Southern Regional Research Laboratory

Research at the Southern Regional Research Laboratory deals primarily with cotton.

Lately the production and consumption of synthetic fibers that compete with cotton have expanded markedly. Rayon is the outstanding example. Not long ago nearly all rayon was used for clothing and household fabrics, where appearance is an important consideration, but during the war the production of a new, high-strength type of rayon was greatly expanded, primarily for truck, bus, and airplane tires.

In this connection the claim has been made that rayon is superior to cotton for tire cord, particularly for heavy-duty tires. The statement must be qualified. Tests have shown that present types of commercial cotton cord are entirely adequate for passenger-car tires. Some tests made by the Army have indicated that tires made with rayon cord are better than tires made from ordinary cotton cord for some types of heavy-duty military service. On the other hand, tires made of cord from selected varieties of cotton stood up so well in other tests made by the Army and by the War Production Board that any assertion that rayon is superior for certain types of service may well be questioned. Of course, the strength and other properties of cotton vary considerably with the variety, and some varieties, such as Wilds 13, are better suited for tire cord than others. This is a fair example of the point that industrial markets for cotton and other agricultural commodities may depend on growing specific varieties that possess the characteristics needed for specific end uses.

Research on tire cord is continuing, with the object of developing a still better cotton cord for use in tires for heavy trucks and busses.

Most persons have had occasion to apply a bandage to a cut or sprain and have found it difficult to bind the injury with just the right amount of tension. Too much tension may interfere with circulation and cause throbbing; too little may permit the bandage to loosen and fail to function. By means of a modified mercerization process developed by the Southern Laboratory, standard cotton gauze may be made semi-elastic and used to advantage in bandages for several types of injuries. This new all-cotton material will bend and give with the flexing of a joint, will expand if there is swelling, and is liked by doctors and nurses, particularly for cases where a mild-pressure dressing is required. About 30,000 rolls of the bandage have been produced at the Southern Laboratory and used in clinical trials by Navy, Army, and private hospitals.

Cotton that must be exposed to the action of the elements will mildew and rot, become weak, and finally fail in its function entirely. This applies to tent material, mosquito netting, fish nets, sandbags that come in close contact with the soil, and so on. Sandbags have uses in peace and war, for fortifications, protection of buildings, levees, and so forth. The Southern Laboratory has developed an accelerated rotting test to discover which of the various mildew- and rot-proofing agents are effective in increasing the life of cotton sandbags. The test is made by burying samples of cloth in warm, moist soil and measuring its loss in strength. One especially effective treatment to preserve fabrics against mildew and bacterial rot is the partial acetylation of the cellulose of the cotton fiber, so that it is more practically proof against attack by cellulose-destroying organisms. Several bags made of acetylated cotton fabric were filled with sand and placed outdoors with one side in contact with the soil. After 2 years these bags were still intact and serviceable.

Unlined cotton fire hose has been constructed from a specially treated cotton yarn, which, when properly woven into the hose, acts like linen yarn in rapidly absorbing water. It swells enough to close the minute openings in the tightly woven structure, so that the hose carries water without too much leakage. The treatment was intended especially to make cotton serve as a substitute for linen in rubberless hose for use in fighting fires in buildings, ships, and forests during the war. The same principle is being applied to the development of water-resistant military and civilian fabrics.

Large amounts of low-grade cotton fabrics, such as osnaburg, are produced, sold, and used as gray goods, that is, without finishing treatment. The improved effect of various finishing agents and processes upon the appearance and utility of these low-grade materials was studied. After extensive tests with several durable-type finishing agents, a modified cellulose compound was selected as the most satisfactory generally as to increased strength and resistance to wear imparted to the fabric and the retention of those properties after repeated launderings. In many cases it was found advantageous to combine a mercerization treatment with the finish. By compacting and rounding the yarns, as well as by increasing luster, mercerization imparts an improved character to cotton cloth. Results of work on a pilot-plant scale indicate that useful and attractive fabrics for household uses and garments may be obtained by further processing of low-grade cotton products.

Because only short cotton fibers, like cotton linters, could be purified with existing commercial equipment and because of the threatened shortage of chemical cellulose during the war, a study was made of cutting machines that would reduce lint cotton to lengths comparable to second-cut linters. A pilot-model machine was designed and constructed, followed by a larger experimental machine that was tested in a commercial linters purification plant. On the basis of the results of these tests, the War Production Board financed a full-size commercial unit designed for cutting both lint cotton and mill-run linters. Preliminary production tests indicated that the machine should be capable of cutting approximately 10 tons of cotton an hour to a length satisfactory for purification and nitration. Although this machine was developed to fill a wartime need, it may possibly be used to advantage for mill-run linters or short-staple cotton to relieve shortages of chemical cellulose.

For many years gossypol was the only pigment known to be associated with cottonseed. Research at the Southern Laboratory led to the detection of many other pigments, three of which have been isolated and identified : Gossypurpurin, purple in color, and gossyfulvin, orange in color, both of them from raw cottonseed, and gossycaerulin, blue in color, from cooked cottonseed. Microscopic investigation of the distribution of the predominant pigments in cottonseed tissue has shown that they are concentrated in distinct organs of the seed, that is, in pigmented glands. The glands are mechanically strong, resist the action of many organic liquids, and have a density less than that of other cottonseed tissue. With this knowledge, a process was devised for the mechanical removal of pigments from cottonseed; it consists in floating the largely intact glands on the surface of a mixture of organic liquids that has a density intermediate between that of the glands and that of the other seed tissue. A fractionation unit of prepilot plant scale has been constructed and operated to separate pigment glands from solvent extracted cottonseed flakes. The liquid for the fractionation process is a mixture of tetrachlorethylene and Skellysolve B, adjusted to a specific gravity of 1.378 at 27 C. For the first time, a sufficient quantity of cottonseed pigments is available for a determination of the physical, chemical, and toxicological properties of these coloring matters, and a study of their functions in relation to seed maturity, seed storage, processing conditions and industrial utilization, and toxicological and nutritional factors.