Progress With Long Vegetable Fibers

Mills H. Byrom.

Most of the long, hard vegetable fibers, such as henequen, sisal, and abaci, come from tropical lands, where climate favors their growth, cheap labor is plentiful, and cultural problems are simple. Other long vegetable fibers, like jute, flax, and hemp, are produced in the temperate zones, but mostly outside the United States.

These fibers are the raw materials of rope, binder twine, burlap, and related products. Despite the importance of these products in peace and war, and despite its varied climate, fertile soils, and great capacity for agricultural production, the United States has never attempted to produce any of them in quantities equal to its needs.

India has supplied jute for burlap, bagging, carpets, and similar products. From Mexico, Cuba, and Africa we get henequen and sisal for binder twine, wrapping twine, and other cordage products. Nearly all of the abaci used for the better grades of rope and cordage is imported from the Philippines.

Because of increased needs and almost complete dependence on foreign countries for their production, an acute shortage of fibers developed in this country early in the Second World War. The Government spent millions of dollars to encourage the production of hemp, a soft fiber, to supplement the supplies of abaci, a hard fiber, when the Philippines were occupied.

The Government also subsidized the production of abaci in Central America with some success, but at costs much above prewar prices. Conditions in the Orient, where the largest amounts of abaci and jute have been produced, are such that adequate future supplies of the fibers from that source appear doubtful.

Some of the long fibers useful for special purposes can be produced in the United States. The research program under way aims to seek out the useful fibers suitable for production in this country, to develop equipment for producing them, and to determine the feasibility of establishing new industries to handle and process them. Other points are the urgent need for a fiber to fill an essential need, the adaptability of the plant and its fiber to mechanical production, and the extent of the probable market. Fibers produced here might supplement scant supplies from abroad.

THE FIRST FIBER selected for investigation was sansevieria, which grows half-wild in Florida. It contains fiber thought to be a good substitute for abaci for marine rope and cordage.

As -the work on sansevieria progressed, we found that many of the basic principles governing its production apply also to production of other long fibers, especially ramie and kenaf, both of which are soft bast fibers. Ramie has potential uses in textiles and in paper making. Kenaf may be a substitute for jute in making sugar bags, twine, burlap, and such.

Sansevieria commonly called the snake plant, is a member of the lily family. It is perennial and will completely cover the ground in which it is planted. More than 80 species are known that are native to Asia and Africa. The plant has been trans-planted to most of the tropical and semitropical areas of the world and has become naturalized quickly.

As a war measure to relieve an acute shortage of cordage fiber, the Department of Agriculture and the Florida Agricultural Experiment Station in 1943 established a fiber research project 4 miles west of Boynton, Fla., and planted 10 acres to several varieties of sansevieria. Studies of all agronomic and engineering phases of propagating, growing, and processing were planned. The investigations have shown that if production is to be mechanized completely, cultural machinery ( planters, cultivators, and harvesters) and processing machinery (decorticators, driers, and other specialized equipment) must be developed.

Of the several methods of obtaining planting stock, leaf cuttings set in nursery beds have given the most satisfactory plants for fiber production. In propagation by this method, strong mature leaves are cut in sections 6 inches long and are planted every 4 inches in rows spaced 12 inches apart. In 6 to 9 months, each leaf piece produces from 3 to 6 plants ready for transplanting to the open field.

Machinery has been developed that will make the cuttings and mark the ends to be placed in the ground, plant the cuttings in the nursery row, and transplant the plants in the field. A crew of five men can set 50,000 leaf cuttings or plants in an 8-hour day.

Weeds and grass must be controlled until the planting is well established. Occasional cutting or pulling of large weeds in the fields and weeding of the turn rows and ditches also are generally necessary during the later period of growth. Some of the new weed-killing sprays and the flame weeder may be effective for controlling weeds in the crop.

The problem of developing a satisfactory harvester for sansevieria is more complicated than that of developing planting and cultivating machinery. Recent tests indicate, however, that the leaves can be cut with the regular cutter bar and sickle of a mowing machine if minor adjustments are made. If harvested by this method, at least 2 inches of the lower end of the leaf will be left as stubble. Because the lower part of the leaf contains a comparatively high percentage of fiber of good quality,, it is desirable to devise a cutter that will follow the contour of the ground and thus eliminate this loss. A rotary-type cutter is being studied as one possible answer to this difficulty. Modifications of the gathering and binding devices used on harvesters designed for other crops should work satisfactorily with sansevieria.

Sansevieria may be held in the field in a growing condition for a period of years, apparently with little deterioration of fiber quality or quantity. This is in marked contrast to the growing habits of other long fibers, either hard or soft. The cycle of production from leaf cutting to harvest for fiber production is 3 years.

The value of sansevieria fiber has long been recognized, but it has never been produced in commercial quantities because of the difficulties of mechanical decortication, resulting from lack of uniformity of fiber content in the leaves, as well as lack of suitable decorticating machinery. (Decortication is the process of separating the fiber from the outer covering, pulp, and other foreign material of the leaf.) Therefore, there is need for breeding or selecting a strain of sansevieria that will have a uniform fiber content in all the leaves, and also for further improvement in decorticating machinery, especially in the gripping chains that hold the leaves while decortication takes place.

Most of the attempts to decorticate sansevieria have been made with the raspador-type machine designed for sisal and henequen, both of which have tougher leaves than sansevieria. However, as this type of machine has simplicity, large capacity, and long life, it was selected as the basic machine for research in decortication, even though it is wasteful of fiber.

The decorticating mechanism of the raspador machine consists of a series of knives on a rotating wheel operating against a stationary bed plate. Clearance on the entering side is wide, and the knives have a beating action on the material. The clearance decreases as the material passes across the face of the wheel and the action of the knives changes gradually from beating to scraping. Floods of water in the decorticating wheel help to remove loose bark, pulp, and plant juice.

Two such wheels are mounted on opposite sides of offset gripping devices. The material to be decorticated is fed into the forward pair of gripping devices and carried through the first decorticating wheel. The fiber from this operation is caught by the rear gripping device and the leaf is carried through the other wheel, thus completing the decorticating process.

Improvement in the shape of the decorticating knife, proper speed of the decorticating wheel, and proper clearance between the knife and bed plate have given clean decortication. The fiber yield of Florida-grown leaves has averaged about 2.5 percent. Results of decortication tests show that 75 to 90 percent of the yield can be recovered as clean, dry fiber, suitable for the manufacture of marine cordage, the higher yields resulting from the use of improved adjustments.

A burnishing machine has been developed for further cleaning the decorticated fiber after it has dried. This machine parallels the fibers and removes pulp and other foreign material.

Extensive tests have been carried on to determine the basic principles governing the artificial drying of fibers. The investigations have been successful to the extent that it now appears possible to dry wet fiber adequately without bringing the temperature to a point high enough to injure it. As a result of the tests, a three-stage drier has been built. The first stage uses circulating air having high humidity and relatively low temperature. The second stage uses air having high temperature and low humidity. The air in the third stage has low humidity and low temperature.

In the first stage, the fiber is heated to drying temperature, but, because of the high humidity of the air, no actual loss of moisture takes place. This is termed the heating stage. In the second stage, the conditions of the fiber and the air favor rapid drying. This is termed the drying stage. Conditions in the third stage are set up to cool the fiber, thus closing the pores and equalizing any wet spots that exist. This is termed the cooling and equalizing stage. Indications are that this type of drying will give maximum production with no damage to the fiber.

The high quality of the American-grown sansevieria fiber has been indicated in spinning tests by the American Manufacturing Co., of Brooklyn, and by the Boston Navy Yard. In both series of tests, sansevieria processed satisfactorily on ordinary rope-making machinery. Rope made of sansevieria fiber was better than that made from American hemp or sisal, and 90 percent as strong as that made from abaca.

The research has progressed to the extent of demonstrating that sansevieria can be mechanically decorticated, that it can be grown in southern Florida, and that it is a good substitute for abaca. As the world figure for annual yields of hard fiber is approximately 1,200 pounds to the acre, sansevieria, having yielded more than 3,200 pounds to the acre where it grows wild, has demonstrated a potential production capacity in Florida that justifies more complete investigation. Under average field conditions, it would be reasonable to expect that yields might average somewhat lower than yields obtained in test plots.

RAMIE has had a romantic history that dates from the days of the Pharaohs. It has qualities that make it a first-class industrial and textile fiber. It is naturally a delicate white, with the soft brilliance of silk. Although its physical properties may have been overrated, a number of them are superior.

Federal procurement agencies became interested in ramie during the Second World War, when it appeared that large quantities would be needed by the Navy for stern-tube packing and many other products.