Sisal or sisal hemp is an agave Agave sisalana that yields a stiff fiber used in making rope. (The term may refer either to the plant or the fiber, depending on context.) It is not really a variety of hemp, but named so because hemp was for centuries a major source for fiber, so other fibers were sometimes named after it.
Sisal plants consist of a rosette of sword-shaped leaves about 1.5 to 2 meters tall. Young leaves may have a few minute teeth along their margins, but lose them as they mature. Sisals are sterile hybrids of uncertain origin; although shipped from the port of Sisal in Yucatán (thus the name), they do not actually grow in Yucatán, the plantations there cultivate henequen (Agave fourcroydes) instead. Evidence of an indigenous cottage industry in Chiapas suggests it as the original location, possibly as a cross of Agave angustifolia and Agave kewensis.
In the 19th century, sisal cultivation (the plant being propagated via offsets), was spread worldwide, from Florida to the Caribbean islands and Brazil, as well as to countries in Africa, notably Tanzania and Kenya, and Asia. Among flax, hemp, abaca, sunn hemp (Crotalaria juncea) and other agro-based fiber species, annual sisal production is the second largest worldwide, after cotton.
Sisal fibers are typed by properties relational to the performance of the fiber. Researcher Sara Kadolph has found that sisal fibers are smooth, straight and yellow and can be long or short. Since sisal is fairly coarse and inflexible, Kadolph finds that sisal is used by itself or in blends with wool and acrylic for a softer hand. Sisal is valued for cordage use because of its strength, durability, ability to stretch, affinity for certain dyestuffs, and resistance to deterioration in saltwater. Sisal is used by industry in three grades The lower grade fiber is processed by the paper industry because of its high content of cellulose and hemicelluloses. The medium grade fiber is used in the cordage industry for making: ropes, baler and binders twine. Ropes and twines are widely employed for marine, agricultural, and general industrial use. The higher-grade fiber after treatment is converted into yarns and used by the carpet industry.
Products made from sisal are being developed rapidly, such as furniture and wall tiles made of resinated sisal. Other products developed from sisal fiber include carpets, spa products, cat scratching posts, lumbar support belts, rugs, slippers, cloths and disc buffers. Sisal wall covering meets the abrasion and tearing resistance standards of the American Society for Testing and Materials and of the National Fire Protection Association. Traditionally, sisal has been the leading material for agricultural twine (“binder” and “baler” twine) but the importance of this is diminishing with competition from polypropylene and other techniques evolving. Apart from ropes, twines and general cordage sisal is used in low-cost and specialty paper, dartboards, buffing cloth, filters, geotextiles, mattresses, carpets, handicrafts, wire rope cores and macramé. In recent years sisal has been utilized as a strengthening agent to replace asbestos and fiberglass as well as an environmentally friendly component in the automobile industry. Products made from sisal fiber are purchased throughout the world and for use by the military, universities, churches and hospitals.
Products made with sisal fiber have the following characteristics. Despite the yarn durability sisal is known for, slight matting of carpeting may occur in high traffic areas. Sisal does not build up static nor does it trap dust, so vacuuming is the only maintenance required. High spill areas should be treated with a fiber sealer and for spot removal, a dry cleaning powder is recommended. Depending on climatic conditions, sisal will absorb air humidity or release it causing expansion or contraction. Sisal is not recommended for areas that receive wet spills, or rain or snow.
The sisal plant has a 7-10 year life-span and typically produces 200-250 commercially usable leaves. Each leaf contains an average of around 1000 fibers. The fiber element, which accounts for only about 4% of the plant by weight, is extracted by a process known as decortication. In East Africa, the leaves are transported to a central decortication plant after which the fiber is dried, brushed and baled for export. In Brazil it is mainly grown by smallholders and the fiber is extracted by teams using portable raspadors. Superior quality sisal is found in East Africa, once washed and decorticated. Sisal is considered a plant of the tropics and subtropics, since production benefits from temperatures above 25 degrees Celsius and sunshine.
| Top ten sisal and |
other agave fibers producers — 2006
(thousand metric tonne)
UN Food & Agriculture Organization (FAO)
Researchers have published fiber extraction information on sisal fiber. In the process of decortication, leaves are crushed and beaten by a rotating wheel set with blunt knives, so that only fibers remain. All other parts of the leaf are washed away by water. Decorticated fibers are washed before drying in the sun or by hot air. Proper drying is important as fiber quality depends largely on moisture content. Artificial drying has been found to result in generally better grades of fiber than sun drying. Dry fibers are machine combed and sorted into various grades, largely on the basis of the previous in-field separation of leaves into size groups.
According to www.advancedbuildings.org, sisal farming initially caused great environmental degradation, because sisal plantations replaced native forests, but is still considered less damaging than most. No pesticides or chemical fertilizers are used in sisal production, and although herbicides are occasionally used, even this impact may be eliminated, since most weeding is done by hand.