JABATAN KEJURUTERAAN MEKANIKAL POLITEKNIK SEBERANG PERAI NATURAL CELLULOSICsurianis dalimin NORHAFIZAH AKMAL SUKRI FIBRES
NATURAL CELLULOSIC FIBER Surianis Dalimin Norhafizah Akmal Sukri 2023 MECHANICAL ENGINEERING DEPARTMENT ©All rights reserved for electronic, mechanical, recording, or otherwise, without prior permission in writing from Politeknik Seberang Perai.
eBook PSP | Natural Cellulosic Fiber ii All rights reserved No part of this publication may be translated or reproduced in any retrieval system, or transmitted in any form or by any means, electronic, mechanical, recording, or otherwise, without prior permission in writing from Politeknik Seberang Perai. Published by Politeknik Seberang Perai Jalan Permatang Pauh, 13500 Permatang Pauh Pulau Pinang Editor Ruhil Naznin Azaman Proofreader Norbahiah Zakaria Content Reviewer Ahmad Azlan Ahmad Cover Designer Azilah Abd Rahim Tel : 04-538 3322 Fax : 04-538 9266 Email : [email protected] Website : www.psp.edu.my FB : politeknikseberangperai Ig : politeknikseberangperai eISBN 978-967-2774-42-6 Surianis Dalimin, editor Norhafizah Akmal Sukri, editor NATURAL CELLULOSIC FIBER/ Editor Surianis binti Dalimin, Norhafizah Akmal Binti Sukri 2023 Politeknik Seberang Perai, Electronic books Textile - - Closed systems - - Open system - - Government publications - - Malaysia - -
iii eBook PSP | Natural Cellulosic Fiber Acknowledgment In the name of Allah, the most compassionate and generous. We are grateful to Allah for providing us with the courage, knowledge, talent, and opportunity to complete the writing of this eBook. Special thanks to the Head of Mechanical Engineering Department, Mr. Muhammad Nasir bin Marzuki and the Head of Course Mr. Ahmad Azlan bin Ahmad for giving us the opportunity and support to complete this eBook. Sincere thanks to Ms Ruhil Naznin Azaman for her guidance in preparing this eBook. We also would like to express our gratitude to the members of the Mechanical Engineering Department for their support and ideas in finishing the writing of the eBook. Many thanks to the director of Politeknik Seberang Perai, Mrs. Roseliza Shaari who has given her full energy in guiding the team to achieving the goals. Lastly, the appreciation goes to everyone who was directly and indirectly involved in the process of publishing this eBook. Surianis Dalimin Norhafizah Akmal Sukri
eBook PSP | Natural Cellulosic Fiber iv Preface Fiber constitutes a fundamental element in the textile sector, broadly categorized as either natural or synthetic. Nature has bestowed upon us a diverse array of natural fibers sourced from plants, animals, and minerals. One prominent category is cellulose fiber, derived primarily from plants. In pursuit of environmental sustainability, the textile industry is now increasingly reverting to the use of natural fibers in their production processes. This eBook starts with the introduction of natural cellulosic fiber. It covers the definition of natural cellulosic fiber, the cellulose family and the general characteristics. The discussion in chapter two continued with natural cellulosic fiber obtained from a seed that is cotton. It covers the cultivation, fiber production, properties and end use of the cotton. The third topic involves bast fibers such as kenaf and flax. The cultivation, fiber production, properties and end use of the two fibers are also discussed. Cellulose fiber gained from the leaf is on fourth topic. Pineapple or Pina and abaca are the two examples of leaf fibers. The discussion also covers the cultivation, fiber production, properties and end use of those fibers. It is believed that this eBook could enhance the understanding and knowledge of students regarding natural cellulosic fibers.
v eBook PSP | Natural Cellulosic Fiber Table of Content 01 Introduction to Natural Cellulosic Fiber 1.1 Definition 1.2 Cellulose Family 1.3 General characteristic 1 2 3 4 02 Seed Fiber : Cotton 2.1 Introduction of seed fiber 2.2 History of cotton 2.3 Cultivation of cotton 2.4 Fiber Production 2.5 Properties of cotton fiber 2.6 End use of cotton fiber 6 7 7 12 16 20 03 Bast Fiber : Kenaf and Flax 3.1 Introduction of bast fiber 3.2 History of kenaf 3.3 Cultivation of kenaf 3.4 Fiber Production 3.5 Properties of kenaf fiber 3.6 End use of kenaf fiber 3.7 History of Flax 3.8 Cultivation of flax 3.9 Fiber Production 3.10 Properties of flax fiber 3.11 End use of flax fiber 21 22 22 23 25 27 28 30 33 35 04 Leaf Fiber : Pina and Abaca 4.1 Introduction of leaf fiber 4.2 Cultivation of pineapple 4.3 Fiber Production 4.4 Properties of pineapple leaf fiber 4.5 End use of pineapple fiber 4.6 Cultivation of abaca 4.7 Fiber Production 4.8 Properties of abaca fiber 4.9 End use of abaca fiber 36 37 37 39 42 45 47 49 52 54 REFERENCES 55
eBook PSP | Natural Cellulosic Fiber vi
Figure 1.1 Cotton Yarn (Image source: xrplovemk.life)
2 eBook PSP | Natural Cellulosic Fiber 01 NATURAL CELLULOSIC FIBER Chapter one description This topic covers the definition of natural cellulosic fiber, the cellulose family and the general characteristics of cellulosic fiber.
2 eBook PSP | Natural Cellulosic Fiber 1.1 Definition of Natural Cellulosic Fiber In the world of textiles, natural cellulosic fibers are a harmonious partnership between humans and the plant kingdom. Natural cellulosic fiber refers to a category of textile fibers primarily composed of cellulose; a natural polymer found in the cell walls of plants. They serve as the raw material for some of the most beloved and enduring textiles in history. These fibers are extracted, processed, and spun into threads, which are then used to create a wide range of textiles, from clothing and household fabrics to industrial materials. These fibers are typically obtained from plants and trees, each with its unique properties and characteristics. Cellulosic fibers can be obtained from a plant’s stem, leaf, or seed. 1.2 The Cellulose Family Table 1.1 shows some fibers of the cellulose family. There are many other cellulosic fibers in the world. These fibers are all cellulosic, but they differ in the percentage of cellulose present and the physical structure. The arrangement of the molecular chains in these fibers is similar, it varies in orientation and length. As that, performance characteristics related to these aspects differ. Table 1.1: Fibers of the cellulose family Seed fibers Bast Fibers Leaf Fibers Fruit Fibers Cotton Flax Pina Coir Kapok Ramie Abaca Milkweed Hemp Sisal Jute Henequen
eBook PSP | Natural Cellulosic Fiber 3 1.3 General Characteristics Natural cellulosic fibers are fibers derived from plants or other biological sources that primarily consist of cellulose, a complex carbohydrate. Here are the general characteristics of natural cellulosic fibers: a. Biodegradability: Natural cellulosic fibers are biodegradable, which means they can be broken down by natural processes over time, making them environmentally friendly. b. Renewable: They are sourced from renewable resources, primarily plants. This ensures a continuous and sustainable supply of raw materials. c. Abundance: Cellulose is the most abundant organic polymer on Earth, making natural cellulosic fibers widely available. d. High Cellulose Content: These fibers are predominantly composed of cellulose, often exceeding 90% of the fiber's weight. This gives them desirable properties such as strength and durability. e. Hydrophilic Nature: Natural cellulosic fibers have a high affinity for water, meaning they can absorb and retain moisture. This property is useful in applications like textiles. f. Breathability: Fabrics made from natural cellulosic fibers tend to be breathable, allowing air and moisture to pass through, which enhances comfort for the wearer. g. Good Insulation Properties: They can provide good insulation, both in terms of thermal and acoustic properties, depending on the specific application. h. Low Thermal Conductivity: Natural cellulosic fibers generally have low thermal conductivity, making them suitable for applications where insulation against heat transfer is important.
4 eBook PSP | Natural Cellulosic Fiber i. Biocompatibility: They are generally non-toxic and biocompatible, making them suitable for medical and healthcare applications. j. Lightweight: Natural cellulosic fibers are lightweight, which is an important property in various applications like textiles and composites. k. Versatility: These fibers can be processed into a wide range of products, including textiles, paper, packaging materials, and even in some industrial applications like reinforcement in composite materials. l. Dyeability: They are generally receptive to dyes, allowing for a wide range of colors and patterns in finished products. m. Elasticity: While natural cellulosic fibers are not as elastic as some synthetic fibers like elastane, they can possess a degree of flexibility and resilience. n. Low Toxicity: Natural cellulosic fibers are typically non-toxic, which makes them suitable for a wide range of applications, including those involving direct skin contact. o. Antimicrobial Properties: Some natural cellulosic fibers, like bamboo, have natural antimicrobial properties, which can be beneficial in certain applications. It's important to note that while natural cellulosic fibers have many desirable characteristics, their properties can vary depending on factors such as the specific plant source, processing methods, and treatment techniques.
eBook PSP | Natural Cellulosic Fiber 5 Figure 1.1 Various types of vegetable fibers (Image source: textileengineering.net)
6 eBook PSP | Natural Cellulosic Fiber Figure 2.1: Cotton Boll (Image source: freepik.com)
eBook PSP | Natural Cellulosic Fiber 7 02 SEED FIBER Chapter two description This topic covers the introduction of seed fiber, the cultivation of cotton plants, the production method of cotton fiber, the properties of cotton fiber and the end uses of cotton.
8 eBook PSP | Natural Cellulosic Fiber 2.1 Introduction of seed fiber Seed fibers are natural fibers derived from the seedpod of various plants. These fibers are obtained from the outer layers or husks of seeds and possess unique characteristics that make them valuable for various industrial and commercial applications. The first step in the production of seed fibers is to separate the fiber from the seed. Soft seed fibers, such as cotton, are obtained from the seeds of the cotton plant. The cotton fibers are extracted from the seed's boll and are composed mainly of cellulose, which makes them soft, light, and comfortable. Cotton is one of the most widely used natural fibers globally, finding applications in textiles, clothing, and various other products. Other than that, milkweed fiber is also vegetable seed fiber. It is obtained from the seed’s milkweed plants (genus Asclepias). The milkweed seed pods produce a silky lightweight fuzz, called silk or floss. Soft, lustrous fibers are yellowish white. It is known as vegetable silk, milkweed floss and so on. Milkweed fibers are too brittle to spin. It is usually used for upholstery padding. Seed fibers play a significant role in sustainability and eco-friendliness due to their biodegradability and renewable sourcing. They are valued for their versatility and various applications in industries such as agriculture, textiles, manufacturing, and more. Their introduction into various products continues to expand as researchers and industries explore innovative uses for these natural, eco-friendly materials. Figure 2.1: Milkweed fiber (Image source: btwberkshires.com)
eBook PSP | Natural Cellulosic Fiber 9 2.2 History of cotton The historical roots of cotton can be traced back to its domestication, playing a pivotal role in the histories of India, the British Empire, and the United States, while remaining a crucial crop and commodity. The precise details of cotton's domestication are shrouded in complexity and remain uncertain. Various civilizations in both the Old and New Worlds independently undertook the domestication of cotton, transforming it into fabric. Alongside this process, a range of tools, such as combs, bows, hand spindles, and rudimentary looms, were invented to work with cotton. The term "cotton" finds its origins in Arabic, specifically stemming from the Arabic words "qutn" or "qutun." This was the common designation for cotton during the medieval Arabic period. It made its way into the Romance languages around the mid-12th century and subsequently entered the English language a century later. Cotton fabric was recognized by ancient Romans as an imported item, but cotton itself was a rarity in Romance-speaking regions until it began arriving at significantly lower prices from Arabic-speaking areas during the later medieval era. Human cultivation and utilization of cotton date back thousands of years, with historical evidence of cotton fabrics dating back to ancient civilizations in India, Egypt, and Peru. The cotton industry played a substantial role in the economic development of the United States, with cotton production serving as a primary source of income for slave owners in the southern United States before the Civil War. In the present day, cotton continues to hold significance as a globally important crop, with China and India standing as the largest producers. 2.3 Cultivation of cotton The cotton plant is a member of the Malvacae or Mallow family. Several species are of the gossypium genus or class. Cotton is cultivated most satisfactorily in warm, humid climates or warm climates with adequate irrigation. A primary growing requirement is a long, frostfree period of from 6 to 7 months with mild temperatures and about 12 hours of sunlight
10 eBook PSP | Natural Cellulosic Fiber each day. During actual growth either an average of 3 to 5 inches of rain a month or the equivalent through irrigation is required, followed by a dry season as fibers mature. The seeds are sown by machine in parallel rows 3 to 4 feet (0.9 to 1.2m) apart. The blossom, which appears approximately 100 days after planting, is exquisite. When it opens, it is creamy white or light yellow; by the second morning the blossom has changed to pink, lavender or red; and by the end of the second day, the flower falls, leaving the seed pod in which the fiber forms. About 50 to 80 days later the pods burst open and the fleecy cotton fibers are ready for picking. The flowers appear over a long period and thus the harvest period of mature cotton is of similar duration. Before picking, especially if mechanical pickers are used, the plants are sprayed with defoliants, which cause the leaves to shrivel and fall off. As the cotton bolls mature and open the fleecy fibers cascade out of the boll in the form of “locks” of fiber. These are ready for picking. Cotton can be picked by hand, by mechanical picking machine, or by stripping devices. Hand picking results in more uniform and better-quality cotton, because the pickers can select the mature fibers only and can repack the field as many times as it is profitable. Figure 2.2: Cotton field (Image source: travlinphoto.com)
eBook PSP | Natural Cellulosic Fiber 11 There are two types of picking machines: the picker and the stripper. The picker pulls the fibers from the open balls, whereas the stripper pulls the entire boll from the plant. The picker works best on fields with lush growth and high fiber yields; strippers are more effective on fields with low yields and long growing plants. Strippers always pull from two rows simultaneously in a “once-over” operation. Pickers are designed to pick one or two rows and can go over the fields several times each season. Figure 2.4: Cotton hand picking (Image source: cottonpickingood.wordpress.com) Figure 2.3: Cotton Picking Machine (Image source: www.farmmachinerysales.com.au)
12 eBook PSP | Natural Cellulosic Fiber 2.4 Fiber production After the cotton is picked, it is taken to the ginnery, where the fiber called cotton lint in the trade is separated from the seed. In addition to separating lint and seed, the modern gin will remove some foreign matter, such as dirt, twigs, leaves and part of bolls. The roller gin is still used for some long-staple fibers, but most cotton is ginned on the saw gin. The seeds are a valuable by-product of the cotton industry and produce cattle feed cottonseed oil. The fiber or cotton lint is packed into large bales at the ginnery. Each bale weighs about 500 pounds (227 kg) gross. Figure 2.5: Cotton gin machine (Image source: supergtrmk.live)
eBook PSP | Natural Cellulosic Fiber 13 Samples of fibers are removed from the bales and used for determining the class. Factors in this classification include the staple length, the grade and the character of the cotton. a. Staple length Staple length, which refers to the length of the lint, is determined to some degree by the variety of cotton. The cotton market recognized five classes of fiber length: 1. very short staple cotton, less than ¾ inch (1.9 cm) 2. short staple cotton, 13/16 to 15/16 inch (2.06 to 2.38 cm) 3. medium staple cotton, 15/16 to 1 1/8 inch (2.38 to 2.86 cm) 4. ordinary long staple cotton, 1 1/8 to 1 3/8 inch (2.86 to 3.5 cm) 5. extra long staple cotton, 1 3/8 inch (3.5 cm) and longer Figure 2.6: Operation diagram of Cotton-gin Machine (Image source: www.pinterest.com)
14 eBook PSP | Natural Cellulosic Fiber Figure 2.7: The cross-section and longitudinal view of cotton fiber (Image source: Understanding Textiles, Sixth Edition) b. Grade Fiber grade is based on color, amount of foreign matter present and ginning preparation. The color can vary from white to grey or yellow. Cotton may be spotted and tinged and it may be bright or dull. The spotted and tinged cotton is a frequent result of “one-time” picking in which bolls that have been opened for some time are mixed with newly opened bolls. Handpicked cotton usually has a low amount of foreign matter, whereas mechanically picked fibers can have much or little, depending on picking conditions. Figure 2.8: Raw Cotton after ginning (Image source: cottonman.com)
eBook PSP | Natural Cellulosic Fiber 15 Fibers pulled off the ground have additional dirt and soil embedded. The quality of the ginning operation influences the grade of cotton fiber. If the ginning is poorly done or incomplete, irregular, low-grade cotton results. The grade of cotton is determined by comparing the sample with standards using such factors as color and waste content. Fiber length is determined using a Digital Fibro graph for short, medium and long staple Upland varieties and the array method for extra long staple Pima and Upland varieties. c. Cotton criteria The fineness and maturity of cotton fiber are important criteria in determining the quality and contribute to yarn strength and appearance of yarn and fabrics. This can be determined by several instruments, all of which use the same scale and report the measurement as “micronire reading”. To maintain an average range of fineness, mills blend various bales of fiber to provide a consistent average fineness for the picker. Cotton is rated or evaluated based on several additional properties. These include fiber strength, uniformity, cohesiveness, pliability, elastic recovery and resiliency. When all the properties have been determined, the final quality of the cotton is registered and then used in establishing the price. 2.5 Properties of cotton fiber The properties of cotton fibers that make them unique are hydrophilicity; medium tenacity, stiffness and modulus; and low elongation and elastic recovery. As cotton fiber gets wet, it increases in tenacity and loses stiffness. Cotton fibers swell considerably in water but dry to their original dimensions. Other properties that make cotton fibers such as widely used are detailed below. Microscopic Properties Cotton fibers are composed of an outer cuticle (skin) and primary wall, a secondary wall and a central core or lumen. Immature fibers exhibit thin wall structures and a large lumen whereas mature fibers have thick walls and a small lumen that may not be continuous because the walls close the lumen in some sections. Fibers that have been swollen, as in mercerization do not show the twist as clearly as does
16 eBook PSP | Natural Cellulosic Fiber untreated fiber. Swollen fibers appear smooth and round when compared to the untreated. Immature fibers also have few convolutions. The longitudinal view of the regular fiber shows a ribbon-like shape with twists (convolutions) at irregular intervals. The diameter of the fiber narrows at the tip. The lumen may appear as a shaded area or as striations; this is more obvious in immature fibers. The cross section of the fiber usually has three areas: the outer skin, the secondary wall and the lumen. The contour varies considerably: some fibers are nearly circular, some are elliptical and some are kidney-shaped. Immature fibers are generally more irregular in contour than mature fibers. Figure 2.9: Cross sectional view of cotton fiber (Image source: Introductory Textile Science, Fourth Edition) Figure 2.10: The shape of the cotton cross section without mercerizing and after mercerizing (Image source: Introductory Textile Science, Fourth Edition)
eBook PSP | Natural Cellulosic Fiber 17 Physical Properties a. Shape Cotton fibers are fairly uniform in width – which varies between 12 and 20 micrometers and the central portion of the fiber is wider than either end. Depending on variety and growing conditions, the length of cotton fiber used in yarn and fabric manufacturing ranges from ½ inch to 2 ½ inches (2.22 to 6.35cm) with most fibers in the 7/8 to 1 ¼ inch (2.22 to 3.18cm) category. The length, fineness and uniformity of fibers aid in distinguishing the common varieties. Long staple cotton can be made into fine quality and beautiful fabrics; some have a silk like appearance. However, it is more costly to process and more difficult to cultivate than Upland varieties of short and medium staple length. b. Luster The luster of cotton is low unless finishes have been added. c. Strength Cotton has a tenacity of 3.0 to 5.0 grams per denier. This produces a fiber of moderate to above-average strength. When wet, cotton increases in strength, so it may have wet strength equal to 110 % to 120 % of its dry strength. This means that fiber care and wet processing techniques do not require modification to compensate for reduced fiber wet strength. d. Elastic recovery and elongation Cotton has elongation of 3 to 7 percent (and may be as high as 10 percent under certain conditions) at the break point. It is relatively inelastic with recovery of only 75 percent at 2 percent elongation. As 5% elongation, it exhibits less than 50 % recovery. e. Resiliency The resiliency of cotton is low. f. Density Cotton is one of the most dense of all commonly used fibers with a density of 1.54 – 1.56.
18 eBook PSP | Natural Cellulosic Fiber g. Moisture absorption The moisture regain for cotton at standard conditions is 8.5 percent. Regain at 95% relative humidity is approximately 15% and at 100% relative humidity it may absorb 25% to 27% moisture. Wet cotton is not only stronger but also more pliable and less rigid than dry cotton. Mercerized cotton fibers have been enlarged (swollen) and can absorb more moisture than nonmercerized fibers. h. Dimensional stability Cotton fibers are relatively stable and do not stretch or shrink. Cotton fabrics, however, do tend to shrink as a result of tensions encountered during yarn and fabric construction. Consequently, the fabrics require treatment to render them less susceptible to shrinkage. Thermal Properties Cotton burns readily and quickly with a smell similar to that of burning paper. It leaves a small amount of fluffy grey ash. Long exposure to dry heat above 149◦C (300◦F) will cause the fiber to decompose gradually and temperatures greater than 246◦C (475◦F0 will cause rapid deterioration. Normal exposure to heat encountered in routine care and processing will not damage cotton but it will scorch if ironed with too-high temperatures. Finishes, such as starch, increase the tendency to scorch. Chemical Properties a. Effect of alkaline Cotton is highly resistant to alkalis. They are used in finishing and processing the fiber. Most detergent and laundry aids are alkaline, so the cotton can be laundered in these solutions with no fiber damage. b. Effect of acid Strong acids destroy cotton and hot acid will cause disintegration. Cold diluted acids cause gradual fiber degradation but the process is slow and may not be immediately evident.
eBook PSP | Natural Cellulosic Fiber 19 c. Effect of organic solvent Cotton is highly resistant to most organic solvents and to all those used in normal care and stain removal. It is however soluble in such compounds as cuprammonium hydroxide and cupriethylene diamine; these solvents therefore are used for chemical analysis of cotton. d. Effect of sunlight, age and miscellaneous factors Prolonged exposure to sunlight will cause the cotton fiber to become yellow and will gradually cause degradation. This damage is accentuated in the presence of moisture, some vat dyes and some sulphur dyes. If properly stored, cotton will retain most of its strength and appearance over a long period. Cotton fabrics should be stored in dark and dry areas. Figure 2.11: Process of drying clothes under the sunlight. (Image source: treasuredgarmentrestoration.com)
20 eBook PSP | Natural Cellulosic Fiber Biological Properties a. Micro-organisms Cotton is damaged by fungi such as mildew and bacteria. Mildew will produce a disagreeable odor and will result in rotting and degradation of cotton. Certain bacteria encountered in hot, moist and dirty conditions will cause decay of the fiber. b. Insects Moths and beetles will not attack or damage cotton. Silverfish will eat cotton cellulose, especially if heavily starched. 2.6 End use of cotton fiber Cotton has many uses, across several different industries. a. Woven fabrics. Cotton is used to make a variety of woven fabrics, including canvas, denim, damask, flannel, and more. b. Clothing. Cotton is a fixture of the textile industry as a result of its mass production, soft feel, durability, and absorbency. Cotton is frequently used for T-shirts, blue jeans, dresses, sweats, and so much more. c. Bed sheets and towels. Since cotton is extremely soft and absorbent, it is an ideal fabric for bedroom linens and towels needed to sop up moisture. d. Underwear. For the same reasons, cotton makes comfortable and durable undergarments. e. Home decor. Cotton is also used throughout the home for upholstery, curtains, rugs, pillows. f. Cottonseed oil. Cottonseed is a byproduct of the cotton production process, and the seeds are used to manufacture cottonseed oil, which is used for salad dressing and margarine. It can also be used in makeup, soap, candles and more.
eBook PSP | Natural Cellulosic Fiber 21 Fabric Care Guide for Cotton: a. Cotton can be machine-washed or dry cleaned, and the instructions vary based on the color of the fabric and its composition (such as a cotton blend). Make sure to check the label for washing instructions. b. Pretreat any stains before washing. c. Wash like colors together to prevent any bleeding. Darker colors should be washed in cold water, while lighter colors can be washed on a warm or cool cycle. d. Bleach can be used on cotton. e. Cotton does tend to shrink, so if you are sewing with cotton, make sure to pre-wash your fabrics.
22 eBook PSP | Natural Cellulosic Fiber Figure 3.1: Bundle of flax (Image source: exhibitions.psu.edu)
eBook PSP | Natural Cellulosic Fiber 23 03 BAST FIBER Chapter three description This topic covers the introduction of bast fiber, the cultivation of kenaf and flax plants, the production method of kenaf and flax fiber, the properties of kenaf and flax fiber and the end uses of both fibers.
24 eBook PSP | Natural Cellulosic Fiber 3.1 Introduction of bast fiber Bast fibers are natural plant-based fibers derived from the phloem or inner bark of certain plants. These fibers are known for their strength, flexibility, and durability, and they have been utilized by humans for various purposes for thousands of years. The term "bast" refers to the tissues that provide structural support to the plant and help in the transportation of nutrients. Plants that yield bast fibers typically have strong, fibrous bundles in their stalks or stems. These fibers are obtained by separating the outer bark or other layers of the plant, often through a process called retting, which involves soaking the plant material to break down the non-fibrous tissues and allow for easier extraction of the fibers. The extracted fibers are then processed and spun into threads or yarns for use in a wide range of applications. Various plants provide bast fibers, with some of the most commonly known being flax, hemp, jute, ramie, and kenaf. Each of these fibers has distinct characteristics and applications. For instance, flax is known for its fine, lustrous fibers and is used in the production of linen, while hemp fibers are strong and versatile, suitable for textiles, ropes, and even composite materials. Bast fibers have been historically used in the manufacturing of textiles, ropes, twines, and even in paper production due to their strength and durability. Additionally, these fibers have gained attention in modern industries for their eco-friendly nature, as they are renewable, biodegradable, and require fewer chemicals and pesticides during cultivation compared to synthetic materials. The introduction and utilization of bast fibers in various industries continue to evolve as researchers and manufacturers explore new ways to incorporate these natural fibers into products, recognizing their sustainability and diverse applications in sectors such as textiles, construction, automotive, and even biodegradable packaging solutions.
eBook PSP | Natural Cellulosic Fiber 25 3.2 History of kenaf Kenaf is an annual spring crop, that has been cultivated for an extended period. Its domestication and early usage began in northern Africa, where it is sometimes referred to as Guinea hemp. While its origins are rooted in Africa, the use of this fiber has spread globally. The ancient Egyptians were cultivating kenaf 3000 years ago and even consumed its leaves. Additionally, it was utilized as animal feed. For approximately 200 years, India has been producing and using kenaf. Russia commenced kenaf production in 1902 and introduced the crop to China in 1935. Southern Europe saw the introduction of the kenaf crop in the early 1900s. It is predominantly grown in India, China, the United States of America, Mexico, and Senegal. Kenaf remained unfamiliar in the West until the late 18th century when products like cordage and sacking made from fiber were brought to Europe. Initially considered a less significant material for bagging, its importance heightened during World War II due to shortages of jute and other bagging fibers. This led to increased interest in kenaf, which continued post-war as established materials remained scarce and prices surged. Despite some producers experiencing a notable decline in 1999, the production of kenaf has generally remained steady in recent years. Presently, India, Bangladesh, China, Myanmar, Nepal, and Thailand stand as major kenaf producers, with India, Bangladesh, and China being the largest among them. Image 3.2: Kenaf plant (Image source: naturalfibersinfo.org)
26 eBook PSP | Natural Cellulosic Fiber 3.3 Cultivation of kenaf Kenaf fiber is a natural fiber derived from the plant Hibiscus cannabinus, commonly known as kenaf. Kenaf is a tall annual plant and is cultivated primarily for its fibrous material. Kenaf fiber is obtained from the outer bast or bark of the plant. It is a long and coarse fiber known for its strength and versatility. The fiber extraction process involves separating the outer bark from the inner core of the plant, followed by further processing to clean, soften, and prepare the fibers for various industrial applications. The fiber is long, light yellow to gray, and harder and more lustrous than jute. Kenaf could be blended with cotton made into yarn and woven into fabrics. Kenaf is a warm-season annual row crop in the same plant family as okra and cotton (Malvaceae). Kenaf plants are capable of growing to a height of 20 feet under favorable conditions, and may or may not develop branches, depending on the cultivar, seed spacing and growing conditions. However, heights generally average 8 to 14 feet in a growing season of 4 to 5 months and produce 6 to 10 tons of dry matter per acre within five to eight months after planting. a. Soil and climate Image 3.3: Kenaf plant and flowers (Image source: www.kvgsb.com)
eBook PSP | Natural Cellulosic Fiber 27 The kenaf plant can grow in different kinds of soils. It can also grow in different climatic conditions and environments. The kenaf reaches maximum growth in tropical and subtropical areas. It requires a field where rainwater doesn't accumulate. It achieves the best growth in neutral soil. The sandy loam soil is considered the best suited soil for the kenaf crop. This crop needs continuous rainfall of 50 CMS to 65 CMS per month over the growing season. The digs well around 20 CMS to 40 CMS depth. The kenaf seeds sow when the soil temperature reaches to 15 °c - 16 °c. b. Sowing and planting To obtain the highest yields of fiber, Kenaf should be planted as early, as possible at the beginning of the rainy season. The flowering should get started when day gets 2.5 smaller than night. The kenaf stems achieve maximum length in this period. The maximum yield of kenaf fibers is obtained. Normally, the seeding is done in April and May. The following takes place in September and October. The kenaf are planted very closely to each other. The seeding of kenaf is done in a row. The plant-to-plant distance is kept at 2 inches. The row-to-row distance is kept at 8 - 12 inches. c. Use of fertilizers The kenaf plant needs some fertilizers to improve the plant's growth. Nitrogen, potash and phosphorus help to improve the plant's growth. The potash helps to maximize the thickness of the bark of the stem. The phosphoric acid helps to increase the number of fiber bundles. The nitrogen accelerates the growth of the plant. 3.4 Fiber Production a. Harvesting: The harvest method depends on the production location, equipment availability, processing method, and final product use. Kenaf crops can be harvested with both hand and machine harvesting. Plant are harvested for their stalk from which the fiber is extracted. Mainly, there are two methods of harvesting fibers, which are hand harvesting
28 eBook PSP | Natural Cellulosic Fiber and using whole stalk harvesters. In hand harvesting, the process starts from harvesting manually. The plant will be cut near the ground level with a sickle or a curved blade. This harvesting process has been used in the last 6000 years ago, and therefore it is the most traditional way of harvesting. This method requires human labor and is timeconsuming. The other method of harvesting and extraction is by using Kenaf Whole Stalk Harvesters. In this method, harvesting could be summarized into three steps which start with pulling and windrowing, followed by retting, and finally balling parallel stalks. Currently, there are two types of harvesters available in the market which are the Sugarcane-type harvesters and forage-type harvesters. Once the kenaf stalks are harvested and the outer fiber is separated it goes through a refinement or combing process making the fiber finer and finer. It is an economic advantage to use presently available commercial harvesting equipment, if possible rather than investing in the development and production of kenaf specific equipment. Figure 3.4: Kenaf harvesting (Image source: uky.edu/ccd/production/crop-resources)
eBook PSP | Natural Cellulosic Fiber 29 b. Retting: After harvesting, it will undergo a retting process to extract the fibers. Currently, four types of retting processes have been used which are biological retting (dew retting, water retting, enzyme retting), mechanical retting (using decorticator), chemical retting, and physical retting. 1. Biological Retting: In biological retting, the dew retting was carried out by spreading out the stalks on the field and exposing them to the rain, sun and dew for several weeks until the stalks begin to separate from the fiber naturally. Due to the long exposure to natural conditions, fibers tend to lose their original color and turn brown. Furthermore, this method reduces the fiber's strength and quality. Water retting involves tying several bundles of stalks and immersing them in streams or water of at least 60 cm in depth. This process usually takes around 2 weeks until the bast fibers naturally separate from the core fibers. These bundles were then taken out of the water and left to dry. Finally, enzyme retting is the safest and fastest process of retting, where the core fibers can be taken out from the bast fibers after several hours. Some examples of enzymes that have been used are pectinase and xylanase. 2. Mechanical Retting: The second type of retting process is mechanical retting which uses Kenaf decorticators. A decorticator is a machine that can separate the bast and core fibers for further processing. It could ensure that the fiber will not be damaged while being extracted. Some of the components of this machine are the frame (to hold all the components), knife (to cut the stalks), knife plate (to hold the knife in place), feeding mouth and security cover (to place the stalks into the machine with safety), and much more. The decorticator machine works by feeding the stalks into the feeding mouth, and then the stalks will be sent to the beaters to be crushed. The crushed stalk that contains both bast fiber and core fiber will be pushed into the delivery plate. Finally, the bast fiber will be separated from the crushed core fiber manually.
30 eBook PSP | Natural Cellulosic Fiber 3. Chemical Retting: The third process which is chemical retting is a process where the stalks are treated with acid and alkalis to remove the core fibers easily from the bast fibers. In this method, the stalks are boiled with chemicals such as sodium hydroxide, sodium benzoate, and hydrogen peroxide, at a specific temperature for several hours, and then washed with clean water. The fibers obtained from this method usually felt coarser and rough compared to other methods. 4. Physical Retting: The last process for fiber extraction is Physical retting. This process involves two steps which start with modifying the surface/volume ratio of fibers through chemical pre-treatment. Then, the stalks will be subjected to a steam explosion where the fibers will be blown apart and separated. In this method, the water will be vaporized completely and increased in volume and it requires a small amount of processing time. However, this method could only produce short fibers. Figure 3.5: Kenaf retting process (Image source: www.kvgsb.com)
eBook PSP | Natural Cellulosic Fiber 31 c. Drying: After the retting process, the bast fibers are taken out from the core fibers and washed with clean water for drying them. Different methods could be applied for the drying of kenaf to a moisture content that allows the storage of the harvested biomass. The different methods that are described are: drying in the field, drying in the storage, and drying in industrial installations. When weather conditions are bad, artificial drying can also be required to reach the low moisture content to avoid mold growth and losses during long storage by natural or forced ventilation. d. Fiber Separation Once the kenaf stalks are dried, the next step involves separating the fibers from the woody core. This can be done through a process known as 'decorticating' or Figure 3.6: Kenaf drying process (Image source: www.kgvsb.com)
32 eBook PSP | Natural Cellulosic Fiber 'scutching,' which involves breaking and scraping away the non-fibrous parts of the plant. e. Cleaning and Finishing: The extracted fibers might still contain impurities or shorter fibers. Further cleaning and refining processes are carried out to remove these impurities and achieve a more consistent, higher-quality fiber. This can involve additional combing, washing, and drying to prepare the fibers for use. f. Spinning or Processing into Yarn: The refined kenaf fibers are spun or processed into yarn through spinning equipment. This step is crucial in preparing the fibers for various applications, including textile production. g. Further Utilization: The processed kenaf fibers can be used in a wide range of products, such as textiles, rope, twine, paper, and composite materials. The fibers can also be blended with other materials, like cotton or synthetic fibers, to create new materials with different characteristics. The processing of kenaf fiber involves a series of steps, each crucial in transforming the raw plant material into usable fibers for various industrial and commercial applications. The process may vary depending on the intended use of the fibers and the specific requirements of different industries.
eBook PSP | Natural Cellulosic Fiber 33 3.5 Properties of kenaf fiber Kenaf fiber has several properties that make it suitable for various applications. Here are some key properties of kenaf fiber: a. Natural and Renewable: Kenaf is a natural fiber derived from the kenaf plant, making it a renewable resource. The plant grows quickly and requires minimal pesticides and fertilizers. b. Lightweight: Kenaf fibers are lightweight, which makes them suitable for applications where weight is a critical factor, such as in the automotive and aerospace industries. c. High Tensile Strength: Kenaf fibers exhibit good tensile strength, which refers to their ability to withstand pulling forces. This property makes them suitable for reinforcing composites and materials. d. Biodegradable: Kenaf fibers are biodegradable, meaning they can be broken down by natural processes over time. This is an environmentally friendly feature, especially when considering end-of-life disposal. e. Good Moisture Absorption: Kenaf fibers have a relatively high moisture absorption capacity, which can be advantageous in applications where moisture management is important, such as in textiles. f. Low Density: The low density of kenaf fibers contributes to the overall lightweight nature of products made from kenaf composites. This is particularly beneficial in applications where weight reduction is a priority. g. Thermal Insulation: Kenaf fibers have good thermal insulation properties, making them suitable for applications where thermal comfort is important. This property is relevant in products such as insulation materials. h. Good Acoustic Properties: Kenaf fibers can contribute to good acoustic insulation, making them useful in applications where sound absorption is desired, such as in the automotive industry.
34 eBook PSP | Natural Cellulosic Fiber i. Versatility: Kenaf fibers can be used in various forms, including as raw fibers, mats, or as part of composite materials. This versatility allows for a range of applications, from textiles to automotive components. j. Economical and Sustainable: Kenaf is often considered an economically viable and sustainable alternative to other natural fibers. Its rapid growth and low environmental impact contribute to its appeal in various industries. Physical Properties of Kenaf Fiber The physical properties of kenaf fiber refer to characteristics that can be observed or measured without altering the fiber's chemical composition. These properties play a crucial role in determining the suitability of kenaf fiber for various applications. Here are some key physical properties of kenaf fiber: a. Length: Kenaf fibers are known for their relatively long length compared to some other natural fibers. The length of kenaf fibers can vary, but they are generally in the range of 1 to 3 meters. Longer fibers are often desirable for improving the mechanical properties of composites and textiles. b. Diameter: The diameter of kenaf fibers is relatively small, typically in the range of 10 to 30 micrometers. The fine diameter contributes to the flexibility and softness of the fibers. c. Color: Kenaf fibers exhibit natural variations in color, ranging from light brown to cream. The color can be influenced by factors such as the age of the plant and the specific processing methods used. In applications where color is a critical factor, the natural hues of kenaf fibers may be considered. d. Density: Kenaf fibers have a relatively low density, contributing to the lightweight nature of materials made from these fibers. The low density is particularly advantageous in applications where weight reduction is important, such as in automotive components. e. Moisture Content: The moisture content of kenaf fibers can impact their weight and performance in certain applications. Moisture absorption can affect the dimensional stability of kenaf-based products, and it is an important consideration in applications where moisture resistance is essential.
eBook PSP | Natural Cellulosic Fiber 35 f. Thermal Conductivity: Kenaf fibers have moderate thermal conductivity. This property can be relevant in applications where thermal insulation is important, such as in building materials or insulation products. g. Elasticity: Kenaf fibers exhibit a degree of elasticity, which can contribute to their flexibility. This property is relevant in applications such as textiles, where flexibility is desirable. h. Tensile Strength: Tensile strength measures a material's resistance to a force pulling it apart. Kenaf fibers generally have good tensile strength, making them suitable for reinforcing composites and textiles. i. Abrasion Resistance: The resistance of kenaf fibers to abrasion is an important consideration in applications where the material may be subjected to wear and friction, such as in textiles or composite materials used in automotive components. j. Flammability: The flammability of kenaf fibers can vary, but in general, natural fibers like kenaf are less prone to burning compared to some synthetic fibers. Flame-retardant treatments can be applied to enhance fire resistance. Understanding these physical properties is essential for selecting and optimizing the use of kenaf fibers in different applications, ranging from textiles and paper products to automotive components and building materials. Microscopic Properties of Kenaf fiber. It's important to note that the specific properties of kenaf fiber can vary depending on factors such as the cultivation conditions, processing methods, and the part of the plant from which the fiber is extracted. The microscopic properties of kenaf fiber provide insights into its structure at the cellular level. Kenaf fibers are derived from the bast (or phloem) of the kenaf plant's stalk, and they consist of complex arrangements of cells. Here are some key microscopic properties of kenaf fiber: a. Cellular Structure: Kenaf fibers are composed of individual cells that are elongated and have a tubular shape. These cells are known as fiber cells or bast cells. The elongated structure contributes to the overall length of the fiber.
36 eBook PSP | Natural Cellulosic Fiber b. Cell Wall Composition: The primary structure of kenaf fiber cells consists of a cell wall, which is composed of various components. The cell wall typically includes cellulose, hemicellulose, and lignin. Cellulose provides strength, hemicellulose contributes to flexibility, and lignin acts as a binder. c. Cellulose Microfibrils: Cellulose microfibrils are aligned in a parallel fashion within the cell walls of kenaf fibers. This alignment contributes to the fiber's strength and stiffness. d. Lumen: The central part of the kenaf fiber cell is called the lumen. It is a hollow space within the fiber. The presence of a lumen contributes to the lightweight nature of kenaf fibers. e. Fiber Bundles: In the plant's stalk, kenaf fibers are often found in bundles, also known as fiber bundles or strands. These bundles are composed of individual fibers held together by natural bonding agents. f. Cellulose Crystallinity: The degree of crystallinity in the cellulose structure of kenaf fibers affects its mechanical properties. Higher crystallinity generally contributes to increased strength and stiffness. g. Pectin and Extractives: In addition to cellulose, hemicellulose, and lignin, kenaf fibers may contain pectin and extractive substances. Pectin contributes to the flexibility of the fibers, and extractives can include various compounds such as waxes and resins. h. Microscopic Variability: The microscopic properties of kenaf fibers can vary depending on factors such as the age of the plant, the specific part of the stalk from which the fibers are extracted, and the processing methods used. Younger fibers may have different properties compared to more mature fibers. Understanding these microscopic properties is essential for optimizing the processing and utilization of kenaf fibers in various applications, such as textiles, composites, and paper products. Researchers and industry professionals often analyze these properties to tailor the material for specific uses and to enhance its overall performance.
eBook PSP | Natural Cellulosic Fiber 37 Image 3.7: Photomicrograph of kenaf fiber bundle (Image source: Understanding Textiles, Sixth Edition) 3.6 End use of kenaf fiber Kenaf fiber has a wide range of end uses due to its versatile and advantageous properties. Here's a detailed explanation of its various end uses: a. Textiles and Fabrics: • Kenaf fibers are spun into yarns and used in textile manufacturing. • They're blended with other fibers (like cotton, wool, or synthetic fibers) to create fabrics used in clothing, upholstery, and household textiles. • The resulting fabric is similar to cotton in texture and appearance, making it suitable for items like clothing, canvas, bags, and more. b. Paper Products: • Kenaf fibers are extensively used in the paper industry for making various types of paper products. • The long and strong fibers contribute to the production of high-quality papers such as newsprint, writing paper, cardboard, tissue paper, and specialty papers.
38 eBook PSP | Natural Cellulosic Fiber • Kenaf's high cellulose content and favorable fiber length make it a sustainable alternative to traditional wood pulp in paper production. c. Biodegradable Products: • Kenaf fibers are employed in creating biodegradable products such as bioplastics and environmentally friendly packaging materials. • These biodegradable materials offer an eco-friendly alternative to conventional plastics and help reduce environmental impact. d. Building and Construction Materials: • Kenaf fibers are used as reinforcement in composite materials for construction purposes. • They're utilized in making boards, panels, door cores, and other building materials due to their lightweight, durability, and insulating properties. • These materials find applications in interior partitions, furniture, automotive components, and other construction-related products. e. Insulation: • Kenaf fibers are used in insulation materials for buildings, providing good thermal and sound insulation properties. • They're incorporated into insulating materials for walls, ceilings, and other structures, contributing to energy efficiency and comfort. f. Soil Erosion Control: • Kenaf fibers are used in erosion control applications such as mats and blankets. • These mats and blankets are used on slopes, riverbanks, and areas prone to erosion to stabilize soil and facilitate vegetation growth, thereby preventing soil erosion.
eBook PSP | Natural Cellulosic Fiber 39 g. Animal Bedding: • Due to their absorbent nature, kenaf fibers are suitable for animal bedding. • They are used as bedding material for animals like horses, poultry, and other livestock, providing comfortable and hygienic bedding options. These varied end uses of kenaf fiber across industries showcase its versatility and ecofriendly attributes, making it a valuable and sustainable material in today's market.
40 eBook PSP | Natural Cellulosic Fiber 3.7 History of Flax During prehistoric times, flax had the broadest geographical distribution among fiberbearing plants. Evidence from archaeology reveals that stems of the flax plant were initially used for basket making long before flax fiber became employed for cloth. Techniques for separating the long fibers from flax stems were developed subsequently. Initially gathered from the wild, the cultivation of flax quickly expanded across the Middle East, Northern Africa, and Europe. Egypt's hot and arid climate has preserved samples of both coarse and fine linen materials dating back to 4000 B.C. Additionally, linen fabrics believed to be approximately 7,000 years old have been unearthed from dried-out lake mud in prehistoric Swiss villages. The colder climates of northern regions were unsuitable for cotton cultivation but favorable for flax growth. Consequently, linen fabrics were widely utilized for many purposes that are now commonly fulfilled by cotton. The extensive use of linen is evident in ongoing terminology, such as bed linens or table linens. However, contemporary bed linens and table linens are frequently made from fibers other than flax. Figure 3.8: Farm Workers Lay out Flax to be Field Retted (Image source: www.thoughtco.com)
eBook PSP | Natural Cellulosic Fiber 41 Interest in linen surged in the early 1990s due to ecological concerns among consumers, as flax cultivation is largely free from herbicides and pesticides. Although flax for fibers is not cultivated in the United States, the country imports linen fibers, yarns, fabrics, and finished garments. Experimental cultivation of flax is underway domestically, alongside research into new processing methods. Specific statistics regarding the quantity of finished fabrics and manufactured goods are challenging to obtain, as economic data for all hard or leaf fibers (such as sisal) and bast fibers (such as linen and ramie) are aggregated. However, linen's global share in fiber consumption remains around 2 percent. Leading exporters of linen include Poland, Ireland, Belgium, China, France, Spain, Italy, Egypt, and the former Soviet Union countries. 3.8 Cultivation of flax The botanical name of the flax plant is Linum usitatissimum. Usitatissimum is Latin for "most useful." Before cotton was available in Western Europe, linen was used extensively in household textiles, for practical and washable garments, and for tents and sails for boats. Its many uses are reflected in the Latin name given to the plant. Some varieties of the plant are grown for fiber, whereas others are grown for seeds. The plant grows to a height of 2 to 4 feet. The varieties grown for fiber have long stems, with few branches and seeds. Figure 3.9: Flax plant (Image soure: exhibitions.psu.edu)
42 eBook PSP | Natural Cellulosic Fiber In most countries, the flax crop is sown in the early spring. The plant thrives best in temperate climates with adequate rainfall. Harvesting is done about 80 to 100 days after sowing when about onehalf of the seeds are ripe and leaves have fallen from the lower two-thirds of the stem. In those countries where inexpensive labor is readily available, flax is still harvested by hand, but in developed countries, much of the labor of flax pulling is now done by machine. Whether done by hand or machine, the flax plant is pulled completely from the ground. Removing plants from the ground retains as long a stem as possible and prevents discoloration of fibers through wicking. Stalks are dried sufficiently so that they can be threshed, combed, or beaten to remove the flax seeds, which are used for sowing future crops or for making linseed oil or livestock feed. Figure 3.10: Harvestable flax crops (Image source: exhibitions.psu.edu)