Abou El Kacem Qaiss, Rachid Bouhfid, and Hamid Essabir

Contents

14.1 Introduction………………………………………………………………………………………………….. 226

14.2 Natural Fiber Characterizations……………………………………………………………………………. 227

14.3 Processing Techniques for Polymer Composites……………………………………………………….. 228

14.4 Problematic…………………………………………………………………………………………………… 231

14.5 Mechanical Properties………………………………………………………………………………………. 233

14.5.1 Tensile Properties………………………………………………………………………………. 235

14.6 Dynamic Mechanical Thermal Analysis………………………………………………………………….. 236

14.7 Interface Fiber/Matrix……………………………………………………………………………………….. 238

14.7.1 Techniques to Improve the Interface Adhesion……………………………………………… 238

14.8 Conclusions and Future Perspective………………………………………………………………………. 243

References ………………………………………………………………………………………………………….. 244

Abstract Natural fibers have recently become attractive to researchers, engineers, and scientists as an alternative reinforcement for fibers-polymer matrix composites. This interest comes from the combination of several advantages of natural fibers such as low cost, low density, non-toxicity, high specific properties, no abrasion during processing, and the possibility of recycling. The lack of compatibility between hydrophilic fibers and hydrophobic polymers (thermoplastics and thermo­sets), results a poor interfacial adhesion, which may negatively affect the final prop­erties of the resulting composites. The tensile properties of composites based on natural fibers are mainly influenced by the interfacial adhesion, dispersion/distribu — tion of fibers, and fibers loading. Several chemical modifications are used to enhance the interfacial adhesion resulting in an improvement of thermal and mechanical properties of the composites. This chapter presents a description of the natural fiber

A. Qaiss (*) • R. Bouhfid • H. Essabir

Moroccan Foundation for Advanced Science, Innovation and Research (MAScIR), Institute of Nanomaterials and Nanotechnology (Nanotech), Rabat, Morocco e-mail: a. qaiss@mascir. com

K. R. Hakeem et al. (eds.), Biomass and Bioenergy: Processing and Properties,

DOI 10.1007/978-3-319-07641-6_14, © Springer International Publishing Switzerland 2014 reinforcement composites/polymer matrix, and the context for the development and use of these products. The fibers used as reinforcement of thermoplastics matrix are Alfa, Doum, Pine cone, Hemp, Coir, and Bagasse. The knowledge of the structure and chemical composition of each component is required to understand the study of interactions between the reinforcing fibers and matrix.

Keywords Natural fibers • Matrix • Thermal properties • Mechanical properties • Interfacial properties

14.1 Introduction

In recent years, the polymer materials are widely used in various applications, such as automotive, construction, aerospace, and sports, the most important polymer benefits are ease in processing, the productivity and reduce costs. Fibers reinforced polymers matrix, such as aramid, basalt, carbon, and glass fibers are most com­monly used in industry applications due to their low cost, ease of production, and their important specific mechanical properties (Ku et al. 2011; Wambua et al. 2003; Pickering et al. 2007). However, the problem encountered in the use of these materi­als is their negative impacts to humans and the environment. Although, addition of renewable resources as reinforcement in materials composite is becoming more frequent (Beckermann and Pickering 2008; Torres and Cubillas 2005). Markets are becoming more oriented to demand more environmentally friendly products. Natural fibers are now promising as replacements for usual synthetic fibers for various applications such as aerospace, automotive parts and applications of high perfor­mance, etc. (Ofomaja and Naidoo 2011; Yanjun et al. 2010). The industry of natural fiber composite has widely invaded the world; the automotive industry is the prime driver of “green composites” because the industry is faced with issues for which green materials offer a solution. These new materials are called eco-materials, bio-composites, or eco-designed materials. The natural reinforced composites have therefore attracted attention more high due to their availability as renewable, and ecological material (Cao et al. 2006). They exhibit advantages such as low cost, low density, biodegradability, availability, good thermal and mechanical properties (Malha et al. 2013), ease of implementation (Arrakhiz et al. 2012a), their ability to be recycled (Essabir et al. 2013 a) and to their environmental friendliness (Arrakhiz et al. 2012b; Essabir et al. 2013c). Polymers reinforced with natural fibers have been shown to exhibit enhancements in thermal (Essabir et al. 2013b), mechanical (Arrakhiz et al. 2012c), and rheological properties (Arrakhiz et al. 2013a; Essabir et al. 2013c). Fibers are often added to a plastic matrix to reduce the cost of a com­ponent and to improve some mechanical properties such as stiffness. In terms of markets and applications, it is particularly the automotive industry, the building and construction industry which have expressed interest in using such materials.

A better understanding of the morphological, structural and chemical composition of natural fibers is essential to developing materials composites. Lack on compatibility

between fibers and matrix is the biggest challenge in developing these composite materials (Freire et al. 2008; Sawpan et al. 2011). Natural fibers are hydrophilic, they are essentially composed of lignocelluloses, which contain hydroxyl groups (Freire et al. 2008) . These hydrophilic fibers are therefore incompatible with hydrophobic thermoplastic matrix, such as polyolefin and have low resistance to humidity (Arrakhiz et al. 2012a). Another important factor to obtain high mechan­ical properties is the fiber dispersion/distribution in matrix. These problems are the main limitations in polymers composites based on natural resources (Essabir et al. 2013b) Several reports show that the properties of composites were improved when the surface of the natural fibers or the polymer was modified (Arrakhiz et al. 2013a, c ).