6-8 Oil in Polymers

8Vegetable Oils in

Production of Polymersand Plastics

Suresh S. Narine and Xiaohua Kong

Agri-Food Materials Science Centre, University of Alberta

Edmonton, Alberta, Canada

1. INTRODUCTION

Polymers are a group of materials made up of long covalently bonded molecules,

which are obtained either from natural or synthetic sources. Within the life

sciences, the study of polymers has helped to foster the emergence of molecular

biology through focus on natural macromolecular substances such as proteins,

nucleic acids, and polysaccharides. Largely through engineering efforts, a series

of commercially synthetic polymers have been successfully used in many applica-

tions in modern society.

Polymers, in the form of plastics, are used in making articles of daily use, such

as knobs, handles, switches, pipes, heart valves, and so on. An overwhelming per-

centage of the polymers to make these commodities are synthesized from petroleum

sources or natural gas raw materials. The key petrochemicals for polymer synthesis

(ethylene, propylene, styrene, vinyl chloride monomer, and others) are produced

largely from naphtha, one of the distillation fractions of crude oil or from natural

gas. Once synthesized, the polymer materials, such as polyethylene, polypropylene,

Bailey’s Industrial Oil and Fat Products, Sixth Edition, Six Volume Set.Edited by Fereidoon Shahidi. Copyright # 2005 John Wiley & Sons, Inc.

279

polystyrene, and polyvinyl chloride, are passed to major consuming industries.

These synthetic polymers are, however, often not environmentally friendly because

they typically do not undergo the process of biodegradation and, of course, are

dependent on a limited petroleum resource. The urgent need of today is to develop

polymers that are biodegradable so that they become environmentally friendly

(1–3). The common biodegradable synthetic polymers include novel aliphatic

polyesters, such as poly(e-caprolactone) (PCL), poly(b-methyl-d-valerolactone),

polylactide, and their copolymers. The most important aspect of synthesizing

biodegradable polymers relates to their ability to undergo degradation within the

biosphere on coming into contact with micro-organisms, enzymes, or under natural

environmental conditions.

In addition, the natural resource of petroleum is being exhausted at a fast rate

(4). The escalating cost of petrochemicals and the high rate of depletion of this nat-

ural resource present a serious challenge to the innovative potential of chemists (5).

Scientists are therefore investigating opportunities to prevent economic losses and

inevitable crisis of lowered standard of living as a result of oil shortages in the

future. They are searching for new raw materials that can be synthesized into

environmentally friendly polymers so as to make available the materials needed

by various industries at lower costs (6, 7). These new materials are, in fact, not

so new; they stem from natural agricultural sources, called ‘‘renewable resources’’

(4, 6, 8). By definition, renewable resources are the agricultural products that are

synthesized by the use of solar energy (3, 4, 9). Some examples of these resources

are polysaccharides, such as cellulose and starch, and glycerol esters of fats and

oils (3, 10).

2. POLYMERS FROM RENEWABLE RESOURCES

This chapter deals with polymers synthesized from oilseed sources. However, to

provide the reader with an appreciation of the area of renewable, biodegradable

polymers and the place within this area that polymers from oil seeds occupy in

terms of functionality, price, and acceptability, some other polymers from major

renewable sources are also discussed. The most well-known and widely used

renewable biodegradable polymers are those from polysaccharides. The principal

polysaccharides of interest to polymer chemists are starches and cellulose, both

of which are polymers of glucose. In addition to these, fibers, polylactic acid

(PLA), and triacylglycerols of oils are of particular interest for the development

of biodegradable industrial polymers.

2.1. Starch

Starch is the most common polymer found in plants. Large amounts of starch can

be obtained from tubers such as potatoes, from cereals such as rice, and from seeds

such as corn. The starch molecule is heavily hydrated as it contains many exposed

hydroxyl groups, which form hydrogen bonds on coming into contact with water.

Starch is constituted of linear polymers (amylose) and of branched polymers

280 VEGETABLE OILS IN PRODUCTION OF POLYMERS AND PLASTICS

(amylopectin) of a-D-glucose. Amylose consists of long linear chains joined by

a (1 ! 4) linkages. Amylopectin, however, is highly branched in that D-glucose

is also joined by a (1 ! 4) linkages, but the branching point linkage between

the two D-glucose molecules have a (1 ! 6) linkages (11). The structures of amy-

lase, amylopectin, and starch are shown in Figure 1.

O

HOH

H

H

OOHH

HOO

O

HOH

H

H

OOH

H

HO

Amylose Unit Linkage α 1 4

O

HHO

H

H

O

OHH

HOO

O

HOH

H

H

OOH

H

HO

O

HH

H

OOH

H

HOO

Amylopectin Unit Linkage α 1 4

O

HOH

H

H

O

OHH

HOO

O

BranchH

OH

H

H

OOH

H

HO

O

HH

H

OOH

H

HOO

Chain Main

Structure of Starch showing α 1 6 branch point linkage

1 6 linkage

Figure 1. Structures of amylose, amylopectin, and starch.

POLYMERS FROM RENEWABLE RESOURCES 281

It may be noted from Figure 1 that the starch molecule contains two important

functional groups, that is the ��OH group, which is important for substitution reac-

tions, and C��O��C, which is susceptible to chain breakage. As a result of these two

important features, starch and its derivatives are used in the synthesis of biodegrad-

able plastics (1).

Starch is generally regarded as a resource that is competitive with petroleum in

terms of the preparation of a compostable polymer (12). It is used as an additive to

plastics, for cross-linking or bridging to change the structures of plastics into

networks, and as fillers for various purposes. Acetylation of starch yields starch

acetate, which is considerably more hydrophobic than starch and has an improved

solubility so that it can be easily cast into films from simple solvents. Degradation

of acetylated starch films occurs when exposed to buffered amylase solution (1).

Starch is used as filler in various resin systems to produce films that are imperme-

able to water but permeable to water vapors. Griffin (13) reported that starch-filled

polyethylene films become porous after the extraction of starch. This porous film

can then be readily invaded by micro-organisms and rapidly saturated with oxygen,

thereby increasing polymer degradation by biological and oxidative methods. Some

work has also been reported in which starch is used as a filler in manufacturing

polyvinyl chloride (PVC) plastics (1). In addition, the hydroxyl group (��OH) of

starch can react with the extremely reactive groups (��N��C��O) of isocyanates

spontaneously, (i.e., cross-linking) which can be used to prepare a large number

of reactive resins with reduced cost and improved solvent resistance and strength

qualities (1, 14).

2.2. Cellulose

Cellulose is the most abundantly occurring natural biopolymer. Cellulose is a linear,

unbranched homopolysaccharide. It resembles amylose, which is the primary poly-

meric constituent of starch. However, the major difference is that glucose residues

in cellulose have b configuration (11, 12, 15). Cellulose is now receiving greater

attention from polymer chemists because of the easy manner in which it undergoes

biodegradation by certain micro-organisms. Aerobic soil is rich in floral bacteria

and fungi, which will operate cooperatively to degrade polymers. Primarily, cellu-

lose is biodegraded to glucose and cellodextrin. Then, by the action of enzymes,

these cellodextrins are converted to glucose. The end products of biodegradation

under aerobic conditions are water and carbon dioxide. The final products of bio-

degradation under anaerobic conditions, on the other hand, are carbon dioxide,

hydrogen, methane, hydrogen sulfide, and ammonia (1).

Cellulose is a fibrous, tough, water-insoluble, and crystalline substance. As a

result of these characteristics, it is often converted to its derivatives in order to

make it more useful. The most commonly used derivatives of cellulose are carbox-

ymethylcellulose, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose,

cellulose acetate, and cellulose xanthate (12). Among these derivatives, cellulose

acetate and cellulose xanthate are cellulose esters, which are now widely used

in the manufacturing of fibers, films, and in injection molding thermoplastics.


Cellulose esters represent a class of polymers that have excellent physical proper-

ties and are relatively low-cost materials with high market potential (1). The struc-

ture of cellulose acetate is shown in Figure 2.

2.3. Fibers

In addition to starch and cellulose, a wide variety of organic materials have signif-

icant commercial importance to the plastic industry. Fibers, among these, are being

currently used as fillers and reinforcing agents in plastic materials. The primary

advantages of using renewable lignocellulosic fibers as additives in polymers are

that they (16):

1. have low densities

2. are low-cost materials

3. have a nonabrasive nature

4. provide high filling levels

5. require low-energy consumption

6. have high specific properties

7. are biodegradable and environmentally friendly

8. have wide varieties available throughout the world

Wood flour, for example, is a finely ground fibrous material obtained primarily from

pine and spruce. Cotton is another plant fiber that is important in thermosetting

molding compounds. Cotton fibers are used in the plastic industry in several forms:

as flock, cordage, woven fabrics, nonwoven fabrics or felts, and chopped fabrics.

The products obtained by using these fibers have reduced cost, increased impact

strength, and other mechanical properties, as well as having improved moldability

and appearance of finished molded parts. Wood flour; cotton fibers; sisal, another

fiber plant; and hemp fiber, obtained from Cannabis sativa (12), are all used as filler

and act as a reinforcing material for plastics. A lot of work has been done by

Mohanty et al. (16–23) using lignocellulosic fibers from jute, pineapple leaf, sisal,

and others, in making biopolymers. They observed that lignocellulosic fibers play

important roles in modifying physical as well as chemical properties of the poly-

mers (17–19). Rout et al. (20) have studied the use of coir as reinforcement in poly-

mer composites. It was found that the efficiency of fiber-reinforced material

O

HOH

HO

OHH

HOO

O

HOH

H

HOH

HHO H

n

HH

Figure 2. Structure of cellulose.


depends on the fiber/matrix interface and the ability of transferring stress from the

matrix to the fiber. Mohanty et al. (22) studied the chemical modifications of jute

yarns in making biopolymers and found that alkali-treated yarns produce better

mechanical properties than the defatted ones because of the improved fiber matrix

adhesion of the previous ones. Mishra et al. (16) studied surface modifications and

mechanical improvements in pineapple leaf polyesters. It was observed that the

surface-modified pineapple leaf fibers were good reinforcing agents for polyester

matrices as well as having increased tensile and flexural strength.

2.4. Polylactic Acid (PLA)

Polylactic acid is not a new polymer. It belongs to the family of aliphatic polyesters

commonly made from a-hydroxy acids, which can be synthesized via two major

routes. One method involves the removal of water using solvent, under conditions

of high temperature and pressure. The polymer yielded using this method may be

coupled with isocyanates, epoxides, or peroxides to produce a variety of other poly-

mers. The other method involves the removal of water without solvent under milder

conditions to produce a cyclic intermediate dimer referred to as lactide (24). Poly-

lactic acid is one of the few polymers in which the stereochemical structure can

easily be modified by polymerizing a controlled mixture of L- or D-isomers

(meso forms) to yield high-molecular-weight polymers. The properties of polylactic

acid depend entirely on the ratio of these two meso forms of lactic acid. The struc-

tures of the two meso forms are shown in Figure 3.

A great variation in the properties of products can be observed by using D, L,

and different D/L ratios of polylactic acid. A product with high melting point and

high crystallinity is obtained by using the L-isomer of lactic acid. On the other

hand, an amorphous polymer is obtained by using a mixture of D and L isomers.

This feature is very important, particularly in the binder fiber area (24). PLA,

furthermore, is environmentally friendly. The products of PLA can completely

degrade to carbon dioxide and water (24, 25).

2.5. Cashewnut Shell Liquid (CNSL)

Cashewnut Shell Liquid (CNSL) is an agricultural product, which as such, qualifies

its inclusion in the category of renewable resource. Major components of CNSL

have been characterized by various researchers using different techniques such as

ultraviolet (UV), infrared (IR), nuclear magnetic resonance (NMR) spectroscopy,

OH

CH3

OOH

D-lactic acid

O

CH3

HOOH

L-lactic acid

Figure 3. D and L forms of lactic acid.


and chromatography. The four major components of cashewnut shell liquid are

cardanol, cardol, anacardic acid, and 6-methylcardol (26). Structures of these

four components of CNSL are shown in Figure 4.

Several resins have been prepared by Guru et al. (27) using cardanyl acrylate,

which is a derivative of cardanol (major constituent of cashewnut shell liquid)

and furfural in the presence of an acid catalyst and a selective organic compound.

They studied the thermal behavior of these resins as well as their solvent absorptiv-

ity using solvents such as toluene and dimethyl formamide. The organic compounds

used were thiourea, o-hydroxybenzoic acid, m-phenylene diamine, and m-chloro-

phenol. The scheme of the reaction of cardanyl acrylate, furfural, and an organic

compound is shown in Figure 5. Thermal studies of these resins has shown that

the first great loss in weight occurs at 700�C and is a result of segmental

fragmentation of cardanyl acrylate and ring unzipping of organic compounds. It

was observed that resins obtained from thiourea had a higher thermal stability

because of the absence of aromatic rings.

In another study, Nayak et al. (26) prepared CNSL-novalac resins by condensing

cardanyl acrylate with p-aminobenzoic acid and formaldehyde in the presence of an

acid catalyst. Thermogravimetric analysis and degradation studies on these resins

have been carried out. It was observed that this resin decomposed with the removal

OH

Cardanol

OH

Anacardic acid

OH

O

OH

Cardol

HO

OH

6-Methylcardol

HO

H3C

Figure 4. Structure of four major components of cashewnut shell liquid (CNSL).


of water. Swain et al. (28) have also reported the preparation of a number of resins

by condensing diazotized cardanol with formaldehyde and organic compounds in

the presence of an acid as a catalyst. They also carried out investigations on the

thermogravimetric properties of the resin, which resulted in a weight loss of this

resin of about 67–74% at 700�C.

Polyesters and polyurethanes can be prepared by bifunctional monomers like

dianhydrohexitols, which are readily available from D-glucose and D-mannose.

The structures of dianhydrohexitols are shown in Figure 6. Okada et al. (2) prepared

polyesters based on furan rings. The scheme of the polyester formation is shown in

Figure 7. They studied the biodegradability of these polyesters by three methods:

hydrolysis in a phosphate buffer solution, soil burial degradation, and enzymatic

degradation. They observed that the hydrolytic degradability of these polyesters

is low, whereas soil burial degradation shows that several spores and hypas of

actinomycetes were grown within 100 days showing erosion of the surface of the

film, meaning these polyesters are biodegradable.

O C

O

CH CH2

R

CH

O

NH2

NH2

O C

O

CH CH2

R

O

CHO

NH2

NH2

CA FF MPDA

+ +∆,4−6 hrs, H+

Resin (CA-FF-MPDA)

Figure 5. Reaction scheme of polycondensation of cardanyl acrylate (CA) with m-Phenylene

Diamine (MPDA) and Furfural (FF) in the presence of acid as the catalyst.

O

O

HO

OH

O

O

HO

OH

Figure 6. Structures of dianhydrohexitols.


2.6. Triacylglycerol Oils

It has been reported above that low-cost biodegradable polymers can be prepared by

using polysaccharides, fibers, and polylactic acid. In addition to these renewable

resources, naturally occurring triacylglycerol (TAG) oils are also significant starting

materials for the production of biodegradable polymers (6, 29). The TAG oils of

linseed, tung, lunaria, Lesquerella gracilis, and crambe have been used as sources

of polymers by virtue of their double bonds; functional groups that can result in

polymerization (8). The double bonds of these and other TAG oils can also be epox-

idized or converted into hydroxyl groups to increase their reactivity (6). Only a few

TAG oils, however, contain naturally occurring special functional groups, i.e.,

hydroxyl and epoxy groups (30, 31). For example, castor oil and Lesquerella pal-

meri (also called bladder pods or pop weed) contain hydroxyl groups in addition to

double bonds. Similarly, vernonia oil contains a natural epoxide functional group

(31–33). The structures of the main triacylglycerols of castor, lesquerella palmeri,

and vernonia oils are shown in Figure 8. The hydroxyl and epoxide functional

groups on these long and complex TAG molecules may be exploited to allow

such molecules to be cross-linked, which allows large macromolecules to be

formed.

Castor oil from castor beans contains high percentage triacylglycerols (TAGs) of

ricinoleic acid (83.6–90%), which is a C-18 fatty acid. Castor oil is unique in that

its TAGs contain both double bonds and nonconjugated hydroxyl groups. The tri-

functional nature of castor oil contributes toughness to the structure, and the long

fatty acid chain imparts flexibility. As a result of its unusual structure, this oil is

very versatile in its applications. It is used in making paints, adhesives, and

urethane foams (34). Lesquerella oil, a C-20 oil, is obtained from a wild plant. It

contains fatty acids similar to ricinoleic acid, but also contains two additional

O

O

HO

OH

+O

O

O OO

O

O

O

O

O

O

O O

ORn

Figure 7. General scheme of polyester formation.


��CH2�� groups on the acid residue. Vernonia oil has a relatively low viscosity

because of high epoxide concentration. It is, therefore, mostly used as a diluent

for coating applications (34).

Soybean oil, another TAG oil, is being used in the manufacturing of plastics,

resins, and adhesives. Soybeans themselves contain 20% oil and 40% proteins;

they contain discrete groups of proteins that have unusual adhesive properties

(35). Soy-based plastics have many applications, which include their use in the pro-

duction of parts for agricultural equipment, such as tractors and farming machines,

and for the automotive industry. The applications also include civil engineering

components for bridges and highways, marine infrastructures such as pipes and off-

shore equipment, rail infrastructure such as carriages, box cars, and grain hoppers,

and in the construction industry such as formaldehyde free particle board, ceilings,

and engineered lumbers (36). Different techniques such as injection molding and

compression molding are used to prepare soy-protein plastics.

Jiratumnukul and Michael (37) have reported the use of different glycol esters

from soybean oil, such as ethylene glycol, propylene glycol, diethylene glycol, and

dipropylene glycol, for making new coalescent aids. They investigated the proper-

ties of these coalescent aids as related to evaporation rates and Minimum Film

O

O

O

O

O

O

OH

OH

OH

Caster oil (triricinolein)

O

O

O

O

O

O

OH

OH

OH

Lesquerella palmeri oil (trilesquerolic acid)

O

O

O

O

O

O

Vernonia oil (trivernolin)

O

O

O

Figure 8. Chemical structures of triricinolein, trilesquerollic, trivernolin, major triacylglycerols,

respectively of castor, Lesquerella palmeri, and vernonia oils.


Formation Temperature (MFFT). Based on their observations, soybean oil glycol

esters are not classified as volatile organic compounds.

3. EXPLOITATION OF THE FUNCTIONAL GROUPSON TRIGLYCEROL MOLECULES FOR THE PRODUCTIONOF POLYMERS

Different functional groups on TAG oils, such as carbon-carbon double bonds and

epoxy and hydroxyl groups, play an important part in the formation of polymers.

Oils from various sources contain different functional groups. The occurrence of

these functional groups in oils from different sources and their significance in the

production of polymers is described below.

3.1. Double Bonds

Among the oils that contain carbon-carbon double bonds as the functional groups,

linseed, tung, corn, cottonseed, rapeseed, and soybean are more widely used as

polymeric sources. Linseed oil is extracted from the seeds of the flax plant (Linum

usitatissimum). The major constituents of linseed oil are a-linolenic acid (60%),

linoleic acid (29%), and oleic acid (27%). This composition varies with changes

in climatic conditions. On the other hand, tung oil, also called china wood oil, is

derived from the seeds or nuts of the trees aleurites fordii and A. montana. The

major constituent of tung oil is eleostearic acid (77–82%), whereas the other impor-

tant components of tung oil are oleic acid (3.5–12.7%) and linoleic acid (8–10%). It

is known that the carbon-carbon double bond in oleic acid is at C9, in linoleic acid

it is at C6 and C9, and in linolenic acid it is at C3, C6, and C9, whereas eleostearic

acid has double bonds at positions C5, C7, and C9.

The structures of oleic, linoleic, linolenic, and eleostearic acids are given in

Figure 9. Linseed oil and the tung oil are collectively called ‘‘drying oils,’’ which

are defined as liquid oils that dry in air to form a solid film (these oils have iodine

values greater than or equal to 150 units). Soybean oil, sunflower oil, and canola oil

are semidrying oils, with iodine values between 110 units and 150 units. The drying

power of such oils is directly related to the chemical reactivity conferred on the

TAG molecules by the carbon-carbon double bonds of the unsaturated acids, which

allows them to react with atmospheric oxygen, thus leading to the process of

polymerization to form polymeric networks.

Linseed oil, which contains 60% a-linolenic acid, is an example of a nonconju-

gated oil, which is rich in polyunsaturated fatty acids. These polyunsaturated fatty

acids contain double bonds, which are separated by at least two single bonds. The

linolenic acid content in nonconjugated oils plays an important role in the drying

process that is generally considered to be the result of a process of autoxidation

followed by polymerization when the oil absorbs large amounts of oxygen. The

process of autoxidation in the case of nonconjugated oil systems begins with the

dehydrogenation of unsaturated fatty acids, such as linolenic acid, by means of

atmospheric oxygen. As a result, dehydrogenated radicals are formed and chain

EXPLOITATION OF THE FUNCTIONAL GROUPS ON TRIGLYCEROL MOLECULES 289

polymerization starts with the formation of hydroperoxide. Furthermore, cross-

linking takes place to form large molecules. A summary of this process is shown

in Figure 10.

Tung oil with eleostearic acid as its major component, on the other hand, is an

example of conjugated oil systems. The conjugated double bonds of oils, such as

those of tung oil, favor polymerization and oxidation more rapidly than nonconju-

gated oils. The principal drying component of tung oil is eleostearic acid. As a con-

sequence of this polymerization, the resultant product obtained is highly resistant to

water and alkali. Drying of films in the case of conjugated oils consists of the fol-

lowing three steps:

1. Induction: This process begins by the autocatalysis of eleostearic acid, and

the oxygen uptake starts increasing slowly.

2. Initiation: The film continues to absorb oxygen from the atmosphere and, as a

result of this absorption, the mass of the film increases and the double bonds

of eleostearic acid undergo a rearrangement process. On rearrangement,

hydroxyl and hydroperoxy groups are formed in the film.

3. Cross-linking: As a result of the above two steps, the number of double bonds

decreases due to cross-linking and, thus, larger molecules are formed.

For many applications, tung oils often cure so rapidly that a highly wrinkled sur-

face forms. Therefore, it is necessary to modify the reactivity of tung oil, which is

HOC

Oa) Oleic acid

HOC

Ob) Linoleic acid

HOC

Oc) Linolenic acid

HOC

Od) Eleostearic acid

Figure 9. Structures of oleic, linoleic, a-linolenic and eleostearic acid.


possible by reducing the number of double bonds present. The reactivity can be

modified by chemical means, such as the Diels-Alder reaction with a reactive die-

nophile (38) and copolymerization with styrene (39) and diacrylate (40); this

reduces the number of double bonds and causes the cure speed of the copolymers

to be slower, resulting in a nonwrinkled surface. Also, by controlling comonomer

stoichometry, sufficient residual double bonds should remain so that oxidative cure

of the copolymers would be still possible.

On the other hand, the high degree of unsaturation of this type of drying oil has

made it a potential monomer for polymerization into useful polymers. More

recently, Li and Larock (41) reported the conversion of tung oil to solid polymers

by cationic copolymerization with divinylbenzene as a comonomor. The result-

ing polymers have proven to be thermosetting materials with good mechanical

ROOH

INITIATION

RO OH

RH

ROH O2RROOHPROPAGATION

RH ROO

H

O2

R

OO

RH

ROOH

HeatHomolytic Cleavage

of a peroxide

MAJOR SOURCE OF RH

POLYMERIZATION

polymers

PRODUCTS OF TERMINATION RR, ROR, ROOR

R

Figure 10. Stepwise drying process of oils with double bond functionality.


properties and thermal stabilities and may find applications in replacing petroleum-

based polymeric materials because of their presumed ability to biodegrade and the

low cost of their preparation from renewable natural resources (i.e., vegetable oils).

Furthermore, the multiple double bonds also make tung oil a thermally polymer-

izable monomer at elevated temperatures. Li and Larock (42) produced a variety of

polymers prepared by thermal copolymerization of tung oil, styrene, and divinyl-

benzene in the temperature range of 85–160�C by varying the stoichiometry, oxy-

gen uptake, peroxides, and metallic catalysts. They found that the stoichiometry

and the addition of metallic catalysts greatly affect the mechanical, thermal, and

physical properties of the resulting polymers. However, the variations of oxygen

uptake and peroxides have little effect. Li and Larock also (43–50) proposed a

direct method to convert soybean oil to polymers by cationic copolymerization

with divinylbenzene or mixtures of styrene and divinylbenzene initiated by boron

trifluoride diethyl etherate or other modified initiators. The polymers obtained can

range from soft rubbers to hard plastics, depending on the reagents, stoichometry,

and initiators used in the synthetic process. The resulting polymers exhibit thermal,

physical, and mechanical properties that were competitive with those of their

petroleum-based counterparts, as well as some other very promising properties,

including good damping and shape memory properties.

Knot et al. (51) converted soybean oil to several monomers for use in structural

applications. They prepared rigid thermosetting resins by using free radical copo-

lymerization of maleates with styrene. The maleates are obtained by glycerol trans-

esterification of the soybean oil, followed by esterification with maleric anhydride.

They also synthesized several TAG-based polymers and composites and compared

their properties. It was found that the moduli and glass transition temperature (Tg)

of the polymers varied and depended on the particular monomer and the resin com-

position. They proposed that the transition from glassy to rubbery behavior was

extremely broad for these polymers as a result of the TAG molecules acting both

as cross-linkers as well as plasticizers in the system.

3.2. Hydroxyl Groups

Triacylglycerol oils, such as castor and lesquerella, are naturally occurring oils that

have hydroxyl groups on their major TAG molecules. The major component of cas-

tor oil is ricinoleic acid (C18), which has a hydroxyl group at C12. On the other

hand, the principal component of Lesquerella palmeri is lesquerellic acid (C21),

having a hydroxyl moiety at C14. The structures of ricinoleic and lesquerolic acids

are shown in Figure 11. Based on the TAG molecules of these acids shown in

Figure 8, these oils are referred to as trihydroxyl polyols or triols. These polyols

are important for the production of cross-linked polymers. The presence of the

hydroxyl groups permit reaction with diisocyanates to form polyurethanes. Polye-

sters are formed when hydroxyl groups react with dibasic acids, such as sebacic

acid obtained from castor oil, to form aliphatic polyesters with the removal of a

water molecule as byproduct (52). Castor oil derivatives, obtained through alkali

pyrolysis can also be useful, such as decanedioic acid (sebacic acid), which is


used as a monomer for nylon 610, and undecylenic acid, which forms 11-aminoun-

decanoic acid, which is the monomer for nylon 11 (34). Nylon is an important poly-

mer that is used for engineering plastics in the automotive and transport industry,

for example. Nylon products are also used in powder coating to cast metals that

require abrasion, impact, and corrosion resistance.

Isocyanates are the derivatives of isocyanic acid (H��N��C��O). The functional-

ity of the isocyanate (��N��C��O) group is highly reactive toward proton-bearing

nucleophiles, and the reaction of isocyanate usually proceeds with addition to the

carbon-nitrogen bond. The reactions of isocyanates fall into two main categories:

(1) active hydrogen donor, and (2) nonactive hydrogen reaction. The more signifi-

cant of these is the first category, where isocyanates react with polyols, which

involves reaction with active hydrogen. The second category of reactions involving

nonactive hydrogen reactions usually leads to cycloaddition products and linearly

polymerized products. Some examples of diisocyanates are: 2,4-toluene diisocya-

nate, 2,6-toluene diisocyanate, 1,6-hexamethylene diisocyanate, and 1,5-naphtha-

lene diisocyanate, among others. The reactivity of isocyanates depends on their

chemical structures. Aromatic isocyanates are usually more reactive than their ali-

phatic counterparts. The presence of electron withdrawing substituents on isocya-

nates increases the partial positive charge on the carbon atom and moves the

negative charge further away from the reaction site. As a result of this character,

the reaction between the donor substance and the carbon atom of isocyanates is

fast. Therefore, whenever polyols or triols react with an isocyanate, the resulting

polyurethane is cross-linked. The extent of cross-linking affects the stiffness of

the polymer. The polymer structure must be highly cross-linked when a rigid

foam is required, whereas less cross-linking gives rise to flexible foams. The degree

of cross-linking is entirely dependent on the NCO/OH ratio. Branching occurs at

the urethane linkage when NCO/OH ratio is low. Low degree of cross-linking

allows the molecules freedom of movement resulting in the improvement in

strength and creep resistance. However, a slight loss in the soft, flexible, rubbery

behavior occurs. On the other hand, when NCO/OH ratio is high, the probability

of the formation of urea linkages is greater and, therefore, the branching takes place

at the urea linkage points. A high degree of cross-linking, in contrast, immobilizes

the polymer molecules and, thus, the resulting polymer becomes a thermoset

HOC

O

a) Ricinoleic acid

OH

HOC

O

b) Lesquerolic acid

OH

Figure 11. Structures of ricinoleic and lesquerolic acid.


plastic. Das and Lenka (53) and Barrett et al. (34) have reported the preparation of

polymers by using toluene diisocyanate and hexamethylene diisocyanate. They

observed that increased ratio resulted in a highly cross-linked product with high

thermal stability.

It is known that increased cross-linking brings the polymer backbone closer

together. There is, therefore, a reduction in molecular mobility and an increase

in glass transition temperature. The weaker and less stable cross-linkages at high

temperatures tend to reopen and revert back to linear structures. Less cross-linked

polymers absorb large amounts of solvent and, thus, swell to form soft gels. Highly

cross-linked polymers, however, absorb less solvent molecules as a result of less

molecular mobility and, thus, cannot move apart to accept solvent molecules.

The preparation of polyols from vegetable oils, such as castor oil, safflower oil,

linseed oil, and soybean oil, has been studied by several groups. There are many

ways to introduce hydroxyl groups into oils, resulting in different polyol structures

and different polyurethanes ranging from elastomers to rigid foams. Polyurethane

prepared from castor polyols exhibits a broad range of properties. Low-viscosity

urethane polymers have been found extremely useful for potting electrical compo-

nents, for which fast penetration without air voids and fast dispensing cycles are

desirable (54). Meanwhile, very low-viscosity polyurethane systems containing

castor polyols have been prepared for use in telephone cable (55). On the other

hand, polymerization, whether chemical or oxidative, of castor oil resulted in oils

with higher viscosity that were more useful in the polyurethane coating industry

than untreated ones (56).

Castor oil and its derivatives have been used in the preparation of rigid, semiri-

gid, and flexible polyurethane foams. Castor oil’s resistance to hydrolysis, pigment

dispersion ability, and compatibility with polyether polyols has also made it useful

as a modifier for polyether-based foam. Castor oil can also be used to formulate

commercially acceptable rigid polyurethane foams for use as thermal insulations

and structural material (57). Superior rigid polyurethane foams have been prepared

from hydroxymethylated polyol esters of castor acids. Frankel et al. (58, 59) pre-

pared castor, safflower, and linseed oil derivatives with enhanced hydroxyl group by

hydroformylation with a rhodium-triphenylphosphine catalyst, followed by hydro-

genation. The polyurethane foams obtained had good compressive strength and

dimensional stability that met the requirements of commercial products.

Recently, Petrovic and coworkers (60–69) developed two technologies to pre-

pare soybean oil-based polyols for general polyurethane use. In the first technology,

the oil was first epoxized using the standard epoxidation procedure, followed by

alcoholysis to form the TAG polyol. In the second, the double bonds of the soybean

oil were first converted to aldehydes by hydroformylation with either rhodium or

cobalt as the catalyst, followed by hydrogenation to alcohols by nickel. The polyols

were then reacted with a diisocyanate to yield polyurethanes. The resulting polyur-

ethane can behave as a hard rubber or a rigid plastic, depending on the methods

used in the reaction process, such as by controlling the degrees of conversion, using

different diisocyanate components, and varying the stoichiometry. They found that

the rhodium-catalyzed hydroformylation of soybean oil with high conversion of


olefins leads to a rigid plastic polyurethane at room temperature, whereas the

cobalt-catalyzed hydroformylation with low conversion of olefins gave a hard rub-

ber. The properties of the product can also be controlled by the cross-linking den-

sity. Polymers prepared with NCO/OH ratio from 1.05–0.8 were glassy, whereas

with the others, less than 0.8 were rubbery. The selection of the diisocyanate com-

ponent affects the cross-linking and properties of the polyurethane as well. Usually,

aromatic isocyanates produce more rigid polyurethanes than their aliphatic counter-

parts, but their oxidative and ultraviolet stability are lower. Within aromatic isocya-

nates, 2,4-toluene diisocyanate (TDI) is chosen to obtain the most flexible product.

Rigid foams can be made from TDI prepolymers but are most often based on a

polymeric diphenylmethane 4,4- diisocyanate (MDI). Aliphatic isocyanates give

rubbery polymers with higher elongation at break, higher swelling, and lower ten-

sile strength. The thermal stability of polyurethanes was also investigated. It was

found that the thermal stability depended on the functionality of the polyol, i.e.,

on the number of urethane groups per unit volume, as well as structural differences.

John et al. (70) studied and compared the properties of polyurethane foam

obtained from soybean oil-based polyols and synthetic polyols and found that the

soybean-based polyols showed enhanced reactivity and that the foaming reactions

proceeded in a very similar way to synthetic polyols. It was also found that their

properties were sensitive to several variables such as water content, isocyanate

index, and catalysts. The reaction rate was mainly controlled by the water and iso-

cyanate content. As the water content increased, the reaction was faster and the

amount of the hard segment increased. In addition, MDI yielded more rigid foams

than TDI.

Polyesters obtained from lesquerella oil have variations in colors and have low

solution viscosity as compared with castor oil polyesters. The viscosity variations

are usually associated with the structural differences of the oil. Solution viscosity of

castor oil-based polyesters is usually high because ricinoleic acid in castor oil

allows extensive hydroxyl hydrogen bonding. Furthermore, lesquerella oil-based

polyesters are effectively plasticized because of longer C20 fatty acid. The hydro-

xyl group of lesquerella oil can be exploited to make acrylates. The scheme for

making lesquerella oil-based acrylates is shown in Figure 12. Lesquerella oil acry-

lates impart excellent gloss to wood, aluminum, and steel and have good adhesive

properties. The hydroxyl groups of lesquerella and castor oil also react with

cycloethers such as propylene oxide, epichlorohydrin, and ethylene oxide. As a

result of these reactions, novel polyhydroxy compounds of much improved reactiv-

ity can be obtained. Epichlorohydrin-modified lesquerella oil has increased reactiv-

ity characteristics. The coatings developed from epichlorohydrin and lesquerella oil

form harder films in shorter dry time. The mechanism is shown in Figure 13.

3.3. Epoxides

Vernonia oil contains a naturally occurring epoxide group on C12. It is, therefore,

important for the productions of polymers. It is also used in making adhesives,

plasticizers, industrial coatings, varnishes, and paints (32). Vernonia oil can be


polymerized through a variety of reactions. A natural elastomer can be synthesized

by reacting vernonia oil with naturally occurring dibasic acids, such as the sebacic

acid derived from castor oil (4). It is known that castor oil is the major source of

dibasic acids, such as decanedioic and nonanedioic acids (subaric and azelaic acids,

respectively), through pyrolitic decomposition. These acids can also be derived

from vernonia oil via an efficient reaction sequence (71). The obtained aliphatic

dibasic acids are established industrial raw materials that can be used as plasticizers

and impact resistant elastomers as well (30).

On the other hand, the rubbery nature of the polymerized oil may be used as

toughening, rigid epoxy materials because it is phase separated into spherical

domains when mixed and cured with bisphenol-A epoxy compounds (72–75). A

GlyO

O

OO

O

Cl

GlyO

O

OH

HN

H

O

NH

O

O

O

O

NH

O

HNO

O

O

O

O

OGly

O

Figure 12. Synthesis of lesquerella oil acrylates.


reinforced elastomer, however, is formed because the vernonia oil-sebacic acid

polyester forms a continuous phase. The reaction is shown in Figure 14. Sperling

and Manson (30) compared the glass transition temperature of vernonia oil polye-

ster with that of epoxidized linseed oil polyester. They observed that the glass tran-

sition temperature of linseed oil polyester was higher than that of vernonia oil

polyester because of dense cross-linking in epoxidized linseed oil. Vernonia oil is

OH

CHO

O

O

Cl

O

CHO

OCl

HO

Figure 13. Epichlorohydrin modification of lesquerella oil.

OH

O

HO

O

O

O

O

O

O

O

O

O

O

2 SA

O

O

O

O

O

O

OH

OH

OH

SA

SA

SA = Sebacic Acid =

Figure 14. Reaction of sebacic acid with vernonia oil.


soluble in many organic solvents and diluents as it contains both oxirane ring and a

double bond. These two features are useful in drying and curing mechanisms.

The epoxide moieties of vernonia oil play an important role in making acrylates,

groups useful in making UV curing formulations. For instance, the methacrylate

ester of vernonia oil is synthesized by reaction with methacrylic acid in the pre-

sence of a tertiary amine. The acrylate ester is UV active and is therefore easily

polymerized through the acrylate vinyl moieties. The mechanism of making verno-

nia oil-based acrylates is shown in Figure 15.

Epoxidized soybean and linseed oils are the two main representatives of the

industrially produced epoxidized vegetable oils. Both are obtained by epoxidation

of the corresponding unsaturated oils, and the degree of epoxidation can be con-

trolled by reaction time. Muturi et al. (76) found that the molecular structures

and properties of partially epoxidized soybean and linseed oils are similar to those

of vernonia oil. They are suitable for the preparation of low volatile organic com-

pound alkyd and epoxy coatings formulations. However, fully epoxidized oils are

not as good as vernonia oil for making reactive diluents for coatings because of

their higher viscosities and melting points. Epoxidized soybean oil is widely

applied as a polyvinyl chloride (PVC) additive to improve PVC processing, stabi-

lity, and flexibility (77). In addition, the double bond of vernonia oil can be con-

verted into an oxirane functional group. These ‘‘super epoxides’’ have the potential

OH

O

O

O

O

O

O

O

O

O

O

3 MA

O

O

O

O

O

O

HO

HO

HO

MA

MA

MA

MA = Methyl Acrylate =

Figure 15. Methyl acrylation of vernonia oil.


to serve as the reactive components of epoxide powder coatings. This super epox-

idized vernonia oil possesses a higher glass transition temperature than natural

vernonia oil. This characteristic is, therefore, useful for excessive plasticization.

The epoxidation of vernonia oil is represented in Figure 16.

As these oils contain multiple functionalities, they provide an alternative to pet-

roleum as a chemical feedstock. They are derived from cultivated or wild plants.

There is an international interest in using these naturally occurring oils as the start-

ing material for polymer production because excessive quantities of nonrenewable

petroleum are now being consumed (34).

4. USE OF NATURALLY FUNCTIONALIZED TRIACYLGLYCEROLOILS IN INTERPENETRATING POLYMER NETWORKS

As mentioned earlier, TAG oils may contain special functional groups that deliver

the potential of converting these oils into biopolymers. Such functional groups

make these oils particularly important as they can be polymerized with an appro-

priate bifunctional reactant to form polymers, if they contain a hydroxyl or epoxide

functional groups (34, 52). These oils contain hydroxyl as well as unconjugated

vinyl groups in their structural backbone. The presence of double bonds can be

exploited via a chain-growth mechanism to form polymerized plastics. On account

of these two features, these oils have the unique quality to control elasticity as well

as plasticity in a single backbone chain structure (78, 79). The cross-linking of

hydroxyl groups in a step-growth polymerization gives rise to ‘‘Interpenetrating

Polymer Networks’’ (IPN) (79). IPN materials contain ‘‘two or more polymers in

a network form with at least one polymer that is polymerized or cross-linked in the

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O

O +

OHO

Cl

OO

Cl

OH

Figure 16. Epoxidation of vernonia oil.

USE OF NATURALLY FUNCTIONALIZED TRIACYLGLYCEROL OILS 299

immediate presence of the other’’ (80, 81). Two major IPNs have been explored.

These are referred to as sequential and simultaneous IPN. Sequential IPNs involves

the preparation of one cross-linked polymer network and a subsequent swelling

with the monomer. This is then cross-linked with a second component and polymer-

ized in a network to a form sequential IPN. These two polymer networks are pre-

pared separately before polymerization. On the other hand, simultaneous IPN

involve the simultaneous mixing of all the components in one step followed by

the formation of both networks via independent reactions proceeding in the same

reaction vessel (32, 52, 80, 81).

Polyurethanes and polyurethane-based IPN have gained great importance in

recent years. Polyurethanes are divided into several classes. Some polyurethanes

are used in foams, whereas others are used for making fibers. Segmented elastomers

are perhaps the most interesting class of polyurethanes. This category of polyur-

ethanes is a kind of multiblock copolymer (82). The block copolymer is defined

as a type of polymer blend that contains two polymer chains that are linked end

to end (81, 83). In addition to various other uses, polyurethane materials are

extensively used in the medical field, such as in the production of medical-grade

tubing (82).

4.1. Use of Castor Oil-Based Polyurethanes/Polyesters for MakingInterpenetrating Polymer Networks

Several scientists have worked on the production of IPN and their characterization

based on a castor oil polyurethane model. Sperling and coworkers (84, 85) have

published a number of very interesting papers on IPNs from castor oils. The hydro-

xyl groups were reacted with 2,4-toluene diisocyanate for polyurethane formation.

Styrene and divinylbenzene were polymerized, and thus interpenetrated, to prepare

IPN and simultaneous interpenetrating networks (SIN) by using either individually

or mixed polyester-urethane. These IPNs and SINs can be tough plastics or rein-

forced elastomers depending on their compositions, which were shown from mod-

ulus-temperature, stress-strain, and impact-resistant studies. Furthermore, the

morphology of these IPNs and SINs depended on the synthetic method, such as

reaction time, stirring time, and time to pour into the mold. Yenwo et al. (84, 85)

synthesized sequential IPNs using castor oil and studied the dynamic mechanical

properties of the IPN. The experimental data showed that the molecular mixing

of the two networks was extensive but incomplete. Mechanical properties of such

systems were related to the degree of phase continuity and inversion.

Siddaramaiah et al. (86) employed an X-ray diffraction method to determine the

microstructural parameters of IPNs of castor oil-based polyurethanes and polystyr-

ene and correlated the changes of microstructural parameters to the physical macro

changes, such as hardness. They found that the addition of polystyrene (PS) resulted

in an increase in hardness that was due to an increase in crystal size.

Nayak and coworkers (7, 29, 87) prepared a series of IPNs by first reacting

castor oil with diisocyanate to form a prepolymer then polymerizing with

methacrylate, acrylamide, and cardanyl acrylate, respectively, using ethylene glycol


dimethacrylate as cross-linker and benzoyl peroxide as initiator, and studied their

high-temperature degradation mechanism and mechanical properties. The thermo-

gravimetric analysis was followed by a computer analysis method for assisting the

kinetic mechanism and a new mechanism of degradation was suggested based on

these kinetic parameters.

A special case of IPN is the SIN (88). The existence of SINs provides a novel

way to control the phase states and mechanical behavior of two-phase materials. As

a result of the multiple chemical compositions and synthetic routes involved in the

formation of SINs, polymers can be made with very different mechanical behavior.

Among the features that control the behavior of the resulting blends, microphase

structures and molecular interactions are of greatest importance for the determina-

tion of mechanical properties of the two coexisting phases. There are usually two

ways of forming a SIN. One involves the simultaneous polymerization of two poly-

mers, whereas the second involves the mixing of two kinds of monomers together,

which are polymerized sequentially (88). The two techniques give different pro-

ducts with different morphologies and different mechanical behaviors. Various

studies have been done on the properties and structures of the resulting SIN.

Devia-Manjarres et al. (88) and Devia et al. (89) studied the morphology and glass

transition behavior of SIN based on elastomeric polymers derived from castor oil

and cross-linked polystyrene by using electron microscopy and dynamic mechan-

ical spectroscopy techniques, respectively. A two-phase morphology was revealed

by electron microscopy. Depending on the synthetic conditions, either phase can be

continuous. Morphological details, however, can be determined by compatibility of

the polymer networks, speed of stirring, and reaction rates of network formation

(80). Dynamic mechanical spectroscopy results showed two glass transition tem-

peratures around the homopolymer glass transition temperatures but shifted inward.

These materials proved to be tougher than their corresponding homopolymer

networks. The toughness of these SINs increased with a decreasing domain size

of the dispersed phase. The use of castor oil-based elastomers in the brittle polymer-

polystyrene produces toughened plastic with an enhanced tensile strength and

impact properties (89).

Suthar and coworkers (83, 90, 91) investigated the SIN prepared from radical

copolymerization of liquid polyester based on castor oil and dibasic acid with poly-

styrene initiated by benzoyl peroxide in the presence of the cross-linker 1,4-divinyl-

benzene. This group also reported the preparation and morphology of sequential

IPN composed of castor oil polyurethane and various polyacrylates using ethylene

glycol dimethacrylate as a cross-linker and benzoyl peroxide as initiator. These

materials were characterized in terms of resistance to chemical reagents, the static

mechanical properties (tensile strength, Young’s modulus, and percent elongation),

thermal properties, and morphology (scanning electron microscopy).

Xie et al. (92, 93) synthesized simultaneous IPN from castor oil polyurethane

and copolymers of vinyl monomers, including styrene, methyl methacrylate, and

acrylonitrile, without cross-linker using a redox initiator at room temperature and

both the formation kinetics of cross-linking and grafting on phase separation were

examined. It was demonstrated that the resulting materials were mainly grafted IPN

USE OF NATURALLY FUNCTIONALIZED TRIACYLGLYCEROL OILS 301

with vinyl or acrylic polymer grafted on the double bonds of castor oil. These IPN

exhibited good properties, including high strength, good resilience, solvent resis-

tance, and high abrasion resistance.

4.2. Use of Polyethylene Terephthalate and Castor or Other NaturallyFunctionalized Triglyceride Oils for Making Semi-InterpenetratingPolymer Networks

Polyethylene terephthalate (PET) is a semicrystalline thermoplastic (79). Semicrys-

talline PET is of particular importance because of its properties, which are suitable

for the production of engineered plastics. It is a widely used polymer because of its

high strength, low price, and good solvent resistance. It is a primary material for the

production of bottles, textile industry components and auxiliaries, recording tapes,

and packaging films. However, it cannot be used in injection molding as it has a

slow crystallization rate. As a result of its slow crystallization rate, the parts molded

with PET have poor dimensional stability. PET, in combination with castor or other

naturally functionalized triglyceride oils, may be used to improve characteristics

such as toughness and faster crystallization rate (32).

As PET is a semicrystalline thermoplastic, the process of synthesizing semi-

IPNs based on PET is different from the above-mentioned method. It is known

that PET is a condensation product of terephthalic acid and ethylene glycol. Castor

oil would polymerize with terephthalic acid in competition with ethylene glycol if

SIN formation method were used. On the other hand, PET is aromatic, whereas cas-

tor oil is aliphatic in nature; they are, therefore, immiscible, which makes sequential

IPN formation impossible. In order to obtain a PET and castor oil network, the two

components must be either miscible or well mixed. It was observed that a miscible

mixture of PET and castor oil could be obtained by continuously heating the blend

together. A bond exchange reaction between ester groups of PET and ester and

hydroxyl groups of castor oil occurs during heating. As a result of this interchange,

a miscible copolymer mixture is formed and a hybrid semi-IPN structure is

obtained (79, 94). The castor oil was shown to improve the crystallization rate of

poly (ethylene terephthalate), and after the polymerization of castor oil, it offered a

mechanism for toughening the materials.

In addition, PET can be used to form semi-IPNs with other naturally functiona-

lized triglyceride oils, such as vernonia oil (31). The procedures for PET/vernonia

semi-IPNs are essentially the same as those of PET/castor ones, but with important

differences. For PET/castor mixtures, the diisocyanate cross-linker was added at

240�C and the mixture was poured into the molds rapidly before the castor gel point

had been reached. In this case, PET/castor polyurethane semi-IPNs were formed, in

which crystallization and gelation occurred simultaneously resulting in a single,

broad glass transition temperature. For PET/vernonia, the sebacic acid was added

at 280�C, which reduced the temperature to about 250�C, where the mixture was

held for another 5 min, then poured into a preheated mold and allowed to cool, dur-

ing which time the PET crystallizes. In this case, PET/vernonia polyester network

was formed, and the PET crystallized prior to network formation because the latter


one took place more slowly. This network displayed two glass transition tempera-

tures. In another case, rather than allowing the mixture to cool, it was kept at 250�C,

which is above the crystallization temperature of PET. Under this condition, the

network is formed prior to crystallization of PET, therefore, the material was

much more rubbery and tough, and it was amorphous. In these semicrystalline

semi-IPNs, network formation before or after crystallization or phase separation

are factors that affect the crystalline and phase morphology considerably. These

factors, in turn, are reflected in the physical properties of the resulting materials.

The amounts of bond interchange, phase separation, crystallization of PET, and net-

work formation of cross-linking are factors that control the morphology and proper-

ties of materials in this and similar polymer systems.

5. CONCLUSIONS

As the world arrives closer to the global realization of our dwindling fossil fuel

resources, concern is increasing about continuity of our way of life, as so much

of the materials and energy we depend on are sourced from petroleum. As scientists

and innovators begin to search in earnest for alternative sources of some of the more

ubiquitous materials in our environment, such as plastics, other important factors,

such as degradability and environmental sustainability, are being considered. Vege-

table oils and other lipids form an important renewable source of such materials,

and based on the work reported here by a growing number of researchers, natural

and modified triacylglycerol oils can be used to produce polymers with important

functional properties. This is an important and growing area of research, and by the

time this chapter has been printed, it will almost certainly be dated, given the rate at

which research is being performed in this area. However, the material presented

here does present a snapshot of the various areas of endeavor to convert TAG

oils into polymers.

Acknowledgments

The help of Asma Saeed and Elizabeth Verghis in preparation of this manuscript is

gratefully acknowledged, as is the financial assistance of the Alberta Crop Industry

Development Fund, AVAC Ltd., the Alberta Agricultural Research Institute,

NSERC, and the Alberta Canola Producers Commission.

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6-8 Oil in Polymers