacetylation, retain the original white, lustrous appearance of the parent acetate fiber. Yet their strength and flexibility are lower (Table I). Deacetylated, oriented acetate fiber should be studied to ascertain what higher strength might be achieved. Deacetylated, oriented amylose filaments are known ( 3 ) to exist in several possible forms, depending upon experimental procedures used. Amylose triacetate fibers at 70' F. and 60% relative humidity were stretched 2OyG a t a n elongation rate of 10% per minute and then allowed to relax. Amylose acetate has less resistance to extension in the range studied (Table 11). Tracings made during the experiment indicate a longer region of plastic flow for the amylose acetate than
Properties of Amylose and Amylose Triacetate Fibers
Fiber
Amylose triacetate Amylopectin triacetate Amylose (deacetylated) Amylose triacetate
%
Secondary Stretch Conditions
0
0 0 100 200 400 600 200
100 200 200
... ... ...
Ga, 170' C. G, 170' C. G, 170' C. G , 170' C. G, 140' C. Air, 170' Air, 170'
Steam
G = glycerol.
1552
INDUSTRIAL AND ENGINEERING CHEMISTRY
Strength,
Ultimate
G./Denier
Elongation,
0.52-0.63 0.23 0.29 0.9 1.1 1.35 1.8
76 8 34 47 56 45 40 36 42 45 32
%
1.0 0.75 1.6 1.0
for the cellulose acetate fibers. However, there is little difference in the elastic recovery of the two materials under the conditions studied.
Table II.
Mechanical Properties Tern-
Load at 20% Young's Modulus, Elonga-
G.!
Fiber Amylose triacetate Cellulose acetate
Denier/
tion G./
porary
Set after 20% Elong.,.
%
Denier
%
0.15
0.39
15.0
0.29
0.98
17.0
Amylose triacetate fibers possess appearance and properties generally similar to cellulose acetate fibers. Use advantages, if any, would apparently have to be based on the relative economics of raw materials and processing costs or on possible advantages conferred by the greater plasticity of amylose acetate, were this desirable for a specific end use.
Acknowledgment The author is grateful to the Harris Research Laboratories, Washington, D. C., for performing tests on single fibers and for permission to publish the results. R. L. Whistler assembled the equipment used for dry spinning. David W. Olds assisted in the experimental work.
literature Cited (1) Chem. Eng. News 35, 89-90 (1957). (2) Schoch, T. J., J . Am. Chem. Sod. 64, 2957-61 (1942). (3) Senti, F. R., Witnauer, L. P., Zbid., 68, 2407 (1946). (4) Whistler, R. L., and Hilbert, G. E., IND.ENG.CHEM.36, 796, (1944). (5) Wolff, I. A,, Olds, D. W., Hilbert, G. E., Ibid., 43, 911-14 (1951); 49, 1247-8 (1957); Wolff. I. A., Davis, 13. A., Cluskey, J. E., Gundrum, L. J., Rist, C. E., h d . , 43, 915-19 (1951). (6) Zuber, M. S., Grogan, C. C., Deatherage, W. L., Hubbard, J. E., Schulze, W. E., MacMasters, M. M., Agron J . 50, 9-12 (1958). RECEIVED May 16, 1958 ACCEPTEDAugust 13, 1958 Reference to specific equipment or organizations does not necessarily constitute endorsement by the U. S. Department of Agriculture.
