ABSTRACT
Background study
Packagingvusing plasticvmaterialsvhas rapidly increasedvin recent times. Its vusevcovers a wide area of applicationvfromvautomobile parts, food, drinks, water, snacks, cloths, fresh and sea foods, vfarm products, vmedicals and pharmaceuticals, to mention but a few. The use of such bombasticvamount of schematicvplastics and itsvadvantage overvother packaging materialsvis due tovits diversevandvadvancevpropertiesvofvlongevity.Thevproperties include resistance tovchemicalvreaction, vthermal strength, mechanical and its tensile strength, vespeciallyvenzymaticvreactions (Ezeoha and Ezenwanne, 2013.).
For example it willvtake avveryvlongvtimevsay avhundredvyears to degradevjustva piece of plastic film (polyethene) used to package snacks (gala) at standard environmental conditions. vBasically, two challenges have been cited with the of conventional polyethene usevits dependence on vpetroleum and the problem vof waste disposal. Most of today’s conventionalvsynthetic polymers vare producedvfromvpetrochemicals that vare not biodegradable. Thesevstable vpolymers are a significant vsourcevof venvironmental pollution, vharming vorganic naturevwhen vthey are dispersedvin thevenvironment, changes thevcarbon dioxide cycle, problemvassociatedvwith increasedvtoxic emission. The sources of synthetic polymersvsuch as fossilvfuel and gas arevnow stimulated by environmental concerns. Scientists arevresearchingvdifferentvmethods ofvimprovingvplastics thatvcanvbevusedvmorevefficientlyvsuchvthat they could be recycled, vreused and to possiblyvdegradevafter 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)
The various degradable plastics definitions classified above offers the only products which are naturally degradable. Starch is been discovered amongst all biopolymers as a high potential material for biodegrable films. Starch consists of two types of polysaccharides, amylose and amylopectin depending on the sucrose (10-20%) amylase and (80-90%) amylopectin. The hydrophlicity of starch can be used to increase the biodegrability of starch-based plastics. Amylose is a linear molecule with a few branches, whereas amylopectin is a highly branchedmolecule. Therefore, amylose content is an important factor to biodegrable plastic film strength. Branched structure of amylopectin generally leads to film with low mechanical properties. To improve the flexibility of plastics, plasticizers are added to reduce internal hydrogen bond between polymer chains while increasing molecular space. The most commonly used starch plasticizers are polyols, sorbitol and glycerol. The key emphasis in biodegrability is that biopolymer materials breakdown into smaller compounds, either chemically or by organisms sooner than synthetic plastics (Bastioli, 2005.). Biodegradable packaging materials are materials that degrades back to the earth surface harmlessly when disposed. This help largely in reducing the amount of packaging materials that goes back into landfills and furthermore, saves energy, as the biodegrable route requires little or no external source of energy its endothermic.
Biodegrable polymer sources are from replaceable agricultural feed socks, vanimal sources, marinevfoodvprocessingvindustriesvwaste, or microbial sources. In addition to replenshiable raw agricultural ingredients, biodegrable materials breakdown into environmental friendly products such; as carbon dioxide, water and quality compost.
Biodegradation takes place in two-steps: degradation/defragmentation 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. Starch-based biopolymer, which swell and deform when exposed to moisture, include amylose, hydroxyalkanote (PHA), polyhydroxybuterate (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 tomoisture (Auras.et al, 2007) PHA, PHB, andvPHB/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 biopolymervsimilar tovcellulose structure. Therevare variousvwaysvstarchvcan be used for biodegrable polymervproduction;
Starchvcompostvcontainingvmore than half byvmass of thevplasticizers.
Biodegrable polymers preparationvusing thevextrusion process of mixtures of granularvstarch.
Compositionvof starchvwith othervplastics of little quantityvof agricultural based material to enhance the biodegrability of conventional synthetic polymer.
Synthetic polymers can alsovbe madevpartially degradablevbyvblending with biopolymers, vincorporating biodegrable components such as starch, or by adding bioactive compounds. vThe bio compoundsvare degradedvto break thevpolymervinto smaller chains. Bioactivevcompounds work through diverse mechanisms. For example, theyvmay be mixed with swelling agents tovincrease thevmolecular structure ofvthe plastic whichvupon exposure tovmoisture vallow the bioactivevcompounds to breakdownvthe 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.
1.3Justification
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 Aimvandvobjectives
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.
PRODUCTION OF BIODEGRABLE PLASTIC FILMS FROM CASSAVA STARCH USED IN FOOD PACKAGING, USING VARIOUS ADDITIVES AND PLASTICIZERS
