**1. Introduction**

 The global demand for light-weight materials calls for the broad use of fiber-reinforced plastic materials [1]. Developing composites using natural fibers provides the chance to improve

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

materials while decreasing their ecological footprint. Even using agricultural and forestry wastes such as rice husks (RHs), coconut fibers, bagasse, and saw dust (SD) can lead to significantly improved material properties [2].

Rice husk and saw dust, by-products of the rice milling and wood sawing processes respectively, are potential reinforcing fillers for thermoplastic matrix composites because of their lignocellulosic characteristics. These fillers offer advantages of easy processing, large volume availability, annual renewability, low cost, light weight, competitive specific mechanical properties, and high sustainability. The morphology differs: Rice husk is made up of rectangular platelets and saw dust of short fiber bundles.

The most common thermoplastics used as matrices for bio-fillers are polyethylene (PE) and polypropylene (PP). When a polylefin is used as a matrix for a bio-filler composite, the incompatibility between hydrophobic matrix and hydrophilic bio-filler is an important issue. Therefore, there have been many studies on improving interfacial interactions between the polymers and bio-fillers. According to previous studies, the best solution of the problem is using an appropriate coupling agent or compatibilizer such as maleic anhydridefunctionalized polylefin, for example, maleic anhydride-grafted polypropylene (MAPP) for PP or maleic anhydride-grafted polyethylene (MAPE) for PE [3–8].

Biomaterials such as saw dust, bamboo powder, or grain husks used as fillers in polymer matrix composites are natural compounds, mainly containing cellulose, hemicellulose, and lignin. Their degradation takes place at a relatively low temperature, around 200°C [1]. Therefore, bio-fillers will be subjected to thermal degradation during composite processing with the majority of common thermoplastic polymers [2]. This leads to undesirable properties, such as odor and browning along with a reduction in mechanical properties of the bio-composite [2, 3]. Therefore, it is important to understand and predict the thermal decomposition processes of bio-filler in order to better design composite processes and estimate the influence of the thermal decomposition on composite properties [4].

In this work, the suitability of rice husk and saw dust as reinforcing agents for composites based on different polyolefine matrices was evaluated. The filler morphology is characterized. Mechanical tests of their composites were evaluated as a function of filler content and filler morphology. The effect of maleated polyolefines as compatibilizers on the mechanical properties of the composites as well as hardness of the composites was studied.

Thermal studies of biomaterial-filled polyolefine (PP, PE) composites included thermomechanical analysis (TMA) and the thermal and mechanical dynamic behavior according to the filler loading and the presence of compatibilizers. The crystallization is characterized by differential scanning calorimetry (DSC) analysis and the thermal degradation by thermogravimetric analysis (TGA).
