Biocomposites, applications materials

Cellulosic fiber reinforced polymeric composites find applications in many fields ranging from the construction industry to the automotive industry. The reinforcing efficiency of natural fiber is related to the namre of cellulose and its crystallinity. The main components of natural fibers are cellulose (a-cellulose), hemicelluloses, lignin, pectins, and waxes. For example, biopolymers or synthetic polymers reinforced with natural or biofibers (termed biocomposites) are a viable alternative to glass fiber composites. The term biocomposite is now being applied to a staggering range of materials derived wholly or in part from renewable biomass resources [23]. 

The experiences made have shown that biocomposites can be excellently processed to make structural material. The weight-related mechanical properties make it possible to strive for application areas that are still dominated by glass fibre-reinforced plastics. At this time, limitations must be accepted in areas with extreme environmental conditions. Main target groups therefore are, for example, panelling elements in automobile and freight car manufacturing, the furniture industry and the entire market of the sports and leisure industry. 

The demand for better fuel efficiency based on the strict governmental regulations on safety and emission has led to the wide application of composites and plastics in the automotive industry in the place of the traditionally used steels [32]. Thermoplastic materials reinforced with natural fibers have reported to have excellent mechanical properties, recycling properties, etc. [33-36]. Several natural and biorenewable fibers such as wheat, isora, soybean, kenaf, straw, jute, and sisal are used in the fiber/plastic composite industry, and the use of namral fibers as reinforcements for composite has attracted many industries [37, 38]. Compared to polymer resin, polymer biocomposites that are reinforced with natural fibers have many applications due to its ease of processing, comparatively lower cost, and excellent mechanical properties [39]. For more than a decade, European car manufacturers and suppliers have been using natural fiber-based composites with thermoplastic and thermoset matrices. These biocomposites and bionanocomposites... 

It is important to emphasize that many natural tissues are essentially composed of nanoscale biopolymers or biocomposites with hierarchical architectures. Therefore, by mimicking the structure and property of their natural counterparts, synthetic nanopoiymers and nanocomposites are very likely to enhance/regulate the functions of specific cells or tissues. This principle has been demonstrated by the success of bioinspired polymers and composites in both clinical practice and in laboratory research. In particular, bone is the hierarchical tissue that has inspired a myriad of biomimetic materials, devices, and systems for decades. This chapter focuses on this well-developed area of biomimetic or bioinspired nanopoiymers and nanocomposites for bone substitution and regeneration, especially those with high potentials for clinical applications in the near future. 

Biomaterials have been defined as materials which are compatible with living systems. In order to be biocompatible with host tissues, the surface of an implant must posses suitable chemical, physical (surface morphology) and biological properties. Over the last 30 years, various biomaterials and their applications, as well as the applications of biopolymers and their biocomposites for medical applications have been reported. These materials can be classified into natural and synthetic biopolymers. Synthetic biopolymers are cheaper and possess better mechanical properties. However, because of the low biocompatibility of synthetic biopolymers compared with that of natural biopolymers, such as polysaccharides, lipids, and proteins, attention has turned towards natural biopolymers. On the other hand, natural biopolymers usually have weak mechanical properties, and therefore much effort has been made to improve them by blending with some filler. 

In general, such agro-based materials are only used as feed for livestock and not as load bearing materials. Therefore, grass reinforced composites have an excellent potential to be used as fibers. There are plenty of grass resources. Elephant grass-based biocomposites are of interest for automotive applications. 

Biocomposites usefulness is no longer in question and more and more reports are focused on applicative aspects in the environment, packaging, agriculture devices, biomedical fields, etc. Moreover, because industrials were concerned about sustainable developments and a controlled end of life, production cost of biopolymers goes on decreasing which will allow strong developments of biopolymer-based materials. Therefore, these materials will be technically and financially competitive towards synthetic polymer-based composites. Then, this class of material opens a new dimension for plastic industry for a better sustainable development. 

Of late many of the major car manufacturers now use biocomposites in various applications, e.g., door trim panels made of polyurethane (PU)-flax/sisal mat in Audi A2 midrange car jute-based door panels in Mercedes E-class polyester-cotton fibres in Trabant car under floor protection trim of Mercedes A class made from banana fibre-reinforced composites and the Mercedes S class automotive components made from different bio-fibre-reinforced composites. All these so-called biocomposites use natural fibres but the resin matrix is always an oil-derived synthetic material. 

The current knowledge related to the structure and chemistry of cellulose, and the development of innovative cellulose derivatives for different applications (coatings, films, membranes, building materials, pharmaceuticals, foodstuffs), as well as the new perspectives, including environmentally-friendly cellulose fiber technologies, bacterial cellulose biomaterials, in-vitro syntheses of cellulose, and cellulose-based biocomposites were highlighted in several important works [30-34]. 

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