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Biofiber-Reinforced Biocomposite

BULETIN TEKSTIL.COM/ Jakarta – Materials including metals, polymers, ceramics and composites, has its own advantages. A composite is a new form of engineered material that consists of two or more components with distinct chemical and physical characteristics. Composite materials are described as a mixture of two or more materials that produces qualities that are superior to the constituent materials’ properties.

Matrix and fiber/filler/additives are the building blocks of composite materials where fiber plays an important role in providing the strength and stiffness of the composite. However, the matrix provides resistance to high temperatures, resistance to shear stress, and the ability to distribute loads, which is a source of composite strength.

The division of composites based on reinforcing materials can be explained in the following table:

Composite Classification based on fiber

Fiber composites are composites consisting of fibers in a matrix. Long fibers are naturally stronger than bulk fibers. The matrix is the bonding or fiber binding substance in a composite material. The matrix should ideally function as a fiber sheath against inter-fiber damage caused by abrasion, as well as provide environmental protection (chemical attack, moisture), fiber support and infiltration, load transfer between fibers, and adhesives, and should be physically and chemically stable after the manufacturing process. The matrix might be made of polymers, metals, carbon, or ceramics.

Metal matrix composites, or composites with a metal matrix, are frequently found in the automotive sector. This material has a metal matrix, such as aluminum, and is reinforced with fibers, such as silicon carbide. This metal matrix composite is used in automotive components, electronic equipment, military equipment, and aircraft (electric racks on aircraft).

Ceramic matrix composites are used in extremely hot settings. The matrix of this material is ceramic, and it can be reinforced with short fibers or fibers made of silicon carbide or boron nitride. Oxides, carbides, and nitrides are often used as reinforcements, whereas inorganic glass, glass ceramics, alumina, and silicon nitride are the commonly used matrices. Applications of ceramic matrix composites are widely used in chemical processing (filters, membranes), power generators (nozzles, heat exchange tubes), etc.

Polymer serves as the matrix in polymer matrix composites. The qualities of these composites are determined by the properties of the reinforcement, properties of the polymer, reinforcement-to-polymer ratio in the composite, and the geometry and orientation of the reinforcement in the composite. Polymer matrix composites can be applied such as polyester based matrices with glass fiber (vehicle door panels, office cabinets and electronic equipment) etc.

Biocomposite materials

Biocomposite

Biocomposites formed by biofibers, such as lignocellulosic fibers and animal fibers are used to reinforce the polymer matrix. To increase the mechanical qualities of the composite, natural fibers such as hemp, sisal, silk, wool, and others are employed as polymer matrix reinforcement. The mechanical strength of fiber reinforced composites is determined by the fiber type and orientation of the fibers in the matrix (unidirectional, random, short fiber, long fiber, weaved). Numerous studies show that the kind of matrix, filler, and reinforcement all have an impact on composite performance.

Due to the hydrophilic character of the biofiber and the hydrophobic nature of the matrix, it is necessary to chemically modify the fiber surface to maximize the adhesion between the fiber and the matrix. With chemical treatment, the hydrophilic properties of plant fibers are reduced by breaking down the hydroxyl and carbonyl groups on the surface of the fiber. Various studies have reported that biofiber can be used as reinforcement in various matrices such as polypropylene, polystyrene, epoxy, polyester, polylactic acid, etc. It is critical to produce biocomposites with appropriate processing procedures in order to attain superior physical, mechanical, and thermal characteristics.

Characteristics of Biocomposites

The use of fillers as reinforcement can enhance the characteristics of biocomposites. Mechanical strength, thermal characteristics, and electrical conductivity may all be affected by strengthening. Several research have documented the use of bio-fillers to improve the mechanical and thermal performance of composites, such as bio-flour, lignocellulosic fillers, seashells, eggshell powder, wood flour, and more. The type of filler, size, quantity, distribution, surface morphology of the filler, chemical treatment, and interaction of the matrix with the filler all have an impact on composite performance and attributes. Physical qualities like as size, density, and porosity vary amongst fillers. Since lignocellulosic fillers are readily accessible, they are classified as conventional fillers. When reinforced in polymers, they increase the mechanical characteristics of the composite by enhancing the contact with the matrix.

Biofiller research on biocomposites is quite limited. Nanofiller is crucial in controlling the rheological properties and density of biocomposites. Current research is concentrating on nanofiller-based composites, which are widely used in medical implants and packaging materials but are still in their early stages. It will be critical in the future to create a sustainable usage of nanofillers in biocomposites.

Biocomposites’ mechanical characteristics are heavily dependent on parameters such as deformation rate and temperature. The types of polymer, crystallinity, molecular weight, shape, chemical composition, cross-linking, plasticization, copolymerization, molecular orientation, concentration, and type of reinforcement all have a role in this condition. The tensile strength of composites is also affected by the processing environment, orientation and polymer. There are various mechanical properties involving tensile strength, tensile modulus, flexural strength, flexural modulus, yield strength, yield modulus, compressive strength, impact strength, hardness, elongation rate, storage modulus, loss modulus, elongation, micromechanical analysis etc. Chemical treatment of natural fibers has been proven in studies to enhance the tensile strength of composites by reducing their hydrophilic properties and therefore improving matrix fiber interactions.

Several studies found that incorporating natural fibers into various polymeric matrices increased flexural strength, interlaminar shear strength, and hardness significantly. The inclusion of nanofibers and nanoparticles to the biopolymer affects these mechanical characteristics as well. The biocompatibility of biofiller-reinforced biopolymers is more important in biomedical applications but there has been little research in this field of bioimplants. Developing bioimplants that are biocompatible in the future is critical in order to help patients avoid additional surgery for implant removal. Dynamic mechanical analysis was used to measure the composite Heat Deflection Temperature (HDT), using a DMA Q800, TA Instruments Inc. Tests were carried out according to ASTM D648, ASTM D5023-15.

The thermogravimetric analysis of biofiber-reinforced polymer composites depends on the thermal stability of the fillers. In general, for fiber-reinforced composites, thermal stability can be reduced by degradation of natural fibres.

The study of the friction and wear of two surfaces in contact is known as tribology. Given recent developments in innovation and applications, it is critical to investigate the tribological characteristics of natural fiber reinforced composites. The pinon disc test process is the most often used test; it includes shear wear where the contact area is constant. Studies have shown that the friction and wear performance of composites can be improved by incorporating natural fibers. There are other test methods such as “dry sand rubber wheel”, the test is carried out according to ASTM G65. This test is used to study the wear performance of tire threads, rollers, bushings and bearings.

When biocomposites are used in building materials and thermal insulation applications, there is a possibility of fire accidents. Fire resistance is a crucial test for biocomposites since it evaluates their flammability and fire retardancy. Researchers are now working on adding flame retardants into biocomposites that will function better and have no negative influence on living creatures after disposal. The fire resistance test for natural fiber composites was carried out using a vertical Bunsen burner test, in accordance with the Federal Aviation Regulation (FAR). A methane gas flame with a standard height of 38 mm above the burner is placed at the center of the specimen for 12 seconds. The test results show the drip flame time, total flame time, and burn length. Vertical and horizontal fire tests are also used to measure fire resistance. The tests were done according to vertical UL-94 and horizontal UL-94 according to DIN EN 60695-11-10. Five and three samples were tested for UL-94 V and UL-94 HB, respectively.

The results are used to study the rate of ignition and flame spread. Natural fibers, in general, burn in a flame, hence flame retardants should be employed to increase their flammability. According to recent study on the flame retardation of thermoplastic starch-based bio composites, the addition of ammonium polyphosphate (APP) improves flame retardation. Gluten-based biocomposites are extremely flammable. There are numerous flame retardants discovered, but it is critical to develop new flame retardants that are compatible with biomaterials without affecting mechanical properties.

The morphological properties of biocomposites such as particle distribution morphology, cavity, bond types, reinforcement in the matrix, etc., are easily studied using microscopic images taken from SEM (Scanning electron microscope), FESEM (Field emission scanning electron microscope), TEM (Transmission electron microscope), AFM (Atomic force microscope), POM (Polarized optical microscope), etc. Images are taken at different magnification factors which allow understanding of surface texture, and particle distribution.

(Red B-Teks/Agung)

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