**1. Introduction**

Nowadays, environmental friendliness is becoming one of the important criterions to be considered in material selection for the introduction of new materials and products resulting from global ecological concern and new rules and regulations [1, 2]. Waste plastic industrial and agricultural materials are currently becoming of interest worldwide in the field of composite materials, as a result of the increasing demand for environmentally friendly raw materials. The development of new biocomposites composed of recycled materials by post-consumer polymers as matrixes and agro-waste fibres as reinforcement phases and the better understanding of their fibre-matrix interactions will enhance their aggregated values and applications. Consequently, these reduce their environmental impact as waste materials and help to close the carbon cycle and manufacture greener composites [3, 4]. Natural fibre-reinforced thermoplastic composites have been used in various applications as furniture and architectural materials and, more recently, in the construction and automotive industry [5, 6].

Malaysia is well endowed with rich and renewable natural tropical forest resources which provide a variety of natural fibres. Rice husk (RH), one type of natural fibres, is an agricultural industrial residue generated during the rice-milling process in rice-producing countries, especially in the Asian, Pacific and North American regions [7]. In the paddy plants of Malaysia, with a land area of approximately 680 thousand hectares, a total of 840 thousand tons of RH is produced annually [8]. For every one million tonnes of paddy rice harvested, it is estimated that about 200 thousand tonnes of the RH was used for the purposes as fuel sources, animal beddings and landfill. The raw RH comprises several components with different percentages that are 25–35 % of cellulose, 18–21 % of hemicellulose, 26–31 % of lignin, 15–17 % of silica, 2–5 % of solubles and 7.5 % of moisture content. The use of RH in composite industry might be because of its low cost and bulk density, abundant, toughness, abrasive in nature, resistance to weathering, renewability, biodegradability and nonhazardousness [9, 10]. Compared to wood-based composites, the composites containing RH possess better water absorption and dimensional stability, as well as higher resistance to biological and termite attack. Therefore, these composites are progressively being used in automotive industry for interior parts such as car trims and door panels and in the building construction like interior panels, decks and window and door frames [7].

The worldwide fabrication and consumption of plastics have resulted in a remarkable contribution to municipal solid waste (MSW) [11]. For example, plastic wastes accounts for 24 % of the annual 7.7 million tonnes of the MSW generated in Peninsular Malaysia with the population of 28.45 million inhabitations in 2010 [12]. Majority of them consist of a significant amount of polyethylene (PE) and polyethylene terephthalate (PET) [13]. High-density polyethylene (HDPE) and PET are widely used in packaging industry, and their annual rates of consumption are kept increasing. Blends of HDPE/PET possess the intermediate characteristics and properties between both polymer components. As compared to PET, they have lower brittleness; as compared to HDPE, they have higher stiffness, flow better and are fast cooling. It has been revealed that ethylene-glycidyl methacrylate (E-GMA) copolymer serves as the most effective compatibilizer in order to enhance the miscibility between the hydrophobic HDPE and hydrophilic PET, thus improving the blend properties [14]. The resultant blends made of recycled polymers have been used in wood-plastic composites (WPC) as matrices [15].

Both thermoplastic and thermoset polymers either in the form of virgin or recycled can be used in the manufacture of natural fibre-polymer composites (NFPCs). Because recycled polymers are produced in large amounts daily and are cheaper than virgin polymers, the waste polymers offer a promising raw material source for the composites [16]. Traditionally, a single type of polymer is used as matrix in NFPCs [16–18]. However, there are very limited studies on the NFPCs made of polymer blends [15, 19].

In this chapter, the influence of rice husk biofibre (RHB) contents (50–80 wt%) on the physical, mechanical, thermal and morphological properties of recycled thermoplastic blend (TPB) was investigated.
