Textile Fibers: Fibers used to make yarn are considered as a textile fiber. Fibers come from different sources. Different types of textile fibers are responsible to make different yarn and then yarn into fabric.
Types of Textile Fibers
Fibers are generally divided into two broad categories: synthetic fibers and natural fibers. A lot of R & D is going on how to use natural fibers to make garments. The main objective is to develop environmentally friendly products. To ensure sustainable development in the textile sector, a movement towards organic fiber is necessary.
Natural fibers can be sourced from different sources such as animal, plant, and mineral fibers. Wool, silk, and hair are examples of fibers that are sourced from animals.
Different factors affect the properties of natural fiber to varying stages of its growth and extraction. The fiber properties and performance are based on factors such as plant growth, harvesting stage, fiber extraction methods, and supply chain. In-plant growth stage, the major determining factors are the plant species, how the crop is cultivated, the location of the crop, part of the plant from which the fiber is extracted, and the local environmental conditions. In the harvesting stage, the development of the fiber, which can be determined by fiber ripeness, plays a crucial role. The fiber ripeness affects the fiber performance through its effect on the fiber surface coarseness, thickness of the cell wall, the bonding between the fibers, and the surrounding matter in the structure. Fiber extraction and treatments play a major role in determining the properties and performance of the natural fiber. Different extraction methods like mechanical decortication, retting, and dehulling have a profound effect on the physical and chemical properties of the natural fibers. Some chemical treatments are performed during the extraction stage of the fiber, which also affects the fiber surface, causing a change in the properties of the fiber. During the supply stage, the conditions in which the fibers are being transported, fiber storage conditions, and duration of storage degrade the properties of the fibers as long duration increase the fibers age.
The favorable features of the natural fibers are:
- Abundance, and
Fibers can be extracted from several parts of the plant like its stem, leaf, seed, fruit, etc. Animal and mineral-based fibers used for producing clothes, paper, handicrafts, etc. A new mineral-based fiber known as the basalt fiber which has very high mechanical, chemical and thermal properties came into the picture. The researchers are trying to use this fiber as an effective alternative to synthetic fibers.
Based on the origin the plant fibers are also categories into wood-based and non-wood based natural fibers. A lot of the applications of the natural fibers come to good use as the bio-composites in the automotive, construction, sports, and marine industries. The uses of the natural fibers as a reinforcement date back in 300 B.C. where straw was used as reinforcement inside the clay to prepare a composite brick. However, the Composite bows were used by Mongolians which were made from horns is another example of the use of the natural composite by humans. Natural fibers have the potential to address the problem of waste management.
The major sources of the synthetic fibers are sourced from petrochemicals. The availability of the petrochemical resources which are rapidly reducing and their reserves are uncertain in nature. Moreover, using these petrochemicals yields a lot of pollution and damages the environment. To counter all these factors, scientists had taken up the task of replacing these synthetic fibers with the natural fibers. This has led to the research on natural fiber-based composites or bio-composites. The strength of the natural fibers has encouraged materials scientists to bring a lot of natural fibers as reinforcements into the composite materials. The natural fibers sourced from different sources such as leaves, bast, minerals, etc.
Wood is a natural composite material. It is made of lignin, cellulose, hemicellulose, and other materials ( fats, protein, inorganic salts, flavonoids, alkaloids, waxes, terpenes, glycosides, simple and complex phenolics, lignans, stilbenes, pectin, starch, tannins, mucilages, gums, saponins, simple sugars crucial oils, proteins, and many more). Extractives tend to weigh around 20% in the total dry weight of the wood. These extractives give the final mechanical strength and quality of the wood. But these also tend to decrease the thermal properties of the wood. Some researchers observed that removing these extractives from wood tends to improve the thermal properties.
Wood can be mainly divided into two types
- Hard Wood: Wood sourced from the angiosperm tree
- Softwood: Wood is sourced from the gymnosperm tree
The woods are made of two types of cells (axial and radial) that are connected inside the wood in different fashions. One type of arrangement is the axial cells that run parallel to the long axis of the wood plant. The second type of arrangement is a radial cell which is aligned perpendicular to the long axis of the wood plant.
Generally, two types of fiber forms can be obtained from both the soft and hardwoods. The mechanical strength and the density is determined along with the thickness direction. The thicker cells yield stronger and dense structures for the wood. Single fibers have higher aspect ratios and small fibers with lower aspect ratios. The single fiber is known as wood fibers and short fiber bundles are extracted as wood flour.
The major sources to obtain the sawdust, shavings after cutting wood, and woodchips are the sawmills and woodworking centers which are postindustrial sources. Generally, the wood flour is one of the sources used as filler materials inside composites rather than as reinforcement materials.
Bast Fibers are collected from the inner bark of different plants. The phloem is one of the sources of strength and stiffness to the plant stem. Bast fibers can be found from the following sources:
Flax: Flax is a plant that is being cultivated for the extraction of fiber and seed oil. This is one of the old natural fibers that is widely used in the manufacturing of modern textiles. It is grown in countries like India, Netherlands, France, Spain, Russia, etc.
Hemp: Hemp usually grows in central Asia and central Europe. It has a very high growth rate. Because of good resistance to pests and viruses it has fewer requirements for pesticides, herbicides, fertilizers, and fungicides. It has higher tensile strength and lower moisture absorption and elongation in comparison with the flax fiber. The root structure of hemp helps to maintain the soil structure and has the capability of restoring nutrients to the soil.
Nettle: Nettle fiber is one of the very ancient fibers. Production of Nettle is decreased because of the very long growth cycle of more than a year, even if it is possessing a higher tensile strength and modulus values in comparison with other fibers.
Jute: Jute is one of the most common fibers that grow in the Mediterranean, and in Asian countries like India, Indonesia, Nepal, Thailand, and Bangladesh. It is well known as golden fiber. Due to high lignin content present in the fiber, it has lower elongation and tensile strength, lower chemical, and moisture resistance in comparison with the hemp and flax fibers.
Kenaf: A plant that is mostly native to central Africa and subtropical Asia. It grows very rapidly and contains long and short fibers, which can be extracted from the same bast. It is very rough in texture and brittle in nature which makes it difficult to processes this fiber. The mechanical properties of the kenaf fiber are very similar to that of the jute fiber.
Ramie: It is one of the oldest crops that is being grown in Asia, which can be harvested several times, around four to six times, a year. The ramie fiber has high specific strength and modulus and has mechanical properties comparable to glass fiber with high chemical resistance as well.
Kudzu: It a fiber from Japan and China and is a plant that has expanded rapidly through the seeds and stolons. The fiber extracted is generally used for basketry also in the clothing industry. The rapid expansion of this plant leads to depletion of the quality of the soil and its expansion has to be controlled.
Okra: This plant was originally from Africa. It is usually grown in the tropical, semitropical, and warm climates. It is a perennial plant which is most often grown not for its fiber, but for the okra vegetable. More concentration is now being given to the fibers that are obtained from the bast of the plant after harvesting the required vegetable.
Roselle: This is a plant that takes a long time for its growth, which is a major drawback of this plant. It is grown in India, China, Thailand, and Africa. China and Thailand are the largest exporters of this fiber which is a very good replacement for jute fiber.
Leaf fibers are the group of multicelled lignocellulose fibers collected from the plant leaves. The leaves that are suitable for fiber extraction should be long, linear in structure. Generally, the fibers are extracted from the leaves through mechanical means.
Sisal: The sisal majorly grows in the tropical climate. Brazil and Tanzania are the major producers of this fiber. It has a very high lifespan of 7–10 years. It has three types of fibers which are the structural, arch, and xylem fibers. The structural fibers are important for the commercial use of the sisal fibers but the mechanical strength is the highest for the arch fibers and is used for the short fiber applications; xylem fibers are lost during the extraction phase of fibers from the leaves of the sisal plants. High strength, durability, resistance to salt-dependent degradation, ability to be dyed, and stretching are some of the favorable characteristics of sisal fibers, but all the favorable characteristics tend to deteriorate with the increase in temperature.
Abaca: Abaca is a fiber extracted from the leaves of the specific species of the banana plant, which is native to the Philippines. This fiber is generally used for producing ropes and twines. It is a hard fiber and is the strongest fiber that can be sourced from the plants. It has excellent resistance to seawater degradation.
Phormium Tenax: Phormium Tenax is a perennial plant that is most commonly cultivated in New Zealand. These plant leaves are one of the sources for the natural leaf-based fibers. The fiber extracted from the leaves of these plants is majorly utilized to prepare the objects such as mats and ropes due to their properties rather than a reinforcement inside a composite material.
Henequen: Henequen is a plant that is related to the sisal fiber family and it has lower properties in comparison with that of the sisal fibers. It is grown in Africa, South and Central America, and Asia. It has low mechanical properties and salt degradation in comparison with those of other leaf fibers. The toughness and resilience are the important properties exhibited by the henequen fiber, which are important properties for some composites.
Pineapple Leaf Fiber: Pineapple leaf fiber is obtained as a by-product coming from the pineapple fruit cultivation, which is majorly grown in tropical climates. The mechanical properties of this fiber are very similar to that of the jute fiber. It is highly hygroscopic in nature. It is commonly combined with silk for creating the fabric for the textile industry.
Banana: Banana fiber is extracted from the banana tree which is a circular leaf structure often mistaken to be as bast. It is useful for preparing biodegradable products in Asia and throughout the world. It has been used as a textile fiber for many years. The cellulose and structure of the banana fibers are similar to the sisal fiber, but the lower spiral angle in the structure of the fiber results in a higher tensile characteristic in comparison with that of sisal fiber.
Curaua: Curaua is a plant that grows in regions with semiarid climates. It is a hard fiber whose chemical composition is similar to that of several other plant fibers. Due to the mechanical properties of this fiber, it has been used for automobile applications.
Date Palm: Data palm trees are mainly cultivated for the fruit known as the dates, which are usually found in the Middle East, Africa, America, India, and Pakistan. The hard shell found on the tree is from which the fibers are extracted that can be used to prepare ropes and basketry.
Piassava: Piassava fibers are extracted from the native palm trees. The tensile properties of these fibers are more in comparison with the coir and lower in comparison with the sisal and jute fibers. It was mainly used for industrial mats and brooms.
Grasses are the source of lignocellulose fibers, which can be derived from a variety of grasses. They are good due to their low cost, simple harvesting, and minimum processing requirements. But the properties of grasses are lower in comparison with that of bast and leaf fibers, which makes them suitable to be used as short fiber reinforcements. Natural fibers can be extracted from a variety of grasses such as bamboo, wild cane, switchgrass, alfa, as well as different types of straws, etc.
Straw: Straws are leftovers obtained from the cereal stalks like rye, rice, and wheat plants. They are obtained from the plants after the grains. They are generally used as the fodder for animals and to produce biofuel, bedding, thatching purposes. The mechanical properties of the fibers extracted from these straws are lower in comparison with bast and leaf fibers.
Bamboo: Bamboo is one of the largest plants in the grass family, with a very high growth rate and low growth cycle. Fiber can be extracted from the pulp of the bamboo plant. It is mainly available in Asia. It is usually used as a traditional food source for construction purposes, making furniture, paper, and textiles. These bamboo fibers are the ones, which have good properties, making them attractive materials for reinforcing the composite materials. Many research efforts are being focused in many parts of Asia and throughout the world on the practical usage of bamboo fibers as the reinforcement phase in composite materials.
Alfa: Alfa is a perennial grass found in the southern region of Spain and the northwest region of Africa. The main application of this grass is for pulp making used in the production of the paper. But, the fibers extracted from this alfa grass are short fibers having high mechanical properties. That is the reason, great attention is given for the usage of this alfa fiber for the preparation of composite materials in recent times.
Wild Cane: Wild cane grass is one of the most abundantly available natural resources of grass. The density and mechanical properties of the fibers extracted from the wild cane grass have comparable properties to that of the sisal and banana fibers.
Fruit and Seed Fibers
Fruit and Seed Fibers are derived from either the fruit of the plant or seeds of the plant. Coir and oil palm are examples of fibers extracted from the fruits of a tree. Cotton is the best example of the fibers extracted from seeds. Cotton fibers form a protective layer around the seeds.
Oil Palm: It is a native plant to the Congo basin and to West Africa. It yields different products such as palm fruit, palm oil, etc. These fibers are extracted from the waste using the process of retting. The major disadvantages of the palm fibers are that the fiber diameters vary significantly, which influences the tensile properties of the fibers, whose properties are lower in comparison with the other natural fibers.
Coir: Coir fiber is a fiber extracted from the outer shell of the coconut fruit, abundantly found in the subtropical and tropical regions. Coir which is extracted before the coconut that is ripened is known as white coir. The coir which is extracted after the ripening of the coconut is known as brown coir. The coir has a relatively low mechanical strength and modulus, which leads to the fact that it is not good reinforcing material. But the major advantages of coir lie in the fact that it has low thermal conductivity, density, and higher elongation. The coir fiber tends to be used as a rope in most countries especially in Asian countries.
Cotton: Cotton plants are usually grown in the tropical and subtropical regions of the world and is the leading fiber crop that is being cultivated across the world. Cotton fibers possess lower mechanical properties in comparison with natural fibers especially the natural fibers which are obtained from the bast part of the plant. But cotton is an abundant fiber used in the modern textile industry. It is also mixed with other natural fibers for the purpose of manufacturing stronger textiles.
Husk or Hull is the by-product obtained after removing the shell from the grains like soybean seeds, wheat grains, rye, rice, palm, kernels, sunflower seeds, etc. Seeds are the main products that will be obtained from the plants. The husk is separated from the grains using the process of mechanical dehulling. This husk/hull is separated from the seed, and then usually sent to be used as animal feed due to the presence of a high amount of fiber content.
Sugarcane bagasse is one another by-product obtained after the crushing of the sugarcane. This bagasse is generally used as the cattle feed, a source for producing biofuel, and a source for producing paper. The fibers extracted from the bagasse are usually around 1.2 mm in length and with an aspect ratio of around 80 and it has similar performance as that of the wood flour and is a candidate for short fiber-reinforced composites.
Corncobs are one of the sources for use in the biofuel industries.
Starch can be extracted from the corn and other starchy plants which can be processed to produce biodegradable polymers.
Feathers: Feathers are a by-product obtained from the poultry industry. Feathers are made up completely with beta keratin proteins. Feathers typically have a length of 5–1700 lm and 10–40 lm in diameter. These fibers have high acoustic and thermal insulation characteristics due to the presence of inherent air gaps in the keratin microfibrils. Along with their lower density, these feather fibers also possess good mechanical properties and modulus values as well.
Natural fiber can also be sourced from various protein sources in addition to the lingo cellulose sources. For the protein-based fibers, the amino acid protein structure is the basic building block. These structures are based on the sequence of amino acids connected by peptide bonds. For the purpose of reinforcements, only a few types of proteins known to be sclero proteins which are in the form of long protein filaments will be considered. Keratin, elastin, Fibroin, and collagen are some of the proteins which contain fiber. These are most abundantly found in different parts of the vertebrates which makes them not a good source of protein fibers. Two types of keratin namely alfa keratin and beta keratin are generally found in nature. Alfa keratin is the primary source found in the hairs, horns, claws of the mammals, while the beta keratin is a source that is found in the structure of the shells, scales on the skins of the reptiles and scales of the birds, etc.
Wool: Wool is harvested from animals like sheep, camels, goats, and alpaca, which is being widely used for producing clothes and fibers for the modern textile industry and is one of the most commonly found protein fibers. The research on how to harvest more wool and use it as a fiber reinforcement phase in the composite materials has increased in recent times and many researchers are currently working on this particular area. But, the major problem lies in the fact that these fibers are costly, has weak mechanical properties, their nature is very similar to that of the cross-linked rubber, and finally the variations in lengths and characteristics of the fibers, which makes it very difficult to use these fibers as a potential reinforcement phase in the composite materials.
Fibroin: Fibroin is a form of protein that is created during the production of silk. Fibroin is a protein that is responsible for inducing good tensile strength and modulus, and performance. Many different types of arthropods produce silks. Still, the most common source of silk is from the bombyx Mori silkworm larvae, which form a cocoon made out of silk fiber. Silkworm silk has a good amount of tensile and Young’s modulus values with the ability to create uniform continuous fibers. But the major challenge occurs in the fact that this fiber is rather expensive. The production of this fiber is also deficient, and this silk extracted from the bombyx Mori silkworm is used for producing high-end textiles. Another well-known source of silk is spider silk which holds good performance characteristics. But the production of this fiber is very costly and a problematic affair. But, seeing its potential for usage as a reinforcement in composite materials, researchers have developed a way to produce this fiber synthetically. Still, the process is also costly and time-consuming and needs future improvements to be applied at a commercial scale.
Synthetic Fibers are artificially derived from the polymers which are not available naturally. They are mostly derived from petroleum-based by-products and are developed in the laboratories and at the industrial scale. These are derived from the combination of different chemicals, they are generally very long and possess high mechanical, thermal, and physical properties. These properties can also be greatly varied by using the different combinations of chemicals and processes that are used to create these synthetic fibers. nylon, polyesters, acrylics, polyurethanes, etc., are some of the so-called polymer forms from which these types of fibers can be developed. Kevlar or aramid, carbon, and glass fibers are the three most commonly used synthetic fibers.
Kevlar Fiber: Kevlar fibers are also known as aramid fibers. Para-phenylenediamine is combined with terephthaloyl chloride, which forms the aromatic polyamide threads. These threads are nothing but the Kevlar fiber strands. This is a very expensive process that is used for manufacturing these fibers, but very high-performance fibers with very good impact resistance can be obtained. Different types of fibers such as Kevlar, Kevlar49, and Kevlar29 exists. Generally, these fibers are used for producing body armors.
Glass Fibers: Glass fibers are the most commonly used synthetic fibers in the composite industry for many several applications. These are the most versatile and cheap fibers in comparison with Kevlar and carbon fibers. These fibers are manufactured by drawing the liquified glass with 50% silica and mineral oxides. These fibers are cheap to produce and possess desirable properties such as lightweight, high strength, less brittle, and beneficial stiffness. Different grades of glass fiber such as E-glass, S glass, A glass C glass, etc. These are mainly used in automotive bodybuilding, bulletproof glasses, fuel tanks, and much other aviation, sports, construction, energy, etc.
Carbon Fibers: Carbon fibers possess very high specific strengths and stiffnesses. They also have extremely high thermal and chemical resistance and properties in addition to their strengths. Polyacrylonitrile is the primary source from which about 90% of the carbon fiber is currently produced. The remaining comes from the rayon and the petroleum pitch. Polyacrylonitrile and rayon are organic polymers that contain long strings of molecules, which are bonded together by carbon atoms. The cost of carbon fiber is very high, limiting its usage in composite materials in other fields except for aerospace applications. Different forms of carbon fibers such as T800, carbon, etc., exist. A lot of research is also being conducted on how to extract carbon from natural sources to produce carbon fibers and how to decrease the manufacturing costs of these carbon fibers. These fibers are used in manufacturing satellites, rockets, aerostructures, high-end luxury, and sports cars.
Basalt Fiber: Basalt fiber is a mineral fiber composed of similar minerals to that of the glass fibers. It has very good thermomechanical, physical properties in comparison with that of the glass fiber. It is produced by the melting of the by-product of basalt rocks obtained from quarries. It is extruded through a small nozzle at a temp of 1500 °C and yields a fiber which is typically around 20 lm in diameter. It has comparable properties to that of carbon fibers. It has very high thermal, chemical resistance. It has all the characteristics similar to that of synthetic fiber but is obtained from a natural means. Some researchers have dealt with the basalt fibers treating it as a synthetic fiber and others have done the opposite by considering as a natural fiber.
Heat Resistance Fibers
There are several kinds of heat resistant fibers, which are selectively used according to the requirement of several applications. Such mechanical high-performance fiber as SiC fiber, alumina fiber, tungsten fiber, carbon fiber, basalt fiber, glass fiber, fiber, and p-aramid also have good or excellent heat resistance.
- Green Composites Processing, Characterisation, and Applications for Textiles Edited by Subramanian Senthilkannan Muthu and Kowloon
- Textile Progress: Fibre Materials for Advanced Technical Textiles written by T. M Atsuo