Fibres and Yarns | News & Insights

Ramie Fibre

Published: November 26, 2024

Author: TEXTILE VALUE CHAIN

Botanical Information

The scientific name of ramie fibre is Boehmeria nivea (L) . Gaudich species belongs to the urticaceae (nettle) family.
Ramie fibre is a bast fibre obtained from the inner bark of the ramie stem.
Ramie fibre has been grown in China for many centuries.
China initiated the idea of ramie fibre production as it abundantly grows over there.
It is also known as China grass.
In India, ramie fibre has been used for clothing since ancient periods, at least before 600 BC.
It is superior to other natural fibres such as cotton, jute, flax, etc.
In India, it is known by different regional names such as Rhea, Popah, KhunKoora, Kurkunda, etc.
The cloth of ramie fibre was ever used by royal families of Egypt for sacred mummification of the deceased.
Ramie fibre is primarily used for blending with cotton and silk for its unique strength and absorbance.
This fibre has tremendous scope for blending with other natural and synthetic fibre for the manufacturing of apparel and also for the production of diversified items.
Ramie is recognized as the strongest of all natural bast fibres in the world which is known as ‘riha’ in Assam.

Agro Climatic conditions for cultivation
Ramie is grown in China, Brazil, Indonesia, Philippines, Korea, Vietnam, Japan, India and other South Asian countries.
China is the major producer of ramie fibre contributing to 96.3% of the global production.
According to FAO (2013), in 2011, China cultivated ramie plants in 72934 hectares of area, producing 124000 tonnes of fibres. The average production was about 1700 kg/ha.
The total lifespan of the crop ranges from 6-20 years.
Lately, India has been cultivating ramie on a wide scale to meet national industrial demand.
The northeastern province of India has suitable soil parameters and climatic conditions to cultivate ramie plants.
In India, about 19 species of ramie have been reported so far.
Regions like the foothills of Himalaya and the Brahmaputra valley of Assam, Arunachal Pradesh and the western ghats have good sources for ramie cultivation.
It proliferates in sandy loam soil with a mild acidity level of pH 6 to pH 7 and hot- humid weather conditions with a temperature of 250C to 310C.
It requires a well-distributed rainfall of up to 1500-2000mm to obtain a good and luxurious quality of ramie fibres.
Ramie has a vigorous growth habit, reaching more than 2 m in height within one month under favourable conditions.
In the first year, the plants have a high growth rate.
In subsequent years, the growth rate of stems is lower, but there is an increase in the percentage of fibre generally by 2 to 4 %.
Ramie possesses the longest filament compared to other fibres obtained from stems, the length varies from 3 to 30 cm with an average of 2 cm, the width is 40-100µm, and the proportion of length to width of the fibre cell varies from 3000 to 3500.
The best output for the plants requires a favourable climate with steady high temperature, a humid atmosphere and a well-distributed annual rainfall of not less than 1.125 mm.
The first harvesting can be done after 17 days of planting and followed by 45-60 days for the succeeding harvesting.
The highest yield is attained in the third and fourth years and maintained until the plant is about six years old. Harvesting is done either by manually or by using mechanical harvesters.
It is important that ramie should be harvested at the right time if the best fibre is to be obtained.
Varieties of ramie plant

Boehmeria nivea L. Gaud., commonly known as ‘white ramie’, and Betula utilis generally referred to as B. nivea var. tenacissima and known as ‘green ramie’ are the two major species of ramie fibre.

Features and Properties of Ramie Fibre
Ramie produces unicellular fibre, which is a longer plant cell and strongest in its own kind.
The fibre is produced in the dark as a bast or phloem fibre.
Ramie fibre possesses excellent quality, lustre, strength and durability of exposition.
It is the strongest natural fibre, thus nicknamed as ‘steel wire fibre’.
The fibre is twice as strong as cotton and has a better length-breadth ratio than cotton.
Ramie fibre exhibits higher fibre strength when it absorbs moisture.
The fibres are also resistant to many solvents and abrasion.

5.Extraction and Processing of ramie fibre

Harvesting and fibre extraction go through a few steps which are described briefly.

Harvesting

Harvesting takes place when the lower portion of the stalk looks brown, and the tips of new stalks appear.
The stalks are usually cut by hand.
Ramie fibres are obtained by decortication, a hand or mechanical process in which the bark and the adhering fibre are separated from the stalk and soaked in water, allowing the fibre to be scraped from the bark.

Decortication

Fibre is extracted from harvested defoliated canes by a decorticator machine.
The scrapper blade breaks the wood during rotation and fibre is extracted.
The raw fibre is then washed thoroughly in clear water to remove some of its gum and then sun-dried for 2 to 3 days.

Fibre yield

The fibre yield (un-degummed fibre), on average, varies from 1600 to 2200 kg/ha.
The average fibre content in ramie is about 3 to 4 % of the green biomass of the crop.

Degumming of ramie fibre

There are two types of degumming processes to remove the gummy materials from fibres.

The conventional method is the chemical treatment of the fibre and in this process, a strong hot alkali solution with or without the application of pressure is the key ingredient to remove the gum.

Chemical degumming

The chemical degumming process is the most widely used degumming technique although this method still involves the use of large quantities of NaOH reagent under high temperature and high-pressure conditions. The development of degumming additives has made it possible to improve hemicellulose removal from ramie materials by including novel reagents in the chemical degumming process, such as penta-sorbates, and surfactants. The result of the degumming process is fibre ready to be spun

Biochemical degumming

The other method of degumming is the biochemical treatment of the fibre where initially the fibre is treated with microorganisms (bacteria or fungi) for a few days and after that, the fibre is washed with mild alkali. In the traditional degumming process, the pectin materials that remain coated on the decorticated fibres are removed by chemical means. After the microbial treatment period of over 24 hours is completed, the treated fibres are boiled with 1% alkali solution (fibre: solution – 1:10) for 1 hour followed by boiling in 0.5 % alkali for an hour in an open vat and the degummed fibre is neutralised with 6 % acetic acid.

Direct extraction of fibre from ramie bark

A high-speed water treatment method has been used for the extraction of the husks. The following steps for improving the fibre extraction process are involved: retting, first high-speed water treatment, oxidative degumming and second high-speed water treatment. The ramie stripped from the ramie plant by hand is used as material for the extraction of fibres. The main chemicals used in this process are sodium hydroxide, hydrogen peroxide and sodium tripolyphosphate.

Modified Fibre extraction process

The treatment process of the ramie involved the following process: Raw material retting followed by high-speed water treatment. Then, oxidative degumming was performed, which was followed by high-speed water treatment and then drying.
Retting: the ramie was retted in the pool from 1 to 9 days.
Oxidative degumming: the ramie sample was treated in a peroxide solution (sodium hydroxide 2g/l (gram/litre), hydrogen peroxide 0.8g/l anthraquinone 2g/l), for 1 hour at the temperature of 800C.
Then, 8 g/l sodium hydroxide was added to the proxied solution, the ramie sample was treated in this peroxide solution for 2 hr at the temperature of 1000C.

High-speed water treatment: the ramie sample was treated by a high-speed water jet for 3 min. the speed of the water jet was approximately 5 m/s (metre per second)
Second high-speed water treatment: when the ramie sample was treated under high-speed water, the husks and gum were removed because of the impact force of the high-speed water.
This means that the high-speed water treatment was beneficial for husk removal; therefore, it is better to treat twice with high-speed water.
Extraction of the fibre occurs in three stages.
Firstly, the cortex or bark is removed, either by hand or machine, in a process called decortication.
The Central Research Institute for Jute and Allied Fibres (CRIJAF) has developed one such machine having the capacity to decorticate 800-1000 kg of fresh canes from an area of 500 m2 yielding about 35-40 kg of dried fibres per day.
The CRIJAF has also developed a more user-friendly and cost-effective 1 HP motorised Bast Fibre Extractor for this purpose in the recent past.
The second stage involves scraping the cortex to remove most of the outer bark, the parenchyma in the bast layer and the Ramie crop in the field during its growing season.

The third stage involves washing, drying and degumming the residual cortex material to extract the spinnable fibre.
Most of the processes involve a treatment with caustic soda to dissolve the residual pectin’s and gums.
The process of degumming improves the tenacity, fineness and lustre of machine-extracted fibre. The fibre may also be chemically and microbially degummed.
It was found that the full-grown plant attains a height of about 5-8 feet and a diameter of stem 5.0-3.0 cm at three different levels, viz. bottom and top.

Dyeing of ramie fibre
For aqueous dyeing, the ramie fibre was immersed in dye solution at room temperature and then heated to 60°C at a 2°C min−1 heating rate, subsequently maintained at 60°C for 10 to 60 min variation in an infrared radiation heated laboratory-rotary dyeing machine.
Liquid ammonia (LA) dyeing is a zero-effluent and sustainable dyeing technology investigated for textiles.
For LA dyeing, the LA dye bath was cooled to −40 °C using a refrigerant machine.
The ramie fibre was immersed in the LA dye bath for 1 to 10 min. After dyeing, the excess LA in the dyed ramie fibre was removed by placing it in a hydro-extracting unit and centrifuged at 1400 revolutions per min (rpm) for 10s. After which, the dyed ramie fibre was dried at 100°C in an oven for 30 min to remove the residual LA in the dyed fibre and to achieve dye-fixation, followed by soaping in a solution of 2 g L−1 non-ionic detergent at 95 °C for 15 min at a liquor ratio of 50: 1
Yarn preparation and spinning

Before spinning, the fibres are sorted into three lengths, i.e., long, medium and short. Normally, about 60% of the total weight of the degummed material will be long fibre. This long fibre is spun separately. The medium–length fibre is either spun on its own or spun together with the short fibre and any waste is obtained during the dressing of the long fibre. To make them suitable for spinning, the decorticated ramie fibre has to be degummed in an effort to separate the individual fibres free from gums, waxes and pectin’s and leave them in a soft, clean state with their strength and other textile characteristics intact. The degummed ramie contains a residual gummy content of 1-5% according to the type of spinning process to be used, dry spinning requires a clean fibre, and wet spinning requires a gum reside.

Parameters	Values
Length of ultimate cell (mm)	20-250
Length to breadth ratio of ultimate cell	3500
Tenacity (g/Tex)	40-65
Extension at break (%)	3-4
Gravimetric fineness (Tex)	0.4-0.8
True density (g/cc)	1.56
Degree of crystallinity	17.5
Crystallinity (Qualitative by X-Ray Diffraction Technique)	Very high

Table 1: Physical Properties

Table 2: Chemical Composition

Constituents	% Share
Cellulose	67-99%
Hemicellulose	13-14%
Pectin	1.9-2.1%
Lignin	0.5-1.0%
Fat /wax	0.3%

Fig.2: Appearance of the ramie sample: (a) raw ramie, (b) ramie sample after retting, (c) ramie sample after the first treatment with high-speed water and (d) ramie sample after the second treatment with high-speed water.

Fig.3: Ramie bast to Ramie fibre

Properties of Ramie Fibre (Table 1 and Table 2)
Ramie is a very strong fibre under wet conditions.
It has the ability to hold shapes.
It does not wrinkle and possesses silky lustre.
It is often used in blends.
It is similar to flax in absorbency, density and microscopic structure.
It is, however, less durable and does not dye well.
The fibre is stiff and brittle.
It shows poor resilience and elasticity.
Therefore, despite its high strength, it has limited use in apparel textiles. The yarn is quite hairy because of the lack of coherence, and the spinning and weaving of the fibre is difficult due to its brittleness and lack of elasticity.
Ramie is resistant to bacteria, mildew, alkalis, rotting, light, and insect attacks.

Uses of Ramie

It is used to make filter cloths, packing materials, industrial sewing thread, upholstery, and canvas.
It is used in clothing, napkins, handkerchiefs, and table cloth.
To gain certain properties, it is blended with other fibres. It offers dye affinity and lustre when blended with high-quality cotton. When blended with rayon, it offers low wet strength. minimises shrinkage and adds lightness when mixed with wool
Long staple fibres of ramie can be used for spinning, whereas short fibres are used for the manufacture of papers, composites, non-woven and other products.

Ramie fibre has generally been used in fine linen and other clothing fabrics, upholstery, canvas, filter cloths, sewing threads, gas mantles, finishing nets and marine packing
When used in admixture with wool.
High-quality papers, such as banknotes and cigarette papers can be produced with short fibres from processing waste.
The fibre is used for making hose pipes, water bags, shoe threads, commercial canvas etc.
Ramie can be used as a very good pig feed and overall, its forage and fodder value is a researchable issue as well.

Properties of ramie and its blends

Ramie is composed of 68.6 – 76.2% of Cellulose, 0.6 -0.7% of Lignin, 13.1 – 16.7% of Hemi-cellulose, 1.9% of Pectin, and 0.3% of wax.
The decorticated ramie fibre contains around 19–30% of non-cellulosic gummy matter.
Ramie blended with different types of silk showed good results, but 50:50 blends showed the best result than 60:40 blends. The breaking load of 50:50 blends ranged from 131.75 – 189.16 lb for different types of silk. Therefore, blending of ramie with different silk with different blend proportions offers excellent scope for producing a
variety of materials for different uses. It is a highly crystalline fibre. It has resistance to heat, light, acid alkali etc.

Bibliography

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Vincentius Yolanda Angger Raditya, Muhammad Adly Rahandi Lubis ORCID, Rita Kartika Sari, Petar Antov, Seng Hua Lee ,Lubos Kristak,Efri Mardawati andApri Heri Iswanto (2023).”Properties of Ramie (Boehmeria nivea (L.) Gaudich) Fibers Impregnated with Non-Isocyanate Polyurethane Resins Derived from Lignin”. https://doi.org/10.3390/ma16165704.
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