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A biocomposite is a composite material formed by a matrix (resin) and a reinforcement of natural fibers. Environmental concern and cost of synthetic fibres have led the foundation of using natural fibre as reinforcement in polymeric composites. The matrix phase is formed by polymers derived from renewable and nonrenewable resources. The matrix is important to protect the fibers from environmental degradation and mechanical damage, to hold the fibers together and to transfer the loads on it. In addition, biofibers are the principal components of biocomposites, which are derived from biological origins, for example fibers from crops (cotton, flax or hemp), recycled wood, waste paper, crop processing byproducts or regenerated cellulose fiber (viscose/rayon). The interest in biocomposites is rapidly growing in terms of industrial applications (automobiles, railway coach, aerospace, military applications, construction, and packaging) and fundamental research, due to its great benefits (renewable, cheap, recyclable, and biodegradable). Biocomposites can be used alone, or as a complement to standard materials, such as carbon fiber. Advocates of biocomposites state that use of these materials improve health and safety in their production, are lighter in weight, have a visual appeal similar to that of wood, and are environmentally superior. [1] [2] [3] [4]
The differential for this class of composites is that they are biodegradable and pollute the environment less which is a concern for many scientists and engineers to minimize the environmental impact of the production of a composite. They are a renewable source, cheap, and in certain cases completely recyclable. [5] One advantage of natural fibers is their low density, which results in a higher specific tensile strength and stiffness than glass fibers, besides of its lower manufacturing costs. As such, biocomposites could be a viable ecological alternative to carbon, glass, and man-made fiber composites. Natural fibers have a hollow structure, which gives insulation against noise and heat. It is a class of materials that can be easily processed, and thus, they are suited to a wide range of applications, such as packaging, building (roof structure, bridge, window, door, green kitchen), automobiles, aerospace, military applications, electronics, consumer products and medical industry (prosthetic, bone plate, orthodontic archwire, total hip replacement, and composite screws and pins). Unfortunately, biocomposites have limitations due to lack of compatibility between synthetic resin and natural fibers [6] [7] [8]
Biocomposites are divided into non-wood fibers and wood fibers, all of which present cellulose and lignin. The non-wood fibers (natural fibers) are more attractive for the industry due to the physical and mechanical properties which they present. Also, these fibers are relatively long fibers, and present high cellulose content, which delivers a high tensile strength, and degree of cellulose crystallinity, whereas natural fibers have some disadvantages because they have hydroxyl groups (OH) in the fiber that can attract water molecules, and thus, the fiber might swell. This results in voids at the interface of the composite, which will affect the mechanical properties and loss in dimensional stability. The wood fibers have this name because almost than 60% of its mass is wood elements. It presents softwood fibers (long and flexible) and hardwood fibers (shorter and stiffer), and has low degree of cellulose crystallinity.
Biocomposites/biofibers | |||||||
---|---|---|---|---|---|---|---|
Non-wood natural fibers | Wood fibers | ||||||
Straw fibers | Bast | Leaf | Seed/fruits | Grass fibers | Recycled | ||
Examples: | Rice, wheat, corn straws | Kenaf, flax, jute, hemp | Henequen, sisal, penneaple leaf fiber | Cotton, coir, coconut | Bamboo, bamboo fiber, switch grass, elephant grass | Soft and hard woods | Newspaper, magazine fibers |
The natural fibers are divided into straw fibers, bast, leaf, seed or fruit, and grass fibers. The fibers most widely used in the industry are flax, jute, hemp, kenaf, sisal and coir. The straw fibers could be found in many parts of the world, and it is an example of a low-cost reinforcement for biocomposites. The wood fibers could be recycled or non-recycled. Thus, many polymers as polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC) are being used in wood composites industries.
Flax linen composites work well for applications seeking a lighter weight alternative to other materials, most notably, applications in automotive interior components and sports equipment. For automotive interiors, Composites Evolution has performed prototype testing for the Land Rover Defender and the Jaguar XF, with the Defender's flax composite 60% lighter than the production counterpart at the same stiffness, and the XF's flax composite part 35% lighter than the production component at the same stiffness [9]
In sports equipment, Ergon Bikes produced a concept saddle that won first place among 439 entries in the Accessories category at the Eurobike 2012, a major bicycling industry trade show. [10] VE Paddles has produced a boat paddle blade. [11] Flaxland Canoes has developed a canoe that has a covering of flax linen. [12] Magine Snowboards has developed a snowboard that incorporates flax linen. [13] Samsara Surfboards has produced a flax linen surfboard. [14] Idris Ski's Lynx won an ISPO Award in 2013 for the Lynx ski [15]
Flax linen composites also work for applications for which the look, feel, or sound of wood is desired, but without susceptibility to warping. Applications include furniture and musical instruments. In furniture, a team at Sheffield Hallam University designed a cabinet with entirely sustainable materials, including flax linen. [16] In musical instruments, Blackbird Guitars has produced a ukulele made with flax linen that has won a number of design awards in the composites industry, [17] [18] [19] [20] as well as a guitar [21]
Green composites are classified as a biocomposite combined by natural fibers with biodegradable resins. They are called green composites mainly because of their degradable and sustainable properties, which can be easily disposed without harming the environment. Because of their durability, green composites are mainly used to increase the life cycle of products with short life.
Another class of biocomposite is called 'hybrid biocomposite', which is based on different types of fibers into a single matrix. The fibers can be synthetic or natural, and can be randomly combined to generate the hybrid composites. Its functionality depends directly on the balance between the good and bad properties of each individual material used. Besides, with the use of a composite that has two more types of fibers in the hybrid composite, one fiber can stand on the other one when it is blocked. The properties of this biocomposite depends directly on the fibers counting their content, length, arrangement, and also the bonding to the matrix. In particular, the strength of the hybrid composite depends on the failure strain of the individual fibers.
Hemp fiber composites work well in applications where weight reduction and increased stiffness is important. For consumer good applications, Trifilon has developed a number of hemp fiber biocomposites to replace conventional plastics. Suitcases, chillboxes, mobile phone cases and cosmetic packaging have been produced using hemp fiber composites.
The production of biocomposites uses techniques that are used to manufacture plastics or composites materials. These techniques include:
Fiber is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorporate fibers, for example carbon fiber and ultra-high-molecular-weight polyethylene.
A composite material is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a material with properties unlike the individual elements. Within the finished structure, the individual elements remain separate and distinct, distinguishing composites from mixtures and solid solutions. Composite materials with more than one distinct layer are called composite laminates.
In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening ("curing") a soft solid or viscous liquid prepolymer (resin). Curing is induced by heat or suitable radiation and may be promoted by high pressure or mixing with a catalyst. Heat is not necessarily applied externally, and is often generated by the reaction of the resin with a curing agent. Curing results in chemical reactions that create extensive cross-linking between polymer chains to produce an infusible and insoluble polymer network.
Fiber crops are field crops grown for their fibers, which are traditionally used to make paper, cloth, or rope.
Fibre-reinforced plastic is a composite material made of a polymer matrix reinforced with fibres. The fibres are usually glass, carbon, aramid, or basalt. Rarely, other fibres such as paper, wood, boron, or asbestos have been used. The polymer is usually an epoxy, vinyl ester, or polyester thermosetting plastic, though phenol formaldehyde resins are still in use.
Wood–plastic composites (WPCs) are composite materials made of wood fiber/wood flour and thermoplastic(s) such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), or polylactic acid (PLA).
Natural fibers or natural fibres are fibers that are produced by geological processes, or from the bodies of plants or animals. They can be used as a component of composite materials, where the orientation of fibers impacts the properties. Natural fibers can also be matted into sheets to make paper or felt.
Biotextiles are specialized materials engineered from natural or synthetic fibers. These textiles are designed to interact with biological systems, offering properties such as biocompatibility, porosity, and mechanical strength or are designed to be environmentally friendly for typical household applications. There are several uses for biotextiles since they are a broad category. The most common uses are for medical or household use. However, this term may also refer to textiles constructed from biological waste product. These biotextiles are not typically used for industrial purposes.
Filler materials are particles added to resin or binders that can improve specific properties, make the product cheaper, or a mixture of both. The two largest segments for filler material use is elastomers and plastics. Worldwide, more than 53 million tons of fillers are used every year in application areas such as paper, plastics, rubber, paints, coatings, adhesives, and sealants. As such, fillers, produced by more than 700 companies, rank among the world's major raw materials and are contained in a variety of goods for daily consumer needs. The top filler materials used are ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, talc, and carbon black.
Polymer engineering is generally an engineering field that designs, analyses, and modifies polymer materials. Polymer engineering covers aspects of the petrochemical industry, polymerization, structure and characterization of polymers, properties of polymers, compounding and processing of polymers and description of major polymers, structure property relations and applications.
Bamboo textile is any cloth, yarn or clothing made from bamboo fibres. While bamboo was historically used only for structural elements, such as bustles and the ribs of corsets, in recent years various technologies have been developed that allow bamboo fibre to be used for a wide range of textile and fashion applications.
Cellulose fibers are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants, or from other plant-based material. In addition to cellulose, the fibers may also contain hemicellulose and lignin, with different percentages of these components altering the mechanical properties of the fibers.
Ekoa is a natural biocomposite of flax available in dry fabrics and pre-pregs, as well as cores and resins. Ekoa can be used for a variety of applications, including the production of musical instruments like the ukulele and guitar, and the manufacturing of sports equipment such as bicycle frames and lacrosse sticks.
Curran is a microcrystalline nanocellulose fibre derived from the pulp of root vegetables. It was developed by Scottish scientists David Hepworth and Eric Whale, with funding from the Scottish Government. The sources of root vegetable pulp used to manufacture Curran include carrots, sugar beets, and turnips. It is named after curran, the Scottish Gaelic word for "carrot". The material was developed as a potential substitute for carbon fibre and is often used in polymer composites. It has numerous industrial and technological applications, especially for the production of paints and sporting equipment.
Fibre modification is a research field in which researchers aim at developing and applying technologies to impart new properties to natural fibres such as those in paper, in order to increase their functionality. Research areas in this field include many different technologies, amongst which the chemical modifications of fibres are widely used. One important sector of application of the chemical modifications is the treatment of wood for giving it enhanced properties such as higher mechanical properties, water impermeability, less hygroscopicity, bacterial and fungal resistance. Transferring and adapting the technical knowledge on fibre modification available for the wood sector to the recycled paper sector is an innovative use of these chemical treatments which has been the subject of studies that have been carried out within an EU co-funded project called Fibre+.
Transparent wood composites are novel wood materials which have up to 90% transparency. Some have better mechanical properties than wood itself. They were made for the first time in 1992. These materials are significantly more biodegradable than glass and plastics. Transparent wood is also shatterproof, making it suitable for applications like cell phone screens.
In materials science, a polymer matrix composite (PMC) is a composite material composed of a variety of short or continuous fibers bound together by a matrix of organic polymers. PMCs are designed to transfer loads between fibers of a matrix. Some of the advantages with PMCs include their light weight, high resistance to abrasion and corrosion, and high stiffness and strength along the direction of their reinforcements.
Hemp paper is a paper variety consisting exclusively or to a large extent from pulp obtained from fibers of industrial hemp. The products are mainly specialty papers such as cigarette paper, banknotes and technical filter papers. Compared to wood pulp, hemp pulp offers a four to five times longer fibre, a significantly lower lignin fraction as well as a higher tear resistance and tensile strength. Because the paper industry's processes have been optimized for wood as the feedstock, production costs currently are much higher than for paper from wood.
In materials science, reinforcement is a constituent of a composite material which increases the composite's stiffness and tensile strength.
Amar K. Mohanty is a material scientist and biobased material engineer, academic and author. He is a Full Professor and Distinguished Research Excellence Chair in Sustainable Biomaterials at the Ontario Agriculture College and is the Director of the Bioproducts Discovery and Development Centre at the University of Guelph.
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