REVIEW OF RECENT TRENDS & DEVELOPMENTS IN BIOCOMPOSITES

Ramesh S Sharma Dr.V.P.Raghupathy Sai Sashankh Rao Shubhanga P

Asst. Professor Professor UG Student UG Student

Dept. of Mech. Engg Dept. of Mech. Engg Dept. of Mech. Engg Dept. of Mech. Engg

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Abstract

In today’s world, there is an increasing demand towards component materials that are durable, reliable, lightweight, and with mechanical properties that are significantly better than those of the traditional materials. At the same time it is preferable if these materials are eco-friendly and bio-degradable. Biocomposite material has shown signs of satisfying most of the above conditions. In this paper we focus primarily on the recent trends and developments in Biocomposites as applied to the medical and building industry, citing some examples. The nano-bio interface, concept of a green kitchen, benefits of using biocomposite material such as cement fibers, wood cement fibers and sisal fibers have been discussed, and their applications have been highlighted. Finally, the advantages of using biocomposite material, its eco-friendly nature and its future in the industry have been indicated with clarity.

Keywords:Bio-degradable, Nano-Bio Interface, Green Kitchen, Biocomposites.

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INTRODUCTION

Composites are those materials that contain two or more distinct constituent phases, on a scale larger than the atomic. The term ‘Biocomposites’ refers to those composites that can be employed in bioengineering. The constituents of the composite retain their identities in the composite. Namely, they do not dissolve or otherwise merge completely into each other although they act in concert. In composites, properties such as the elastic modulus can be significantly different from those of the constituents alone, but are considerably altered by the constituent structures and contents. From a structural point of view, composites are anisotropic in nature. Biocomposites are composite materials, that is, materials formed by a matrix (resin) and a reinforcement of natural fibres (usually derived from plants or cellulose). Biocomposites are the combination of natural fibers (biofibers)such as wood fibers (hardwood and softwood) or non - wood fibers (e.g., wheat, kenaf, hemp, jute, sisal, and flax) with polymer matrices from both of the renewable and nonrenewable resources. Biofibers are one of the major components of Biocomposites. The fibrous material derived from the tree, plant, or shrub sources is defined as biofiber. Biocomposites often mimic the structures of the living materials involved in the process, in addition to the strengthening properties of the matrix that was used, but still providing biocompatability, e.g. in creating scaffolds in bone tissue engineering. The degree of biodegradability in bio - based polymers depends on their structure and their service environment. Natural/Biofiber composites are emerging as a viable alternative to glass fiber composites, particularly in automotive, packaging, building, and consumer product industries, and becoming one of the fastest growing additives for thermoplastics [1]. Further, research into biological-inorganic interfaces focuses on the design, synthesis, and characterization of novel amalgams that fuse biological and inorganic materials. The integration of “soft” biological and organic molecular assemblies with “hard” inorganic nano-architectures is of special interest because of the opportunity to combine normally disparate chemical and physical properties within a single system. This nano-bio interface is indicated in Figure 1.

Figure 1: The Concept of NanoBio Interface.

NEED FOR BIOCOMPOSITES

Regular polymer composites are non-biodegradable and pollute the environment. There is an increasing movement of scientists and engineers who are dedicated to minimizing the environmental impact of polymer composite production. Environmental footprints must be diminished at every stage of the life cycle of the polymer composite [2]. Using natural fibers with polymers based on renewable resources will allow many environmental issues to be solved. By embedding biofibers with renewable resource–based biopolymers such as cellulosic plastics; polylactides; starch plastics; polyhydroxyalkanoates (bacterial polyesters); and soy-based plastics, the so-called green Biocomposites could soon be the future.

APPLICATIONS OF BIOCOMPOSITE MATERIAL

a)MedicalIndustry Human bone and tissue are essentially composite materials with anisotropic properties. The anisotropy of the elastic properties of the biological tissues has to be considered in the design criterion for implants made from composite biomaterials. The solution to this is a new porous resorbable ceramic-polymer biocomposite, with morphology and a mechanical resistance similar to those of natural cancellous bone [3]. Moreover surgeons can easily cut the graft directly in the surgery room to adapt its shape to the defect. Since they offer both, low elastic modulus and high strength, they have been proposed for several orthopedic applications. Also by controlling the percentage of the reinforcing and continuous phase the properties and design of the implant can be tailored to suit the mechanical and physiological conditions of the host tissues. Moreover problems of corrosion and release of allergenic metal ions, such as nickel or chromium, are totally eliminated. The composite provides high fracture toughness and high resistance against fatigue failure. These biocomposites are highly compatible with modern diagnostic methods, such as computed tomography (CT) and magnetic resonance imaging (MRI) as they show very low X – Ray scattering and their magnetic susceptibility is very close to that of human tissue. To top it all they are lightweight. For some applications as in dental implants, biopolymers offer a better aesthetic characteristic. The cost of productions of these implants is low and the production process is highly sophisticated. Biocomposites are used for hard tissue applications, including prosthetic socket, dental post, external fixator, bone plate, orthodontic archwire, orthodontic bracket, total hip replacement (Figure 2), and composite screws and pins. An example of the use of Biocomposites in clinical application is cages for spinal fusion. Benefit for patients is a faster bone healing, no risk of pathogen transfer compared to allograft, faster and cheaper surgery and less pain compared to auto graft.


Figure2: Hip Replacement Figure 3: Linear Osteoblast

b)BuildingIndustry Nowadays, Biocomposites have been the subject of extensive research, specifically in construction and building industry due to their many advantages such as lower weight, and lower manufacturing costs. People know about ethanol made from wheat or corn, but bioproducts also consist of other products as clothing (shown in Fig. 4) made from hemp, decking from plant fiber and plastic water bottles made from corn instead of oil. GreenBuilding is a movement that has gained global attention over the past few years. Green buildings are planned to be environmentally responsible, economically viable, and healthy places to live and work. One of the main materials that are currently used in green buildings is Biocomposite. Biocomposites may be classified, with respect to their applications in building industry into two main groups: structural and nonstructuralbiocomposites [4].

Figure 4: Woven Textiles

c)Structural Biocomposites A structural Biocomposite can be defined as one that is needed to carry a load in use. For instance, building industry, load-bearing walls, stairs, roof systems and sub - flooring are examples of structural biocomposites. Structural biocomposites can range broadly in performance, from high performance to low performance materials. The study on a few of the structural Biocomposites is as indicated below:

  1. Roof Structure Bio-based composite materials have been tested for suitability in roof structure [5]. Structural beams have been designed, manufactured and tested, yielding good results. Soy oil-based resin and cellulose fibers, in the form of paper sheets made from recycled cardboard boxes may be used for the manufacture of the compositestructures.
  1. Bridge Figure 5 represents, Stay-in-place bridge forms (SIP) are utilized to span the distance between bridge girders. The SIP forms made from Biocomposites have many benefits in comparison to steel forms. Biocomposite-based SIP forms are porous or breathable. Therefore, this lets water to evaporate through the form and to avoid any rebar corrosion. The form is also biodegradable; a bio-based form has the potential to break down in the future, allowing underside inspection of the bridge deck. In addition, the form is lighter compared to a steel form, allowing faster and cheaper installations.

Figure 5: Stay-In-PlaceBridge Form

d)Nonstructural Biocomposite A nonstructural Biocomposite can be defined as one that need not carry a load during service. Materials such as thermoplastics, wood particles, and textiles are used to make this kind of Biocomposites. Nonstructural Biocomposites are used for products such as ceiling tiles, furniture, windows, doors, and so on. The study on a few of the nonstructural Biocomposites is reported below:

  1. Exterior Construction

In exterior construction, wood fiber plastic composites are made in standard lumber profile cross-section dimensions. These bioproducts are utilized as dock surface boards, deck, picnic tables, landscape timbers, and industrial flooring. Many manufacturers recommend that Biocomposites need gaps on both edges and ends for their thermal expansion. Furthermore, wood-based bioproducts are gapped for expansion due to the moisture absorption.

  1. Window and Door

Clear ponderosa pine is utilized in clad components. Currently, it is becoming limited and expensive. In addition, ponderosa pine needs broad cutting, edge gluing, and finger jointing to get clear sections for window and door fabrication. Also, the glued up material have to be milled to the accurate cross section to be used in the assembly which results in increasing cost and waste wood. Therefore, manufacturers use wood fiber plastic composites as an alternative for solid wood in clad components.

  1. Composite Panel

There are three types of panels: fiberboard, particleboard, and mineral-bonded panels. Bagasse fibers are used for particleboards, fiberboards, and composition panel production. Cereal straw is the second most usual agro-based fiber in panel production. The high percentages of silica in cereal straw make them naturally fire resistant. Also, the low density of straw panels has made them resilient. Results show that houses built by these panels are resistant to earthquake. Straw is also used in particleboards. Rice husks are also fibrous and need little energy input to make the husks ready for use. Rice husks or their ash are used in fiber cement blocks and other cement products. The presence of rice husks in building products helps to increase acoustic and thermal properties. A stress-skin panel-type product has been made by using polyurethane or polyester foam in the core and ply-bamboo in the faces [6]. Figure 6 indicates the use of Biocomposites in the manufacture of Composite Panel.

Figure 6: Variable Density Panel made from Biocomposites

  1. Green Kitchen

The Green Kitchen in Toronto, ON is an effort towards building a kitchen completely built from bioproducts [7]. In the Green Kitchen, renewable plant-based systems are replacing finite petroleum-based systems to reduce greenhouse gas emissions. Some of the bioproducts used in the Green Kitchen are as follows:

  • Carpets:Corn has shown to be a flexible component in many of the enzyme processes used to build bioproducts. For instance, polylactic acid (PLA), a polymer derived from cornstarch, may be used to make carpet fibers. The PLA polymers have unique properties of breaking down under composting conditions.
  • Cupboard: Cupboard is made from wheat straw fibers and polyurethane resin instead of the formaldehyde. Wheat straw is bound with resin and is pressed into board. They can also be laminated or stained similar to other wood-based products. Generally, the end product is earth-friendly due to using waste by-product that would normally be burned at the end of the growing season.
  • Countertop: One may make use of the strength of hemp fibres and injection moulding to create countertops that are uncommonly light but durable. Bacterial enzymes are required to break down the hemp into a material that can be bound by polyurethane to harden the mass. Fermentation methods, like those used to make wine and beer, are used in the process with specifically designed bacteria. In general, countertop is interesting due to its biodegradability characteristics.

BIOCOMPOSITE MATERIALS

a)Fiber Cement

Fiber cement composite products can be made use of in exterior and interior of a building such as siding, roofing, external cladding, internal lining, floors, walls, building boards, bricks, bracing, fencing and decorative elements. Fiber cement is also used in construction works such as dam, bridge deck, road building, sidewalk, flagstone paving, and so on. One of the main ingredients of fiber cement products is cellulose fiber from wood or non-wood sources, which are added to reinforce the cement composite. Also, small amounts of chemical additives are utilized to help the process, or provide products with particular characteristics.

b)Wood Fiber Cement Composites

In recent decades, wood fiber cement composites are utilized in many products such as non-structural building materials specifically, thin sheet products and fiber cement siding materials called “tomorrow’s growth products”[8]. Some examples of recent commercial wood cement products include panel and lap siding, slate roofing, tile backer board and underlayment, cladding, lumber substitutes such as fascia, trim, soffit and corner boards. However, these components have to be maintained by painting to prevent moisture problems due to degradation to ambient wetting and drying. Wood fiber cement composites are used to substitute asbestos cement products. However, in comparison to conventional wood and other products, wood fiber cement composites have higher fire and moisture resistance and better durability. Furthermore, such problems as rot and insect attack have been removed in this kind of product.

c)Sisal Fibers Cement Composites

The role of sisal fibers in cement composites is to improve the toughness and the post-cracking of the matrix. Fibers have two functions in the post-cracking zone [9]. First, they increase the means of transferring stresses and loads across the cracks. Secondly, fibers increase the toughness of cement composites by making energy absorbing mechanisms regarding the cracks and the debonding. Sisal fibers can be the replacement asbestos-cement composites, which are hazardous for human and animal health. Sisal fibers increase the toughness of cement composite. In addition, it is understood that the addition of sisal fibers can improve the impact resistance.

d)Flax Fiber Reinforced Concrete- a natural fiber biocomposite for sustainable building materials

Flax fibers in concrete were sought in obtaining the highest possible ultimate strength, toughness and crack management from the various samples. While strength was shown to increase with the inclusion of particular fiber lengths and decrease with others, results from the optimized formulation indicated the potential to substantially increase the flexural toughness of the concrete composite. A theoretical analysis confirmed the empirical results of an optimum length of 3cm for flax fiber in concrete [10].

ADVANTAGES OF BIOCOMPOSITES

The advantages of natural fibers have currently attracted the manufacturers’ attention. These benefits can be classified into the following categories:

  1. Environmental Aspects: Plant fibers are renewable resources. They need low energy requirements during production. Furthermore, natural fibers show carbon dioxide neutrality and their disposal can be done by composting.
  2. Biological Aspects: They are natural organic products. There is no dermal issue for their handling compared to glass fibers and do not pose a bio-hazard upon disposal.
  3. Production Aspects: Natural fibers are non-abrasive and exhibit great formability.
  4. Component Weight Issues: Natural fibers are lightweight (less than half the density of glass fibers).
  5. Financial Aspects: Natural fibers are very cheap in comparison to glass fibers.
  6. General Aspects: Natural fibers show a safer crash behavior in tests (i.e., no splintering). In addition, they exhibit good thermal insulating and acoustic properties due to their hollow tubular structures.
  7. High specific strength.
  8. Good sound insulation.

FUTURE OF BIOCOMPOSITES

Sustainability, industrial ecology, eco-efficiency, and green chemistry are guiding the development of the next generation of materials, products, and processes. Biodegradable plastics and bio-based polymer products based on annually renewable agricultural and biomass feedstock can form the basis for a portfolio of sustainable, eco-efficient products that can compete and capture markets currently dominated by products based exclusively on petroleum feedstock [11]. The only source available today that focuses on biobased materials, Natural Fibers, Biopolymers, and Biocomposites integrates the principles of sustainability, industrial ecology, eco-efficiency, and green chemistry and engineering into the development of the next generation of materials, products, and processes. Figure 7 indicates the growing trend in the use of Biocomposites.

Figure 7: Growth outlook for Biocomposites

CONCLUSIONS

Development of Biocomposites as an alternative to petroleum based materials is addressing the dependence on imported oil, reducing carbon dioxide emission, and generating more economical opportunities for the agricultural sector. Furthermore, Biocomposites offer opportunities for environmental gains, reduced energy consumption, insulation and sound absorption properties. Nowadays, Use of Biocomposites in building materials offers several advantages such as cheap, lightweight, environmental friendly, bio - renewable, and more durable. However, they have some disadvantages as well, such as moisture absorption and photochemical degradation because of the UV radiations. In this regard there is some on-going research to address these issues. Furthermore, biocomposites offer opportunities for environmental gains, reduced energy consumption, insulation and sound absorption properties.