Agave Americana : The Natural Leaf Fiber

India being a tropical country is blessed with plenty of renewable resources obtainable from the plant kingdom. There are various plants in the kingdom which having the various uses, but due to lack of knowledge we are unable to use that. Different plants in the plant kingdom having different uses. From the plant kingdom, one of the abundant sources of strong natural fiber is Agave Americana. Agave Americana is having the different uses; one of them is for the fiber extraction. The plant based fibers are cellulosic in nature and are classified as hard and soft fibers. Generally the bast fibers are called soft fibers and the leaf fibers are called-hard fibers. Fibers are extracted from the leaves of the Agave Americana plant that's why these are hard fibers.

Agave Americana is the cheaply available plant which commonly known as"Aloevera". It having many uses, one of them is for extracting the fiber from their leaves. Due to the lack of knowledge about Agave Americana fiber, it is used in non-textile area such as for preparing ropes and mats. But in research on Agave Americana fiber, found excellent properties such as length, strength, and luster therefore; it is used in textile area for producing fabric.

The plant Agave Americana is a monocotyledon plant belongs to Agavaceae family. It normally grows in tropical, subtropical and a temperate region of the world. Itis called 'Maguey' in Latin. This century plant is common on the arid hillsides. It is locally called as 'Rail Kathali'. The Botanical Classification of Agave Americana plant is given here.

Plant Characteristics

1. An evergreen perennial growing at a slow rate. Mass per plant is about 150 Kg.
2. It is in leaf form in all year. Leaf length is 250m, width 20cm and thickness 5 cm.
3. The flowers are hermaphrodite (have both male and female organs) and are pollinated by Lepidoptera (Moths & Butterflies and bats).
4. The plant prefers light (sandy) and medium (loamy) soils and requires well-drained soil. The plant prefers acid, neutral and basic (alkaline) soils.
5. It cannot grow in shade. It requires dry or moist soil and can tolerate drought.
6. The yield per hector of this plant is 300 tons which give near about 6 tons fiber.

Extraction of Agave American Fiber

Collection of leaves

Agave Americana plant is abundantly available in nature. It is found in various areas like sides of roads, farm, various rocky region, droughty region ete. The leaves are collected from the plant manually. All lower leaves, standing at an angle of more than 45 degrees to the vertical, are cut away from the bole of the plant with a sharp flexible knife. After harvesting, the leaves are transported to a central factory for fiber extraction.

Fiber extraction

Agave Americana fibers run along the length of the plant leaves and are part of the vascular system. These fibers can be extracted from leaves using several methods as described by Zwane and Cloud. Fiber extraction can be achieved through mechanical and chemical processing.

Mechanical Process

Mechanical means are usually done by rural folks, where manual decorticators using rudimentary tools like cans or lids of aluminum containers are used. Alternatively, manual decortications can be done efficiently through the use of a machine decorticator modified to have a rotor, which prevents the blockage of machine by the pulp or fiber waste.

In the process of decoration, 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 and packed into bales.

Mechanical extraction methods are not efficient in the removal of cementing compounds between fibers, mostly waxes, hemicelluloses, lignin and hydrocarbons, but they do work in rural areas.

Chemical Process

Chemical fiber extraction involves the use of acids, alkali and enzymes. The use of acids in fiber extraction hydrolyses lignin and hemicellulose into shorter chain pentose molecules for cellulosic fibers. Acid treatment results in the formation of reactive groups and causes fibers to fibrillate, revealing a higher degree of crystallinity of fibrils. Alkali use in fiber extraction dissolves the lignocellulosic material between fibers and lead to increased surface area, degree of polymerization, separate structural linkages between lignin and cellulose, and lower the breaking strength. Enzymatic processing degrades the lignocellulosic complex in fibers and increases the volume of extracted fibers. Furthermore, enzymes increase fiber swelling, lower the degree of polymerization and make fibers more pliable and softer. A group of enzymes that include cellulose, pectinase and hemicellulase have been used to control hydrolysis of the constituents in jute and made the fibers soft, more pliable and spinnable than untreated fibers.

Evaluation of Fibers

The agave Americana fibers extracted from the plant leaves are white to yellowish and have a hard touch due to the existence of lignin on their surface. After removal of lignin from their surface fibers becomes flexible, smooth and lustrous and had similar burning characteristics like other known cellulosic fibers. The fibers are significantly long with a mean length of 65.2cm and coarser with an average linear density equal to 24 tex and mean diameter, supposing cylindrical form of fiber is 0.15mm. This implies that the fiber has good spinning quality. The fiber has a tenacity of 2.94g1d (35.96cN/tex) when dry and 2.3g1d (20.60 cN/Tex) when wet. Generally natural fibers are hydrophilic in nature and this was evident with tile Agave Americana fiber with a moisture regain of9.98% and moisture content of 9.19%. In comparison with other textile fibers, the agave Americana fibers are more hydrophilic than cotton, flax, and other vegetable fibers. The fiber disintegrated when exposed to strong acid and alkalis, but was resistant to weak acids and alkalis.

Slah Msahli et al. studied the Mechanical behavior of Agave Americana fiber. In their study they found that, mechanical results show a specific behavior [Figure 4 & Table 1], which reminds caoutchoutic one with great extensibility (50%) before rupture, therefore, most of vegetable fibers doesn't exceed 10%. The tenacity of Agave Americana fibers is near those of vegetable fibers such as sisal or flax, therefore, their initial modulus is much less than those of the other natural fibers. The rupture work is higher than the one of the other natural fibers, especially vegetable ones.

Table 1: Mechanical Properties

Longitudinal streaks which are characteristics of long vegetable fibers can be observed in figure 5 below. By examining these technical fibers in SEM (Scanning Electron Microscope) it is observe that, a composite structure where ultimate fibers are held together by sticky and waxy substances to finally form technical fiber with section forms difficult to define and found to have many cells within one fiber particle. The ultimate fibers show oval and irregular sections with large lumen.

Chaabouni et al. showed that Agave Americana fibers have some properties that are different from other fibers. Their ultimate fibers have very low diameters with an average of 3.1 μm. They contrast this with flax ultimate fibers which range from 10 to 30 μm and sisal ultimate fibers with diameters of around 24 μm. This study also reports that Agave Americana fiber bundles have exceedingly high strain ranging from 39% to 49% owing to the helical nature of ultimate fibers and their ability to behave like a spring.

Conclusion

According to their properties, Agave Americana fibers can be used in technical applications such as reinforced composite materials, paper making, non-woven fabrics,

geotextiles, etc.

This fiber was bound to qualify as a potential source of textile fibers and this could provide a secondary source of raw materials for textile products. Similarly the allied activities of cultivating and processing the plant could be a potential source of employment opportunities and income generation. The plant is Frown as an ornamental outdoor and indoor plant and as a fence.

This article was originally published in the Textile Review, July, 2012.

About the authors:

P.P. Kolte, A.M. Daberao & Miss Aarti Sharma are associated with Anuradha Engineering College, Chikli in district Buldana.