1.1 Background study
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
resistance tovchemicalvreaction, vthermal strength, mechanical and its
tensile strength, vespeciallyvenzymaticvreactions (Ezeoha and Ezenwanne,
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
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)
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
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.
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,
hydroxyalkanote (PHA), polyhydroxybuterate (PHB), and avcopolymer 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
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
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.
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).
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.