Handbook of Composites from Renewable Materials, Biodegradable Materials

Vijay Kumar Thakur, Manju Kumari Thakur, Michael R. Kessler

• Publisher: Wiley-Scrivener
• Year: 2017
• ISBN:
  9781119224396
• Edition: 1
• Topic: Tecnologia e ingegneria
• Subtopic: Ingegneria chimica e biochimica

This unique multidisciplinary 8-volume set focuses on the emerging issues concerning synthesis, characterization, design, manufacturing and various other aspects of composite materials from renewable materials and provides a shared platform for both researcher and industry.

The Handbook of Composites from Renewable Materials comprises a set of 8 individual volumes that brings an interdisciplinary perspective to accomplish a more detailed understanding of the interplay between the synthesis, structure, characterization, processing, applications and performance of these advanced materials. The Handbook comprises 169 chapters from world renowned experts covering a multitude of natural polymers/ reinforcement/ fillers and biodegradable materials.

Volume 5 is solely focused on 'Biodegradable Materials'. Some of the important topics include but not limited to: Rice husk and its composites; biodegradable composites based on thermoplastic starch and talc nanoparticles; recent progress in biocomposites of biodegradable polymer; microbial polyesters: production and market; biodegradable and bioabsorbable materials for osteosynthesis applications; biodegradable polymers in tissue engineering; composites based on hydroxyapatite and biodegradable polylactide; biodegradable composites; development of membranes from biobased materials and their applications; green biodegradable composites based on natural fibers; fully biodegradable all-cellulose composites; natural fiber composites with bioderivative and/or degradable polymers; synthetic biodegradable polymers for bone tissue engineering; polysaccharides as green biodegradable platforms for building up electroactive composite materials; biodegradable polymer blends and composites from seaweeds; biocomposites scaffolds derived from renewable resources for bone tissue repair; pectin-based composites; recent advances in conductive composites based on biodegradable polymers for regenerative medicine applications; biosynthesis of PHAs and their biomedical applications; biodegradable soy protein isolate/poly(vinyl alcohol) packaging films; and biodegradability of biobased polymeric materials in natural environment.

Chapter 1
Rice Husk and its Composites: Effects of Rice Husk Loading, Size, Coupling Agents, and Surface Treatment on Composites’ Mechanical, Physical, and Functional Properties

A. Bilal, R.J.T. Lin* and K. Jayaraman

Centre for Advanced Composite Materials, Department of Mechanical Engineering, University of Auckland, Auckland, New Zealand

*Corresponding author: [email protected]

Abstract

Among the many natural fibers used as reinforcements/fillers in the manufacture of natural fiber composite materials, rice husk (RH) has not been attracting the deserved attention despite its significant annual yield of tens of million tons due to the huge worldwide rice-consuming population. This chapter presents an introduction to natural fibers and their composites with an emphasis on RH and its use in the manufacture of composite materials. A thorough review has been carried out on the manufacturing of RH composites with various polymers and manufacturing processes. The effects of RH loading, size, surface treatment, and the use of coupling agents on mechanical, physical, and functional properties of RH composites have been discussed in detail. Although RH has also been used in the form of ash in manufacturing different composites, this chapter only focuses on RH used in its natural form and its resulting composites.

Keywords: Rice husk, coupling agents, surface treatment, composites manufacturing, mechanical, physical and functional properties

1.1 Introduction

By definition, natural fibers are fibers which are not artificial or manmade (Ticoalu et al., 2010). Natural fibers can be plant based such as wood, sisal, flax, hemp, jute, kenaf, and ramie or animal based, e.g., wool, avian feather, and silk or mineral based such as basalt and asbestos. They have been used as reinforcements with a variety of materials for over 3000 years (Taj et al., 2007) and have demonstrated immense potential to replace synthetic fibers, such as glass and carbon fibers, because of their ecofriendly and biodegradable characteristics.

There is a large variation in the properties of natural fibers, which is affected by several factors such as fiber’s place of growth, cultivation conditions, growth time, moisture content, and form (yarn, woven, twine, chopped, and felt) (O’Donnell et al., 2004; Ochi, 2008; Pickering et al., 2007). Table 1.1 shows various plant-based natural fibers and their regions or countries of origin.

Table 1.1 Fibers and their origin (Taj et al., 2007; Kim et al., 2007).

Fibers	Regions/countries of origin
Flax	Borneo
Hemp	Former Yugoslavia, China
Sun hemp	Nigeria, Guyana, Sierra Leone, India
Ramie	Honduras, Mauritius
Jute	India, Egypt, Guyana, Jamaica, Ghana, Malawi, Sudan, Tanzania
Kenaf	Iraq, Tanzania, Jamaica, South Africa, Cuba, Togo
Roselle	Borneo, Guyana, Malaysia, Sri Lanka, Togo, Indonesia, Tanzania
Sisal	East Africa, Bahamas, Antigua, Kenya, Tanzania, India
Abaca	Malaysia, Uganda, Philippines, Bolivia
Coir	India, Sri Lanka, Philippines, Malaysia
Rice husk	Asia, Pacific rim, North America

The mechanical and physical properties of natural fibers are greatly affected by their chemical composition and structure (Taj et al., 2007). The majority of plant-based natural fibers have cellulose, hemicellulose, and lignin as their main constituents along with pectin and waxes (John & Thomas, 2008). The reinforcing ability of natural fibers depends on cellulose and its crystallinity (Bledzki & Gassan, 1999, John & Thomas, 2008), whereas biodegradation, micro-absorption, and thermal degradation of natural fibers depend on hemicelluloses (Taj et al., 2007), which is hydrophilic in nature (John & Thomas, 2008). On the other hand, lignin which is hydrophobic in nature plays a critical role in protecting the cellulose/hemicellulose from severe environmental conditions such as water (Thakur & Thakur, 2014), and is thermally stable but prone to UV degradation (Olesen & Plackett, 1999); pectin gives plants flexibility, while waxes consist of various types of alcohols (John & Thomas, 2008). Each of these constituents of natural fibers plays an important role in determining the overall properties of natural fibrous materials (Thakur et al., 2014b).

These fibers are chemically active and decompose thermo-chemically between 150 °C and 500 °C (cellulose between 275 °C and 350 °C; hemicellulose mainly between 150 °C and 350 °C; and lignin between 250 and 500 °C) (Kim et al., 2004).

The relative percentages of cellulose, hemicellulose, and lignin vary for different fibers (John & Thomas, 2008). Table 1.2 shows the chemical composition of some natural fibers.

Table 1.2 Chemical composition of some natural fibers (Malkapuram et al., 2009).

Fiber	Cellulose (wt%)	Hemicellulose (wt%)	Lignin (wt%)	Pectin (wt%)	Wax (wt%)	Moisture content (wt%)
Wood	40–50	15–25	15–30	–	–	8–16
Jute	61–71.5	13.6–20.4	12–13	0.4	0.5	12.6
Hemp	70.2–74.4	17.9–22.4	3.7–5.7	0.9	0.8	10
Kenaf	31–39	21.5	15–19	–	–	–
Flax	71	18.6–20.6	2.2	2.3	1.7	10
Sisal	67–78	10–14.2	8–11	10	2.0	11
Coir	36–43	10–20	41–45	3–4	–	8
Bamboo	26–49	15–27.7	21–31	–	–	–

Generally, an increase in the cellulose content increases tensile strength and Young’s modulus of fibers, whereas stiffness also depends on the micro-fibrillar angle. Fibers are rigid, inflexible, and have ...