Polymerization Of Various Starches Biology Essay
Every year, approximately 140 million tonnes of synthetic polymers are produced worldwide. Most of these polymers end up by simply disposal at dump sites. These polymers resist degradation and remain many years. These polymers also do not readily enter into the degradation cycles of the biosphere due to their extremely stable. Due to their extremely stable, they tend to produce toxic substance subsequently endanger stability of ecosystem. A large problem has been recognized with environmental pollution by synthetic polymers. The accumulation of plastic waste will also make our landfill area become short and causes diseases when dispose into the sea and river. There are conventional techniques to minimizing these plastic wastes that are by recycling and incineration. Recycling viable for high cost and low volume specially plastics. Emission of corrosive, high capital cost, toxic gases and high temperature make incineration less attractive (Shah et al., 1995).
In order to support continue sustainable development throughout the world, this problem must be addressed. In view of this, the biodegradation of plastics has been studied extensively for the many years. Some types of plastic have been shown to be biodegradable, and their degradation mechanisms have progressively become clearer. There have been increase demands to used biodegradable polymer that are compatible with environment to replace the increasing use of non-biodegradable synthetic plastic waste (Tudorachi et al., 2000).
Starch is a very attractive source for the development of biodegradable plastic packaging due to its price and degradable properties. The price of biodegradable plastic based starch is much lower than the conventional plastic packaging derived from oil, such as polyethylene. This is because the price of oil based polymer may still increase due to the rise in the crude oil prices. Besides, as the starch content is increased, the polymer composites become more biodegradable and leave less recalcitrant residues. Unfortunately, the starch has no physico-mechanical characteristics, as well as processing properties, good enough to allow the whole replacement of the composite materials based on petroleum hydrocarbons. The products from starch are mostly water soluble and brittle. Some properties of starch can be improved by blending with synthetic polymers (Tudorachi et al., 2000).
Usually, starch-based polymers are blended with high-performance polymers such as aliphatic polyesters and poly (vinyl alcohols) to achieve the necessary performance properties for different applications (Curvelo et al., 2001; Ma et al., 2007). Poly (vinyl alcohol) (PVA) is a hydrolysis product of poly (vinyl acetate) having very good water absorption and bio-compatibility (Ramaraj et al., 2005). In a number of studies, polymer blends were prepared on the basis of PVA containing different kinds of starches (tapioca, corn, potato, and others) (El-Mohdy et al., 2007, Ramaraj et al., 2007, Yang et al., 2008) and lignocellulosic materials.
Starch can be readily metabolised by a range of to fermentation products such as ethanol, hydrogen and methane. PVA is susceptible to biological degradation. However, the process is slow especially under anaerobic conditions (Russo et al., 2009). Researchers have employed aqueous anaerobic environments (Pšeja et al., 2006), starch-specific degrading bacterium (Bacillus subtilis) and a PVA degrading bacterium (Pseudomonas vesicularis var. povalolyticum strain PH) (Fujita and Hashimoto, 1985) to degrade the PVA/starch blends. There has been no systematic study on the effect of blend ratios on the degradability of the PVA/starch components.
Nevertheless, several research efforts are still in progress for the purpose of finding new techniques. Heerenklage et al (2000) have shown that PCL (poly-e-caprolacton-PCL tone polymer 767) and Ecoflex did not biodegrade under anaerobic conditions. Ecoflex is in fact biodegradable under aerobic conditions. In aerobic liquid conditions (ISO 14852), showed that starch and synthetic resin followed the same trend of degradation as that pure cellulose, demonstrating degradation of 94% and 92% for pure cellulose (Mohee et al., 2008). Biodegradable polymer accordance with ISO 14855, showed a degradation of about 85% within 45 days under dry aerobic condition (Bidlingmaier and Papadimitriou., 2000). Thermoplastic starch (TPS) and thermoplastic dialdehyde starch (TPDAS) have been investigated by Du et al (2008), showed that TPS fastest degradation than TPDAS. Modified starch-degrading strains isolated from compost are mainly actinomycete. Only a little fungi and hardly any bacteria could be obtained. The assessment of the biodegradability of biodegradable plastic under aerobic or anaerobic conditions is very important if these materials are going to be biologically treated in future.
In this research, various starches will be blended with poly (vinyl alcohol) to form a biopolymer product. Studies on composition of starch, morphological, and rate of degradation will be done to achieve the biodegradation studies of these various starches (tapioca, sago, and rice). Study on the optimum rate of degradation also will be done to improve the percentage of starch blended with poly (vinyl alcohol). This study is important because currently no study has been done on using effective microorganism in biodegradation study for plastic packaging.
1.2 Problem Statement
An alternate tactic to deal with solid plastic waste is to make plastic degradable. In reality, biodegradable have many problems. Some materials degrade very slowly. Other degrades into substances that are hazardous and therefore are polluting.
In general, naturally occurring polymers are more biodegradable than synthetic polymers. Although biodegradation may have significant potential to alleviate some of problems associated with plastic waste disposal, they remain some controversy as to whether any significant biodegradation will actually occur in modern.
Thus, the proposed project aim to study the biodegradation of tapioca, sago, and rice starch at different percentage of starch loading blended with PVA according to International Organization for Standardization (ISO). In this study several questions which need to be answered are as follows:
What the effects of composition of starch blended with PVA improve the rate of biodegradation under aerobic and anaerobic conditions?
What the possibility using an effective microorganism increase the rate of biodegradation?
Which various starches blended with PVA have a faster rate of degradation?
1.3 Objectives of Research
The objectives of the research are to determine the potential of PVA/tapioca starch, PVA/sago starch, and PVA/rice starch as a biodegradable plastic. This can be divided into three:
i ) To prepare polyvinyl alcohol (PVA) with different amount of tapioca, sago, and rice starch loading by compression technique.
ii) To investigate biodegradability of tapioca, sago, and rice starch under aerobic and anaerobic condition enriched with effective microorganism (EM) and without EM.
iii) To study the rate of degradation of tapioca, sago, and rice starch under aerobic and anaerobic conditions.
1.4 Scope of Research
This scope focuses on biodegradation studies of PVA/ tapioca starch, PVA/ sago starch, and PVA/ rice starch.
Formulating PVA with different percentage of starch and plasticizer.
Compounding of PVA/ starch using melt mixer.
Preparation of testing sample by injection moulding.
Flow Behaviour - Melt Flow Index (Analysis after compounding process to investigate for injection moulding process)
Morphological Analysis (before and after degradation)
Optical Microscopy with Image Analyzer
Scanning Electron Microscop
Chemical Structure Determination (before and after degradation)
Fourier Transform Infra-Red Analysis
Design and Setting up Aerobic and Anaerobic test Apparatus (This standard to satisfy the ISO 13432 - Packaging -Requirements for packaging recoverable through composting and biodegradation - Test scheme and evaluation criteria for the final acceptance of packaging- )
ISO 14851(Liquid Medium - Method by Measuring the Oxygen Demand in a Closed Respirometer)
ISO 14852(Liquid Medium - Method by Analysis of Evolved Carbon Dioxide)
ISO 14853(Composting Medium - Method by Analysis of Evovled Carbon Dioxide)
ISO 14855(Liquid Medium - Method by Measurement of Biogas Production)
Usage of Effective Microorganism
2.1 Introduction to Bio-based Polymer
Bio-based polymer is derived from renewable sources. In this term, the bio based and biodegradability not the equal term. Bio-based materials may have biodegradability as one of their properties, whereas biodegradable materials not necessarily are bio based. The basic polymer from bio-based directly removed/extracted from natural materials, such as protein like gluten and casein and polysaccharides like starch and cellulose. (Weber et al., 2002). Furthermore, The term ''bio-based polymers'' comprises polymeric materials obtained from renewable resources that can be processed to engineer plastic-like products of desired structural and functional properties for applications (Chiellini et al., 2004).
There are many renewable sources in nature, which include polysaccharides such as cellulose, starch, chitosan, proteins like wool, silk and gelatins, oils and fats, lignin, polynucleotides, polyisoprenoids, as well as polymers derived from monomeric components. Advantage using bio-based polymer are ecocompatible, relatively inexpensive, and environmental friendly (Chiellini et al., 2004).
Several major options for the production of consumer as well as high performance industrial grade plastic products from bio-based polymers are outlined in Figure 2.1.
Figure 2.1: Major options for the production of environmentally degradable bio-based polymeric materials and plastics (Chiellini et al., 2004)
2.2 Starch and Sources
Starch is an inexpensive, easily available and renewable raw material. One of the most successful materials currently used as protective loose-fill is a starch-based polymer. Other materials have been developed, specifically, starch-based materials with biodegradable properties (Carrillo et al.,2003). The commercial starches can be divided into three groups. First group comprises the tuber (potato), root (tapioca, arrowroot and sweet potato), and pith (sago) starches. The second group comprises the common cereal starches (corn, wheat, sorghum and rice). These two groups are distinctly different from each other with respect to chemical composition and physical properties. The third group comprises the waxy starches (waxy maize, waxy sorghum and waxy rice).
These starches are obtained from cereal but physical properties of the waxy starches are similar to those of the root starches. (Swinkels, 1985). The starch produced nearly 50% of is already used for non-food applications and about 30% of the starch production is industrially precipitated from aqueous solutions because of its very good film-forming properties. It is for these reasons that have conducted promising research and development along the lines of starch-based thermoplastic materials (Lorcks., 1997).
2.2.1 Composition of Starch
Starch is a linear polymer (polysaccaride) made up of repeating glucose groups linked by glucosidic linkages in α-D- (1-4) carbon positions. The length of the starch chains will vary with plant source but in general the average length is between 500 and 2 000 glucose units. There are two major molecules in starch - amylose and amylopectin (Wurzburg, 1986). The alpha linkage of amylose starch allows it to be flexible and digestible.
Amylose is essentially a linear polymer in which the anhydroglucose units are predominantly linked through α-D-(1-4) glucosidic bonds. Figure 2.3 shows the amylose structure. Their molecular size varies depending upon the plant sources and processing conditions employed in extracting the starch. It may contain anywhere from about 200 to 2000 anhydroglucose units.
Figure 2.3: Representative structural of amylose (Jayasekara et al., 2005)
On the other hand, Amylopectin is a branched polymer containing anhydroglucose unit linked together as in amylose through α-D-(1-4) glucosidic bonds, periodic branches at the carbon - 6 positions. Figure 2.3 shows the amylopectin structure. These branches are linked to the 6 carbons by α-D-(1-6) glucosidic bonds. Each branch contain about 20 to 30 anhydroglucose unit.
Figure 2.4: Representative structural of amylopectin (Jayasekara et al., 2005)
Starches of different origin have different amylose -amylopectin ratios, as presented in table 2.2. This table also shows the average degree of polymerization (DP) of both fractions in various starches (Swinkels, 1985).
Table 2.2: Amylose and Amylopectin Content and Degree of Polymerization of Various Starches (Swinkels, 1985)
Amylose % (w/w)
Amylopectin % (w/w)
Average DP, amylose
Average DP, amylopectin
Starch granules contain usually 10-29% (w/w) moisture and small amounts of protein, fatty materials, phosphorus, and traces of inorganic materials.
Recent researches have been devoted to the relationship between starch structure and gelatinization behaviors. Variation in the structural features of two polysaccharides including amylose content, molecular size, average degree of polymerization and chain length distribution, result in differences in physicochemical properties of starch granules, such as swelling power, and thermal, rheological and textural properties (Wang et al., 2010)
2.2.3 Tapioca Starch
Tapioca starch is an important carbohydrate in tropical countries. The price in the world market is low when compared to starches from other sources. It becomes interest to add value by finding other sources. Tapioca starch is as dry, white, odourless, tasteless, insoluble and neutral ( Atichokudomchai et al.,2003). The world production of tapioca starch is about 900 000 ton. Tapioca starch is manufactured from the root of a tropical plant called cassava or manioc (Swinkels, 1985).
2.2.4 Sago Starch
Sago is now only a minor crop in Peninsular Malaysia, occupying less than 1% of the total agricultural land. The largest sago-growing areas in Malaysia are to be found outside the
Peninsula, in the state of Sarawak, which is now the world's biggest exporter of sago, exporting annually about 25,000 to 40,000 t of sago products to Peninsular Malaysia, Japan, Taiwan, Singapore, and other countries (Suriani Abd. Aziz.,2002). Sago starch accumulates in the pith core of the stem of the sago palm.
2.2.5 Rice Starch
Rice is one of the most important cereal crops and is a staple food in Southeast Asia. Starch is the major component of rice and an important part of human nutrition. Rice starch granule is non-allergic due to the hypoallergenicity of the associated proteins. Rice starch, in its gelatinized form, has a bland taste and is smooth, creamy and spreadable, which makes it a good custard starch (Singh et al., 2005).
Poly(vinyl alcohol) (PVA)
PVA is a crystalline polymer, with the degree of crystalinity depending on the compound's structure and previous history. Acetyl groups and other incorporated groups of any type reduce the crystallinity. The degree of crystallinity of fully hydrolyzed PVA is increased by heat treatment, but these also reduce solubility in water.
The main uses of PVA are in textile and paper sizing, adhesive, fibers, emulsion polymerization, and the production of poly(vinyl butyral) (Matsumura and Steinbuchel, 2003). Significant volume are also used in joint cements for building construction, water soluble films for laundry bags, cold water soluble packaging for pesticides, herbicides, and fertilizers, nonwoven fabric binders, thickeners, emulsifier in cosmetics, temporary protective films, soil binding to control erosion, and photo printing plates.
The basic chemical structure of PVA is composed mainly 0f 1,3-diol units. However, a very small amount of head to head 1,2-diol units exists in PVA (usually <1-2%) (Matsumura, 2003). The content of the 1,2-sequences can be reduced by lowering the polymerization temperature of vinyl acetate. Biodegradability properties of PVA are depend on the content of 1,2-diol.
PVA is probably the only carbon chain polymer which has been widely accepted to be fully biodegradable in various environments and confirmed in current standard test (McCarthy, 2003; Swift, 2003).
PVA has been used in solution form to produce film with thermoplastic starch (TPS) by casting and calendaring for several uses such as agricultural mulch films and water-soluble laundry bags. Cast films made from PVA and cellulose showed a good miscibility due to their mutual ability to form intra- and intermolecular hydrogen bonds between hydroxyl groups. (Cinelli et al., 2008)
Glycerol as a plasticizer (Plasticized PVA)
PVOH have been limited to end uses despite its excellent chemical, mechanical and physical propertiesto those uses in which it is supplied as a solution in water. This limitation partly due to the fact that vinyl alcohol polymer in the unplastised state have a high degree of crystallinity and show little or no thermoplasticity before the occurrence of decomposition which start at bout 1700C and becomes pronounced at 2000C which is below its crystalline melting point (Famili et al., 1994). Therefore the important of plastisized PVOH before it is used to blend it with tapioca starch in order to have bio-compatibility between matrix (PVOH) and the filler (Tapioca starch).
Plasticizers is one of the additives that tremendously used to improve the processing ability of the polymers. Choice of plascticizer is important to impart flexibility to a plastic product depends on whether the base polymer is hydrophilic or hydrophobic (Preechawong et al., 2004a and Preechawong et al., 2004b). Preechawong et al., (2004a) and Preechawong et al. ,(2004b) also reported that hydrophobic plasticizers are used extensively with petroleum-based polymers and also can be used in starch-based plastics but the molecules must be polar to allow partial compatibility with the starch molecules. This is due to the fact that starch without any addition of fillers or reinforcements have poor mechanical and physical properties.
The relatively poor mechanical properties of starch-based materials have been tentatively modified by adding large amounts of plasticizers, such as glycerol or ethylene glycol, or by modifying the chemical properties of starch itself (Chiellini et al., 2003). Nevertheless, increasing amount of plasticizer content in the compound may lead to lower interaction between polymer chains and therefore the resistance to the shear flow decreased (Lin and Ku, 2008).
Glycerol or its trade name glycerin commonly used as the plasticizer in the polymer processing. Starch foams containing glycerol as the plasticizer had a higher tendency to absorb moisture than those containing urea or ammonium chloride and for a given type of added plasticizer, the moisture content was found to monotonically increase with an increase in its content (Preechawong et al., 2004a; Preechawong et al., 2004b and Preechawong et al., 2005).
Most of the study that have been conducted on production of PVA products used glycerol as the plasticizer such as Alexy et al., (2004), Jang and Lee, (2003), Preechawong et al., (2004a); Preechawong et al., (2004b) and Preechawong et al., (2005). Alexy et al., (2004) study on the effect of melt processing on thermo-mechanical degradation of poly (vinyl alcohol)s stated that presence of glycerol showing that use of glycerol as a plasticizer does not improve the processing stability of tested PVAs whereby its role is to decrease the internal viscosity of PVA processed at the same temperature as in the case of processing without glycerol.
Effect of plasticizer was different according to the degree of hydrolysis and decreased due to the phase separation of a plasticizer in PVA caused the fully hydrolyzed PVA is affected by the amount of plasticizer where else thermal history is the main factor influenced the partially hydrolyzed PVA (Jang and Lee., 2003). Jang and Lee, 2003 study on the plasticizer effect on the melting and crystallization behavior of polyvinyl alcohol said that glycerol takes part in the crystallization behavior of a fully hydrolyzed PVA and widens the distribution of the PVA crystallite but it does not affect largely in the crystallite size distribution of a partially hydrolyzed PVA.
Biodegradation mechanism of Poly(vinyl alcohol)
Biodegradable polymer is an essential behaviour for the alternative material to replace conventional plastic due to their potential to protect environment. Biodegradable polymers are polymers that under action of a biological enzyme break down to biomass, CO2 and water in a given time period (as defined by a biodegradation standard) and in a given environment (i.e., marine, compost, anaerobic sludge) (Halley, 2005). It suggested the occurrence of two PVA degradation mechanisms, a random-type attack and a terminal unzipping depolymerization process of the polymer chains (Solaro et al., 2000). The polymer structures of PVA, such as degree of saponification and polymerization, tacticity, 1,2 glycol content, are responsible for it biodegradability (Matsumura, 2003).
Microbial degradation of PVA
The biodegradation of PVA has a long history of over 65 years since its first degradation by soil was reported by Nord in 1936 (Matsumura, 2005). PVA identified as a biodegradable synthetic polymer due to the bacterial strains as biodegrading PVA which are Pseudomanas, Flavobacterium, Acinetobactor, and many others as well as fungi, moulds and yeast (Swift, 2003). These microbes are acting as an agent inside the PVA molecule to degrade at certain rate depending on what medium of PVA dispose. Apart from the aqueous PVA solution, the biodegradation of the PVA film and fibers was also demonstrated but the rate of degradation was relatively slow compared to that of the aqueous solution of PVA (Chiellini et al., 2001). In addition to aerobic biodegradation, the anaerobic biodegradation of PVA was confirmed using the anaerobic microbes (Matsumura, 2005).
2.5.2 PVA biodegradation mechanisms and related enzymes
The generally accepted biodegradation mechanisms occur via a two-step reaction by oxidation (dehydrogenation) of the hydroxyl group followed by hydrolysis. However, details of each degrading enzyme are varied according to the origin of the enzyme as shown in Figure 2.6 and 2.7 (Matsumura, 2005). In the first step of the degradation, there are two enzymes that have been reported, oxidase and dehydrogenase. The former requires molecular oxygen and the latter requires pyrroloquinoline quinone (PQQ). In the second step, two types of enzymes, hydrolase and aldolase, are reported.
Figure 2.6: PVA degradation mechanism by SAO/PVADH* and BDH *(PVA biodegradation by oxidation (dehydrogenation) enzyme and β-diketone hydrolase) (Matsumura. 2005)
126.96.36.199 Secondary Alcohol Oxidase (SAO)
Secondary Alcohol Oxidase (SAO), or PVA oxidase, catalyzed conversion of the hydroxyl group of PVA into the corresponding carbonyl group (Matsumura, 2003). The following two successive reactions, the first catalyzed by the SAO and the second by β-diketone hydrolase (BDH) were presented as the mechanism of bacterial degradation of PVA (Matsumura, 2003).
188.8.131.52 β-Diketone Hydrolase (BDH)
A hydrolase, named β-diketone hydrolase (BDH), which catalyzes the degradation of SAO-oxidized PVA, was purified to an electrophoretically homogenous state from culture of P.vesicularis PD (Matsumura, 2003). Acidic BDH was also purified from the same culture broth of P.vesicularis PD containing PVA as the sole carbon source.
184.108.40.206 PVA Dehydrogenase (PVADH)
A PQQ-dependent PVA dehydrogenase (PVADH), was partially purified from the membrane fraction of a PVA-degrading symbiont, pseudomonas sp. The enzyme required PQQ for the PVA dehydrogenation, with phenazine methosulfate, phenazine etholsulfate, and 2,6 dichlorophenollindophenol as electron acceptors and did not show PVA oxidase activity leading hydrogen peroxide formation (Matsumura, 2003).
220.127.116.11 Enzymatic degradation by PVADH and Aldolase
A novel PVA degradation pathway was confirmed such that the hydroxyl group of PVA was first dehydrogenated by PVADH into the corresponding carbonyl group to form β-hydroxy ketone. It was followed by an aldolase-type cleavage to produce the methyl ketone and aldehyde by the enzymatic degradation of PVA by the PVA-assimilating strain, Alcaligenes faecalis KK34 (Figure 2.7) (Matsumura, 2003)
The biodegradation of PVA first occurs by dehydrogenation to produce β-hydroxy ketone moiety:this is then cleaved by the aldolase-type reaction to produce the lower molecular weight fragments of PVA as shown in Figure 2.7 Matsumura, 2003)
Figure 2.7: PVA degradation mechanism by PVADH and aldolase (Matsumura, 2005)
Poly (vinyl alcohol) (PVA) fully hydrolyzed grade (BF17) will be used as the synthetic biodegradable polymer supplied by Chan Chun Petrochemical Co. Ltd.
Tapioca, sago, and rice starch will be obtained from the local suppliers. The particle size of those starches ranged from 9.73 Î®m to 83 Î®m with an average particle size of 32.97 Î®m will be used in this research. The moisture content of starch is in the range of 11.5%.
Glycerol (glycerine, C3H8O3) from Fisher Chemicals (molecular weight = 92gmol-1) will be used as a plasticizer. It will be added as the plasticizer for the formation of plasticized PVA (PPVA).
Calcium stearate (CaS) act as the lubricant in the formulation of PVA/tapioca starch blend. CaS will be supplied by SunAce Kakoh (Malaysia) Sdn. Bhd.
3.2 Formulation Development
3.2.1 Preparation of plasticized PVA (PPVA)
PVA resin will be plasticized with the glycerol to improve its process ability. The method described by Bastioli et al. (1995) will be used to prepare the PPVA. This method described that the best percent of glycerol content in PPVA is between 15-40%.
The preparation of PPVA in this study will consist of compounding PVA with 35wt% of glycerol. Table 3.1 shows the glycerol percentage in the formulation of PPVA. Glycerol will be added into PVA in a high speed mixer in order to homogenously distribute the plasticizers within the polymer. Then the component will be mixed and matured via twin screw extruder. The main screw speed will be 200rpm. Extrudates of plasticized PVA will be then pelletized using pelletizer.
Table 3.1: Formulation of Plasticized PVA (PPVA)
Glycerol (wt %)
PVA (wt %)
3.2.2 Formulation of PPVA/ various starches blends
The effect of glycerol in PVA and various starches composition will be investigated. Calcium stearate (CaS) will be used as a lubricant during the compounding of PPVA/ starch.
PPVA, various starches and CaS will be mixed in a high speed mixer followed by melt compounding. The compound will then be pelletized for further uses. Table 3.2 shows the propose formulations of PPVA/ various starch blend.
Table 3.2: The propose formulations of PPVA/various starches blend
PPVA (wt %)
Tapioca starch (wt %)
CaS (wt %)
PPVA (wt %)
Tapioca starch (wt %)
CaS (wt %)
PPVA (wt %)
Tapioca starch (wt %)
CaS (wt %)
All of these formulations after pelletizing will be proceeded to undergo injection moulding process. Sample for material testing will be produced by this process.
Melt Flow Index (MFI)
ASTM D 1238 will be used as a guideline to determine the processability of the compound on the injection moulding by benchmarking the flow rate of the formulated compound with the flow rate of the injection moulding grade biomaterial. MFI will be done by measuring the rate of extrusion of molten resins through a die of a specified length and diameter. Approximately 10 g will be loaded or fully loaded to the MFI barrel. 2.16 kg of load will be used with the testing temperature of 190 ± 5 ËšC. Extrudates are cut for 10 minutes and weighed the samples to obtain the flow rate in grams per 10 minutes.
Chemical Structure Determination
18.104.22.168 Fourier Transform Infra-Red Analysis (FTIR)
FTIR test will be used to obtain some qualitative information about the functional groups compatibility and structural characteristic of the PPVA/various starches blend. About 5 mg of samples ass mix with about 95 mg of potassium bromide (KBr). This mix will be pressed to a powder form at a thickness of 10-100 µm for the measurement by using hydraulic press for about 3 minutes. Potassium bromide (KBr) disc technique will be applied and the spectrum will be scan for 16 scans. Resolution used in this testing is 4 cm-1 and range for about 4000-300 cm-1.
Optical Microscopy with Image Analyzer
Electron microscope (Leica equipment) will be used to show the interface of PPVA/ various starches before and after biodegradation studies. The specimens will be cut using microtome to approximately 10 µm thicknesses at room temperature. The specimens will be then mounted and viewed under the bright mode with the light microscopy fitted with surface imaging analysis system.
Scanning Electron Microscopy (SEM)
Scanning electron microscopy will be used to study the changes on surface morphology and mode failure of the PPVA/ starch blends. Samples will be coated with gold in order to prevent electrical discharge during examination. The PPVA/ various starches blends will be examine its fracture surface. The micrograph of the specimens will be taking before and after biodegradation studies.
3.4 Biodegradability Studies
All the biodegradability studies will be tested with effective microorganism and without effective microorganism.
3.4.1 Aerobic Conditions
Degradation test will be monitored according to ISO 14851, 14852, 14855 standards. This standard will be discussed in liquid medium, and in composting medium. Assessment of material degradation will be made on plates with an area of 1 cm2.
22.214.171.124 Liquid Medium - Method by Measuring the Oxygen Demand in a Closed Respirometer (ISO 14851)
The standard that will be used is ISO 14851 (1999) procedure. This standard specifies a method of determining the biochemical oxygen demand (BOD) in a closed respirometer. The test material, inorganic medium and inoculums will be stirred in closed flasks of the respirometer. Evolved carbon dioxide (CO2) is absorbed in a suitable absorber (sodium hydroxide solution) in the headspace of the test flasks. The oxygen consumption is determined by measuring the pressure change in the respirometer flask, or by measuring the change in volume or pressure. Biodegradation rate will be calculated by comparing the BOD with the theoretical oxygen demand (ThOD) and expressed in percent.
Test will be performed in 500 mL bottles containing tested material, 2 mL of inocolum and 50 mL of mineral medium which is composed of three solutions:
-solution A: KH2PO4: 28.25g; K2HPO4: 146.08g in distilled water to make 1000 mL
-solution B: CaCl2.2H2O: 3.66g; NH4Cl: 28.64g in distilled water to make 1000 mL
-solution C: MgSO4.7H2O: 3.06g, FeSO4: 0.7g, ZnSO4: 0.4g in distilled water to make 1000 mL
1000 mL test medium contained 40 mL of solution solution A, 30 mL of solution B and 30 mL of solution C and sufficient distilled water to make 1000 mL. pH was fixed at 7. Consequently, the only source of organic carbon usable by the microorganism will be represented by tested sample.
The inocolum used under aerobic conditions will be a microbial inoculums extracted from an activated sludge from a municipal wastewater treatment plant. These inoculums will be stored in a laboratory for predigestion of organic carbon contained in the sludge, by incubation at the temperature at which the tests will be carried out at 30±2°C. Test bottles will be incubated in darkness and regularly stirred.
126.96.36.199 Liquid Medium - Method by Analysis of Evolved Carbon Dioxide (ISO 14852)
The standard that will be used is ISO 14852 (1999) procedure. The same test mixture as for ISO 14851 (1999) wll be agitated in test flasks and aerated with CO2- free air over the test period. The level of biodegradation will be calculated by comparing the evolved CO2 with the theoretical amount (ThCO2) and again expressed in percent.
3.4.4 Composting Medium - Method by Analysis of Evovled Carbon Dioxide (ISO 14855)
The standard that will be used is ISO 14855 (1999) procedure. The biodegradation test will be performed in a controlled compost at 58°C for 60 days. The test material (16.5g) was mixed in 210g of the controlled compost. Compost containing no sample will be used as a blank to determine the respiration activity of compost. The CO2 produced from the reaction vessels was trapped in alkaline solution bottles. The amounts of trapped CO2 will be determined by the titration of the acid solution to trap solution. The percentages of biodegradation will be calculated from the produced CO2 amount which will be cancelled respiration CO2 amount determined from a blank, and theoretically produced CO2 amount of added sample. Once a week, the sample and compost will be well mixed and the water content controlled.
3.4.5 Anaerobic Conditions
Degradation test was monitored accordance with the ISO 14853 standards. This standard will be discussed in liquid medium. Assessment of material degradation will be made on plates with the area 1 cm2.
3.4.6 Liquid Medium - Method by Measurement of Biogas Production (ISO 14853)
This standard specifies a method of determining the biogas generation in a closed respirometer. The test material, inorganic medium and inoculums will be stirred in flasks closed using gas tight rubber stoppers, crimped by an aluminium ring. During the microbial degradation, biogas (primarily CO2 and CH4) will be produced and consequently the pressure inside bottles increases. The pressure inside bottles will be measured regularly using a manometer thus making it possible to follow the pressure evolution. From these pressure measurements, the percentage of degradation will be deduced. Firstly the volume of generated biogas (Vb) will be calculated from the ideal gas law then this volume will be compared with the volume of biogas theoretically generated (Vth) if 100% of the material will be degraded. The biodegradation percentage will be expressed as the ratio Vb/Vth expressed in percent. Regularly a qualitative analysis of produced biogas will be carried out in order to know its composition.
Biogas will be taken in test bottles and then is analysed with a micro-chromatograph (mGC). Tests will be performed in pressure resistant penicillin bottles of 125 ml. The bottles will be filled (by leaving approximately 30-40% of headspace gas) with tested material, 2 ml of microbial inoculum and 80 ml of mineral medium (M3) which will be composed of KH2PO4 (0.270 g), Na2HPO4.12H2O (1.12 g), NH4Cl (0.53 g), CaCl2.2H2O (0.075 g), MgCl2.6H2O (0.1 g), and Na2S.9H2O (0.1 g) will dissolved in sufficient distilled water to make up 1000 ml. This medium does not contain any source of organic carbon. Consequently, the only source of organic carbon usable by the micro-organisms will be represented by the tested sample. pH was fixed at 7. The inoculum used under anaerobic conditions, will be a microbial inoculum extracted from a digester from the same wastewater treatment plant. This inoculum will be stored in the laboratory for predigestion of organic carbon contained in the sludge, by incubation at the temperature the tests will be carried out at 35±2°C. If necessary, they were revivified and their activities were regularly controlled. The test will be prepared in an oxygen-free atmosphere (anaerobic conditions) under controlled nitrogen atmosphere.
4.1 Expected results
According to ISO/CEN 14851, ISO/CEN 14852, and ISO/CEN 14855, in aerobic biodegradation test, for the test material, the percentage of biodegradation shall be at least 90% in total or 90% of the maximum degradation of suitable reference substance after a plateau has been reached for both test material and reference substance. The reference substance is microcrystalline cellulose powder. The period of this test method about 6 month.
According to ISO/CEN 14853, in anaerobic biodegradation test, the percentage of biodegradation based on biogas production shall be 70% or more of the theoretical value for the test material. The period of this test method about 2 months.
From the research, PVOH/starch will degrade faster with effective microorganism rather than without effective microorganism in soil. Furthermore, more starch than PVOH in test material will make the test material become degrade faster too. The test material in aerobic condition will degrade faster than anaerobic condition.
If you are the original writer of this essay and no longer wish to have the essay published on the UK Essays website then please click on the link below to request removal: