Introduction:
Sisal fiber is a vegetable fiber obtained from the leaves of the sisal plant. It belongs to the family “Asparagaceae”. It comes under the genus “agave”. World production of sisal fiber is about 300,000 tones. Each plant produces 180 to 240 leaves in lifetime yielding and each leaf contains an average of around 1000 fibers. One leaf weighs around 500 to 700 grams. 90% of the weight being moisture. The leaves are dagger-shaped and when mature 1 m to 1.5 m long and about 10 cm wide. The first harvesting can be done When the plant is about 2 years old and they remain productive for 7 to 12 years. It requires the average temperature between 20 to 28 ͦ c and the annual rainfall average is 600 to 1500 mm. It grows best at hot and dry areas. This plant adapts well to tropical and subtropical regions.
Processing of sisal fiber:
It has to be extracted as soon as after the leaf has been cut. If the leaf allowed to dry, the leaf will damage in the cleaning process.
Extraction of fibers from leaves can be done in 2 ways.
1.retting followed by scraping
2. mechanical means using decorticators
Second method i.e. By using decorticators is superior to the first method as it yields about 2-4% fiber with good quality and lustrous color and poor quality fiber with dull color is produced by the retting method.
Extraction of fiber by mechanical means:
By decorticating machine: this machine used for scrapping the leaf of the sisal. It has 3 rollers i.e. Feed roller which is used for feeding of leaves into the machine, leaf scratching roller which scratches upper layer of leaf and removes the waxy layer and the serrated roller which crushes the leaves.
After extraction, fibers are washed with clean water to remove the wastes such as chlorophyll, pulp, plant material, adhesive solids and leaf juices. And the fibers have to be dried in the sun, bleached and combed with rotating brushes. The dried fiber represents only 4% of the total weight of the leaf.
Classification:
The sisal leaf consists of 3 types of fibers, namely
Mechanical fibers: extracted from the periphery of the leaf.
Ribbon fibers: extracted from the tissues in the median line of the leaf. These are the longest fibers compared to mechanical fiber.
Xylem fibers: These occur opposite to ribbon fibers and have an irregular shape and composed of thin-walled cells therefore easily broken up and lost during the extraction process.
Structure of sisal fiber:
Chemical composition:
Identification of sisal fiber:
Properties of sisal fiber:
Length: 1.0 to 1.5m
Diameter: 100 to 300 mm
Density: 1.28 to 1.42 g/cm3
Tensile strength: 400 to 700 MPa
Young’s modulus: 9.0 to 38.0 Gpa
Elongation: 1.54 to 3.85 %
Moisture content: 10 to 22%
It does not absorb moisture, dust easily.
It can be dyed easily is durable with low maintenance with minimal wear and tear.
It is hydrophilic fiber.
Its the cross-section is circular or sometimes elliptical depending on the location and rainfall.
Its longitudinal shape is a cylinder.
It is astatic.
Youngs modulus increases with fiber length.
It exhibits good sound and impact absorbing properties.
Benefits:
It is 100% biodegradable.
It is used as fertilizer, cattle feed and as fuel for biogas production.
Uses of sisal fiber:
Sisal is divided by 3 grades and applied in various industries according to the grade.
Low grade: it can be used in the paper industry and cordage industry.
Medium grade: it can be used in agriculture, marine and general industrial applications. And used for making binder twine and ropes.
High grade: it can be used in the carpet industry, the automobile industry.