48
CHAPTER 1
INTRODUCTION
CHAPTER 1
INTRODUCTION
India endowed with an abundant availability of natural fiber such as Jute, Coir, Sisal, Pineapple, Ramie, Bamboo, Banana, Ram-Bans etc. has focused on the development of natural fiber composites primarily to explore value-added application avenues. Such natural fiber composites are well suited as wood substitutes in the housing and construction sector. The development of natural fiber composites in India is based on two pronged strategy of preventing depletion of forest resources as well as ensuring good economic returns for the cultivation of natural fibers. The developments in composite material after meeting the challenges of aerospace sector have cascaded down for catering to domestic and industrial applications. Composites, the wonder material with light-weight; high strength-to-weight ratio and stiffness properties have come a long way in replacing the conventional materials like metals, wood etc. The material scientists all over the world focused their attention on green composites reinforced with Jute, Sisal, Coir, Pineapple, Ram-Bans etc. primarily to cut down the cost of raw materials.
COMPOSITE
"Composites are multifunctional material systems that provide characteristics not obtainable from any discrete material. They are cohesive structures made by physically combining two or more compatible materials, different in composition and characteristics and sometimes in form".
Over the last thirty years composite materials, plastics and ceramics have been the dominant emerging materials. The volume and number of applications of composite materials have grown steadily, penetrating and conquering new markets relentlessly. Modern composite materials constitute a significant proportion of the engineered materials market ranging from everyday products to sophisticated niche applications. While composites have already proven their worth as weight-saving materials, the current challenge is to make them cost effective. The efforts to produce economically attractive composite components have resulted in several innovative manufacturing techniques currently being used in the composites industry. It is obvious, especially for composites, that the improvement in manufacturing technology alone is not enough to overcome the cost hurdle. It is essential that there be an integrated effort in design, material, process, tooling, quality assurance, manufacturing, and even program management for composites to become competitive with metals.
DEFINITION OF GREEN COMPOSITE
Green composites combine plant fibres with natural resins to create natural composite materials that are environment friendly and bio-degradable. To develop green composite materials, natural fibers, such as hemp, flax, jute, kenaf and sisal have been used to replace conventional synthetic fibers. In other words, they can be defined as biopolymers or bio-derived polymers reinforced with natural fibers.
1.2.1 CHARACTERISTICS OF THE COMPOSITES
Composites consist of one or more discontinuous phases embedded in a continuous phase. The discontinuous phase is usually harder and stronger than the continuous phase and is called the 'reinforcement' or 'reinforcing material', whereas the continuous phase is termed as the 'matrix'. Properties of composites are strongly dependent on the properties of their constituent materials, their distribution and the interaction among them. The composite properties may be the volume fraction sum of the properties of the constituents or the constituents may interact in a synergistic way resulting in improved or better properties. Apart from the nature of the constituent materials, the geometry of the reinforcement (shape, size and size distribution) influences the properties of the composite to a great extent. The concentration distribution and orientation of the reinforcement also affect the properties.
The shape of the discontinuous phase (which may by spherical, cylindrical, or rectangular cross-sanctioned prisms or platelets), the size and size distribution (which controls the texture of the material) and volume fraction determine the interfacial area, which plays an important role in determining the extent of the interaction between the reinforcement and the matrix.
Concentration, usually measured as volume or weight fraction, determines the contribution of a single constituent to the overall properties of the composites. It is not only the single most important parameter influencing the properties of the composites, but also an easily controllable manufacturing variable used to alter its properties.
COMPONENTS OF A COMPOSITE MATERIAL
In its most basic form a composite material is one, which is composed of at least two elements working together to produce material properties that are different to the properties of those elements on their own. In practice, most composites consist of a bulk material (the 'matrix'), and a reinforcement of some kind, added primarily to increase the strength and stiffness of the matrix.
Matrix
Many materials when they are in a fibrous form exhibit very good strength property but to achieve these properties the fibres should be bonded by a suitable matrix. The matrix isolates the fibres from one another in order to prevent abrasion and formation of new surface flaws and acts as a bridge to hold the fibres in place. A good matrix should possess ability to deform easily under applied load, transfer the load onto the fibres and evenly distributive stress concentration.
1.4.2 Reinforcement
The role of the reinforcement in a composite material is fundamentally one of increasing the mechanical properties of the neat resin system. All of the different fibres used in composites have different properties and so affect the properties of the composite in different ways. For most of the applications, the fibres need to be arranged into some form of sheet, known as a fabric, to make handling possible. Different ways for assembling fibres into sheets and the variety of fibre orientations possible to achieve different characteristics.
1.4.3 Interface
It has characteristics that are not depicted by any of the component in isolation. Then interface is a bounding surface or zone where a discontinuity occurs, whether physical, mechanical, chemical etc. The matrix material must "wet" the fibre. Coupling agents are frequently used to improve wettability. Well "wetted" fibres increase the interface surfaces area. To obtain desirable properties in a composite, the applied load should be effectively transferred from the matrix to the fibres via the interface. This means that the interface must be large and exhibit strong adhesion between fibres and matrix. Failure at the interface (called debonding) may or may not be desirable.
CLASSIFICATION:
Composite materials can be classified into many categories depending on the type of matrix material, reinforcing material type etc. According to the type of matrix material they can be classified as follows:
Metal matrix type composites: MMC are composed of a metallic matrix (Al, Mg, Fe, Co, Cu)
Ceramic matrix composites: CMC is a material consisting of a ceramic combined with a ceramic dispersed phase.
Polymer matrix material: PMC are composed of a matrix from thermosetting (unsaturated polyester, epoxy) or thermoplastic (nylon, polystyrene) and embedded glass carbon, steel or Kerler fibres (dispersed phase). Some of the major advantages and limitations of resin matrices are shown in Table1.1.
Table1.1. Advantages and limitations of polymeric matrix materials
____________________________________________________________________________
Advantages Limitations
____________________________________________________________________________
Low densities Low transverse strength
Good corrosion resistance Low operational temperature limits
Low thermal conductivities
Low electrical conductivities
Translucence
Aesthetic Color effects
____________________________________________________________________________
Generally speaking, the resinous binders (polymer matrices) are selected on the basis of adhesive strength, fatigue resistance, heat resistance, chemical and moisture resistance etc. The resin must have mechanical strength commensurate with that of the reinforcement. It must be easy to use in the fabrication process selected and also stand up to the service conditions. According to the type of reinforcing material type they can be classified into the following categories:
Particle composites- particle reinforced composites consist of a matrix reinforced by a dispersed phase in the form of particles. It can be either of random orientation or preferred orientation.
Fibrous composite-.Short fibre: they consist of a matrix reinforced by a dispersed phase in the form of discontinuous fibres either of random or preferred orientations.
Long fibre- they consist of a matrix reinforced by a dispersed phase in the form of continuous fibres. They can be either unidirectional or bidirectional.
Laminate composites- when a fibre reinforced composite consists of several layers with different fibre orientations, it is called multilayer composite. Apart from that the two broad classes of composites are (1) Particulate composites and (2) Fibrous composites.
Particulate Composites
As the name itself indicates, the reinforcement is of particle nature (platelets are also included in this class). It may be spherical, cubic, tetragonal, a platelet, or of other regular or irregular shape, but it is approximately equiaxed. In general, particles are not very effective in improving fracture resistance but they enhance the stiffness of the composite to a limited extent. Particle fillers are widely used to improve the properties of matrix materials such as to modify the thermal and electrical conductivities, improve performance at elevated temperatures, reduce friction, increase wear and abrasion resistance, improve machinability, increase surface hardness and reduce shrinkage.
.
Fibrous Composites
A fibre is characterized by its length being much greater compared to its cross-sectional dimensions. The dimensions of the reinforcement determine its capability of contributing its properties to the composite. Fibres are very effective in improving the fracture resistance of the matrix since a reinforcement having a long dimension discourages the growth of incipient cracks normal to the reinforcement that might otherwise lead to failure, particularly with brittle matrices.
Man-made filaments or fibres of non polymeric materials exhibit much higher strength along their length since large flaws, which may be present in the bulk material, are minimized because of the small cross-sectional dimensions of the fibre. In the case of polymeric materials, orientation of the molecular structure is responsible for high strength and stiffness. Fibres, because of their small cross- sectional dimensions, are not directly usable in engineering applications. They are, therefore, embedded in matrix materials to form fibrous composites.
CHAPTER 2
REVIEW OF LITERATURE
CHAPTER 2
REVIEW OF LITERATURE
This section of project report provides background information on the bio-fibres and green composites. At the end of this chapter a summary of the literature survey and knowledge gap in the published literature is presented.
D. Maldas et al (1991), Studies on the preparation and properties of particle boards made from bagasse and PVC: II. Influence of the addition of coupling agentsThis article is not included in your organization's subscription. However, you may be able to access this article under your organization's agreement with Elsevier.
. Under study was the effect of thermoplastics (e.g. polyvinyl chloride and polystyrene), as well as a coupling agent — poly (methylene (polyphenylisocyanate)) (PMPPIC) — and bagasse lignin, on the mechanical properties of particle boards of sugarcane bagasse. The mechanical properties of bagasse particle boards were compared to those of hardwood aspen fiber particle boards, delignified bagasse particle boards, as well as those of composites made from bagasse, polymers and coupling agents. Particle boards of bagasse comprising both thermoplastics and a coupling agent offer superior properties compared to those made of only thermoplastic or a coupling agent. The extent of improvement in the mechanical properties of particle boards depended on the concentration of polymers and the coupling agent; nature of the fiber, polymer and coupling agent; composition of PMPPIC and bagasse; as well as lignin content of the bagasse. Moreover, the mechanical properties and dimensional stability of coupling agent-treated particle boards are superior to non-treated ones.
G. C. Stael et al (2001) studied on Impact behavior of sugarcane bagasse waste–EVA composites. They evaluated the impact performance of chopped bagasse–EVA matrix composites and compared it with the behavior of bagasse filled PP and PE matrix composites and wood based materials. The volume fraction and size of the chopped bagasse used as filler was varied. The experimental results show that the incorporation of bagasse strongly reduces the deformation capacity of EVA polymer. The reduction of the deformation capacity of the composites was also inferred by solid-state NMR relaxation analysis. The impact strength was independent of the bagasse size, but varied with the volume fraction. As a function of the volume fraction it was shown that the mechanical performance of bagasse–EVA composites could be tailored to reproduce the behavior of wood based particle boards.
K. N. Matsui et al (2004) analyzed the influence of impregnation with starch acetate on tensile strength and water absorption properties in their study. A fibrous residue rich in non-extracted starch (bagasse) obtained from the industrial production of cassava starch was used to obtain a composite that is similar to cardboard, through a technique used in small scale artisan production of recycled paper. A mixture of 90% cassava bagasse and 10% of Kraft paper was used for the production of these composites. Kraft paper was added as a source of long fibres, in order to improve the mechanical properties of the material. The prepared material has similar characteristics to the molded fibre packaging made using recycled paper, as used in egg boxes. However, cassava bagasse has advantages over recycled paper, in view of the fact that it is obtained from known and renewable sources. The impregnated and non-impregnated materials were submitted to tests of tensile strength and to direct contact with water by complete immersion of the samples. The cassava bagasse-Kraft paper composites obtained had a slight resistance to direct contact with water. The water mass absorbed by the materials impregnated with starch acetate was approximately half that of the materials without impregnation. However, the impregnation had little influence on the tensile strength of the tested samples. Starch acetate is therefore an attractive additive for use in the manufacture of waterproof materials, such as disposable trays.
William Hoareau et al (2004), Sugar cane bagasse and curaua lignins oxidized by chlorine dioxide and reacted with furfuryl alcohol: characterization and stability. Sugarcane bagasse and curaua acidolysis lignins were used to get a better understanding of the mechanism involved in a new chemical modification of sugar cane bagasse and curaua fibres, consisting in a selective oxidation of lignin by chlorine dioxide and reacting some of the created unsaturated units (quinones or muconic derivatives) with furfuryl alcohol (FA). The objective of the treatment was to create a fibre coating increasing compatibility between fibres and phenolic resins in composites. The lignins were reacted with chlorine dioxide to oxidize the phenolic units of the polymer and then treated with furfuryl alcohol. Weight percent gain of 14% and 10% were obtained for sugar cane bagasse and curaua, respectively. 1H and 31P NMR, as well as FT-IR results showed that bagasse lignin had more guaiacyl than syringyl units and the reverse for curaua lignin. 1H NMR of oxidized lignins revealed a decrease of the aromatic and methoxy content after the ClO2 oxidation, due to partial degradation of the macromolecule. Thermal analysis showed that sugar canelignin decomposes at lower temperature than curaua lignin, partly due to the high content of condensed structural units present in curaua lignin. Condensed units decompose at higher temperatures than uncondensed ones. The reaction of oxidized lignin with FA shifted the decomposition exotherm to lower temperature for both curaua and sugar cane bagasse lignins, due to the modification introduced into their structures.
S.M. Luz et al (2004), Cellulose and cell lignin from sugarcane bagasse reinforced polypropylene composites: Effect of acetylation on mechanical and thermal properties. This current work is concerned with the development of polypropylene composites reinforced with cellulose and cellulignin fibers attained from sugarcane bagasse. Moreover, the fibers were chemically modified by acetylating process and its effects on the fiber/matrix interaction were also evaluated. The chemical modification efficiency was verified by FTIR analysis and the fibers morphological aspects of fibers by SEM. Likewise, the influence of modified fibers content in the composites was studied by mechanical (tensile, shear and flexural tests) and thermal analyses (TGA and DSC). After the chemical modification, the FTIR results showed the appearance of acetyl groups and reduction of OH bonds for all fibers. Together with, SEM characterization showed that the acetylation changed the morphology of fibers, resulting in mechanical properties decreases, probably because of the new morphological aspect. The thermal characterization of composites based on untreated and treated cellulose and cellulignin presented intermediary stability in respect to matrix and fiber. Finally, DSC results revealed that the composites reinforced with untreated fibers were more crystalline than neat Polypropylene.
J. Zandersons et al (2004), Carbon materials obtained from self-binding sugar cane bagasse and deciduous wood residues plastics. It is demonstrated that dispersed biomass residues (bagasse, sawdust) can be processed into hard carbonaceous blocks, panels or boards with good strength and thermodynamic properties. There are two possible approaches: to mould dispersed biomass charcoal with a phenol–formaldehyde binder or to produce this material by carbonising the biomass fiberboard prepared by making use of steam explosion autohydrolysis pulp or steam explosion lignin as a binder. In the first step, steam explosion lignin, as a modifier and a binder is introduced to the lignocellulosic biomass by impregnation or during the hot pressing process to form a hard fiberboard. By subsequent carbonisation of the fiberboard panels or blocks, carbonised panels or blocks with high bending and crushing strength and suitable thermodynamic properties are obtained due to the formation of an internal lignin reinforcement in cell lumina and impregnation of cell walls with lignin solution or molten lignin. The carbonised panels demonstrate a good dimensional stability after a standard treatment with water. The bending strength of the carbonised panels after 24 h soaking in water is 93% of that in dry state. The thermodynamic properties and porosity of the carbonised panels demonstrate their suitability for use as a building material. Lignin, a natural binder of fiberboards, has proven to be suitable for preparation of cabonaceous panels and boards. In this respect new carbon building blocks and panels from moulded biomass and carbonised steam exploded biomass act as a concentrated form of long term carbon storage and will be a factor stabilizing the growing CO2 concentration in the atmosphere. [Proceedings of the First Workshop of QITS, Materials Life-Cycle and Environmentally Sustainable Development, March 2–4, Campinas, UNU/IAS San Paulo, Brazil, 1998, pp. 95–101; Proceedings of the Workshop in "Targeting Zero Emissions for the Utilization of Renewable Resources", ANESC, Tokyo, 1999, pp. 2–11.]
P. Rezayati-charani et al (2005), Effect of pulping variables with dimethyl formamide on the characteristics of bagasse-fiber. Organosolv pulping of bagasse was conducted following a central composite design using a two-level factorial plan involving three pulping variables (temperature: 190–210 °C, time: 120–180 min, organic solvent ratio: 40–60% dimethyl formamide). Responses of pulp and hand sheets properties to the process variables were analyzed using statistical software (MINITAB 14). Using values of the independent variables the variation ranges considered provided the following optimum values of the dependent variables: 82.7% (yield), 92.9 (kappa number), 1.403% (ash), 370 ml (freeness), 6290 m (breaking length), 9.4 (folding endurance), 5.955 mN m2 g 1 (Tear index) and 2.811 kNg 1 (Burst index) for pulps and hand sheets. Results showed that acceptable physical and mechanical properties of pulps and papers similar the pulp used for bleaching could be achieved at 210 °C for 150 min and 50% DMF. These are the most suitable conditions for obtaining paper sheets with a high breaking length, tear and burst indices. Also bagasse could be pulped with ease to about 55.72% yield with kappa number -35. The cooking temperature was a significant factor while the DMF ratio and cooking time were not as important in term of the properties of the resultant pulps and papers.
P. Rezayati-Charani et al (2006), Influence of dimethyl formamide pulping of bagasse on pulp properties. Organosolv pulping of bagasse was conducted following a central composite design using a two-level factorial plan involving three pulping variables (temperature: 190–210 °C, time: 120–180 min, organic solvent charge: 40–60% dimethyl formamide). Responses of pulp properties (yield and holocellulose, α-cellulose, kappa number, ash and ethanol–dichloromethane extractives contents) and the pH of the resulting wastewater to the process variables were analyzed using statistical software (MINITAB). Main factor analysis revealed that optimum pulp has the following characteristics: 82.7% (yield), 92.9 (kappa number), 95.84% (holocellulose), 83.53% (α-cellulose), 1.403% (ash), 2.562% (ethanol–dichloromethane extractives contents) and 6.39 (pH). These results showed that acceptable properties of pulps could be gained at 200–210 °C for 150 min and 40–60% DMF. Based on these results, this method could be used for pulping of bagasse equivalent NSSC concerning high yield at a fixed kappa number. In addition, bagasse could be pulped with ease to approximately 55% yield with a kappa number approximately 31. Numerical analyses showed that cooking temperature had the greatest influence on properties of obtained pulps within the DMF concentrations and cooking time as cooking variables.
K. Ganesan et al (2006), Evaluation of bagasse ash as supplementary cementitious materialThis article is not included in your organization's subscription. However, you may be able to access this article under your organization's agreement with Elsevier. The utilization of waste materials in concrete manufacture provides a satisfactory solution to some of the environmental concerns and problems associated with waste management. Agro wastes such as rice husk ash, wheat straw ash, hazel nutshell and sugarcane bagasse ash are used as pozzolanic materials for the development of blended cements. Few studies have been reported on the use of bagasse ash (BA) as partial cement replacement material in respect of cement mortars. In this study, the effects of BA content as partial replacement of cement on physical and mechanical properties of hardened concrete are reported. The properties of concrete investigated include compressive strength, splitting tensile strength, water absorption, permeability characteristics, chloride diffusion and resistance to chloride ion penetration. The test results indicate that BA is an effective mineral admixture, with 20% as optimal replacement ratio of cement.
Yu-Tao Zheng et al (2007), Study on the interface modification of bagasse fibre and the mechanical properties of its composite with PVC. The surface treatments of bagasse fibre (BF) with benzoic acid as a surface/interface modifier and the mechanical properties of BF-polyvinyl chloride (PVC) composite were studied. A typical process for the preparation of the composite was as follows: A mixture of PVC, BF, benzoic acid, and other processing additives were dry-blended in a two-roll mill followed by compression molding. The experimental results indicated that the ratio of PVC/BF, the content of benzoic acid, and processing temperature had a significant effect on the mechanical properties of the composite, which was examined by the orthogonal optimal method. The interface modifier improved significantly on the tensile strength and little on the impact strength of the composite, for example, the tensile strength changed between 42 and 52 MPa comparing to the tensile strength of untreated BF/PVC composite (38 MPa), and the impact strength changed between 8.3 and 9.2 kJ/m2 comparing to the impact strength of untreated BF/PVC composite (7.5 kJ/m2) when the content of benzoic acid changed between 3 and 10%
S.M. Luz et al (2007), Mechanical behavior and micro-structural analysis of sugarcane bagasse fibers reinforced polypropylene composites. The compression and injection molding processes were performed in order to evaluate the better mixer method for fiber (sugarcane bagasse, bagasse cellulose and benzylated bagasse) and matrix (polypropylene). The samples (composites and polypropylene plates) were cut and submitted to mechanical tests in order to measure flexural and tensile properties. The morphological and microstructural analyses of fracture surface and specimens from composites can be easily evaluated by microscopic techniques. The fracture surface was evaluated by SEM and selected specimens from composites were analyzed by reflected light in OM. The better tested method for composites obtainment was the injection molding under vacuum process, by which composites were obtained with homogeneous distribution of fibers and without blisters. The mechanical properties show that the composites did not have good adhesion between fiber and matrix; on the other hand, the fiber insertion improved the flexural modulus and the material rigidity.
K. Bilba et al (2008) studied on Silane treatment of bagasse fiber for reinforcement of cementitious composites. Silane coating of fibers is a promising process for improving durability and adhesion of vegetable fibers used as reinforcement material in a cementitious matrix. The work presented in this paper gives an insight into the effect of combining pyrolysis treatment with silane treatment. Indeed, this study focuses on silane treatment of unpyrolyzed and pyrolyzed sugar cane bagasse fibers with an alkyltrialkoxysilane (RSi(OR )3), S1 or a dialkyldialkoxysilane (R2Si(OR )2), S2. The silane solutions used vary from 0.5% to 8% by volume. This paper describes the effect of two silane compounds on parameters such as the porosity, dimension, morphology and hygroscopic character of silane-coated sugar cane bagasse fibers. Preliminary studies on natural fiber reinforced composite setting time show the importance of the silane chemistry/structure, for fiber treatments with silane solution containing up to 6% (volume percent) silane. In the case of composites reinforced with unpyrolyzed bagass fibers, setting time increases with silane coating. Combining pyrolysis and silane treatment improve the water resistance of the fibers, which become more hydrophobic.
Dimitrios Kalderis et al (2008), Production of activated carbon from bagasseand rice husk by a single-stage chemical activation method at low retention times. The production of activated carbon from bagasse and rice husk by a single-stage chemical activation method in short retention times (30–60 min) was examined in this study. The raw materials were subjected to a chemical pretreatment and were fed to the reactor in the form of a paste (75% moisture). Chemicals examined were ZnCl2, NaOH and H3PO4, for temperatures of 600, 700 and 800 °C. Of the three chemical reagents under evaluation only ZnCl2 produced activated carbons with high surface areas. BET surface areas for rice husk were up to 750 m2/g for 1:1 ZnCl2: rice husk ratio. BET surface areas for bagasse were up to 674 m2/g for 0.75:1 ZnCl2: bagasse ratio. Results were compared to regular two-stage physical activation methods.
S.C. Lee et al (2008), The effect of bagasse fibers obtained (from rind and pith component) on the properties of unsaturated polyester composites. In the present study, two major component of bagasse, namely rind (outer part) and pith (inner part) were used as reinforcement in unsaturated polyester (USP) composites. The bagasse fiber filled USP composites were produced by vacuum bagging method and the volume percentage of fiber was varied at 0%, 5%, 10% and 15%. Characterizations such as flexural, impact and water absorption were carried out to measure the properties of the composites. Based on the result, it was found that the rind fiber composites produced higher flexural and impact properties, and lowered water absorption rate compared to inner fiber composite. In short, the flexural, impact and water absorption properties of bagasse composites are governed by the two major component of bagasse; rind and pith.
V. Vilay et al (2008) published a paper on Effect of fiber surface treatment and fiber loading on the properties of bagasse fiber–reinforced unsaturated polyester composites. In this research, bagasse fiber directly obtained from sugarcane milling process, has been used as reinforcing component for unsaturated polyester resin (USP) to open up further possibilities in waste management. The chemical treatments using sodium hydroxide (NaOH) and acrylic acid (AA) were carried out to modify the fiber properties. The effect of different fiber treatment and the fiber content on the composite properties were investigated. At different fiber loadings, AA treated fiber composites shows better mechanical properties compared to those of NaOH treated fiber composites. SEM investigations show that the surface modifications improve the fiber–matrix interaction. Moreover, the storage modulus of dynamic mechanical analysis (DMA) indicated that NaOH and AA treated fibers based composites enhance the storage modulus of the composites. From water absorption study, it was observed that the treated fiber composites show lower water absorption properties compared to those of untreated fiber based composites.
Nilza G. Jústiz-Smith et al (2008), Potential of Jamaican banana, coconut coir and bagasse fibres as composite materials. This paper presents an evaluation of the alternative use of three Jamaican natural cellulosic fibres for the design and manufacturing of composite materials. The natural cellulosic fibres under investigation were bagasse from sugar cane (saccharumofficinarum), banana trunk from the banana plant (family Musacae, genus Musa X paradisiaca L), and coconut coir1 from the coconut husk (family Palm, genus coco nucifera). Fibre samples were subjected to standardized characterization tests such as ash and carbon content, water absorption, moisture content, tensile strength, elemental analysis and chemical analysis. The banana fibre exhibited the highest ash, carbon and cellulose content, hardness and tensile strength, while coconut the highest lignin content.
Carlos Eduardo da Silva Pinto et al (2009), Studies of the effect of molding pressure and incorporation of sugarcane bagasse fibers on the structure and properties of poly (hydroxy butyrate). Poly (hydroxy butyrate) (PHB) is a biodegradable polymer that can be obtained from both renewable and synthetic resources. There have been many attempts to improve its structure and properties by different methods. This paper, while mentioning briefly PHB and sugarcane bagasse fibers, focuses on the effect of compressive/molding pressure on its structure and thermal properties with incorporation of sugarcane bagasse fibers, with and without steam explosion treatment. Thermal behavior (thermosgravimetry and dynamic mechanical analysis), X-ray diffraction, Fourier transform infrared spectroscopy, optical microscopy methods were used to understand the changes in PHB resulting from the pressure and incorporation of fibers while scanning electron microscopy is used to understand the morphology of both the fiber and PHB.
Eliangela de M. Teixeira et al (2009), Cassava bagasse cellulose nanofibrils reinforced thermoplastic cassava starch. Cellulose cassava bagasse nanofibrils (CBN) were directly extracted from a by-product of the cassava starch (CS) industry, viz. the cassava bagasse (CB). The morphological structure of the ensuing nanoparticles was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), presence of other components such as sugars by high performance liquid chromatography (HPLC), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) experiments. The resulting nanofibrils display a relatively low crystallinity and were found to be around 2–11 nm thick and 360–1700 nm long. These nanofibrils were used as reinforcing nanoparticles in a thermoplastic cassava starch matrix plasticized using either glycerol or a mixture of glycerol/sorbitol (1:1) as plasticizer. Nanocomposite films were prepared by a melting process. The reinforcing effect of the filler evaluated by dynamical mechanical tests (DMA) and tensile tests was found to depend on the nature of the plasticizer employed. Thus, for the glycerol-plasticized matrix-based composites, it was limited especially due to additional plasticization by sugars originating from starch hydrolysis during the acid extraction. This effect was evidenced by the reduction of glass vitreous temperature of starch after the incorporation of nanofibrils in TPSG and by the increase of elongation at break in tensile test. On the other hand, for glycerol/sorbitol plasticized nanocomposites the transcrystallization of amylopectin in nanofibrils surface hindered good performances of CBN as reinforcing agent for thermoplastic cassava starch. The incorporation of cassava bagasse cellulose nanofibrils in the thermoplastic starch matrices has resulted in a decrease of its hydrophilic character especially for glycerol plasticized sample.
Daniella R. Mulinar et al (2009), Preparation and properties of HDPE/sugarcane bagasse cellulose composite obtained for thermokinetic mixer
This article is not included in your organization's subscription. However, you may be able to access this article under your organization's agreement with Elsevier.
. The use of natural fibers as reinforcement for thermoplastics has generated much interest due to their low cost, possibility of environmental protection and use of locally available renewable resources. In this work the mechanical and morphological properties of high density polyethylene/pre-treated and modified residues from sugarcane bagasse cellulose composites were analyzed. Composites were produced by a thermokinetic mixer. The microstructural analyses of fracture surface from composites can be easily evaluated by microscopic techniques. Results showed that the modification of sugarcane bagasse cellulose with zirconium oxychloride was successfully accomplished and that this reinforcement material with high density polyethylene showed tensile strength higher than non-modified sugarcane bagasse cellulose. Modification in the sugarcane bagasse cellulose influenced directly in mechanical properties of the composite material. This can be observed by the fracture surface, which showed that modified cellulose sugarcane bagasse improved interfacial adhesion between fiber and matrix.
Daniella Regina Mulinari et al (2009), Sugarcane bagasse cellulose/HDPE composites obtained by extrusion. Natural fibers used in this study were both pre-treated and modified residues from sugarcane bagasse. Polymer of high density polyethylene (HDPE) was employed as matrix in to composites, which were produced by mixing high density polyethylene with cellulose (10%) and Cell/ZrO2·nH2O (10%), using an extruder and hydraulic press. Tensile tests showed that the Cell/ZrO2·nH2O (10%)/HDPE composites present better tensile strength than cellulose (10%)/HDPE composites. Cellulose agglomerations were responsible for poor adhesion between fiber and matrix in cellulose (10%)/HDPE composites. HDPE/natural fibers composites showed also lower tensile strength in comparison to the polymer. The increase in Young's modulus is associated to fibers reinforcement. SEM analysis showed that the cellulose fibers insertion in the matrix caused an increase of defects, which were reduced when modified cellulose fibers were used.
R. Hoto et al (2014), Flexural behavior and water absorption of asymmetrical sandwich composites from natural fibers and cork agglomerate core. This work addresses an experimental investigation concerning flexural and water absorption behavior of a novel low-cost green composite asymmetric sandwich. For specimen manufacturing, an agglomerate cork panel and natural fiber reinforcements, namely basalt and flax fiber were used. A bio-based epoxy resin was used as matrix and the specimens were manufactured using vacuum assisted hand lay-up. For some specimens the core material was altered allowing resin infiltration between the granules. Results show that both, the core type and specimens' stance influence the flexural behavior. More importantly, all specimens showed a very good energy absorption behavior during bending tests. The water absorption of the specimens was significantly reduced by the infiltration of resin inside the core material. These attractive performances reveal that the green composites based sandwich proposed in this work can be a good alternative to traditional ones.
Alexandre Gomes et al (2007), Development and effect of alkali treatment on tensile properties of curaua fiber green composites. This paper describes development and improvement of mechanical properties of a so-called green composite that was fabricated by reinforcing a cornstarch-based biodegradable resin with high-strength natural fibers extracted from a plant named curaua. Two fabrication methods are proposed, in which stretched slivers of curaua fibers are prepared as reinforcement to increase the composite strength. Moreover, highly concentrated alkali treatment was applied to curaua fibers to improve mechanical properties of green composites. Tensile test results showed that alkali-treated fiber composites increased in fracture strain twice to three times more than untreated fiber composites, without a considerable decrease in strength. This result proves that appropriate alkali treatment is a key technology for improving mechanical properties of cellulose-based fiber composites.
Hitoshi Takagi et al (2007), Effects of processing conditions on flexural properties of cellulose nano-fiber reinforced green composites. Environmentally-friendly ''green'' composites were fabricated from starch-based, dispersion-type biodegradable resin and cellulose nano-fibers. Dispersion-type biodegradable resin and cellulose nano-fibers were blended well using a home-use mixer and a stirrer; the mixture was then dried in air or in vacuum. Composites were hot-pressed at 140 _C and 10–50 MPa. Their flexural strength and flexural modulus increased with increasing molding pressure. They were also affected by preparation methods and conditions. Their mechanical properties such as strength and modulus showed good correlation with their density. Especially, it is apparent that the stirrer mixing process is effective, yielding enhanced uniform dispersion of nano-fibers.
F.P. La Mantia et al (2011), Green composites: A brief review. The rising concern towards environmental issues and, on the other hand, the need for more versatile polymer-based materials has led to increasing interest about polymer composites filled with natural organic fillers, i.e. fillers coming from renewable sources and biodegradable. The composites usually referred to as green, can find several industrial applications. On the other hand, some problems exist, such as worse process ability and reduction of the ductility. The use of adhesion promoters, additives or chemical modification of the filler can help in overcoming many of these limitations. These composites can be further environment-friendly when the polymer matrix is biodegradable and comes from renewable sources as well. This short review briefly illustrates the main paths and results of research (both academic and industrial) on this topical subject, providing a quick overview (with no pretense of exhaustiveness over such a vast topic), as well as appropriate references for further in-depth studies.
Michael P.M. Dicker et al (2013), Green composites: A review of material attributes and complementary applications. Despite the large number of recent reviews on green composites, limited investigation has taken place into the most appropriate applications for these materials. Green composites are regularly referred to as having potential uses in the automotive and construction sector, yet investigation of these applications reveals that they are often an inappropriate match for the unique material attributes of green composites. This review provides guidelines for engineers and designers on the appropriate application of green composites. A concise summary of the major material attributes of green composites is provided; accompanied by graphical comparisons of their relative properties. From these considerations, a series of complementary application properties are defined: these include applications that have a short life-span and involve limited exposure to moisture. The review concludes that green composites have potential for use in a number of applications, but as with all design, one must carefully match the material to the application.
Xiaosong Huang et al (2007), Characterization of flax fiber reinforced soy protein resin based green composites modified with nano-clay particles. In this research, fully environment-friendly, sustainable and biodegradable 'green' composites were fabricated using modified soy protein concentrate (SPC) resins and flax yarns and fabrics. The modified SPC resin was prepared by blending SPC with nano-clay particles, and then cross-linked using glutaraldehyde. The modified SPC resin showed significantly improved mechanical properties. Flax fiber was used as the reinforcement, in both yarn and fabric forms, individually, to fabricate 'green' composites. The unidirectional flax yarn reinforced SPC resin composites showed longitudinal tensile failure stress of 298 MPa and Young's Modulus of 4.3 GPa. These 'green' composites also exhibited excellent flexural properties in the longitudinal direction. The flexural stress was 117 MPa and the flexural modulus was 7.6 GPa. Flax fabric reinforced composites had failure stress of 62 MPa and 82 MPa in the warp and weft directions, respectively. The Young's Modulus values, in both directions, were around 1.2 GPa.
Anil Netravali et al (2009), Biodegradable green composites made using bamboo micro/nano-fibrils and chemically modified soy protein resin. Micro/nano-sized bamboo fibrils (MBF) and a modified soy protein resin were used to fabricate environmentally friendly composites. With the incorporation of MBF the fracture stress and Young's modulus of the soy protein concentrate (SPC) increased significantly. With the addition of 30 parts of MBF (SPC is 100 parts, based on weight), the fracture stress and Young's modulus were increased from 20.2 MPa to 59.3 MPa and from 596 MPa to 1816 MPa, respectively. The addition of MBF, however, did not show significant decrease in the fracture strain of the specimens. As a result, the toughness of the MBF reinforced SPC increased. The toughness of the SPC based composites containing 30 parts of MBF was 6.0 MPa compared to 2.7 MPa for SPC without MBF. MBF reinforced SPC was then cross-linked using a silane, (3-isocyanatopropyl) triethoxysilane (ITES). Although the fracture strength and Young's modulus did not show significant increase, the modification using ITES showed significant increase in the fracture toughness. SPC containing 30 parts of MBF, 10 parts of ITES and 2 parts of glycerol showed fracture stress of 82 MPa, Young's modulus of around 3.2 GPa and toughness of 4.3 MPa. The environment-friendly, fully biodegradable green composites, based on MBF and modified SPC resins, have excellent properties and great potential to replace the traditional petroleum-based materials in many applications.
Jun Tae Kim et al (2011), Development of aligned-hemp yarn-reinforced green composites with soy protein resin: Effect of pH on mechanical and interfacial properties. Unidirectional hemp yarn-reinforced green composites were fabricated with soy protein concentrate (SPC) resin processed at various pH values. To preserve the yarn alignment during the fabrication of green composites, hemp yarn was wound onto a metal frame with slight tension and precured SPC resin was applied to the yarns. Effects of pH values on the tensile properties of the SPC resin and hemp yarn/SPC resin interfacial shear strength (IFSS) were investigated. Increasing pH of the SPC resin from 7 to 12 decreased its fracture stress and Young's modulus from 13.1 MPa and 357.5 MPa to 8.1 MPa and 156.2 MPa, respectively. At the same time fracture strain and moisture content increased from 31.5% and 15.65% to 53.4% and 19.30%, respectively, indicating resin plasticization. However, hemp yarn/SPC resin IFSS increased from 17.7 MPa at pH 7 up to 28.0 MPa at pH 10, after which it decreased. The fracture toughness of the composites increased up to pH of 10 but further increase in pH reduced the toughness. SEM photomicrographs showed fracture surfaces of hemp yarn-reinforced green composites that indicated better resin/fiber interaction at pH of 10 than 7 or 12.
Zengshe Liu et al (2006), Green composites and nano-composites from soybean oil. In this study, we report preparation of epoxidized soybean oil (ESO)-based green composites and nano-composites. The high strength and stiffness composites and nano-composites are formed through flax fiber and organoclay reinforcement. The epoxy resin, 1,1,1-tris(phydroxyphenyl) ethane triglycidyl ether (THPE-GE) is used as a co-matrix for flax fiber-reinforced composites. For the clay-reinforced nano-composites, the dispersion of the clay layers is investigated by X-ray diffraction (XRD) and by transmission electron microscopy (TEM). XRD and TEM data reveal that the intercalated structure of ESO/clay nano-composites has been developed. Mechanical properties of both materials are investigated. As curing agent, triethylenetetramine (TETA) is used for both systems.
Yeng-Fong Shih et al (2009), Biodegradable green composites reinforced by the fiber recycling from disposable chopsticks. The use of disposable chopsticks is very popular in chopsticks-using countries, such as Taiwan, China and Japan, and is one of the major sources of waste in these countries. In this study, the fiber recycling from disposable chopsticks was chemically modified by coupling agents. Furthermore, the modified fiber was added to the biodegradable polymer (polylactic acid, PLA), to form novel fiber-reinforced green composites. These composites prepared by melt-mixing method, were examined by scanning electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and mechanical tests. The results indicated that the Tg of PLA was increased by the addition of fiber, which may improve the heat resistance of PLA. The thermogravimetric analysis of the composites showed that the degradation process of fiber-filled systems started earlier than that of plain PLA, but possessed a higher char yield. Mechanical tests showed that the tensile strength of the composites markedly increased with the fiber content, reaching 115MPa in the case of being reinforced with 40 phr fiber, which is about 3 times higher as compared to the pristine PLA. Furthermore, this type of reinforced PLA would be more environmental friendly than the artificial additive-reinforced one, and could effectively reduce and reuse the waste of disposable chopsticks.
B.S. Kaith et al (2010), Development of corn starch based green composites reinforced with Saccharumspontaneum L fiber and graft copolymers – Evaluation of thermal, physico-chemical and mechanical properties. In this paper, corn starch based green composites reinforced with graft copolymers of Saccharumspontaneum L. (Ss) fiber and methyl methacrylates (MMA) and its mixture with acrylamide (AAm), acrylonitrile (AN), acrylic acid (AA) were prepared. Resorcinol–formaldehyde (Rf) was used as the cross-linking agent in corn starch matrix and different physico-chemical, thermal and mechanical properties were evaluated. The matrix and composites were found to be thermally more stable than the natural corn starch backbone. Further the matrix and composites were subjected for biodegradation studies through soil composting method. Different stages of biodegradation were evaluated through FT-IR and scanning electron microscopic (SEM) techniques. S. spontaneum L fiber-reinforced composites were found to exhibit better tensile strength. On the other hand Ss-g-poly (MMA) reinforced composites showed maximum compressive strength and wear resistance than other graft copolymers reinforced composite and the basic matrix.
Georgios Koronis et al (2010), Green composites: A review of adequate materials for automotive applications. This study provides a bibliographic review in the broad field of green composites seeking-out for materials with a potential to be applied in the near future on automotive body panels. Hereupon, materials deriving from renewable resources will be preferred as opposed to the exhaustible fossil products. With the technical information of bio-polymers and natural reinforcements a database was created with the mechanical performance of several possible components for the prospect green composite. Following the review, an assessment is performed where aspects of suitability for the candidate elements in terms of mechanical properties are analyzed. In that section, renewable materials for matrix and reinforcement are screened accordingly in order to identify which hold both adequate strength and stiffness performance along with affordable cost so as to be a promising proposal for a green composite.
Georgios Koronis et al (2012), Green composites: A review of adequate materials for automotive applications. This study provides a bibliographic review in the broad field of green composites seeking-out for materials with a potential to be applied in the near future on automotive body panels. Hereupon, materials deriving from renewable resources will be preferred as opposed to the exhaustible fossil products. With the technical information of bio-polymers and natural reinforcements a database was created with the mechanical performance of several possible components for the prospect green composite. Following the review, an assessment is performed where aspects of suitability for the candidate elements in terms of mechanical properties are analyzed. In that section, renewable materials for matrix and reinforcement are screened accordingly in order to identify which hold both adequate strength and stiffness performance along with affordable cost so as to be a promising proposal for a green composite.
Chensong Dong et al (2013), Flexural properties of cellulose nano-fibre reinforced green composites. A study on the flexural properties of environmentally friendly green composites made from starch-based, dispersion-type biodegradable resin and cellulose nano-fibres is presented in this paper. Models were developed for correlating the flexural modulus and flexural strength with voids and fibre length–diameter ratio due to processing. It shown voids and fibre length–diameter ratio have large effect on the flexural modulus. The flexural modulus decreases with increasing void content and increases with fibre length–diameter ratio. Thus, the flexural modulus can be increased by choosing the processing method. This study shows the stirrer mixing process yields the highest average fibre length–diameter ratio. Flexural strength decreases as expected with increasing void content. The stirrer mixing process yields the highest overall flexural strength, which is due to the lowest void content and enhanced uniform dispersion of nano-fibres. It can be derived from the regression model that flexural strength is dependent on the average fibre length–diameter ratio, and the critical fibre length–diameter ratio for reinforcing the matrix is about 80. The sensitivities of the flexural strength to voids were also studied, and it was found that the stirrer-treated composites were least sensitive to voids.
Table 2.1: The properties evaluated for each green composite
S.No.
Author
Components
Results
1
Anil Netravali
Soy protein concentrate,
nano-sized bamboo fabrils,NaOH,
Glycerol, ethanol, anhydrous tetrahydro furan and triethoxysilane.
Environment friendly fully bio-degradable green composites based on MBF and modified SPC resins have excellent properties and great potential to replace the traditional petroleum base in many applications.
2
X.huang
MBF(bamboo fabrils)
Renewable materials for matrix and reinforcement were screened accordingly in order to identify adequate strength n stiffness performance along with affordable cost so as to be a promising proposal for a green composite
3
Ajaya kumar behera
Jute felt, jute fabrics, ammonium hydroxide and soy bean
The composition of the developed composites was novel. The fabricated composites can be used in various fields for replacing plastic
4
R. Hoto
Agglomerate cork panel and natural fiber reinforcements, namely basalt and flax fiber
These attractive performances reveal that the green composites based sandwich can be a good alternative to traditional ones.
5
Alexandre Gomes
Starch-based biodegradable resin with high-strength natural fibers extracted from a plant named curaua
Results showed that alkali-treated fiber composites increased in fracture strain twice to three times more than untreated fiber composites, without a considerable decrease in strength.
6
Xiaosong Huang
Modified soy protein concentrate (SPC) resins and flax yarns, fabrics,
Glutaraldehyde,
nano-clay particles
The modified SPC resin showed significantly improved mechanical properties. These green composites also exhibited excellent flexural properties in the longitudinal direction.
7
Zengshe Liu
Epoxidized soybean oil (ESO)
flax fiber and organoclay
The ESO-based green composites and nano-composites have been developed. The flexural modulus and tensile modulus of the composites increased proportionally with the amount of THPE-GE. The flexural modulus also increased with fiber contents lower than 10 wt.%, but showed a decrease beyond 10 wt.%. The tensile modulus increases with fiber content until a maximum, at 13.5 wt.%, and then it decreases..
8
Yeng-Fong Shih
Polylactic acid (PLA),
fiber recycling from disposable chopsticks
This type of reinforced PLA would be more environmental friendly than the artificial additive-reinforced one, and could effectively reduce and reuse the waste of disposable chopsticks.
and little on the impact strength of the composite.
CHAPTER 3
MATERIAL PREPARATION
CHAPTER 3
MATERIAL PREPARATION
This section describes about the material used in casting of hybrid composite, their physical properties and chemical properties etc. In this section, the method used to prepare the composite is also described.
3.1. Material
3.1.1. Soy Seed
Soy protein contained in soy seeds has been used to fabricate biodegradable green plastics and composites due to its low cost and worldwide availability. Soy protein contains 18 amino acids including those that contain polar functional groups, such as carboxyl, amine and hydroxyl groups that are capable of chemically reacting. These reactive groups can be utilized for chemically modification to improve the mechanical and physical properties of protein and thus improve the properties of the composites made using them.
3.1.2.Ram-Bans Fibre
Figure3.1: Ram-bans Plant
Family: Agavaceae
Vernacular name: Ram-Bans, Kandala
Part used: Leaf
Uses of fibre: Making ropes, mats, twines, nets, cordage, etc.
Brief description:
These are robust acaulescent shrubs. The leaves are thick, flat, 0.5-2.2 m long, and crowded in the basal part. Flowering stem stout, up to 2 m high, covered with scales.
Flowering & fruiting: July - December
Distribution: Commonly grows in dry exposed waste places like edges of scrub jungles in Himalayan region.
Extraction method
Fresh leaves (3-4 years old) are cut from the base with the help of a sickle. After removing the terminal and marginal spines, the leaves are beaten with the help of a wooden hammer until the complete separation of fibres. After separation, the fibres are sun dried for one or two days and stored in a dry place. The dried fibres are used for making different products. Another method of fibre extraction follows the process of retting, wherein the leaves are kept in the open for two to four weeks for retting. Then the leaves are beaten with a wooden hammer until the separation of fibres. Combining the retting and beating method of fibre extraction is easier and less time consuming than only the beating method. However, the fibres obtained from the retting and beating method become brownish. On the other hand, fibres obtained from the beating method remain white in colour, and can be used for making diverse colorful products. Various products are then prepared from the fibre for household as well as other purposes.
3.1.3. Jute fibres
Jute fibres are very long (1 to 4 metres), silky, lustrous and golden brown in colour. In contrast to most textile fibres which consist mainly of cellulose, jute fibres are part cellulose, part lignin. Cellulose is a major component of plant fibres while lignin is a major component of wood fibre; jute is therefore partly a textile fibre and partly wood. Jute fibre has strength, low cost, durability and versatility.
Figure3.2: Jute Fibres
Family: Tiliaceae
Vernacular name: Narehha, Narcha, Kalasaka, Mora Pat, Jute
Part used: Stem bark
Uses of fibre: Making gunny bags, ropes, carpets, rugs, rough cloth and many other similar articles of daily use.
Extraction method
The plants are cut close to the ground with sickles. Cut plants are tied into bundles up to 23 cm in diameter. Jute is retted in any type of clean water that is available in the vicinity of the fields. In low-land areas it is retted in slow running water, and the fibre of very good quality is obtained. If water is stagnant it is usual to steep the bundles twice or thrice with short intervals between successive steeping. The fibre obtained is somewhat dark in colour. For steeping, the bundles are generally arranged in two or three layers. Each individual float is called Jak. The surface of the Jakis covered with weeds or other refuse and it is submerged by weighting it down with logs, banana stems or mud. Complete submersion is essential for uniform retting, but care should be taken that the Jakdoes not sink to the bottom. Retting results in the separation of fibre strands from the central woody portion due to the disintegration of soft tissues in which fibres are embedded. When retting is completed the bundles are removed for stripping the fibres. The retted stems are broken into two or three parts by a mallet, and the fibre is separated from the sticks by jerking and washing in water. The stripped fibres are washed and dried in the sun for two to three days. Dried fibres are made up in hanks or lots of about 4 kg each, tied at the top ends. In some parts, lots are given a slight twist and folded into small compact bundles, varying in weight from 40-50 kg each. The extracted fibre is weaved through machines and subsequently the products prepared for marketing.
3.1.4. Binding Element
3.1.4.1. Glyoxal: Glyoxal is an organic compound with the formula OCHCHO. It is a yellow-colored liquid that evaporates to give a green-colored gas. Glyoxal is the smallest dialdehyde. Glyoxal is efficient crosslinker which decreases water uptake in crosslinking cellulose.
3.1.4.2. Glycerol: Glycerol is a nontoxic, sweet tasting, and viscous fluid that has the chemical formula C3H8O3. It is a polyol, a compound that is made up of more than one hydroxyl group. Its chemical structure consists of three hydroxyl groups, which are [OH]- groups attached to the carbon atoms. It is a colorless, odourless, viscous liquid that is widely used in pharmaceutical formulations. Its three hydroxyl groupsthose are responsible for its solubility in water and its hygroscopic nature. Glycerol behaves as a plasticizer. Glycerol can form strong hydrogen bonds with soy protein molecules. This will reduce the interaction between soy protein molecules.
3.1.5. Ammonium hydroxide (NH4OH): Ammonia liquid or ammonium hydroxide (NH4OH) chemical, which is a compound of nitrogen and hydrogen, is a colorless chemical solution which has a strong smell. It is primarily used as a solvent in many processes and industries.
3.2. Experimental Procedure
1. Extraction of soymilk from soy seeds
Soy seeds will be washed properly and soaked in distilled water (1:4, w/v) for 4 h. Water soaked soy seeds will be crushed in a mixer grinder to get soy paste. Soymilk will be extracted from soy paste by squeezing through nylon cloth. About 3:1 (v/w) of soy milk was obtained from soy seeds. Soymilk will be then made alkaline (pH 9) by adding ammonium hydroxide (NH4OH) in order to stabilize it.
Figure3.3. pH Testing
Solid content of soy milk will be determined by taking 10 ml of soy milk in a dry 10cm diameter petridish and weighed (W1). It will be kept in an oven at 70 C for 6 hrs. After that petridish will kept in a vacuum desiccator at room temperature for 24 h and final weight (W2) is to be taken. The solid content of soy milk will be calculated as 20% by the following formula:
Solid content (%) = (W2-W1) / (W1x100)
2. Preparation of soy resin film (SRF)
Different weight percentages of glyoxal (1, 5, 10, 15, and 20) (w/w, solid content of soy milk) along with 10 wt% of glycerol (w/w, solid content of soy milk) will be added to required amount of soymilk and stirred for 30 min to prepare soy resin using a magnetic stirrer as shown in figure4.
Figure3.4. Magnetic Stirrer
100 ml of soy resin will be poured on a flat glass petri dish of diameter 15 cm, which will be kept in a thermal chamber at 125 C for 25 min. Then dark brown soy resin film (SRF) will form. Soy resin films will be coded as SRF1, SRF5, SRF10, SRF15, and SRF20 with respect to wt% of glyoxal. The resin film will be kept in open air for 30 min to absorb some moisture, which helps for easy peeling. Tensile specimens were prepared from different sets of SRF and tested.
The results of tensile properties of different percentage of glyoxal in soy film resin that soy film resin prepared with 10% glyoxal and 10% glycerol showed the highest tensile strength which may be due to better cross linking between soy protein and glyoxal. The NH2 group present in soy protein reacts with glyoxal land produce strong electrovalent bonds to improve mechanical strength of cross linked resin. Addition of excess of crosslinking agent does not increase tensile strength as there are less number of available sites in protein of soy milk for bonding. Hence, 10 wt% of glyoxal was considered optimum as crosslinking agents for preparing fibre reinforced bio composites.
3. Preparation of Agriculture fibre soy composites
Agriculture fibres will be use as reinforcing material for composite preparation. Varying the wt% of agriculture fibres composites will be fabricated. Glyoxal (as optimized from tensile testing of SRF) and glycerol (10 wt%, w/w solid content of soymilk) will be mixed with soymilk with continuous stirring for 20 min to prepare soy resin Agriculture fibres will be soaked in this resin by dipping process and then partially dried in an oven at 600C for 45 min.
Figure3.5. Fibre Soy Milk mixture prepared in petri dish
Figure3.6. Microwave oven
Partially dried soy resin impregnated jute felts will be compressed using a hydraulic press at 1250C and a pressure of 8 ton for 25 min (curing time) to obtain composites.
Specimen Preparation
The pieces of required sizes will be cut from the casted material. After that each specimen will be polished with sandpaper. Finally, the specimen will be post-cured at 120°C for 2 h in a mechanical convection oven.
The dimensions for the Ram-Bans specimens taken for the testing are
Gauge Length: 30mm
Width: 20mm
Thickness: 1.5mm
CHAPTER 4
MECHANICAL TESTING
CHAPTER 4
MECHANICAL TESTING
4.1. TENSILE TEST
4.1.1. What is Tensile Testing?
A tensile test, also known as tension test, is probably the most fundamental type of mechanical test you can perform on material. Tensile tests are simple, relatively inexpensive, and fully standardized. By pulling on something, you will very quickly determine how the material will react to forces being applied in tension. As the material is being pulled, you will find its strength along with how much it will elongate.
The tensile testing is carried out by applying longitudinal or axial load at a specific extension rate to a standard tensile specimen with known dimensions (gauge length and cross sectional area perpendicular to the load direction) till failure. The applied tensile load and extension are recorded during the test for the calculation of stress and strain. A range of universal standards provided by Professional societies such as American Society of Testing and Materials (ASTM), British standard, JIS standard and DIN standard provides testing are selected based on preferential uses. Each standard may contain a variety of test standards suitable for different materials, dimensions and fabrication history.The equipment used for tensile testing ranges from simple devices to complicated controlled systems. The so-called universal testing machines are commonly used, which are driven by mechanical screw or hydraulic systems. A hydraulic testing machine uses the pressure of oil in a piston for load supply. These types of machines can be used not only for tension, but also for compression, bending and torsion tests. A more modernized closed-loop servo-hydraulic machine provides variations of load, strain, or testing machine motion (stroke) using a combination of actuator rod and piston. Most of the machines used nowadays are linked to a computer-controlled system in which the load and extension data can be graphically displayed together with the calculations of stress and strain.
4.1.2. Why Perform a Tensile Test or Tension Test?
You can learn a lot about a substance from tensile testing. As you continue to pull on the material until it breaks, you will obtain a good, complete tensile profile Tensile testing, also known as tension testing, is a fundamental materials science test in which a sample is subjected to a controlled tension until failure. The results from the test are commonly used to select a material for an application, for quality control, and to predict how a material will react under other types of forces. Properties that are directly measured via a tensile test are ultimate tensile strength, maximum elongation and reduction in area. From these measurements the following properties can also be determined: Young's modulus, Poisson's ratio, yield strength, and strain-hardening characteristics. Uniaxial tensile testing is the most commonly used for obtaining the mechanical characteristics of isotropic materials. For anisotropic materials, such as composite materials and textiles, biaxial tensile testing is required. A curve will result showing how it reacted to the forces being applied. The point of failure is of much interest and is typically called its "Ultimate Strength" or UTS on the chart.
Figure4.1: Universal Tensile Testing Machine
4.1.3. Sample size
Length (L) =30mm
Width (W) =20mm
Thickness (D) =1.5mm
20
1.5
1.5
30
30
Figure4.2: Specimen for tensile test
WATER ABSORPTION CAPACITY TEST
The water absorbed by the composites panels was measured along with the thickness and volume swelling. The exact masses of the specimens were measured and recorded before starting the tests. After removal of samples from water, the excess water on their surfaces was wiped off by a dry wipe and then their weights were measured. According to ASTM D 570, the water absorption percentage was estimated using the relation:
%water absorbed=final weight-initial weightinitial weight*100
Mass can be thinly distributed as in a pillow, or tightly packed as in a block of lead. The space the mass occupies is its volume, and the mass per unit of volume is its density. Mass (m) is a fundamental measure of the amount of matter. Weight (w) is a measure of the force exerted by a mass and this force is force is produced by the acceleration of gravity. Therefore, on the surface of the earth, the mass of an object is determined by dividing the weight of an object by 9.8 m/s2 (the acceleration of gravity on the surface of the earth). Since we are typically comparing things on the surface of the earth, the weight of an object is commonly used rather than calculating its mass.
4.2.1. Procedure for measuring water absorption capacity-
First we weighted the mass of the specimen whose size was (20mm*20mm*1.5mm), and then the exact size of the specimens was measured and recorded before the tests. Then, the specimens were submerged in distilled water and samples were taken out after certain times for size measurements. At the beginning, the measurements were done every 5 minutes, then it was increased to 10.The total measurement duration was 40 minutes, when all the test results reached steady state. Weight of the sample specimen is measured after every 10 minute untill a saturation state is reached means when change in weight is almost zero .Water absorption capacity of the sample is determined as the relative change in weight of the sample.
%Relative change in weight=final weight-initial weightinitial weight*100
Jute fibers have about 60% of their mass as cellulose. The cellulose molecule has a polar group which attracts water molecules through hydrogen bonding. Attachment of water molecules to cellulose molecules leads to moisture build-up within cell walls which also appears as swelling in jute fibers. The higher percentage of jute fibers in the composite implies a higher percentage of cellulose molecules in the composite, which inturns leads to higher water absorption.
Since the matrix swell less than the fibers, so when fibers in a composite start to swell, they exert stress on the matrix through the fiber/matrix interface. This stress causes the matrix to stretch and make more space for the swelling of fibers. This process continues until the stress exerted by the fibers is balanced by the countervailing stress of the matrix.
CHAPTER 5
RESULTS AND DISCUSSION
5
CHAPTER 5
RESULTS AND DISCUSSION
5.1 Water Absorption capacity
Water absorption capacity is another crucial factor to be taken into account when considering the effect of water on the composite material developed. The effect of water absorption is important in case the material that has been developed when used for applications comes in contact of water. The effect is presented in Table5.1.
Table5.1: Water Absorption Capacity of Ram-Bans
S. No.
Ram-Bans %
% Water Absorption
1.
8
39.285
2.
10
40.54
3.
12
71.42
Figure5.1. Water Absorbed after specific time interval by different wt% of Ram-Bans specimen
It can be seen from Table5.2 that the tendency for water absorption of Ram-Bans reinforced composite increases as the weight of the fibre in the matrix increases.
Table 5.2: Water Absorption Capacity of Jute
S. No.
Jute %
% Water Absorption
1.
6
65.06
2.
8
60
3.
10
47.8
Figure5.2. Water Absorbed after specific time interval by different wt% of Jute specimen
Whereas it can be seen from Table 4 that the tendency for water absorption of jute decreases as the weight of the fibre in the matrix increases.
5.2 Mechanical Properties
5.2.1Tensile stress-strain curve
The tensile stress-strain curve for Ram-Bans (wt % 8, 10, 12) and Jute (wt % 6, 8, 10) reinforced composite is shown in figure 11 and12.
Figure5.3. Stress-Strain Curve for different wt% of Ram-Bans Fibre Reinforced Soy Composites
Figure5.4. Stress-Strain Curve for different wt% of JuteFibre Reinforced Soy Composites
5.2.2 Tensile strength
The mechanical properties of the composite materials were determined by universal testing machine. Tensile tests were carried out at strain rates of 0.1 mm/min. The tensile strength of Ram-Bans and Jute are shown in Table 5.3 and 5.4.
Table5.3. Maximum Tensile Strength of Rambans reinforced composites
S. No.
Ram-Bans %
Ultimate Tensile Strength (MPa)
1.
8
2.449
2.
10
5.386
3.
12
3.34
Table5.4. Maximum Tensile Strength of Rambans reinforced composites
S. No.
Jute %
Ultimate Tensile Strength (MPa)
1.
6
4.603
2.
8
2.58
3.
10
2.34
It has been observed from tensile testing that as the weight % of Ram Bans increases, the tensile strength of composite increases, and after reaching a maximum value at 10%, it starts decreasing. This is because after 10% composition, if more fibres are added in the given volume of Soy milk, it serves insufficient to bind them in the matrix. The wettability of the fibres decreases as their amount exceeds a certain weight %.In case of jute, the tensile strength decreases with increase in weight % Jute fibers. This may be due to inadequate wetting of jute fibre surface by soy resin or may be due to the presence of high percentage of Jute causing easy crack initiation and propagation to the fibre end.
CHAPTER 6
CONCLUSION
CHAPTER 6
CONCLUSION
The following conclusions can be drawn from the present study:
As the weight % of Ram Bans increases, the tensile strength of composite increases, and after reaching a maximum value at 10%, it starts decreasing. This is because after 10% composition, if more fibres are added in the given volume of Soy milk, it serves insufficient to bind them in the matrix. The wettability of the fibres decreases as their amount exceeds a certain weight %.
As per the readings, the water absorbed by the given weight of the composite increases as the % of fibre in the matrix increases. This is due to the fact that as the weight of fibres in the matrix is increased, the porosity and number of voids in the composite material also increases, thus, their ability to hold water increases.
It has been observed for jute the tensile strength decreases with increase in weight % Jute fibers. This may be due to inadequate wetting of jute fibre surface by soy resin or may be due to the presence of high percentage of Jute causing easy crack initiation and propagation to the fibre end.
The tendency for water absorption decreases as the weight of the fibre in the matrix increases, for jute. This is because of better cross-linking of resin and fibre surface that does not allow water to easily penetrate.
REFERENCES
REFERENCES
Arnold RG, Nelson JA, Verbakc JJ. Recent advanced in isocyanate chemistry, Chem Rev 1957, 57:47–76
Jaya B, Sridevi A., Ratan B, Krishna SR, Adhikari B, Fabrication and characterization of bio degradable jute reinforced soy based green composites, Carbohydrates Polymers 88,2012, 329-335
Chabba S, Netravali AN, 'Green' composites Part 1: characterization of flax fabric and glutaraldehyde modified soy protein concentrate composites, J Mater Sci 2005, 40, 6263–73
Chaudhary A K, Singh VK, Tewari M. Utilization of Waste Agriculture Byproduct to Enhance the Economy of Farmers, Indian Research Journal of Extension Education Special Issue (Volume I), January, 2012, 1, 89-92
Fatima S, Mohanty AR, Acoustical and re-retardant properties of jute composite materials, ApplAcoust 2011, 72, 108–14
Goda K, Sreekala MS, Gomes A, Kaji T, Ohgi J, Improvement of plant based natural bers for toughening green composites – effect of load application during mercerization of ramie bers Compos, Part A: ApplSciManuf 2006, 37, 2213–20.
Huang X, Netravali AN, Biodegradable green composites made using bamboo micro /nanofabrils and chemically modified soya protein resin, Composite Science and technology ,Volume 9,2009, 1009-1015
Huang XS, Netravali AN, Characterization of Nano-clay reinforced Phytagel-modified soy protein concentrate resin, Bio macromolecules 2006, 7, 2783–9
Keller A, Compounding and mechanical properties of biodegradable hemp bre composites, Compos SciTechnol 2003,63, 1307–16
Georgios K, Arlindo S, Mihail F, Green composites: a review of adequate materials for automotive applications, Composites: part B,2013, 44, 120-127
Khatib KA, Herald TJ, Aramouni FM, MacRitchie E, Schapaugh WT. Characterization and functional properties of soy beta-conglycinin and glycinin of selected genotypes, J Food Sci 2002, 67, 2923–9
Krochta JM, DeMulder Johnston CLC, Biodegradable polymers from agricultural products, ACS SymposSer 1996, 647, 120–40
Kylma J, Seppala JV. Synthesis and characterization of a biodegradable thermoplastic poly(ester-urethane) elastomer, Macromolecules 1997, 30, 2876–82
Lodha P, Netravali AN, Characterization of stearic acid modified soy protein isolate resin and ramie fiber reinforced 'green' composites, Compos SciTechnol 2005, 65, 1211–25
Wang S, Jane JL, Morphology and mechanical behaviour of engineering soy plastics. Polymer, 1996, 38, 5035–40
Wollerdorfer M, Bader H, Influence of natural fibres on the mechanical properties of biodegradable polymers, Ind Crop Prod 1998, 8, 105–1
Yu T, Ren J, Li S, Yuan H, Li Y, Effect of ber surface-treatments on the properties of poly(lactic acid)/ramie composites, Compos, Part A: ApplSciManuf 2010, 41, 499–505.
