BIO- DEGRADABLE COMPOSITE MADE FROM STARCH AND COCONUT FIBER : MECHANICAL STRENGTH AND BIODEGRATION CHRACTERSTICS 55 Rahul Sen*, N.C.Upadhayay**, Upender Pandel*** *Research Scholar **Associate Professor ***Professor Department of Metallurgical and Materials Engineering Malaviya National Institute of Technology, Jaipur- 302017, India Abstract Conventional plastics are predominantly made from crude oil. When plastics made from petroleum are burned in air, they release the carbon dioxide contained in the petroleum into the atmosphere, leading to global warming. Most of the pollution in environment is from petroleum based plastics as their wastes are toxic and non- degradable, directly affecting plants, animals and human beings. These wastes are mostly of such plastic made items which are required for short span of time like plastic bottles, plates, cups, spoons and other catering items. Recycling the plastics is always not the great idea as it requires great effort in collection and even not all the plastic wastes are approachable or fully recycled. Waste management and bio- degradation are important criterion. Material of items should be made from waste products or from renewable resources, possess good mechanical strength and after use, do not stuck in environment, get easily degrade. In this paper an attempt has been made to develop biocomposite from starch and coconut waste (coir). The tensile strength, hardness, density and absorptivity were examined at various proportions, which are directly linked with their mechanical strength and bio- degradation characteristic. The SEM micrographs reveal the changes on surface of biocomposite samples and tests show that with increase in fiber content mechanical strength increases upto a limit and then decreases. Absorptivity and density increases with in fiber content and could be utilized as material for catering items required for short span of time. Keywords: bio- composite, bio- degradation, mechanical strength, starch, coconut waste or coir, density, absorptivity Introduction Plastic is versatile materials since the properties of this material can be made to meet specific demands by varying molecular weight distribution and side chain branching. Petroleum based plastic made items, create maximum pollution in the environment, as they are not easily degradable, highly inflammable, and relatively toxic. Bio plastics (green plastics) and green composites (Bio Composite = Bio Plastic + Bio Fibers) tends proportional to degradation and have more environment friendly processing. Bio plastics have limited mechanical strength but composites made by green-plastics and natural fibers are having higher mechanical properties and good decomposing characteristic. In this this study an attempt has been made to develop biocomposite from corn starch and coconut fiber also called coir, and studied the effect of addition of fiber (0.25gm- 1.5gm) on strength and biodegrading characteristics of bio-
composite. First bioplastic made and then coconut fibers were incorporated to increase the strength. [1-4] Classification of Polymers: Polymers derived from renewable resources ( biopolymer ) are generally classified in three categories according to the method of production as follows: 1.Polymers directly extracted/removed from natural materials (mainly plants). Examples are starch and cellulose and proteins such as casein and wheat gluten etc 2.Polymers produced by microorganisms or genetically transformed bacteria. 3.Polymers produced by classical chemical synthesis from renewable bio-derived monomers [5,6] Starch as Bio Polymer The Chemical formula of starch is (C 6 H 10 O 5 )n. It is the main source of carbohydrate for growing seeds and leaf tissue development and is found in tubers, fruits, leaves, and seeds. The length of the starch chain can vary with plant sources but in general the average length is in between 600-20,000 glucose units. There are actually two types of starch molecules: Amylose and Amylopectin. The difference between these two starch molecules, is molecular arrangement Amylose is necessarily linear while amylopectin has many branches like a tree shown in below figure 1.2 Amylopectin Amylose Figure 1.1 Schematic diagram of molecular arrangement in starch molecule.[7] Chemistry of Starch Amylose: These molecules consist of single mostly-un-branched chains with 600-20,000 D- glucose units depend on the source. Hydrogen bonding between aligned chains causes to releases some of the bound water and retro gradation Figure 1.3 Schematic diagram of Amylose molecule Amylopectin: it is formed by non-random 16 branching of the amylase type D-glucose structure. Figure1.2: Schematic diagram of Amylopectin molecule Varieties of Starch: Corn Starch, maize starch, potato starch, rice starch, wheat starch soya bean starch etc. Corn Starch for Bioplastic: Corn starch has 25% amylose and 75% amylopectin. The amylose molecules loose lose water increase biodegradation characteristic and amylopectin molecule is responsible for plasticizer properties.their granule size ranges between 5 to 20 microns. i.e. good absorption capacity,rapid gel formation & good strength. It is easily available and cheap in cost also.[8, 9] 56
Experimental work Corn starch, distilled water coconut fibers and glycerin which works as natural plasticizer were raw material for the experiment. Composites were made by maintain constant starch concentration and with varying fiber concentration. Water (50ML) and glycerin (3ML) concentration (50ml) kept remains same for all samples. Composites containing 0.25, 0.5, 0.75, 1, 1.25, 1.5 gram weight of fibers, Mechanism: The experiment mechanism can be divided in two major parts: Gel formation & Drying Gel formation: Corn starch has 75% amylopectin molecules which are responsible for rapid gel formation properties during heating. First when raw uncooked starch granules heated in water, at that time these corn starch granules absorb the water and become large (swelling), due to which some amylose molecules come out from ctarch granules and get collapsed, here gelation and casting process gets complete and on cooling collapsed granules start compressing and starts coming towards fibers and form a narrow junction. The fibers get entrapped in these narrow junction and are responsible for drying process of corn starch based bioplastic and composite. TESTING OF BIO COMPOSITES 1) Tensile Test Tensile test of Corn starch based Bio Polymer(Maximum stress 0.227MPa) Coconut Hairs Bio Composite Samples Tensile Test Graphs 2) Density Measurement - By Archimedes Principle Method Calculation of density by the formula: Density = Ma x σ w Ma-Mw Here, Ma = Mass of sample weighted in air, Mw = Mass of sample weighted in distilled water for 1minute and σ w = Density of distilled water at N.T.P = 0.99777 g/cm 3 whereas starch was kept 10 gram by weight. For Bio Polymer: Density of Bio Polymer is 1.003 g/cm 3 57
3) Absorptivity (Capacity to Absorb) in Water Measurement Test Calculation of absorptivity can be done by change in weight percentage method. For this, put the sample in an electric oven kept to remove the moisture content in it, measure the weight of dry samples. Dip them afterwards in the beaker containing distilled water for 24hrs and then take them out and again weigh them. Water Absorptivity (M %) of sample can be calculated as : Absorptivity, M % = (M 1 M 0 ) x 100 M 0 Here, M 1 = Mass of dry sample in air in grams M 2 = Mass of water content sample in grams M%= Absorptivity or Capacity to absorb in distilled water For Bio Polymer: Absorptivity or Capacity to absorb water for Bio polymer is found to be 42.78% For Bio Composite 4) SEM: SEM examination conducted to find out, the Surface Morphology of the prepared samples. Result and conclusion Bioplastics (Green plastics) prepared from corn starch by = 10gram starch+50 ML water+3 ML glycerin, is found to have Tensile strength = 0.22MPa.Bio plastic have limited strength and Bio Composite is prepared by in compositing Jute fibers into Bio Plastic from 0.25g to 1.5g. 58 It is found that with increase in fiber percent, strength of bio composite increases upto a particular level then decreases with further addition. It is due to the saturation of fibers and increase of porosity in composite. SEM Micrographs revels the presences of fibers into the matrix, the fibers are embedded nicely into the
matrix. Shows the surface is heterogeneous and rough. At higher concentration of fibers into the matrix, the fibers sprouting outside the surface of the Bio Composite, shows the saturation of fibers into the matrix. Absorptivity or Capacity to absorb water for corn starch based Bio polymer is found to be 42.78% and density of is found to be 1.003 g/cm 3. Corn starch as well as the natural fibers both are hydrophilic in nature, so the starch as well as fibers absorb the water. With the increase in percentage of fiber in the matrix- Absorptivity increases and slightly density also increases. The overall results show that the biocomposite has higher mechanical strength than bioplastic and good absorption characteristic, implies that it could be utilized as material for catering items like plates, cups, spoons etc. which are required for short span of time, possess sufficient mechanical strength and after use get easily degrade. References [1] McKeen. W.Laurence (2010), Introduction to Plastics and Polymers,Permeability Properties of Plastics and Elastomers (Third Edition), pp 21-37 [2] Sperling, L. H., Introduction to Physical Polymer Science, 2nd ed., JohnWiley and Sons, New York (1992), 487. [3] Iles.Alastair, Martin Abigail N.( 2010), Expanding bioplastics production: sustainable business innovation in the chemical industry,journal of Cleaner Production, Vol-3, pp.56-74 [4] Sarasa.J, Gracia.M.J, Javierre.C.(2009), Study of the biodisintegration of a bioplastic materialwaste, Bioresource Technology, vol.100, No-15, pp. 3764-3768 [5]Claus J Weber Biobased Packaging Materials for the Food Industry, report Directorate 12. November 2000 ISBN 87-90504-07-0 [6] Bertolini. Andrea.( 2009), "Starches: Characterization, Properties, and Applications", Source:http://www.livestrong.com/article/501985- types-of-starch/ [7]Emmanuel Nepolo, Isolation and Characterization of Starch, Starch biosynthetic Genes and Protease Inhibitors Frommarama Bean, Thsis of Phd, pp 31, 2014 [8] Maya J. John, Sabu, ThomasNatural Polymers-Volume 2 (2001), chapter 7, pp186. [9] Kawaljit Singh Sandhu, Narpinder Singh Some properties of corn starches II: Physicochemical,gelatinization,retro-gradation, pasting and gel textural properties,sciencedirect, food chemistry 101(2007), pp 4. 59