MURSHID IMAN and TARUN K. MAJI

ABSTRACT

Modern scenario about the conservation of natural resources and recycling has led to the renewed interest concerning biomaterials with the focus on renewable raw materials. The use and removal of traditional composite materials usually made of glass, carbon, aramid fibers being reinforced with unsaturated polyester, epoxy or phenolics are considered crucially due to increasing global awareness and de­mands of legislative authorities. Therefore, the growing awareness of the pressing need for greener and more sustainable technologies has focused attention on use of bio-based polymers instead of conventional petroleum based polymers to fabricate biodegradable materials with high performance. Another aspect, which is receiving more attention, is the use of alternate resource prior to the use of the conventional materials. The important aspect of composite materials is that they can be designed and tailored to meet different desires. Natural fibers such as hemp, ramie, jute, etc. are cheap, biodegradable and most importantly easily available worldwide. The bio composites prepared by using natural fibers and varieties of natural polymers such as soy flour, starch, gluten, poly(lactic acid), etc. have evoked considerable inter­est in recent years due to their ecofriendly nature. These natural polymers have some negative aspects also. Thus modification by cross-linking, grafting, blending and inclusion of nanotechnology provide desired properties and widen the spectrum of applications of bio composites. Biocomposites offer modern world an alterna­tive solution to waste-disposal problems associated with conventional petroleum based plastics. Therefore, the development of commercially viable “green products” based on natural fibers and polymers for a wide range of application is on the rise. Moreover, using nanotechnology for the synthesis of biocomposites provide better mechanical properties and thermal stability. In short, the use of bionanocomposites may provide us a healthier environment owing to its multifaceted advantages over conventional polymers. This chapter discusses on the potential efficacy of natural

polymers and its various derivatives for preparation of biocomposites to be used for varieties of applications.

17.1 INTRODUCTION

With the advancement of science and technology, the people of the current civilized world are becoming more dependent on the advanced materials. In this regard, the chemist from all over the world has contributed a lot for the modernization of our society. One of such major gift-that chemist has ever bestowed to the human society is the “polymer” or “polymeric materials” without which the world have been in a totally different situations. However, as the environmental and health effects of a chemical or chemical process have begun to be considered, therefore, there has been an expanding search for new materials with high performance at affordable costs in recent years. With growing environmental and health awareness, there has been a significant focus within the scientific, industrial, and environmental communities on the use of ecofriendly materials, with terms such as “renewable,” “recyclable,” “sus­tainable,” and “triggered bio-degradable” becoming buzzwords. The development or selection of a material to meet the desired structural and design requirements calls for a compromise between conflicting objectives. This can be overcome by resorting to multiobjective optimization in material design and selection. Composite materials, which are prepared using natural reinforcements and a variety of renew­able matrix, are included in this chapter.

Since, most of the renewable materials are associated with bio-logical and plant based products as a source of raw materials, particularly to plastic industries, and these could generate a non-food source of economic development for farming and rural areas in developing country. The development of such materials has not only been a great motivating factor for materials scientists, but also an important provider of opportunities to improve the living standard of people around the world. This can also provide a potential for economic improvement based on these materials even though major thrust for their use has been driven by the needs in industrialized coun­tries. For example, natural fibers such as jute, sisal, hemp, pineapple, etc., whose ex­traction is an important process that determines the properties of fibers, can generate rural jobs since those fibers have established their potential as reinforcing fillers in many polymers, and products based on these have found increasing use on a com­mercial scale in recent years.131 Another example for the generation ofjobs by agro­based materials is provided by the use of rice husk, which constitutes more than 10% of a world rice production. These examples underline not only the development of new materials, but also the possible generation of additional employment through the collection, transportation and development of new materials. It is reported that increasing use of renewable materials would create or secure employment in rural areas, the distribution of which would be agriculture, forestry, industry, etc.

The use of natural polymers was superseded in the twentieth century as a wide- range of synthetic polymers was developed based on raw materials from low cost petroleum. However, since 1990s, there is a simultaneous and growing interest in developing bio-based products and innovative process technologies that can reduce the dependence of fossil fuel and move to a sustainable materials basis. The main reasons for development of such material are stated below:32

1. Growing interest in reducing the environmental impact of polymers or com­posites due to increased awareness to ecofriendliness;

2. Finite petroleum resources, decreasing pressures for the dependence of pe­troleum products with increasing interest in maximizing the use of renew­able materials; and

3. The availability of improved data on the properties and morphologies of natural materials such as lignocellulosic fibers, through modern instruments at different levels, and hence better understanding of their structure-proper­ty correlations.

These factors have greatly increased the understanding and development of new materials such as biocomposites.

Commodity polymer-based composite materials are now well established all over the world. Because of their high specific strength, modulus and long durabil­ity compared to conventional materials such as metals and alloys, these materials have found wide applications. However, the use of large volumes of polymer-based synthetic fiber composites in different sectors has led to disposal problems. There­fore, scientists have been looking for the reduction of such environmentally abusive materials, and triggering greater efforts to find materials based on natural resources in view of the letter’s ecofriendly attributes. Such natural resources are organic in nature and also a source for carbon and a host of other useful materials and chemi­cals, particularly for the production of “green” materials.1’56’22’33

In parallel, researchers have focused their works on the processing of nano­composites (materials with nanosized reinforcement) to enhance mechanical prop­erties. Similar to traditional microcomposites, nanocomposites use a matrix where the nanosized reinforcement elements are dispersed. The reinforcement is currently considered as a nanoparticle when at least one of its dimensions is lower than 100 nm. This particular feature provides nanocomposites unique and outstanding prop­erties never found in conventional composites. Bio-based nanocomposites are the next generation of materials for the future.