Chapter 1 Overview of advanced fiber materials

Abstract

Fiber-based materials have shown their important role in almost all fields of science, including energy harvesting, optics, communication, water purification, and electrocatalysis. Their abundance, flexibility, structural reformation, high surface area, tunable chemical composition, and abundant composite forms make the fiber one of the most desirable materials for current and future devices. Earlier, considerable research efforts have been carried out with natural fibers, especially in the field of textiles; however, once synthetic fibers came into the picture, they changed the scenario. Synthetic fibers are nowadays highly used in wearable devices. The network of synthetic fibers facilitates charge transportation, and their large surface makes them vibrant candidates for electrochemical application. Our daily life has utilized several types of fiber materials for a long time. In the early days, natural fibers, including loops of jute, coir, and bamboo, were utilized for several applications. However, nowadays, synthetic fibers and their composites with natural fibers play a major role in making human life easy. The advanced fiber-shaped materials can be used in various applications including electronics, sensors, catalysis, and photonics. The present chapter deals with the basics of natural and advanced fibers and their few applications. Finally, the research challenges have been discussed and the prospects of fiber materials have been proposed.

1.1 Introduction

Fibers have always been available in the history of mankind. In early days of mankind, woven textiles such as cotton, hemp, linen, silk, and wool have been used in world civilizations across the globe. Later on, synthetic fibers, nanofibers, functionalized fibers, and several fiber-based devices were developed. In the last century, fibers got a boost when silica and plastic optical fibers showed their importance in "shrinking our world" by contribution to the development of science and technology. Artificial fibers applications have been changing the world deeply day by day, and it is believed that in the future, fibers will change our daily life seamlessly. In recent days, fiber technology has been widely used in various fields, including chemistry, condensed matter physics, engineering, materials, polymer science, renewable and green energy, and so on. If one says that the present century is the cellulosic century, no one will wonder. Natural fiber comes from bioplants and is generally categorized into two types: primary fibers and secondary fibers. In the primary fiber, the fiber content is initially available in plants, that is, plants grown with fibers; whereas fiber is in the form of a by-product in secondary natural fibers [1]. Most research has been done on natural fibers, which do not cause any harmful impact on our environment, and they are relatively more economical than synthetic fibers, such as glass fibers and carbon fibers. The end application can be made more significant by making fiber composites. Fibers such as jute, sisal, coir, bamboo, banana, pineapple, etc. are primary natural fibers, and jute was the first material that attracted the interest of researchers in the early part of 1981. The interesting fact about jute fibers is that it very useful; the fibers are lightweight and economical but, at the same time, their low strength and modulus are obstacles to their use in various applications. The major uses of jute-reinforced plastics are in housing and in the manufacture of fishing boats. Much work has been carried out to overcome the limitations of jute-reinforced plastics [2]. After the utilization of jute fibers in the preparation of composites, bamboo fibers were used successfully in 1995. Bamboo fibers overcome the limitation of the mechanical properties (modulus and strength) of jute as well as that of reinforced plastics of glass fiber in a unidirectional orientation. Later on, coir fiber was introduced in 1998 [3]. Coir is a lingo-cellulosic fiber obtained from coconut trees and grows mostly in the tropical region. Its durability, wearing quality, low cost, and other factors make coir fiber to be utilized in rope making, yarn, and floor furnishing. The strength in coir fibers arises due to the presence of silica in its lingo-cellulosic matrix. Apart from that, it gets its properties such as not being brittle, nonhazardous, and ability to being disposed off easily from the lingo-cellulosic fiber. The low performance of the coir-reinforced composite is due to the reduced cellulose content along with high micro-fibrillar angle and hemicellulose content. Sisal is another natural fiber of a lingo-cellulosic material derived from the AgaveSisalana plant. The addition of the sisal fiber limits the cost of elastomers and plastics. The development of natural fibers has been shown in Figure 1.1 [3]. In the present chapter, the types of fibers and a few of their applications have been discussed, which will give a further research scope to any scholar in the natural fiber composites field.

Figure 1.1: Development of natural fibers.

1.2 Types of fibers

Fibers can mostly be classified into two categories: (1) natural fibers and (2) synthetic fibers. A few examples of natural and synthetic fibers are listed below. For better clarity, Figure 1.2 has been given; it describes the progress of natural fibers to synthetic fibers. At the same time, it is very challenging to incorporate the types of fibers in one place. Fiber types can be classified based on their application or synthesis protocol.

Figure 1.2: Progress of fiber-based materials and their potential applications.

1.2.1 Natural fibers

1.2.1.1 Jute

Jute fibers are natural fibers having structures of multi-cellulose, and are made up of random micro-fibrils and cross-sections [4]. Some plastics are fabricated using jute reinforcement, and they provide the plastic a high moisture retention capability; however, during the hybridization process, the density also increases. At the same time, it is a suitable reinforcement in plastic due to its economical cost and lightweight factor. Sometimes, the limitation of jute reinforcement is overlooked by the utilization of a feasible glass solution; however, it makes the plastic brittle and leads to enhanced erosion. Conventional glass fibers are not economical; they take in too much resin. Therefore, hybrids of jute and glass have been used, which make the composite one of higher strength and stiffness than single jute-reinforced plastics [5]. Erosion occurs at the interface of fiber and the adjacent matrix. The impingement angle plays an important role in the erosion process. It has been seen that a higher strength toward erosion has been obtained with increased hybridization of the jute fiber with synthetic-specific fabric [6]. The mechanical properties can be further enhanced by the treatment of the hybrid composites (glass fiber and jute fiber) with silane and titanate. The alkali treatment of hybrids adds some additional sites for mechanical locking and for an enhanced interfacial bonding strength [7]. The treatment of jute fiber with alkali-treated fiber shows improved mechanical properties. Bio-resin, in the presence of soya milk, has been utilized for the fabrication of jute composite, and it shows higher damage tolerance and impact strength, while these composites also being completely bio-degradable [3].

1.2.1.2 Bamboo

The high modulus of bamboo fiber, as compared to unidirectional glass-reinforced plastic, makes it appropriate for large-scale applications in various sectors of fibers. This fiber can be obtained from the bamboo tree. It is economical and environment friendly [8]. It is sometimes mentioned as natural glass fiber. Bamboo fibers have around 40% higher tensile strength than non-twisted fiber; however carious cells are found in bamboo [9]. The matrix of rubber with bamboo fiber enhances the stiffness of the composite. It has been seen that when natural rubber is used with...