Format: MS WORD | Chapter: 1-5 | Pages: 65-80 | .
PRODUCTION OF BIODEGRABLE PLASTIC FILMS FROM CASSAVA STARCH USED IN FOOD PACKAGING, USING VARIOUS ADDITIVES AND PLASTICIZERS
CHAPTER ONE
INTRODUCTION
Background study
Packaging using plastic materialsvhas 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 materialsvis 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 willvtake 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 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 source of environmental pollution, harming vorganic naturevwhen vthey are dispersedvin the environment, changes the carbon dioxide cycle, problem associated with increasedvtoxic emission. The sources of synthetic polymersvsuch as fossilvfuel and gas arevnow stimulated by environmental concerns. Scientists are researching different methods of improving plastics that can be used more efficiently such that they could be recycled, vreused and to possiblyvdegradevafter use.
Alternation is towards greener agricultural sources, which also would lead to the reduction of CO2 emissions (Narayan, 2001). According to the Biodegradable Products Institute (BPI), a biodegradable plastics is one in which degradation results from the action of naturally occurring micro-organismsvsuch as bacteria, fungi or algae. Degradablevplastics are classified by American Society for Testing and Materials (ASTM) into four these are:-(1) Photodegradable plastics: Degradation of the plastic results from natural daylight.
(2) Oxidative degradable plastics: A degradation of plastics as a result of oxidation.
(3) hydrolytically degradable plastics: – The degradability results from hydrolysis, vand
(4) Biodegradable Plastics: – Degradable plastics in which there is breakdown of long chain polymer molecule into smaller or shorter lengths. It undergoes oxidation which is triggered by heat, ultraviolent light (UVlight), and mechanical stress. It occurs in the presence of moisture and actions from naturally occurring microorganisms such as bacterial, 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 ofvstarch canvbe used tovincrease the biodegrability of starch-basedvplastics. Amylose is a linear molecule with a few branches, whereasvamylopectinvis a highlyvbranchedvmolecule. Therefore, amylose content is an important factor to biodegrable plastic filmvstrength. Branched structure of amylopect in general 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 emphasisvin biodegrability is that biopolymer materialsvbreakdownvintovsmaller compounds, either chemically or b 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 reducingvthe 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, marine food processing industries waste, or microbial sources. In addition to replenshiable raw agricultural ingredients, biodegrable materials breakdown into environmental friendly products such; as carbon dioxide, vwater and quality compost. Biodegradation takesvplace in two-steps: degradation/defragmentation initiated by heat, moisture, or microbial enzymes, and second 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 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 avcopolymer of PhB and valeric acid (PhB/V). These are made from lactic acid formed from microbial fermentation of starch derivatives, polylactide does not degrade when exposed tovmoisture (Auras.et al, 2007) PHA, PHB, and PHB/V are formed by bacterial actionsvonvstarch (Krochta, 1997). In addition, biodegrable films can also bevproduce from chitosan, vwhich 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 bioactive compounds. The bio compounds are 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 applicationvof synthetic polymer plastics for packaging sincevits inventionvin the 1930s: They are total reliance on petrochemical product as its main feed stock and the problem of waste disposal. Most of today’s conventional synthetic polymers arevproduced from petrochemicalsvandvare not biodegradable. These stable polymers are avsignificant source of environmental pollution, harmful to organic nature when they are dispersed in the environment. The rawvmaterials such as fossil fuel and gas could 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 introducing various forms ofvbiodegradablevplastics. The alternative rawvmaterialsvare nowvfrom plants products, the main amongvmanyvothers is cornvstarch.
1.3 Justification
Biovplastics were too expensive for consideration of replacement for petroleum based plastics. The lower temperature needed for the production of bio plastics and the more Table supply of biomass combined with the increasing cost of crude oil make bio plastics prices more competitive with regular plastics. Starch is inexpensive and abundancevin nature, Nigeriavbeing the world largestvproducer of cassava (FAO, 2009) and being a root crop that canvbe grown in every part of the nation, Starch is totally biodegradable in a wide range of environmentsvand can be usedvin the developmentvof biodegrable packaging products for various market uses. Incineration of starch product is a way of recycling, the atmospheric CO2 trapped by starch-producing plant during growth, thus closing the biological carbon cycle (Ceredavet al).
1.4 Aim and Objectives
The aim of this research 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.
