PRODUCTION OF BIODEGRADABLE PLASTIC FILMS FROM CASSAVA STARCH USED IN FOOD PACKAGING, USING VARIOUS ADDITIVES AND PLASTICIZERS
1.1 Background study
Packagingvusing plasticvmaterialsvhas rapidly increasedvin recent times. Its use covers a wide area of application from automobile parts, food, drinks, water, snacks, clothes, fresh and seafood, farm products, vmedicals and pharmaceuticals, to mention but a few. The use of such bombastic amount of schematic plastics and its advantage over other packaging materials is due to to its diverse and advance properties of longevity. The properties include resistance to a chemical reaction, thermal strength, mechanical and its tensile strength, especially enzymatic reactions (Ezeoha and Ezenwanne, 2013.).
For example, it will take a very long time say a hundred years to degrade just a piece of plastic film (polyethene) used to package snacks (gala) at standard environmental conditions. basically, two challenges have been cited with the conventional polyethene use its dependence on petroleum and the problem of waste disposal. Most of today’s conventional synthetic polymers vare produced from petrochemicals that are not biodegradable. Thesevstable polymers are a significant source of environmental pollution, harming organic nature when they are dispersed in the environment, changes the carbon dioxide cycle, the problem associated with increased toxic emission. The sources of synthetic polymers such as fossil-fuel and gas are now stimulated by environmental concerns. Scientists are researching different methods of improving plastics that can be used more efficiently such that they could be recycled, reused and to possibly degrade after use.
Alternationvisvtowardsvgreenervagriculturalvsources, which also would lead to a reduction of CO2 emissions (Narayan, 2001). According to the Biodegradable ProductsvInstitutev (BPI), biodegradable plastics is one in which degradation results from the action of naturally occurring micro-organisms such as bacteria, fungi or algae. Degradablevplastics are classified byvAmericanvSociety for testing and Materials (ASTM) into four these are:-
(1) Photodegradablevplastics: Degradation of the plastic results from natural daylight.
(2) Oxidativevdegradable plastics: A degradation of plastics as a result of oxidation.
(3) hydrolytically degradable plastics: - The degradability results from hydrolysis, and
(4) BiodegradablevPlastics: - Degradablevplastics in which there is a breakdown of long-chain polymer molecule into smaller or shorter lengths. It undergoes oxidation which is triggered by heat, ultraviolet light (UV light), and mechanical stress. Itvoccurs in the presence of moisture and actions from naturallyvoccurringvmicroorganismsvsuch asvbacterial, fungi and algae. (ASTM Standards, 1998)
Thevvariousvdegradablevplastics definitions classified above offers the onlyvproducts whichvarevnaturallyvdegradable. Starch isvbeenvdiscoveredvamongst all biopolymers as a high potentialvmaterial for biodegrablevfilms. Starchvconsists of two types of polysaccharides, amylose and amylopectinvdepending on the sucrose (10-20%) amylase and (80-90%) amylopectin. The hydrophlicity ofvstarch canvbe used tovincrease the biodegrability of starch-basedvplastics. Amylosevis avlinearvmolecule with a fewvbranches, whereasvamylopectinvis avhighlyvbranchedvmolecule. Therefore, vamylosevcontentvis an importantvfactor to biodegrable plastic filmvstrength. Branchedvstructure of amylopectin generallyvleads to filmvwith lowvmechanical properties. To improve thevflexibilityvof plastics, plasticizers arevadded tovreduce internalvhydrogen bondvbetweenvpolymer chainsvwhile increasing molecular space. The mostvcommonly used starchvplasticizers are polyols, sorbitol and glycerol. Thevkey emphasisvin biodegrability is thatvbiopolymer materialsvbreakdownvintovsmaller compounds, either chemically or byvorganisms sooner than synthetic plastics (Bastioli, 2005.). Biodegradablevpackagingvmaterials are materials that degrade back tovthe earth surfacevharmlessly when disposed of. This help largely in reducingvthe amount of packaging materialsvthat goes back into landfills andvfurthermore, saves energy, as the biodegrable route requires little or novexternal source of energy its endothermic.
Biodegrable polymervsources are fromvreplaceable agriculturalvfeed socks, vanimal sources, vmarinevfoodvprocessingvindustriesvwaste, or microbial sources. In addition to replenshiable raw agricultural ingredients, biodegrable materials breakdownvinto environmental friendlyvproducts such; as carbon dioxide, vwater and quality compost.
Biodegradationvtakesvplace in two-steps: vdegradation/defragmentationvinitiated by heat, moisture, or microbial enzymes, andvsecond step – biodegradation – where the shorter carbonvchains passvthrough the cellvwalls of the microbesvand are used as anvenergy source. Biodegrable plastics are made from cellulose-based starchvand has been in existence for decades, with first exhibitionvof a cellulose-basedvstarch (which initiated thevbiodegradable plasticvindustry in 1862). Cellophanevisvthevmost cellulose-basedvbiopolymer. vStarch-based biopolymer, which swellvandvdeformvwhen exposedvtovmoisture, include amylose, hydroxyalka note (PHA), polyhydroxy butyrate (PHB), and a copolymer of PhB and valeric acid (PhB/V). These are made from lactic acid formed fromvmicrobial fermentation of starch derivatives, polylactide does not degrade when exposed tovmoisture (Auras.et al, 2007) PHA, PHB, andvPHB/V are formedvby bacterial actionsvonvstarch (Krochta, 1997). In addition, biodegrable films can also bevproduce from chitosan, vwhich isvderivedvfromvchitin of crustacean and insectvexoskeletons. Chitin is a biopolymer similar to cellulose structure. Therevare variousvwaysvstarchvcan be used for biodegrable polymervproduction;
Starchvcompostvcontainingvmore than half by mass of the plasticizers. Biodegradable polymers preparation using the extrusion process of mixtures of granular starch. Composition of starch with other plastics of little quantity of agricultural-based material to enhance the biodegradability of conventional synthetic polymer.
Synthetic polymers can also be made partially degradable by blending with biopolymers, incorporating biodegradable components such as starch, or by adding bioactive compounds. vThe bio compoundsvare degradedvto break thevpolymervinto smaller chains. Bioactive compounds work through diverse mechanisms. For example, they may be mixed with swelling agents to increase the molecular structure of the plastic which upon exposure to moisture allow the bioactive compounds to breakdown the plastics.
1.2 Problem statement
There is basically, two harms connected to the wide application of synthetic polymer plastics for packaging since its invention in the 1930s: They are total reliance on the petrochemical product as its main feedstock and the problem of waste disposal. Most of today’s conventional synthetic polymers are produced from petrochemicals and are not biodegradable. Thesevstable polymers are avsignificant source ofvenvironmentalvpollution, harmfulvtovorganicvnaturevwhen they are dispersed in the environment. The raw materials such as fossil fuel and gas could be replaced by greener agricultural sources, which contribute to the reduction of Co2vemissions (Narayan, 2001). Based on the above it becomes of value to produce plastics that are biodegradable, in excess of the past few years synthetic polymer users have been introducing various forms of biodegradable plastics. Thevalternative rawvmaterialsvare nowvfrom plants products, the main amongvmanyvothers is cornvstarch.
Biovplasticsvwere too expensive for considerationvof replacementvfor petroleumvbased plastics. The lowervtemperature needed for the production of bioplastics and the more stable supply of biomass combined withvthevincreasing cost of crude oil make bioplastics prices morevcompetitivevwithvregular plastics. Starch is inexpensive and abundance in nature, Nigeriavbeing the world largest producer of cassava (FAO, 2009) and is a root crop that can be grown in every part of the nation, Starchvis totally biodegradable in a wide range of environments and can be used in the development of biodegradable packaging products for various market uses. Incineration of starch product is a way of recycling, the atmosphericvCO2 trapped by the starch-producing plant during growth, thus closing the biological carbon cycle (Ceredavet al).
The aim of this research is to produce biodegradable plastic films from cassava starch used in food packaging, using various additives and plasticizers. This will be achieved via the following objectives.
Extraction of starch from fresh cassava. Improving the extracted starch with the addition of plasticizers and various additives, Determining the biodegradability and tensile strength of the produced biodegradable products and comparing with that of synthetic polyethene. Testing for the validity of the produced biodegradable film.
1.5 Scope of the study
The scope of theses work is strictly limited to:
I. Extraction of starch from cassava.
II. Physical and chemical properties of plasticizers and additives in resumption.
III. Cost estimation.
IV. Biodegrability test, and the characterization of the produced film..