BIODEGRADABLE POLYMERS FROM CORN’S STARCH

NIK ABD HAFIIDZ BIN NIK ABDUL MALEK

(2014688106)

KHAIRUL IZWAN BIN AHMAD ROBERT

(2014472518)

MOHD ARSHAD BIN ABDUL RASHID

(2014683386)

FARIS AZRI BIN ASWANDI

(2014679658)

TIMOTHY ALVIN

(2014696804)

PREPARED FOR

DR. NIK RAIKHAN BINTI NIK HIM

FACULTY OF CHEMICAL ENGINEERING

UNIVERSITI TEKNOLOGI MARA

SHAH ALAM

2014

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TABLE OF CONTENTS

PAGE

Introduction 3

1.1 Biodegradable Polymers 4

1.2 Polysaccharides 5

1.3 Starch 5

1.3.1 Amylose 6

1.3.2 Amylopectin 7

1.3.4 Minor Components 7

1.4 Starch-Based Biodegradable Polymers 8

1.5 Preparation of Starch-Based Biodegradable Polymers 8

1.5.1 Physical blends 9

1.5.1.1 Blend with Synthetic Degradable Polymers 9

1.5.1.2 Blend with Biopolymers 11

1.5.2 Chemical Derivatives. 11

1.6 Thermoplastic Starch Products. 12

1.6.1 Starch Reactions And Modifications 13

1.7 Starch – Aliphatic Polyester Blends 13

1.8 Starch Based Superabsorbent Polymers 15

1.9 Polylactic Acid or Polylactide 18

1.10 1,4:3,6-Dianhydrohexitols-Based Polymers 19

1.11 Isosorbide 20

1.11.1 Isosorbide Synthesis 22

1.11.2 Isosorbide In Plastic Production 22

1.11.3 Isosorbide in UV Absorption 24

Conclusion 25

References 26

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Introduction

Our dependence on plastic in our daily life is very high, almost 100 million

tons annually (Anonymous, n.d). Plastic which is derived from petroleum has some

future constraints due to limited resource and difficulty in degrading so it can cause

environmental problems. In addition, the migration of monomers from the plastic

packaging into food products can cause various health problems.

One of the most studied and promising raw materials for the production of

biodegradable plastics is starch and cellulose which is natural renewable carbohydrate

polymer obtained from a great variety of crops. Starch and lignocellulose are low cost

material in comparison to most synthetic plastics. Starch has been investigated widely

for the potential manufacture of products such as water soluble pouches for detergents

and insecticides, flushable liners and bags, and biomedical delivery systems and

devices (Fishman et al., 2000). Large scale corn productions in Malaysia have to be

expanded in order to meet the growing demand parallel to the expansion of the swine

and poultry industry. The annual import of corn worth 400 million ringgit is expected

to increase to one billion ringgit by the year 2020 (Index mundi, n.d). This versatile,

natural, biodegradable, and renewable resource has many commercial applications. As

a raw material, it is replacing petroleum in many industrial applications, from plastic

containers to clean-burning ethanol. The development of biodegradable polymers is a

high priority from the standpoint of environmental preservation; biodegradable

polymers from corn chemistry have a number of advantages over other synthetic

materials. Starch based biodegradable polymers has many its types of production

which is thermoplastic-starch products, starch-aliphatic polyester blends, starch and

pbs/pbsa polyester blends, starch-based superabsorbent polymers, polylactic acid or

polylactide, 1,4:3,6-Dianhydrohexitols-based polymers, and Isosorbide.

Polymers derived from starch (a component of corn) or other carbohydrates

made from entirely renewable resources have been used in the manufacture of quality

plastics, packaging materials, and fabrics (Koch and Röper, 1988), as well a variety of

biomedical materials for example bioMEMs, biochips, and bioscaffolds. Utilization of

corn starch for biodegradable polymer, will provide greater added value and also

decrease the environmental problem.

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1.1 Biodegradable Polymers

Biodegradable polymers are a specific type of polymer that breaks down after its

intended purpose to result in natural byproducts such as gases (CO2, N2), water,

biomass, and inorganic salts. (Avérous & Pollet, 2012). These polymers are found both

naturally and synthetically made, and largely consist of ester, amide, and ether

functional groups. A polymer based on a C-C backbone tends to resist degradation,

whereas heteroatom-containing polymer backbones confer biodegradability.

Biodegradability can, therefore, be engineered into polymers by the judicious addition

of chemical linkages such as anhydride, ester, or amide bonds, among others. (Maung,

2004).

The usual mechanism for degradation is by hydrolysis or enzymatic cleavage of

the labile heteroatom bonds, resulting in a scission of the polymer backbone.

Macroorganisms can eat and, sometimes, digest polymers, and also initiate a

mechanical, chemical, or enzymatic aging (sigmaaldrich.com, N.D). Different

classifications of various biodegradable polymers have been proposed from previous

studies and our focus is biodegradibles plolymers from starch and more specific is

from corn starch.

Figure 1: Classification of the main biodegradable polymers (Luc Avérous & Eric

Pollet, 2012)

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1.2 Polysaccharides

Polysaccharides are the most abundant macromolecules in the biosphere.

These complex carbohydrates constituted of glycosidic bonds are often one of the

main structural elements of plants and animals exoskeleton such as cellulose,

carrageenan, and chitin. The polysaccharides presented in this chapter are starch.

1.3 Starch

Depending on the botanical origin of the plant, starch grains can have different

shapes and size (from 0.5 to 175 lm). These granules are composed of two a-D-

glucopyranose homopolymers, the amylose and the amylopectin (Guilbot,1985).

Their proportions in the grains depend directly on the botanical source. The amylose

is a mostly linear α-D(1, 4’)-glucan and branched amylopectin, having the same

backbone structure as amylose but with many α-1, 6’-linked branch points (figure )

Figure 2: Molecular structure of starch (Avérous & Pollet, 2012)

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There are a lot of hydroxyl groups on starch chains, two secondary hydroxyl

groups at C-2 and C-3 of each glucose residue, as well as one primary hydroxyl group

at C-6 when it is not linked. Evidently, starch is hydrophilic. The available hydroxyl

groups on the starch chains potentially exhibit reactivity specific for alcohols. In other

words, they can be oxidized and reduced, and may participate in the formation of

hydrogen bonds, ethers and esters (Tomasik et al., 2004) Starch has different

proportions of amylose and amylopectin ranging from about 10–20% amylose and

80–90% amylopectin depending on the source.

Amylose is soluble in water and forms a helicalstructure. Starch occurs

naturally as discrete granules since the short branched amylopectin chains are able to

form helical structures which crystallize. Starch granules exhibit hydrophilic

properties and strong inter-molecular association via hydrogen bonding formed by the

hydroxyl groups on the granule surface. The starch granule organization consists in

alternation of crystalline and amorphous areas leading to a concentric structure. The

amorphous areas are mainly constituted of amylose chains and amylopectin branching

points. The crystalline parts are mainly composed of amylopectin side chains

(Avérous, Pollet, 2012).

Because of numerous intermolecular hydrogen bonds existing between the

chains, the melting temperature (Tm) of starch is higher than its degradation

temperature. Consequently, to elaborate a plastic-like material, it is necessary to

introduce high water content or/and some non-volatile plasticizers which decrease the

glass transition temperature (Tg) and the Tm (Stepto, 2003). These plasticized

materials are currently named ‘‘thermoplastic starch’’ or ‘‘plasticized starch”. To be

transformed, the starch granular structure has to be disrupted. The disruption can be

obtained either by a solvent-casting process or by a melting process where starch and

plasticizers are mixed under thermo-mechanical treatment.

1.3.1 Amylose

Amylose is defined as a linear molecule of D-glucopyranosyl units joined by α

(1-4) linkage, but it is today well established that some molecules are slightly

branched by α (1-6) linkages Amylose solutions can be easily characterized by size-

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exclusion chromatography coupled on-line to multi-angle laser light scattering (SEC–

MALLS). It is the smaller of the two polysaccharides making up starch molecule. The

amylose is essentially linear but not purely and its solution properties are generally

regarded as typical for those of a linear polymer. (Tomasik et al., 2004) Amylose is

located in the granule as bundles between amylopectin clusters and or randomly

dispersed. They could be located therefore among the amorphous and crystalline

regions of the amylopectin clusters. In starch granules, the amylose chain displays a

natural twist in a helical conformation with six anhydroglucose units per turn

(Guilbot,1985). Amylose is probably the first biopolymer for which a helical structure

was proposed. The ability of amylose to form complexes with butanol provides a

method for separating amylose from amylopectin by selective precipitation according

to Avérous & Pollet, (2012).

1.3.2 Amylopectin

Amylopectin is the highly branched component of starch and it is formed

through chains of α -D glucopyranosyl residues linked together mainly by α (1.4)

linkages but with 5–6% of α (1,6) bonds at the branch points. Thus, the outer chains

(A) are glycosidically linked at their potential reducing group through C6 of a glucose

residue to an inner chain (B); such chains are in turn defined as chains bearing other

chains as branches. The single C chain per molecule likewise carries other chains as

branches but contains the sole reducing terminal residue. The ratio of A-chains to B-

chains is an important parameter which is also referred to as the degree of multiple

branching.

1.3.4 Minor Components

Minor components associated with starches correspond to three categories of

materials: (i) particulate material, composed mainly of cell-wall fragments; (ii)

surface components, removable by extraction procedures; and (iii) internal

components. Lipids represent the most important fraction associated with the starch

granules. Starch quality is also influenced by the presence of lipids, proteins and

phosphorous. Lipid levels are lower in tuber than in cereal starches.

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1.4 Starch-Based Biodegradable Polymers

Starch, a major component of corn, is a linear polysaccharide made up of

repeating glucose groups with glycosidic linkages in the 1-4 carbon positions with

chain lengths of 500 to 2000 glucose units. There are two major polymer molecules in

starch which are amylose and amylopectin. Amylose, which has alpha linkage, is both

flexible and digestible. (Sanjay et al., 2007)

There are three types of biodegradable materials which are agricultural

polymers used alone or blended with biodegradable synthetic polymers, microbial

polymers produced from the fermentation of agricultural products used as substract

and monomers or oligomers polymerized by means of conventional chemical

processes and obtained from the fermentation of agricultural raw materials used as

substract. (Guilbert, 2000)

Starch-based blends present an enormous potential to be widely used in the

biomedical and the environmental fields, as they are totally biodegradable,

inexpensive (when compared to other biodegradable polymers) and available in large

quantities. (Glover, 1993)

1.5 Preparation Of Starch-Based Biodegradable Polymers

Various physical or chemical modifications of starch have been investigated to

improve the properties of starch such as blending and graft polymerization.

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Figure 3: Molecular structure of amylase and amylopectin(starch) (Lu et al., 2009).

1.5.1 Physical blends

1.5.1.1 Blend With Synthetic Degradable Polymers

Griffin (1977) first started to adopt starch as a filler of polyolefin and its

concentrations is as low as 6-15%. Bikiaris et al. (1998) attempted to enhance

biodegradability of the vinyl polymers by incorporating starch to a carbon-carbon

backbone matrix. The starch granules were used to increase the surface area available

for attack by microorganisms but the system is partially biodegradable and not

acceptable from an ecological point of view. (Lu et al. 2009).

Biodegradable polymers are introduced to prepare completely biodegradable

starch-based composites. Aliphatic polyesters, polyvinyl alcohol (PVA) and

biopolymers were usually used to blend with starch. Poly(β-hydroxyalkanoates)

(PHA) that was obtained by microbial synthesis, and polylactide(PLA) or poly(ε-

caprolactone) (PCL) that were derived from chemical polymerization are the

commonly used polyesters. (Lu e. al. 2009). The blending of starch with degradable

polyesters was done in order to improve its cost competitiveness while maintaining as

well as improving other properties such as mechanical properties.

PLA is one of the most important biodegradable polyesters with many

excellent properties and has been widely applied in many fields, especially for

biomedical one. PLA possesses good biocompatibility and process ability, as well as

high strength and modulus. However, PLA is very brittle under tension and bend

loads and develops serious physical aging during application. Moreover, PLA is a

much more expensive material than the common industrial polymers. (Jun, 2000)

Many efforts have been made to develop PLA/starch blends to reduce total

raw materials cost and enhance their degradability. The major problem of this blend

system is the poor interfacial interaction between hydrophilic starch granules and

hydrophobic PLA. Mechanical properties of blends of PLA and starch using

conventional processes are very poor because of incompatibility. (Wang et al. , 2008)

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Glycerol, formamide, and water are used alone or combined as plasticizers to

enhance the dispersion and the interfacial affinity in thermoplastic starch (TPS)/PLA

blends. This is to improve the compatibility between hydrophilic starch granules and

hydrophobic PLA. The strong intermolecular and intramolecular hydrogen bonds in

starch can be weakened in the presence of water and other plasticizers. (Wang et al. ,

2008) A suitable compatibilizer is needed to enhance the compatibility between PLA

and starch. Another way to enhance the interfacial affinity is by using gelatinization

of starch. Starch is gelatinized to disintegrate granules and overcome the strong

interaction of starch molecules in the presence of water and other plasticizers, which

leads to well dispersion. (Park et al. , 2000)

PCL is a synthetic biodegradable polymer which is linear, hydrophobic,

partially crystalline polyester, and can be slowly degraded by microbes. (Scott and

Gilead 1995) The weakness of pure starch materials including low resilience, high

moisture sensitivity and high shrinkage has been overcome by adding PCL to starch

matrix even at low PCL concentration. Blending with PCL, the impact resistance and

the dimensional stability of native starch is improved significantly. The glass

transition temperature and mechanical properties of TPS/PCL blend are varied with

its composition and the content of plasticizer. TPS/PCL blend is similar to TPS/PLA

blend in both the compatibility and the role of components. (Averous et al., 2000)

PCL/starch blends can be further reinforced with fiber (Franco. et al., 2004) and nano-

clay respectively which results in hydrolytic stability, degradation rate, and

compatibilization between PCL and starch are improved. (Vertuccio. et al., 2009)

1.5.1.2 Blend With Biopolymers

Natural polymers such as chitosan and cellulose and their derivatives are

naturally biodegradable, and exhibit unique properties. A number of researches have

been devoted to study the blend of them with starch. Starch and chitosan are abundant

naturally occurring polysaccharide. Both of them are cheap, renewable, non-toxic, and

biodegradable. The starch/chitosan blend exhibits good film forming property, which

is attributed to the inter- and intra-molecular hydrogen bonding that formed between

amino groups and hydroxyl groups on the backbone of two components. The

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mechanical properties, water barrier properties, and miscibility of biodegradable

blend films are affected by the ratio of starch and chitosan (Bourtoom & Chinnan,

2008)

Extrusion of the mixture of corn starch and microcrystalline cellulose in the

presence or absence of plasticizers (polyols) is used to produce edible films. By

increasing the content of the cellulose component, the rupture strength is increased,

whereas the elongation at break and the permeability of films for water vapor are

decreased. Starch can form thermodynamically compatible blend films with water-

soluble carboxymethylcellulose (CMC) when the starch content is below 25 mass%.

Such films are biodegradable in presence of microorganisms. (Lu et al. 2009).

1.5.2 Chemical Derivatives.

The problem that occurs for starch-based blends is that starch and many

polymers are immiscible. This results in poor mechanical properties of starch/polymer

blends. Therefore, chemical modifications are applied to the starch/polymer blends.

Chemical modifications of starch are generally carried out via the reaction with

hydroxyl groups in the starch molecule. (Bao et al., 2003) Graft copolymerization is

an often used powerful means to modify the properties of starch. Moreover, starch-g-

polymer can be used as an effective compatibilizer for starch-based blends.

(Kiatkamjornwong et al., 2002)

PCL and PLA are chemically bonded onto starch and can be used directly as

thermoplastics or compatibilizer. The graft-copolymers starch-g-PCL and starch-g-

PLA can be completely biodegraded under natural conditions and exhibit improved

mechanical performances. To introduce PCL or PLA segments onto starch, the ring

opening graft polymerization of ε-caprolactone or L-lactide with starch is carried out.

(Dubois et al., 1999) (Choi. et al., 1999)

Starch-g-poly(vinyl alcohol) can be prepared via the radical graft

copolymerization of starch with vinyl acetate and then the saponification of the

starch-g-poly(vinyl acetate). Starch-g-PVA behaves good properties of both

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components such as processability, hydrophilicity, biodegradability and gelation

ability. (Fanta et al., 1979) (Samaha et al., 2005)

1.6 Thermoplastic Starch Products.

When biodegradable thermoplastic-starch plastics, which have a starch

(amylose) content of more than 70 percent, are combined with specific plasticizing

solvents, they produce thermoplastic materials with good performance properties and

inherent biodegradability. The hydrophilic nature of high-starch content plastics,

which readily disintegrate on contact with water, can be overcome by blending and

chemically modifying the material by acetylation, esterification, or etherification.

Starch-based polymers are often plasticized, destructured, and/or blended with other

high-performance polymers (e.g., aliphatic polyesters and polyvinyl alcohols) to

provide useful mechanical properties for different packaging applications. (Sanjay et

al., 2007)

Thermoplastic starch has gradually increased in commercialization. However,

there are still a lot of challenges needed to be overcome to make commercially viable

biodegradable and compostable starch polymers. Thermoplastic starch films generally

need to have starch content greater than 70% to have biodegradable or compostable

action. High amylose starch is preferred for thermoplastic film formation. (Nolan,

2002)

Myllarinen et al. (2002) showed that, while glycerol plasticised amylose films

do retrograde and display slight B and V type diffraction patterns, their crystallinity

remains stable over time and changes in humidity. Conversely, glycerol plasticised

amylopectin films were initially amorphous, but over weeks displayed a steady

increase in B type crystallinity. Interestingly, amylopectin films without plasticiser

remained amorphous during ageing. From both researchers, it can be concluded that

the functional properties of amylose films are in general slightly better than those of

amylopectin films regarding both film strength and barrier properties.

1.6.1 Starch Reactions And Modifications

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The modification of starch has been attracting researchers for applications as

biodegradable packaging materials. Hydroxypropylation is the most important

reactive process in starch film processing where the chemically modified starch which

is Hydroxypropyl (HP) starch has wide range of applications.

HP starches have enhanced solubility, low gelatinisation temperatures, low

retrogradation and crystallinity and superior mechanical properties when compared

with native starches. (Lafargue, et al., 2007) HP starches are completely

biodegradable, and are commonly found in food packaging and film industries. (Kim,

2003) The amylose content and HP modification of native starches have been

demonstrated to have a significant effect on their extrusion characteristics.

(Chaudhary,. et al., 2009)

1.7 Starch – Aliphatic Polyester Blends

Among the natural polymers, starch is of interest. It is regenerated from

carbon dioxide and water by photosynthesis in plants. Owing to its complete

biodegradability, low cost and renewability, starch is considered as a promising

candidate for developing sustainable materials (Lu et al., 2009). Synthetic aliphatic

polyesters have also been developed. Polylactic acid (PLA) is an example of such

polymers. In this case, the monomer used, lactic acid, is a natural product, which

could be obtained from microorganisms through fermentation. Many species of

bacteria, such as those belonging to the genus Lactobacilli, are used to mass-produce

lactic acid.

Organisms such as L. amylophilus produce predominantly the L isomer of

lactic acid, while others, produce mainly the D isomer or a mixture. Synthesis of

polylactic acid usually proceeds through cyclic dimers of lactic acid, also known as

lactides.Two polymerization methods are possible. Condensation polymerization

involves removal of water as esters are formed. This route, however, cannot be used

to produce high molecular weight polymers, unless additives, such as chain extenders,

are added. The additives must later be removed, adding to the cost of production.

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As a result, condensation is more expensive to perform. To obtain higher chain

lengths without the use of additives, Mitsui Chemicals in Japan has developed

azeotropic condensation methods. As the name implies, the water is removed

azetropically, increasing the efficiency of polymerizatioin. Unfortunately, this method

requires a high quantity of toxic catalysts, which may remain in the polymer. Another

method of PLA production involves ring-opening polymerization (ROP) of lactides.

High molecular weight polymers can be produced using this method. The mechanism

may be either ionic or coordination-insertion, where the latter involves a catalyst.

Ionic ROP may suffer from high levels of racemization, transesterification and

impurities. Various copolymers can be produced to modify the characteristics of the

final product. Examples of monomers that can be used to produce copolymers include

glycolide and valerolactone. Due to its intrinsic brittle nature, plasticizers are

necessary to produce PLA thermoplastic.

Figure 4: Core structure of poly(lactic acid) (source :

http://www.writework.com/uploads/5/57417/skeletal-formula-poly-lactic-acid.png)

Aliphatic polyesters are odorless and can be used for trash bags, diapers, and

cosmetic and beverage bottles. They can be processed on conventional processing

equipment at 140-260 °C, in blown and extruded films, foams, and injection moulded

products. Aliphatic polyesters are biodegradable but often lack in good thermal and

mechanical properties. Vice versa, aromatic polyesters, have excellent material

properties, but are resistant to microbial attack.

1.8 Starch Based Superabsorbent Polymers

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Superabsorbent polymer (SAP) materials are hydrophilic networks that can

absorb and retain huge amounts of water or aqueous solutions. They can uptake water

as high as 100,000% (Zohuriaan-Mehr, et al., 2008). They are lightly cross-linked

networks of hydrophilic polymer chains. The network can swell in water and hold a

large amount of water while maintaining the physical dimension structure. It was

known that commercially used water-absorbent polymeric materials employed are

partial neutralization products of cross-linked polyacrylic acids, partial hydrolysis

products of starch–acrylonitrile copolymers and starch–acrylic acid graft copolymers.

At present, the material’s biodegradability is an important focus of the research in this

field because of the renewed attention towards environmental protection issues (Lenzi

et al., 2003). The half life is in general in the range 5 - 7 years, and they degrade into

ammonium, carbon dioxide and water.

SAPs are widely used in personal hygiene products. Recent research is

focused in other application areas of SAPs, viz., biosensing, soft actuators/valves,

catalysis, concentration of viruses, vitamin, bovine serum albumin and controlled

drug delivery. SAPs or hydrogels have been also studied for the concentration of

macromolecules. SAPs are used in soil to create a water reserve, near the rhizosphere

zone (roots) and benefit agriculture.

SAPs as hydrogels, relative to their own mass can absorb and retain

extraordinary large amounts of water or aqueous solution. These ultrahigh absorbing

materials can imbibe deionized water as high as 1,000-100,000% (10-1000 g/g)

whereas the absorption capacity of common hydrogels is not more than 100% (1 g/g).

The SAP particle shape (granule, fibre, film,etc.) has to be basically preserved

after water absorption and swelling, i.e., the swollen gel strength should be high

enough to prevent a loosening, mushy, or slimy state. This is a major practical feature

that discriminates SAPs from other hydrogels (Zohuriaan-Mehr,.et al., 2008)

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Figure 5: A visual comparison of the SAP single particle in dry (right) and swollen

state (left) (Zohuriaan-Mehr,.et al., 2008)

Graft copolymerization of starch with vinyl monomers (viz.

acrylamide, acrylonitrile, acrylic acid) has gained importance in improving some

properties of synthetic absorbent polymers. Moreover, the graft products have

received considerable attention because of their immense industrial potential with

their biodegradability, low cost, and renewability. However, so far more attention has

been put only in the graft products of original starch. Compared with anionic or

cationic graft copolymers, amphoteric absorbent polymers have potential salt-tolerant

swelling character (Li‐Qin et al., 2005).

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The earliest commercial SAPs were produced from starch and AN monomer

by the first mentioned method without employing a cross-linker (Zohuriaan-Mehr, et

al., 2008). The starch-g-PAN copolymer (SPAN) was then treated in alkaline medium

to produce a hybrid SAP, hydrolyzed SPAN (H-SPAN) while an in-situ cross-linking

occurred simultaneously

1.9 Polylactic Acid or Polylactide

The terms Polylactide (PLA) can be defined as biodegradable polymer

production based on renewable resources with a range of applications which is similar

to Polyethylene terephthalate (PET) (R.Hagen, 2012). Uhde Inventa-Fisher, a

German-based company, has been developing a Polylactide (PLA) process for the last

10 years (http://www.uhde-inventa-fischer.com), and Cargill in the United States and

Teijin in Japan are investing in large scale production facilities for the manufacture of

Polylactide (PLA).

Glucose is a common feedstock for the process of Polylactide (PLA), which

can be produced by the hydrolysis of starch. The production of sodium lactate and

some impurities, such as proteins, cellular mass, and so on by the fermentation of

glucose. The sodium lactate is transformed into lactic acid after done a number of

purification steps, which is then concentrated to remove residual water (Chaniga,

2012).

Thermal polymerization or known as self-condensation which yields a low-

molecular weight Polylactide (PLA) pre-polymer, then a distillable cyclic dimmer

(dilactide, or simply lactide) produced by thermally depolymerised. Among these

methods, cross-linking seems to be a particularly good method to improve the thermal

stability of Polylactide (PLA) while maintaining its biodegradability (Quynh et al.,

2007; Mitomo et al., 2006).

High-molecular weight Polylactide (PLA) by the ring-opening polymerization

of the purified dilactide with a suitable catalyst, often a tin salt such as stannous

octoate. The final polymer is then granulated and further processed for the desired

application. The Polylactide (PLA) has good mechanical properties such as it is used

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as packaging material (e.g., film, sheet, or bottles), textiles (e.g., filaments or fibers),

engineering plastics, and medical polymers (e.g, surgical thread or implants), (Reis et

al., 1997).

1.10 1,4:3,6-Dianhydrohexitols-Based Polymers

It is difficult to incorporate the simple carbohydrates directly into polymer

structures because both primary and secondary hydroxyl functionalities interfere with

the synthesis of well defined products in carbohydrates (Fenouillot, 2009). Then, the

1, 4:3, 6-dianhydrohexitols had been used to circumvent the problem.

Dianhydrohexitols are well documented by-products of the starch industry obtained

by dehydration of D-hexitols, which are made by a simple reduction of hexose sugars

(Stross and Hemmer, 1991). There is about 650,000 tons of Dianhydrohexitols are

produced annually worldwide (Sheldon, 1993).

The chiral biomass derived products transforms or exists as three main

isomers (isosorbide, isomannide, and isoidide), in which depending on the

configuration of the two hydroxyl functions (derived from D-glucose, D-mannose,

and L-fructose, respectively) (Rousseau, 2009). The most widely available

Dianhydrohexitol is Isosorbide in which produced from glucose via sorbitol (Pascault.

1995).

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Figure 6: The Uhde Inventa-Fisher process of making polylactide from starch.

Source: www.udhe-inventa-fisher.com.

1.11 Isosorbide

Isosorbide is a non-toxic biodegradable diol derived from bio-based feedstock. It can

be used for preparing thermoplastic starch through a semi-industrial process of

extrusion. Isosorbide allows some technological advantages with respect to classical

plasticizers: namely, direct mixing with starch, energy savings for the low processing

temperature required and lower water uptake.(Battegazzore, Bocchini, Nicola,

Martini, & Frache, 2014)

Figure 7:isosorbide (source: google image)

With molecular formula C6H10O4 (Molecular weight = 146.14), it is chiral, large

and bulky, making it look like white crystalline powder, very hygroscopic (~8

kilo/liter of water). Its melting point is around 61-64°C and boiling point of 1600C

(10mm Hg). It is soluble in water, alcohol, dioxane, ketones but almost insoluble in

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hydrocarbons, esters, ethers. Aside from that, it is very heat stable, non-toxic and

generally recognized as safe. It is difunctional, reactivity of hydroxyl groups not

equivalent. It is a renewable, sustainable and biodegradable resource because it is

derived from sorbitol, a low cost product made from corn.(Michael Jaffe & Friedhoff,

2008)

1.11.1 Isosorbide Synthesis

Figure 8 : isosorbide synthesis

1.11.2 Isosorbide In Plastic Production

The chemistry of isosorbide is highly flexible with the ability to be

manipulated for specific polymer backbones. It can be tailored by different methods

of esterification and develop a proprietary technology platform. The compounds can

have performance similar to dioctyl pthalate in PVC applications. Isosorbide is an

innovative renewable solid plasticizer for thermoplastic starch and is much more

feasible than using petroleum resins. Crystallinity and mechanical properties do not

change in the course of time using isosorbide. (Michael Jaffe & Friedhoff, 2008).

Early work that focused on isosorbide used it as a constituent for the development of

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thermoplastic polymers for coatings applications (Noordover, 2007)These studies

showed that adding isosorbide in increasing concentrations increased the mechanical

properties of otherwise poor materials, and isosorbide could increase the Tg of their

materials by as much as 73% depending on concentration (Jasinska, 2010). The

temperature profile necessary for the processing is about 20°C lower than that

employed for the classic glycerol plasticization, allowing energy savings. The

obtained TPS is easily processable and film production from compression molding

was proven. The collected data by thermogravimetry have shown that the plasticized

starch is stable up to 200°C in nitrogen as well as oxygen atmosphere like a common

starch plasticized with glycerol. The mechanical properties and oxygen permeability

of starch plasticized with isosorbide are dependent from water content related to the

air relative humidity.

Thermoplastic starch plasticized with isosorbide is not subjected to

retrogradation. Retrogradation is a reaction that takes place in gelatinized starch when

the amylose and amylopectin chains realign themselves, causing the liquid to gel.

(Battegazzore et al., 2014)

Figure 9:

21

Figure 10: PVC Plastic

1.11.3 Isosorbide in UV Absorption

Isosorbide based UV stabilizers like isosorbide bis ferulate ester and related

compounds could be synthesized using a carbodiimide route. Isosorbide enables the

creation of a biodegradable UV stabilizer derived from natural sources. It can absorb

UV light strongly between 230-360 nm, hence suitable to be applied by both plastics

and cosmetics industries. The fact that isosorbide is an antioxidant also incline to the

application in cosmetics. (Michael Jaffe & Friedhoff, 2008)

Conclusion

Studies of biodegradable polymers are very important in ensuring a greener

and more sustainable future. A common misunderstanding is that all biodegradable

polymers are made from renewable resources but they can be produced via synthetic

and biotechnological means for example from petroleum. In order to slow down the

declination of non-renewable resource, high quality polymers can be produced from

alternative, cheaper renewable resources like corn and maize.

There are many advantages in using biodegradable polymers from corn starch

such as biodegradable plastics applies to environmental properties, primarily when it

comes to the handling of waste plastics and the effects of their decomposition on the

22

environment. When biodegradable plastics decompose biologically, the resulting

natural components do not affect the environment in any harmful way. Even though

the ordinary, non-biodegradable plastics do not release harmful substances into the

environment, they are relatively durable and although the threat posed by plastics is

not removed completely, the damage that could be done is significantly lower.

The uses of biodegradeable polymers are wide. Making use of the easily obtained

isosorbide, we can improve the production of multiple industries. In plastic

production, isosorbide reduces production cost while simultaneously improving the

mechanical properties of the plastic. The plastics produced from isosorbide also will

not retrograde (Battegazzore et al., 2014). Meanwhile in the cosmetic industries, the

polymer can be used in improving skin protection against harmful UV rays.

Another advantage of biodegradable polymers is that they decompose into natural

substances and do not require separate collection, sorting, recycling or any other final waste

solution like landfills as is the case with non-biodegradable plastics. While these measures

reduce the environmental impact of waste they cannot eliminate it or establish the state of

natural processes as can be done with biodegradable polymers. Their natural degradation

allows artificial materials-bioplastics to enter the natural cycle and be reused.

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