PRODUCTION OF BIODEGRABLE PLASTIC FILMS FROM CASSAVA STARCH USED IN FOOD PACKAGING, USING VARIOUS ADDITIVES AND PLASTICIZES
1.1 Background study
Packaging using plastic materials has rapidly increased in recent times. Its use covers a wide area of application from automobile parts, food, drinks, water, snacks, cloths, fresh and sea foods, farm products, medicals 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 its diverse and advance properties of longevity. The properties include resistance to 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 of conventional polyethene use its dependence on petroleum and the problem of waste disposal. Most of today’s conventional synthetic polymers are produced from petrochemicals that are not biodegradable. These stable polymers are a significant source of environmental pollution, harming organic nature when they are dispersed in the environment, changes the carbon dioxide cycle, problem associated with increase dtoxic 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, vwhich valsovwouldvlead vto the reduction of CO2 emissions (Narayan, 2001). According to the Biodegradable ProductsvInstitutev (BPI), avbiodegradable plastics isvone in which degradation results from the vactionvofvnaturallyvoccurring vmicro-organismsvsuch as bacteria, vfungi or algae. Degradablevplastics are classified byvAmericanvSociety forvTesting 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 resultsvfromvhydrolysis, vand
(4) BiodegradablevPlastics: – Degradablevplastics invwhich there isvbreakdown of long chain polymervmoleculevinto smaller or shorter lengths. It undergoes oxidationvwhich is triggered by heat, ultraviolent light (UVlight), and mechanical stress. Itvoccurs in thevpresencevof 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 degrades back tovthe earth surfacevharmlessly when disposed. 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 from replaceable 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.
Biodegradation takes place in two-steps: degradation/defrag mentation initiated by heat, moisture, or microbial enzymes, and second step – biodegradation – where the shorter carbon chains pass through the cell walls of the microbes and are used as an energy source. Biodegrable plastics are made from cellulose-based starch and has been in existence for decades, with first exhibition of a cellulose-based starch (which initiated the biodegradable plastic industry in 1862). Cellophane is the most cellulose-based biopolymer. vStarch-based biopolymer, which swell and deform when exposed to moisture, include amylose, hydroxy alkanote (PHA), polyhydroxy buterate (PHB), and a copolymer of PhB and aleric acid (PhB/V). These are made from lactic acid formed from microbial fermentation of starch derivatives, polylactide does not degrade when exposed to moisture (Auras.et al, 2007) PHA, PHB, and PHB/V are formed by bacterial actions on starch (Krochta, 1997). In addition, biodegrable films can also be produce from chitosan, which is derived from chitin of crustacean and insect exoskeletons. Chitin is a biopolymer similar to cellulose structure. There are various ways starch can be used for biodegrable polymer production;
Starch compost containing more than half by mass of the plasticizers.
Biodegrable 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 biodegrability of conventional synthetic polymer.
Synthetic polymers can also be made partially degradable by blending with biopolymers, incorporating biodegrable components such as starch, or by adding bioactie compounds. The bio compounds are degraded to break the polymer into smaller chains. Bioactie 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 bioactie compounds to breakdown the plastics.
1.2 Problem statement
Therevisvbasically, vtwo harmsvconnected to the wide applicationvof synthetic polymer plastics for packaging sincevits inventionvin the 1930s: They arevtotalvreliance on petrochemicalvproduct as itsvmain feedvstockvand the problemvof wastevdisposal. Most of today’s conventional synthetic polymers arevproduced from petrochemicalsvandvare not biodegradable. Thesevstable polymers are avsignificant source ofvenvironmentalvpollution, harmfulvtovorganicvnaturevwhen they are dispersed in the environment. The rawvmaterials such as fossil fuelvand gasvcould be replaced by greenervagriculturalvsources, which contributevto the reductionvof Co2vemissions (Narayan, 2001). Basedvon the abovevit becomes ofvvalue to producevplastics that are biodegradable,vin excess of the past few years syntheticvpolymer usersvhave been introducingvvarious forms ofvbiodegradablevplastics. Thevalternative rawvmaterialsvare nowvfrom plants products, the main amongvmanyvothers is cornvstarch.
1.3 Justification
Biovplasticsvwere too expensive for considerationvof replacementvfor petroleumvbased plastics. The lowervtemperature needed for the production of bio plastics and the more sTable supply of biomass combined withvthevincreasing cost of crude oil make bio plastics prices morevcompetitivevwithvregular plastics. Starch isvinexpensivevand abundancevin nature, Nigeriavbeing the world largestvproducer of cassava (FAO, 2009) and being a root crop that canvbe grown in every part of the nation, Starchvis totally biodegradable in a wide range of environmentsvand can be usedvin the developmentvof biodegrable packaging products for variousvmarket uses. Incineration of starch product is a way of recycling, the atmosphericvCO2 trapped by starch-producingvplant duringvgrowth, thusvclosing the biological carbonvcycle (Ceredavet al).
1.4 Aim and objectives
The aimvof thisvresearch is to produce biodegrable 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 addition of plasticizers and various additives,
Determining the biodegrability 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 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.
