Pineapple fiber is a natural, lignocellulosic, leaf fiber that is obtained from the leaf of the pineapple. It belongs to the family Bromeliaceae. It comes under the genus “ananas”. It grows up to a height of 1.5 meters. It requires rainfall of 100 to 150 cm and optimal temperature must be between 22 and 32 ͦc .while the leaves grow best at 32 ͦc. This type of climate found in coastal regions.it grows well in tropical and subtropical countries under a humid climate. Cultivation of pineapple originated in central and south America and later spread throughout the world. A kilo of leaves may produce up to 15 to 18 pieces of creamy, white and lustrous as silk fiber about 60 cm long. Only in India, the yield of fibers could be about 6 lacks tones a year. The worldwide production of pineapple leaf fiber in the year 2017 is 1318 thousand tons.
Processing of pineapple fiber:
Selection of pineapple leaves :
The first step is the selection of fiber which plays the most important role as it decides the fiber characteristics. A fiber that is extracted from young leaves is generally soft and weak. Over matured leaves, particularly the plants grown in the open and not under the shade, yield short coarse and brittle fibers. Therefore in order to obtain the stronger and pliable fibers, moderately mature leaves from the plants which have been grown partly suitable for extraction of fibers. Kews is one variety of pineapple found to have longer, heavier, and wider leaves.
Extraction of pineapple leaf fibers (PALF) :
By decorticating machine: this machine used for scrapping the leaf of the pineapple. It has 3 rollers i.e. Feed roller which is used for feeding of leaves into the machine, leaf scratching roller which scratches the upper layer of leaf and removes waxy layer and the serrated roller which crushes the leaves.
Retting of Pineapple Leaves: in this process, the scratched leaves are tied and immersed in a retting tank that contains Urea or di-ammonium phosphate. It can extract many chemical constituents like pentosans, lignin, fat, wax, ash content, pectin, and nitrogenous matter. At the end of retting, leaves are taken out and washed mechanically by freshwater that is dried and hanging place by air.
Degumming of Pineapple Leaf Fiber:
Pineapple leaf fiber consists of gummy material which renders the fiber to be brittle and coarser and varies between 25 to 35 denier therefore it has to be degummed in order to make the fibers soft and fined. It can be done by using alkali, acid. the first step is to boil the fibers in aqueous alkaline solution and then wash the fibers with water for neutralization. The linear density of pineapple leaf fiber after degumming was found to lie between 12-20 deniers.
Chemical Modifications: Alkali treatment or mercerization using sodium hydroxide (NaOH) is the most commonly used treatment for bleaching and cleaning the surface of natural fibers to produce high-quality fibers. NaOH reacts with hydroxyl groups of the cementing materials in natural fibers and brings on the destruction of the cellular structure, thereby spiting the fibers into filaments. Hydrogen peroxide (H2O2) bleach improves PALF fineness by 5-6% but reduces the tensile strength by 40-45%.
Types of pineapple fibers:
Linuan: referred to as fine fibers. Bastos: referred to as coarse fibers.
Chemical Composition of Pineapple Leaf Fiber:
Properties of pineapple fiber:
length(mm): 10-90
Fineness(tex) : 2.44-3.56
Fiber Tenacity (gm/tex) : 30.00-51.00
Elongation %: 2.5-3.5
Moisture regain % : 11.5-12.00
Water swelling % : 48.96
True density gms/cc : 1.5260
Porosity % : 9.00
Flexural rigidity dyne/cm2 : 3.80
Torsional rigidity dyne/cm2 X1010 : 0.36
L/B ratio : 450
Moisture content(wt%) : 11.8
Tensile strength (MPa) : 413–1627
Young’s modulus (GPa) : 34.5–82.51
Specific strength (GPa/g/cm3) : 0.3–1.1
Specific modulus (GPa/g/cm3) : 22.7–54.3
Initial modulus(cN/tex): 570-700
Elongation at break (%) : 1.6 -3
Dia.(mm) : 20–80
Microfibril angle : 8-14
It has high insulation power and high absorbency.
The thermal conductivity of this fiber is below at 0.0273 watts/m2/k which suggests that these fibers can be used as good thermal insulators.
It has high flexural and torsional rigidity than that of cotton fiber.
It has a high degree of crystallinity with a spiral angle of 15 ͦ.
Effect of alkali: when it is treated with 18% NaOH results in length shrinkage and enhances breaking elongation.
Effect of H2O2: H2O2 improves its fineness up to 5 to 6% but reduces tensile strength by 40 to 45%.
Pineapple fiber dissolves in 60% sulphuric acid in 5 min.
Characteristics:
The pineapple fiber is soft, translucent, white or ivory in color and has luster.
It has an elegant appearance similar to linen and is lightweight and easy to care for.
Pineapple silk is considered the queen of Philippine fabrics.
It is durable and resistant to moisture.
The yield of fiber is 2.5 to 3.3% of the weight of green leaves.
It can blend efficiently with any other fabrics.
It can be washed and doesn’t need to be dry cleaned.
An embroidered Pina garment is called as Pina calado.
When the pineapple fiber is woven with silk it is called Pina Seda or Pina silk.
A blend of abaca or silk is known as Pina jusi.
It is 10 times coarser than cotton and the fiber and has a higher dye absorption tendency due to its higher moisture regain.
It can be dyed with direct, reactive, vat, and azo dyes with better fastness properties as compared to that of cotton.
It can also be dyed with basic dyes at room temperature due to the presence of lignin and hemicellulose, which are more than 15% amorphous in character with acidic nature.
Use of Pineapple Fiber:
The pineapple fibers can be used in wide applications from apparel to technical textiles.
Used in industrial applications like tires and conveyor belts and can be used in the paper manufacturing industry.
The pineapple fabric used to make upholstery and furnishing.
It is used for making table linens, bags, mats, and other clothing items.
It is used for making a thin and transparent embroidered garment known as barong Tagalog which has worn over a shirt and other formal wear in the Philippines.
It is used for making wedding attire for men, blouses for women, kimonos, panuelos, gowns, and handkerchiefs.
Sports items, baggage, automobiles, cabinets, and mats. Surface modified PALF is introduced for making machinery parts like belt cord, conveyor belt cord, transmission cloth, and air-bag tying cords.
It is generally used in making threads for textile fabrics.
It can be suitable for various other applications such as cosmetics, medicine, and biopolymers coating for chemicals.
It is used to reinforce the corrugated roofing sheets.