Chemical modifications of natural fibres for composite applications

Chemical Modifications of Natural Fibres for Composite Applications  KETKI SURESH CHAVAN Final Year B.Tech F.T.P.T. 201003021052 Seminar Report Presentation on: Introduction to Composites…  Heterogeneous nature  created by the assembly of two or more components with fillers or reinforcing fibres and a compactable matrix  Constituents of a Composite material are: Reinforcement: Discontinuous, Stiffer, Stronger. Matrix: Continuous, Less Stiff, Weaker Interface: A third phase exists between reinforcement and the matrix because of chemical interactions or other processing effects plays an important role in controlling failure mechanisms, fracture toughness 2 Fibre Reinforced Composites Single Layer (same orientation & properties in each layer) Continuous fibre Reinforcement Unidirection Reinforcement Bi directional Reinforcement (woven fabric) Discontinuous fibre Reinforcement Random Orientation Preferred orientation Multi layer (angle ply) Laminates Hybrids Classification of FRCs. 3 Ref.:Agrawal B D & Broutman L J, 1980 Market Trends for NFRCs  Automotive & Construction were largest segment among all natural composite applications.  Several automobile models, first in Europe and then in North America, featured natural reinforced thermosets and thermoplastics in door panels, package trays, seat backs and trunk liners.  Dräxlmaier Group and Faurecia supply interior parts such as headliners, side and back walls, seat backs, and rear deck trays to GM, Audi, and Volvo among others.  Bast fibre composites for Automotive & Wood plastic composites for Construction & Building. 4 Ref:[http://www.researchandmarkets.com/reports/1933235] The Reinforcement Conventional Fibres:  Carbon  Glass  Aramids  Others include: Boron, Alumina, Silicon Carbide, Quartz fibres. Their Major Disadvantages:  High Densities  Non Renewable  Non Recyclabable  High Energy Consumption during Manufacture  Not CO 2 Neutral  Non biodegradable  Expensive 5 The Natural Fibres 6 The Natural Plant Fibres Classification:  Leaf (pineapple, sisal, banana)  Seed (cotton, milkweed)  Bast (hemp, flax, jute)  Fruit (coir, kapok, oil palm)  Grass (bagasse, bamboo)  Stalk (rice straw)  Wood fibres (soft & hard wood) Advantages:  Abundantly available Renewable resources  Relatively less costly  Biodegradable  Flexible for processing  No health hazards during manufacture  Desirable aspect ratio, low density and relatively good tensile and flexural modulus. 7 Structure of Plant Fibres  Natural plant fibres are constitutes of cellulose fibres, consisting of helically wound cellulose micro - fibrils, bound together by an amorphous lignin matrix.  Lignin keeps the water in the fibre; acts as a protection against biological attack and as a stiffener to give stem its resistance against gravity forces and wind.  Hemicellulose found in the natural fibres is believed to be a compatibilizer between cellulose and lignin. 8 Mechanical properties of Natural fibres 9 Disadvantages of Natural fibres for applications in composites.  Enormous Variability in Properties  Lack of FIBRE – MATRIX adhesion  Poor Moisture resistance  Poor Fire resistance  Lower durability  Limited Maximum Processing Temperatures These problems are being dealt with today by carrying out various modifications & treatments. These have different efficiencies for improving the mechanical properties of fibres, the adhesion between matrix and fibre result in the improvement of various properties of final products. 10 [...]... be used to modify natural fibres to introduce new function onto the surface of fibres and enhance the performance of final natural fibre – based products It is believed that the application of NT to modify natural fibres offers high economic potential for the development of natural fibre – based industry A combination of Biological treatment & NT has also been studied on Hemp & Sisal fibres by using... bacteria: Gluconacetobacter xylinus treatment on the fibres & then fabricated this treated cellulose on the surface of natural fibres This helped increase the strength of the Bio composites made from them Chemical Modifications Chemical modification utilizes chemical agents to modify the surface of fibres or the whole fibre throughout The chemical treatment of fibre is aimed at:    14 improving the adhesion... Bleaching with Sodium Chlorite: Composite material:0 to 30% fibre loading; 1-pentene/ polypropylene copolymer matrix 34 Ref: Journal of Reinforced Plastics and Composites, 2008, Vol 27, pp.1533-1544 HEMP FIBRE COMPOSITES 2 Alkaline Treatment Composite material: 40% (by volume) fibre loading; PLA matrix 35 Ref: Journal of Composite Materials, 2007, Vol 41, pp.1655-1669 Applications of hemp 36 ... (CH2=CH–C≡N)) is also used to modify fibres The reaction of Acrylonitrile with fibre Hydroxyl groups occurs in the following manner: SILANE TREATMENT  Silane is a chemical compound with chemical formula SiH4 Silanes are used as coupling agents to let natural fibres adhere to a polymer matrix, stabilizing the composite material Silane coupling agents may reduce the number of cellulose hydroxyl groups in... are used in natural fibre surface modifications In peroxide treatment, fibres are coated with BP or DCP in acetone solution for about 30 min after alkali pre-treatment Free Radical Reaction 27 SODIUM CHLORITE TREATMENT   28 This treatment involves the bleaching of natural fibres with sodium chlorite which cleans the fibres thoroughly but makes them rough This roughness is responsible for better Fibre... Separation of pectic & hemicellulosic substances helps the main fibres to become clean & get exposed to the matrix effectively for better interfacial adhesion  12 Involves the use of naturally occurring microorganisms, namely bacteria and fungi Process is time consuming, water polluting & the quality of fibres obtained is very much dependent on quality of water used Retting is the controlled degradation of. ..Physical modifications  Thermo treatment followed by Calendaring & Stretching: Softening the lignin & hemicellulose, bringing it to surface & forming of Water resistant surface (Hydrophobic layer)  Plasma Treatment: Two types: Corona Discharge at Atm Press High Frequency Cold Plasma This treatment does not at all affect the bulk properties of the natural fibres 11 Biological Modifications ... fibre – matrix interface  In the presence of moisture, hydrolysable alkoxy group leads to the formation of silanols The silanol then reacts with the hydroxyl group of the fibre, forming stable covalent bonds to the cell wall that are chemisorbed onto the fibre surface  Therefore, the hydrocarbon chains provided by the application of silane restrain the swelling of the fibre by creating a crosslinked... surface and the polymer matrix not only modify the fibre surface but also increase fibre strength Reducing water absorption by composites (increasing moisture resistance) & improving mechanical properties of the composite materials Chemical Compositions of Natural fibres 15 Various Chemical Treatments           16 Alkaline treatment Silane treatment Acetylation Benzoylation Acrylation & Acrylonitrile... solution for 2h, 4h & 8h at R.T Result: Mechanical properties of fibres improved due to increase in Crystallinity Composite material: treated and untreated jute (15 wt%) reinforced unsaturated polyester (UPE) Result: .DSC analysis it was found that thermal stability enhanced due to the resistance offered by the closely packed cellulose chain in combination with the resin .Flexural strength of the composite . of natural fibres. This helped increase the strength of the Bio composites made from them. 13 Chemical Modifications Chemical modification utilizes chemical agents to modify the surface of fibres. enhance the performance of final natural fibre – based products. It is believed that the application of NT to modify natural fibres offers high economic potential for the development of natural fibre. Chemical Modifications of Natural Fibres for Composite Applications  KETKI SURESH CHAVAN Final Year B.Tech F.T.P.T. 201003021052 Seminar Report Presentation on: Introduction to Composites…  Heterogeneous