Prog. Polym. Sci. 31 (2006) 633–670 Polymers from triglyceride oils F. Seniha Gu¨ner a , Yusuf Yag˘cı b, , A. Tuncer Erciyes a a Chemical Engineering Department, Istanbul Technical University, Maslak 34469 Istanbul, Turkey b Department of Chemistry, Istanbul Technical University, Maslak 34469 Istanbul, Turkey Received 8 December 2005; received in revised form 7 July 2006; accepted 17 July 2006 Abstract Recently, the use of renewable sources in the preparation of various industrial materials has been revitalized because of the environmental concerns. Natural oils are considered to be the most important class of renewable sources. They can be obtained from naturally occurring plants, such as sunflower, cotton, linseed. They consist predominantly of triglycerides. This review covers the structure, property and modification of triglyceride oils and synthesis of polymers there from. Polymers from triglyceride oils are prepared via conceptually different strategies. Various polymerization methods, including condensation, radical, cationic and methathesis procedures have been applied. The scope, limitations, and possibility of utilizing such methods for various applications have been highlighted. r 2006 Elsevier Ltd. All rights reserved. Keywords: Renewable sources; Triglyceride oils; Oxypolymerized oils; Polymers; Composites; Inorganic–organic hybrid materials Contents 1. Introduction ..................................................................... 634 2. Structure of triglyceride oils .......................................................... 634 3. Oil-based polymers ................................................................ 637 3.1. Oxypolymerized oils ........................................................... 637 3.2. Polyesters ................................................................... 638 3.2.1. Alkyd resins ............................................................ 638 3.2.2. Liquid crystalline alkyd resins ............................................... 640 3.2.3. High-solid content alkyd resin ............................................... 640 3.2.4. Water-soluble alkyd resins .................................................. 642 3.2.5. Polyhydroxyalkanoates .................................................... 642 3.3. Polyurethanes ................................................................ 642 3.3.1. Organic solvent-soluble polyurethanes ......................................... 642 3.3.2. Water-soluble polyurethanes ................................................ 644 3.3.3. Interpenetrating polymer networks ............................................ 644 3.3.4. Urethane alkyds ......................................................... 645 ARTICLE IN PRESS www.elsevier.com/locate/ppolysci 0079-6700/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.progpolymsci.2006.07.001 Corresponding author. Tel.: +90 212 285 3241; fax: +90 212 285 6389. E-mail address: [email protected] (Y. Yag˘cı).
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ARTICLE IN PRESS
0079-6700/$ - se
doi:10.1016/j.pr
�CorrespondE-mail addr
Prog. Polym. Sci. 31 (2006) 633–670
www.elsevier.com/locate/ppolysci
Polymers from triglyceride oils
F. Seniha Gunera, Yusuf Yagcıb,�, A. Tuncer Erciyesa
aChemical Engineering Department, Istanbul Technical University, Maslak 34469 Istanbul, TurkeybDepartment of Chemistry, Istanbul Technical University, Maslak 34469 Istanbul, Turkey
Received 8 December 2005; received in revised form 7 July 2006; accepted 17 July 2006
Abstract
Recently, the use of renewable sources in the preparation of various industrial materials has been revitalized because of
the environmental concerns. Natural oils are considered to be the most important class of renewable sources. They can be
obtained from naturally occurring plants, such as sunflower, cotton, linseed. They consist predominantly of
triglycerides.
This review covers the structure, property and modification of triglyceride oils and synthesis of polymers there from.
Polymers from triglyceride oils are prepared via conceptually different strategies. Various polymerization methods,
including condensation, radical, cationic and methathesis procedures have been applied. The scope, limitations, and
possibility of utilizing such methods for various applications have been highlighted.
Fig. 1. Life cycle of polymers based on triglyceride oils.
1. Introduction
Polymers are widely used for technical purposes.Depending in their usage area, it should be expectedthat they exhibit some specific properties such asthermal stability, flexibility, resistance to chemicals,biocompatibility, biodegradability, adhesion to me-tallic substances, gas permeability, electrical con-ductivity and non-flammability. The structure ofmonomer used in polymer preparation is directlyeffective on these properties. Aromatic polymers,for example, should be resistant to high tempera-tures, polymers having high halogen content areinherently nonflammable, and fluorine-containingpolymers resist both water and solvents. In manycases the properties are significant in specialtyproducts. Degradable polyesters, for example, arealready used as disappearing surgical sutures.
For the coating purposes, triglyceride oils aresubjected to heat treatment or air blowing to yieldbodied and blown oils, respectively. While in thebodied oils, triglyceride molecules combined witheach other through the Diels–Alder reaction, thecorresponding linkages are achieved by the couplingof the free radicals, formed from the decompositionof hydroperoxides. These hyrdoperoxides are intro-duced during the air-blowing process.
In order to improve end-product properties,triglyceride oils have been used in the preparationof polymers. Although they have been used since 19thcentury in the paint formulation, in the last decadeinvestigation on oil-based polymers have beenfocused for different purposes. Particularly, after thepetroleum shortage, preparation of polymers fromrenewable sources has become more important.
Nowadays, there is a growing interest to producebiopolymers. Triglyceride oils are one of the most
important sources for biopolymers. Oil-based bio-polymers have many advantages compared withpolymers prepared from petroleum-based mono-mers. They are biodegradable and, in many cases,cheaper than petroleum polymers. The life cycle ofpolymers based on triglyceride oils is given in Fig. 1.
2. Structure of triglyceride oils
The word ‘‘oil’’ is used for triglycerides that areliquid at ordinary temperatures. They are water-insoluble products of plants. A triglyceride is anester product obtained from one molecule of glyceroland three molecules of fatty acids (Scheme 1). Theycan also be artificially produced from the reaction ofglycerol and fatty acids (Scheme 2).
The fatty acids contribute from 94–96% of thetotal weight of one molecule triglyceride oil. Themost common fatty acids in natural oil composi-tions are given in Table 1. As shown, some fattyacids are saturated (Scheme 3a) and some of themare unsaturated (Scheme 3b). Saturated fatty acidshave no double bonds. On the other hand,unsaturated fatty acids have one or more than onedouble bond. If the double bonds in the carbon
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chain are separated by at least 2 carbon atoms,double bonds are called isolated (Scheme 3c). Ifsingle and double bonds alternate between certaincarbon atoms, double bonds are called conjugated(Scheme 3d). Additionally, some natural fatty acidshave different structures, with acid chains havinghydroxyl, epoxy or oxo groups, or triple bonds.Because of their structural differences, each fattyacid has various physical properties (Table 2).
Among the triglyceride oils, linseed, sunflower,castor, soybean, oiticica, palm, tall and rapseed oilsare commonly used for synthesis of oil-modifiedpolymers. Although fatty acid pattern varies be-tween crops, growth conditions, seasons, and
CH2 O
CH
CH2 O CO R
O CO R
CO RCH2 OH
CH
CH2 OH
OH + 3RCOOH
Scheme 2. Synthesis of triglyceride.
CH2 O
CH
CH2 O CO R3
O CO R2
CO R1
R1, R2, R3: fatty acid chain
Scheme 1. A triglyceride molecule.
Table 1
Some fatty acids in natural oils
Name Formula St
Myristic acid C14H28O2 CH
Palmitic acid C16H32O2 CH
Palmitoleic acid C16H30O2 CH
Stearic acid C18H36O2 CH
Oleic acid C18H34O2 CH
Linoleic acid C18H32O2 CH
Linolenic acid C18H30O2 CH
a-Eleostearic acid C18H30O2 CH
Ricinoleic acid C18H33O3
Vernolic acid C18H32O3 CH
Licanic acid C18H28O3 CH
purification methods, each of triglyceride oils hasspecial fatty acid distribution. Linseed oil, forexample, consists of largely linoleic and linolenicacids. In castor oil, the greater part of fatty acids isricinoleic acid (12-hydroxy-9-octadecenoic acid).Fatty acid compositions of these oils are shown inTable 3 [1,2]. Depending on the fatty acid distribu-tion, each type of oil has specific physical andchemical properties (Table 4).
One of the most dominant parameter affecting offatty acid and oil properties is the degree ofunsaturation. The average degree of unsaturationis measured by iodine value. It is calculated from theamount of iodine (mg) reacted with double bondsfor 100 g sample under specified conditions. Trigly-ceride oils are divided into three groups dependingon their iodine values; drying, semi-drying and non-drying oils. The iodine value of a drying oil is higherthan 130. This value is between 90 and 130 for semi-drying oils. If the iodine value is smaller than 90, oilis called non-drying oil. Iodine values of somecommon fatty acids and their triglycerides are givenin Table 5 [3].
ructure
3(CH2)12COOH
3(CH2)14COOH
3(CH2)5CH ¼ CH(CH2)7COOH
3(CH2)16COOH
3(CH2)7CH ¼ CH(CH2)7COOH
3(CH2)4CH ¼ CH-CH2-CH ¼ CH(CH2)7COOH
3-CH2-CH ¼ CH-CH2-CH ¼ CH-CH2-CH ¼ CH(CH2)7COOH
3-(CH2)3-CH ¼ CH-CH ¼ CH-CH ¼ CH(CH2)7COOH
CH3(CH2)4CH-CH-CH2-CH=CH(CH2)7COOH
OH
3(CH2)4CH-CH-CH2-CH=CH(CH2)7COOH
O
3(CH2)3CH=CH-CH=CH-CH=CH(CH2)4C-(CH2)2COOH
O
–CH2–CH2–CH2–CH2–
–CH2–CH=CH–CH2–
–CH2–CH=CH–CH2–CH=CH–CH2–
–CH2–CH=CH–CH=CH–CH2–
(a)
(b)
(c)
(d)
Scheme 3. Type of fatty acid chain; saturated (a), unsaturated
(b), isolated (c) and conjugated (d).
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Table 4
Some physical properties of triglyceride oils
Name Viscosity (cSt at 37.8 1C) Specific gravity (201/4 1C) Refractive index (nD20) Melting point ( 1C)
Castor oil 293.4 0.951–0.966 1.473–1.480 �20 to �10
Linseed oil 29.6 0.925–0.932 1.480–1.483 �20
Palm oil 30.92 0.890–0.893 1.453–1.456 33–40
Soybean oil 28.49 0.917–0.924 1.473–1.477 �23 to �20
Sunflower oil 33.31 0.916–0.923 1.473–1.477 �18 to �16
Table 5
Iodine values of unsaturated fatty acids and their triglycerides
Fatty acid Number of carbon atoms Number of double bonds Iodine value of acid Iodine value of
triglyceride
Palmitoleic acid 16 1 99.8 95.0
Oleic acid 18 1 89.9 86.0
Linoleic acid 18 2 181.0 173.2
Linolenic acid and
a-Eleostearic acid
18 3 273.5 261.6
Ricinoleic acid 18 1 85.1 81.6
Licanic acid 18 3 261.0 258.6
Table 2
Some physical properties of fatty acids
Name Viscosity (cP, 110 1C) Density (g/cm3, 80 1C) Melting point (1C) Refractive index (nD70)
Myristic acid 2.78 0.8439 54.4 1.4273
Palmitic acid 3.47 0.8414 62.9 1.4209
Stearic acid 4.24 0.8390 69.6 1.4337
Oleic acid 3.41 0.850 16.3 1.4449a
aValue at 60 1C.
Table 3
Fatty acid composition of various oils
Fatty acid Castor oil
(%)
Linseed oil
(%)
Oiticica oil
(%)
Palm oil (%) Rapeseed oil
(%)
Refined tall
oil (%)
Soybean oil
(%)
Sunflower oil
(%)
Palmitic acid 1.5 5 6 39 4 4 12 6
Stearic acid 0.5 4 4 5 2 3 4 4
Oleic acid 5 22 8 45 56 46 24 42
Linoleic acid 4 17 8 9 26 35 53 47
Linolenic
acid
0.5 52 — — 10 12 7 1
Ricinoleic
acid
87.5 — — — — — — —
Licanic acid — — 74 — — — — —
Other — — — 2 2 — — —
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670636
Since triglyceride oils vary widely in their phy-sical properties depending on fatty acids in theirstructure, the choice of triglyceride oil plays
an important role on polymer properties. Linseedoil, for example, is commonly used for the pre-paration of paint binder, because it consists of
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Table 7
Some representative 1H chemical shift values for fatty acids
1H chemical shift (ppm) Protons
0.88 (CH3–(CH2)n–CH ¼ CH–where n 4 3)
0.97 (CH3–CH2–CH ¼ CH–)
1.2–1.3 –CH2–
1.6 – CH2–C ¼ O
2.0 – CH2–CH2–CH ¼ CH–
2.3 –CH2–C ¼ O
2.8 – CH2–CH ¼ CH–
4.1–4.3 Protons of the glyceride moiety
5.3 –CH ¼ CH–
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 637
reactive unsaturated fatty acids curing with atmo-spheric oxidation. Castor oil is an importantreactant for interpenetrating polymer networks(IPNs) because it contains hydroxyl groupscapable of reacting with isocyanate and carboxylgroups. It is possible to select fatty acid distributionfunction of oils via computer simulation and themolecular connectivity in order to produce linear,branched, or cross-linked polymers [4]. Materialsprepared by this way can be used to producepressure-sensitive adhesives, elastomers, rubbersand composites.
The most widely used method to characterizematerial is infrared spectroscopy, particularly Four-ier transform infrared (FTIR) spectroscopy. It canalso be used for the structural analysis of oils [5]. InTable 6, the absorption bands and the correspond-ing function/groups are assigned.
Nuclear magnetic resonance (NMR) spectro-scopy is another important technique for thedescriptions of the chemical microstructure of anorganic material. The assignment of the relevantpeaks for the protons present in triglyceride oils isreported in Table 7. It is possible to calculatethe fatty acid content of triglyceride oil fromNMR data. The calculation of the surfaces of thepeaks corresponding to the methylene groups, forexample, gave an assessment of the linoleic acidcontent [5]. Gas chromatography is also widely usedfor the determination of fatty acid composition ofthe oils.
Table 6
Some representative IR absorpsion band values for fatty acids
Absorpsion
bands (cm�1)
Functionality
3500 –OH functions corresponding to free glycerol
and/or residual moisture
2930–2850 –CH2– groups (with an additional weak
shoulder around 2960 cm�1 reflecting the
presence of terminal methyl groups)
1745 –COOH groups
1160 C–O–C functions of the ester group
720 –(CH2)n– sequences of the aliphatic chains of
the fatty acids
1650, 3010 Non-conjugated unsaturation of linoleic acid
chain for linseed oil
990 Conjugated unsaturation of eleostearic acid
chain for tung oil
970 Trans configuration of eleostearic acid chain
for tung oil
3. Oil-based polymers
Although the biggest usage area is in the coatingindustry, in the last decade triglyceride oil-basedpolymers have been used for many differentapplications. Some type of polymers prepared fromtriglyceride oils are listed below.
In the following sections preparation methods,properties and uses of oil-based polymers arediscussed in more detail.
3.1. Oxypolymerized oils
Oxypolymerization is one of the common meth-ods used for the modification of triglyceride oils.When the oils having double bonds are oxidized,they undergo polymerization. During the reaction,the double bonds were consumed (Scheme 4). Someinvestigators have focused on oxypolymerizationmechanism of drying oils [6–8]. New methods forthe analysis of oxidized samples have also receivedinterest [9,10].
Oxidized oils are widely used in the manufactur-ing of oil-based binders because they give the finalproducts having high viscosity and good filmproperties [3,11].
From the point of design and process control,knowledge of some physical properties such asviscosity and density is essential. How these properties
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change during reaction should be monitored. At thatpoint, in literature, changes in some properties ofoxidized oils such as viscosity, density, refractiveindex, iodine and peroxide values were determinedduring the reaction and some empirical equationswere obtained [12]. Additionally, a kinetic investiga-tion was carried out and, the reaction order and therate constant were determined. Change in the reactionorder with the temperature could be explained withdifferent reaction mechanism for each temperature.Rheological behavior of the final product wasinvestigated using Bingham, Power-law and Casson
(a)
(b)
(c)
Scheme 5. Poyester synthesis; polycondensation of hydroxyl acid
polymerization of lactones (c).
Scheme 4. Oxypolymerization reaction.
equations. It was found that the sample behaved asnon-Newtonian fluid at high temperature.
It was reported that oxidized soybean oil wasprepared via permanganate oxidation with sub/supercritical CO2 [13]. By this way, a semi-drying oilcan be oxidized without using a drying agent asactivator.
3.2. Polyesters
Polyesters can be synthesized via several routes:polycondensation of hydroxyl acids or a diacid anda diol or by ring-opening polymerization of lactones(Scheme 5). In the last decade, synthesis and usageof biodegradable polymers have been very popular.Especially, biodegradable polyesters are usefulmaterials for medical purposes. In this respect,ricinoleic acid-based copolymers were successfullyprepared and characterized [14].
3.2.1. Alkyd resins
One of the oldest polymers prepared fromtriglyceride oils is alkyd resin produced by theesterification of polyhdroxy alcohols with polybasicacids and fatty acids (Fig. 2). Actually, thepreparation of polyester resin from tartaric acidand glycerin was reported by Berzelius dates back asearly as 1847. However, the resulting polymer wasbrittle. In 1901 Watson and Smith used phthalicacid instead of tartaric acid. The resin was also notflexible. In 1914 Kienle used fatty acids in thepreparation of polyester resin. The resulting alkydresin exhibited good film properties. Obviously,chemistry and applications alkyd resins haveattracted the interests of many chemists from bothacademia and industry as can be seen from the hugenumber of papers and patents covering this field.This article aims by no means at reviewing allpublished work but rather intends to illustrate someprominent examples. In this connection the reader’sattention is also directed to the book solely devotedto this field [2].
(a), polycondensation of diacid and diol (b), ring-opening
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 639
Alkyd resins have acquired a good reputationbecause of their economy and ease of application.Additionally, they are to a greater extent biologi-cally degradable polymers because of the oil andglycerol parts.
In general, monoglyceride and fatty acid methodsare used to prepare alkyd resin [2]. In the formercase, the first stage is alcoholysis of the oil by a partof the polyol. Then, the free hydroxyls of the
alcoholysis product are esterified by a polyacid. Therelated reactions are schematically represented inScheme 6 when glycerol and phthalic anhydride(PA) are used as polyol and polyacid components,respectively.
The later method is more often used than theformer because it requires no intermediate step.Polyacid, polyalcohol and fatty acid are added fromthe start and heated. Alkyd resins obtained by this
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Table 8
The chemical structures, molecular weights and acid values of
anhydrides
Anhydride Code Acid Value
(mg KOH/g)
Formula
Glutaric
anhydride
GA 983.4
Maleic
anhydride
MA 1144.2
Phthalic
anhydride
PA 757.5
Succinic
anhydride
SA 1121.1
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670640
way have high viscosity, good drying and hardnessproperties.
Alkyd resins are classified according to their oillength. Oil length refers to the oil percentage of analkyd. A short oil alkyd contains below 40% of oil.When oil amounts increase between 60% and 40%,it is called medium oil length. Above 60%, the resinis a long alkyd. Oil length is the important factor,which affects the properties of the final product [3].Short oil alkyds are most used for baked finishes onautomobiles, refrigerators, stoves, washing ma-chines, etc. Long oil alkyds are used in brushingenamels.
Generally, a few drying and semi-drying oils, suchas sunflower, soybean and linseed oils are used inthe preparation of oil-modified polyesters. Addi-tionally, new vegetable oils, such as rubber seed,karinatta, orange seed and melon seed oils wereused for polyester resin synthesis [15–17].
Alkyd resins modified by triglyceride oils are alsovery common components for offset printing inks[5]. The most commonly used alkyd resins in theprinting industry are linseed and soybean oils-basedresins. For economical reasons, sunflower andrapeseed oils were utilized as oil components forprinting ink formulations [18,19].
The viscosity and film properties of alkyd resinsdepend on the type and amount of raw materialsused for the synthesis. In the literature, four types ofanhydride, namely glutaric anhydride (GA), maleicanhydride (MA), PA and succinic anhydride (SA),were used in alkyd resin formulation, and the flowand film properties were determined [20]. Thechemical structures of anhydrides are presented inTable 8. One of the most important film propertiesof a coating material is drying time that is the filmformation time. Comparing the drying times of thepolymers prepared from different type and amountof anhydride (Fig. 3), for the same anhydride-basedsamples while anhydride amount increases, dryingtime decreases. For the same amount of anhydride-based samples, resin prepared from MA has theshortest drying time.
3.2.2. Liquid crystalline alkyd resins
Liquid crystalline (LC) polymers are widely usedin plastic and fiber industry. LC alkyd resins havebeen studied for reducing volatile organic com-pound and improving properties of alkyd-typecoatings [21,22]. LC phases were formed by graft-ing: (a) p-hydroxybenzoic acid (PHBA) to hydroxy-terminated alkyd resin (Scheme 7a), (b) PHBA to
carboxy-terminated alkyd resin (Scheme 7b), (c)PHBA to an excess SA-modified alkyd resin(Scheme 7c). Reaction was carried out at roomtemperature in the presence of p-toluene sulfonicacid (p-TSA) as catalyst. Formed water wasremoved from the reaction medium by usingdicyclohexylcarbodiimide (DCC) for promotingesterification of PHBA with alkyd. Such preparedLC alkyd resin had low viscosity and good filmproperties.
3.2.3. High-solid content alkyd resin
Production of high-quality organic coatings withlow solvent amount is important target in coatingindustry. Decreasing the viscosity of the polymerreduces the amount of organic solvent. Preparationof a low viscosity coating requires the use ofpolymers having either a low molecular weight ora narrowed molecular weight distribution. For thispurpose, many investigators suggested new methodsfor preparation of low viscosity resins [22–24]. Oneof the methods involves reaction of carboxylicacids/anhydrides and alcohols with DCC in thepresence of pyridine at room temperature. Alkydresins prepared by this way, have lower Mn andMw/Mn, and consequently lower viscosity, thanthose of the corresponding resins obtained by theconventional method.
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(a)
(b)
(c)
Scheme 7. Preparation of liquid crystalline alkyd resin by three methods.
0
50
100
150
200
250
300
350
Dry
ing
Tim
e (m
in)
MA based-resinPA based-resinSA based-resinGA based-resinConventional resin
6.24x10-4 8.91x10-4 11.6x10-4 14.3x10-4
Anhydride Amount (mol) for 1 g Oil Part
Fig. 3. Drying times of the resins.
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 641
Reducing organic solvent amount can also beachieved by synthesizing resins having a highlybranched structure [25]. For this purpose, star
and hyperbranched structure resins were preparedand tested in the form of varnishes and whiteenamels. For synthesizing alkyd resins having a
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hyperbranched structure, trimethylpropane anddimethylolpropionic acid were used. In the firststep, saturated polyester with hydroxyl end groupswas obtained. Then, alkyd resin was obtained byesterification of polyester with unsaturated fattyacids. On the other hand, star-like-resins with threeor four arms formed by esterification of dipenthaer-ythritol with fatty acids.
3.2.4. Water-soluble alkyd resins
Water-based organic coatings are ecologicallyfriendly materials and more economic than sol-vent-based coatings. For water-soluble applications,mostly alkyd resins with high acid numbers areprepared and neutralized with amines [26–28].Aigbodion et al. [29] used rubber seed oil in theproduction of alkyd emulsion. Oil was initiallytreated with different amounts of 2–20% of MA.Then maleinized rubber seed oils were used toprepare water-soluble alkyd samples.
Nakayama [30] described several specific exam-ples of the oil-based resin blend for water-bornepaints. Scheme 8 shows the structure of some water-soluble resins used for the preparation of polymerblends. The first resin (Scheme 8a) was syn-thesized by the copolymerization of acrylic acid,glycidyl methacrylate esterified with unsaturatedfatty acid, styrene and methyl methacrylate. Forobtaining the second resin (Scheme 8b), first,styrene-allylalcohol copolymer was esterifiedwith linseed oil fatty acids and then additionreaction of MA was achieved.
(a)
(b)
Scheme 8. Structure of water-soluble resins.
3.2.5. Polyhydroxyalkanoates
To alleviate problems associated with degreasingorganic solvent amount in paint formulation,polyhydroxyalkanoates (PHAs) are alternativepolyesters [31–35]. They are optically active, biode-gradable, water-insoluble polyesters of carbon,oxygen and hydrogen. The majority of PHAs arealiphatic polyesters. Their general formula is shownin Scheme 9.
PHAs are naturally synthesized by a large varietyof bacteria. The first PHA prepared in plants wasthe homopolymer, polyhydroxybutyrate. But it wastoo stiff and brittle. Oils have been studied assubstrates for PHA preparation. Incorporation of alow amount of longer chain monomers into thepolymer increases toughness and flexibility, sincethe crystallinity of the polymer decreases. For thispurpose, olive [36], castor [37], tallow [32,38],soybean, sunflower (high oleic) and coconut oils[39] and, soybean [40], linseed, tall oil fatty acids[34,41] and other fatty acids obtained from regionaloils [42] were used.
3.3. Polyurethanes
Polyurethanes are the reaction products ofdiisocyanates with hydroxyl-containing materialsas shown in Scheme 10. Aromatic and aliphaticdiisocyanates are used in the polyurethane formula-tion. Monomers used are directly affective on thepolymer properties. The most widely used diisocya-nate components are listed in Table 9.
3.3.1. Organic solvent-soluble polyurethanes
To obtain oil-modified organic solvent-solublepolyurethanes (urethane oils), diisocyanates werereacted with hydroxyl-containing oils, such ascastor oil, or with partial glycerides prepared fromoil and glycerol. The overall reaction for thepreparation of oil-modified polyurethanes frompartial glycerides using hexamethylenediisocyanate(HMDI) may be generalized in Scheme 11.
Scheme 9. General formula of PHAs.
Scheme 10. Preparation of polyurethane.
ARTICLE IN PRESS
Table 9
Diisocyanate components
Component Code Structure
Toluenediisocyanate TDI CH3
NCO
NCOMethylene-4, 40-diphenyldiisocyanate MDI
Nafhthalene-1, 5-diisocyanate NDI NCO
NCOIsophoronediisocyanate IPDI
Hexamethylenediisocyanate HMDI OCN-(CH2)6-NCO)
6n
Partial glyceride
O CH2 CH CH2 O C
O
NH CH2 NH C
O
O
C O
R
6OCN CH2 NCO
Triglyceride oil + Glycerol
Scheme 11. Preparation of partial glycerides and oil-based
polyurethane.
CH3
OCN
NH-C-O-((CH2))4O)n-C-NH
O
NCO
CH3
O
Scheme 12. Formula of PBTDI.
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 643
When the polymers are prepared from drying andsemi-drying oils, such as sunflower and linseed oils,they can be used in the paint formulation because oftheir good film properties. In a study, polymers wereprepared from three kinds of diisocyanates, toluene2,4-diisocyanate (TDI), HMDI and poly(1,4-butan-diol) TDI (PBTDI) [43]. Sunflower oil partialglycerides were used as polyol component. In thisstudy, the effects of amount and type of diisocya-nate component on the film properties of polymerwere investigated. Depending on the monomerstructure used, polymers showed various filmproperties. Polymers based on aromatic diisocya-nates (TDI and PBTDI), for example, had goodwater resistance. Additionally, with greater amountsof diisocyanate components in the polyurethaneformulation, the shorter drying time was achieved.
The monomer structure is also effective on theflow properties. For investigating the effects of
monomer ratio and type on the flow properties,polymers were prepared from two different diiso-cyanates at three different monomer concentrations[44]. TDI and PBTDI were used as diisocyanatecomponents, and sunflower oil partial glycerideswere used as polyol component. In the polymerpreparation, the lowest diisocyanate concentrationwas 6.38� 10�4mol/g polyol, and the highestdiisocyanate concentration was 12.61� 10�4mol/gpolyol. Although both diisocyanates have aromaticstructure, for the same monomer concentrationPBTDI-based samples have higher viscosity thanTDI-based samples. Because of the existence oftwo aromatic rings per a molecule in PBTDI(Scheme 12), the chain of polymer was not flexible.Apparently, this causes an increase of viscosity.
Some various seed oils, Ecballium elaterium andP. mahaleb, were used as the oil component for thepreparation of oil-modified polyurethanes [45].Since these oils contain conjugated trienoic acids,polymers prepared from them have good filmproperties such as short drying time, good water,alkali and acid resistances.
Oil-modified polyurethane films were preparedfrom HMDI and/or MDI for wound-dressingapplications [46]. It was found that the amountand type of diisocyanates affected the film and
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+CH2-OHCH -OHCH2-OH
O CCH3
CH2-CH3
+ H2OO
O
CH2-OH
CH2 -CH3
CH3
CH2 -CH3
CH3
CH2-O-CO-O
O
O
O
O
CH2-COOHCH -COOH
O
O
CH2-O-CO-
CH2 -CH3
CH3
O
O
O
CH2-O-COCH -OHCH2-OH
H2O
Fatty acid
Scheme 14. Maleinization of triglyceride oil.
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670644
mechanical properties, and gas permeabilities ofpolymeric membranes. Notably, films were flexibleand permitted to flow oxygen and carbon dioxide.
For the preparation of millable polyurethaneelastomers, difunctional castor oil or its blends withpoly(propylene glycol) with two different ratios of1,4-butane diol as chain extender and TDI wereused as reactants [47]. Investigation of physical,mechanical and thermal properties showed that theelastomers obtained could be used for industrialapplications.
3.3.2. Water-soluble polyurethanes
Water dispersion of polyurethanes is usuallyprepared by quarternizing carboxyl acid groups onthe backbone by tertiary amines. The most usedacid monomer is dimethylol propionic acid. In orderto prepare oil-based polyurethane resin, malenizedfatty acid can be used instead of dimethylolpropionic acid [48]. While malenized fatty acid partprovides water dispersion, fatty acid chain providesair drying. Malenized oil product could be preparedby two procedures; a. reaction of oil with MA andthen addition of glycerol (Scheme 13), b. reaction ofglycerol, methylethyl ketone (MEK) and fatty acid,and addition of MA (Scheme 14). After preparationof malenized oil product, diisocyanate componentwas reacted with the prepared product to give oil-based polyurethane. Polyurethanes thus obtainedexhibited good physical and mechanical properties.
3.3.3. Interpenetrating polymer networks
IPNs are combinations of two or more polymer innetwork form [49,50]. One or more polymer(s) is
O
O
OCH2-O-COCH-O-CO
CH2-O-CO+
CH2-
CH-O
CH-O
Scheme 13. Maleinization
synthesized and/or crosslinked in the presence of theother. Polyurethanes, polystyrene, poly(methylmethacrylate) and poly(ethyl acrylate) are the mostcommon polymers that can be used in the prepara-tion of IPNs.
Castor oil is widely used for the preparation ofpolyurethane for IPNs. For this purpose, castor oilis reacted with a diisocyanate to form a polyur-
CH2-O-CO
CH-O-CO
CH2-O-CO
O
O
O
O-CO
-CO
-CO
CH2-COOH
CH-CO-O-CH2
CH-OH
CH2-OH
Glycerol
of triglyceride oil.
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(a) (b)
Scheme 15. Structures of a semi-IPN (a) and an IPN (b).
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 645
ethane network, followed by swelling with vinyl oracrylic monomer using an initiator. If a crosslinkingagent is not used for the second polymerization,only a polyurethane network will result. In this case,the polymer network is called a semi-IPN. Thestructures of an IPN and a semi-IPN are shown inScheme 15 [51].
IPN was first synthesized from castor oil byYenwo et al. [52]. The same research groupprepared IPN from castor oil and TDI to formpolyurethane, followed by polymerization of styreneand divinylbenzene in the presence of benzoylperoxide at 80 1C [53]. In almost all the publishedstudies, researchers focused on physical, thermaland/or mechanical properties of IPNs. A largenumber of examples are presented in tabular formin Table 10 [54–99].
3.3.4. Urethane alkyds
Urethane alkyds (uralkyds) are one of the mostcommon oil-based polymers for coating purposes,because they have superior film properties ascompared to traditional alkyd resins. In the firststep of the synthesis, triglyceride oil was reactedwith a polyol, and then a dianhydride and adiisocyanate were added separately to the reactionmixture. Since cured uralkyds is elastomeric innature, they are used to develop IPNs (Scheme 16)[100–102].
3.4. Polyamides
The most common application of oil-modifiedpolyamides is in paint industry. For modifying paintflow some thixotropes can be prepared from dimeracids obtained from tall and soybean oils, andamines (Scheme 17) [103]. Thixotropy preventssetting and sagging, and cause easy applicationand improves film appearance.
Thixotropy is an increase of viscosity in a state ofrest and a decrease of viscosity when submitted to aconstant shear stress [104]. In other words, thixo-tropy is time-dependent fluid behavior in which theapparent viscosity decreases with the time ofshearing and in which the viscosity recovers to, orclose to, its original value when shearing ceases[105,106]. In polymer systems, weak intermolecularinteractions, such as hydrogen bonds can cause athixotropic behavior [107]. Chemical bonds can bebroken reversibly under flow achieved by mechan-ical actions. In Schemes 18 and 19, hydrogenbonding between different groups is shown.
One of the most commercially used polymer,Nylon 11, was developed from castor oil [99,108].The product had a wide range of flexibility, excellentdimensional stability and electrical properties, goodchemical resistance and low cold brittleness tem-perature.
3.5. Vinyl polymers
3.5.1. Classical methods
One of the oldest methods for the modification oftriglyceride oils is the copolymerization of dryingand semi-drying oils with vinyl monomers likestyrene, a-methylstyrene or cyclopentadiene. Sincethe products have improved film properties, theycan be used in the formulation of surface-coatingmaterials. Styrene is the most important monomerfor this purpose [3]. Styrene polymerization withoils involves free radical initiated polymerization inclassical method. Generally, free radical typeinitiator, such as benzoyl peroxide and ditertiar-ybutyl peroxide, has been used to accelerate thecopolymerization reaction. Hewitt and Armitage[109] proposed two types of reaction mechanism forconjugated and non-conjugated oils (Scheme 20).According to these authors, styrene chains arepropagated across the conjugated dienes as in thestyrene-butadiene reaction, while non-conjugatedfatty acid radicals serve to modify the growth ofstyrene chains by a chain transfer mechanism.
Styrene-oil copolymerization has been investi-gated by several other researchers [110–114]. Saxenaet al. discussed the polymerization in view ofreaction mechanisms, preparation techniques, rawmaterials and, analysis and properties of theproducts [115,116].
Linseed, tung, soybean, sunflower and oiticicaoils and dehydrated castor oil (DCO) obtained bydehydration of castor oil, are widely used in the
ARTICLE IN PRESS
Table 10
Interpenetrating polymer networks based on castor oil-polyurethanes and vinyl/acrylic components
Polyurethane component Vinyl/Acrylic
component
Aim of study Comment Reference
Polyol Isocyanate
CO TDI St Preparation of both
toughed plastic and
reinforced elastomer
compositions, and
determination of their
stress-strain and impact
loading behavior
Both the plastic and the
elastomeric IPNs proved
tougher than their
corresponding homopolymer
networks. Elongations at
break of about 8–16 percent
were found for the plastics,
while the elastomers ranged
from 55 to 125 percent.
[54]
CO TDI St Determination of
morphology and glass
transition behavior of
IPNs
A two-phase morphology and
two well-defined glass
transitions near their
respective homopolymer glass
transitions emerged.
[55]
CO TDI DVB, St Determination of
correlation of mechanical
property, crosslinked
density and
thermogravimetric
behavior of IPNs
A marginal increase in tensile
strength and crosslink density
from CO polyurethane to IPN
prepared from the ratio of
60% polyurethane:40%
polystyrene divinyl benzene.
[56]
CO MDI St Investigation of the effect
of PU/polystyrene ratio on
morphology, chemical
resistance, thermal and
mechanical properties
The incorporation of
polystyrene component into
PU improved the tensile
modulus. Thermal
decomposition of IPNs
occurred in four different
steps because of complicated
structure of IPNs. Two
distinct phases were indicated.
[57]
CO MDI St Investigation of the effect
of PU/polystyrene ratio
and amount of
crosslinking agent on
mechanical properties
Mechanical properties showed
a significant improvement
beyond a critical styrene level
(25% by weight). %
elongation at break was
determined a maximum at
40% styrene. With increasing
concentration of crosslinker
mechanical properties
improved.
[58]
CO MDI St Synthesis of IPNs and
determination of
morphogical and
mechanical properties
IPNs exhibited good
mechanical properties and
phase mixing behaviour.
[59]
CO MDI St Characterization of
physical, optical and X-ray
diffraction properties of
IPNs before and after
extraction of polystyrene
Transparency and hardness
increased because of
increasing in crystal size and
strain.
[60]
CO MDI St Generation of computer-
simulated concentration
Computer-simulated
concentration profiles of
aqueous salt solutions through
[61]
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670646
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Table 10 (continued )
Polyurethane component Vinyl/Acrylic
component
Aim of study Comment Reference
Polyol Isocyanate
profiles in IPNs
membranes
IPN membranes were
generated with Fick’ s second-
order differential equation,
and the results were examined
in terms of diffusion
anomalies.
CO IPDI St Investigation of the
mechanical, thermal and
dielectric relaxation
properties, and
morphology of IPNs
Tough and transparent film
wer obtained by the transfer
moulding technique.
[62]
CO TDI St Determination
morphology and
mechanical properties of
IPNs
The tougness of IPNs
increased with degreasing
domain size of the polystyrene
dispersed phase.
[63]
CO TDI BMA, MMA, St Preparation of novel
dielectrics from IPNs, and
determination of the
effects of monomer type,
composition on the
dielectric properties
IPNs behave like
homogeneous materials due to
topological interpenetration of
the components during IPN
formation
[64]
CO TDI MMA, St Determination of the effect
of vinyl polymer or
polyurethane amount in
IPN on morphology and
thermalproperties
The polystyrene phase size of
IPN was shown to decrease
with increased crosslinking of
the CO component and with
increased polystyrene
contents. Two distinct glass
transitions were observed for
IPNs.
[65]
CO MDI MMA Preparation of IPNs and
determination of
morphology, their
resistance to chemicals,
thermal behavior, and
mechanical and dielectric
properties
IPNs exhibited better
resistance to chemical reagents
and poor solubilities in
organic solvents. They
possessed greater thermal
stability than that of
homopolymers (PU and
PMMA).They behaved like
semiconductors. Toughness in
the elastomeric PU increased
with the increase in the
PMMA content of the IPNs.
[66]
CO HMDI MMA Investigation of the effect
of reaction conditions and
NCO/OH ratio on
morphology, chemical
resistance, thermal,
dielectric and mechanical
properties
SEM micrographs indicated
homogeneous phase domains
of PU and PMMA. IPNs were
less resistance to alkali. They
showed complete weight loss
around 550 1C. They were
ranked as insulators.
[67]
CO TDI MMA Determination of
properties and
morphology of IPNs
IPNs showed excellent
mechanical properties and
thermal stability.
[68]
CO TDI MMA [69]
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 647
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Table 10 (continued )
Polyurethane component Vinyl/Acrylic
component
Aim of study Comment Reference
Polyol Isocyanate
Preparation of BaTiO3
superfine fiber/IPNs
nanocomposites
The domains of the
simultaneous systems were on
a nanometer scale.
CO TDI MMA Synthesis of polyaniline
filled IPNs and
determination of their
physico-mechanical,
electrical, chemical,
thermal and surface
morphology
Incorporation of polyaniline
into IPNs improved tensile
strength. All the electrical
properties of polyaniline filled
IPNs were increased with
increase in polyaniline
content. Thermal
decomposition of filled IPNs
occurred in three different
stages. There were two distinct
phases due to individual
component networks. The
crystal growth was observed
above 5% polyaniline
addition to IPN.
[70]
CO IPDI AA, MAM Synthesis of IPNs and
determination of their
thermal properties
Thermogravimetric analysis of
the polymers was conducted
using a computer analysis
method for assigning the
kinetic mechanism.
[71]
CO HMDI MAM Investigation of the effect
of prepolymer (pre-PU)
content on thermal
properties, morphology
and crystallinity of IPNs
All IPNs decomposed by
about 95wt% in the
temperature range
400–500 1C. The degree of
crystallinity increased with
increase of the prepolymer
content. The heterogeneity
gradually degreased and the
morphology changed from a
discontinuous to a continuous
phase, when the prepolymer
content increased from 35 to
45%.
[72]
CO IPDI AA, MAM Synthesis of IPNs and
determining of their
chemical and thermal
properties
IPNs decomposed around
600 1C
[73]
CO MDI EMA Investigation of the effect
of NCO/OH molar ratio
on morphology, optical,
dielectric and mechanical
properties
IPNs exhibited better
resistance to chemicals and
poor solubility in organic
solvents.
[74]
CO IPDI EMA Investigation of the effect
of NCO/OH ratio on
chemical resistance,
thermal, dynamical-
mechanical properties
IPNs exhibited better
resistance to chemicals and
poor solubility in organic
solvents.
[75]
CO, PEG TDI BMA, EMA Determination of the
effects of compositional
Both BMA and EMA were
good choice for the monomer
[76]
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Table 10 (continued )
Polyurethane component Vinyl/Acrylic
component
Aim of study Comment Reference
Polyol Isocyanate
variation of IPNs on phase
transfer catalytic efficiency
and mechanical properties,
and determination of
conductivity of IPNs
in the synthesis of IPNs for
use as phase transfer catalysts
and ion conducting materials.
IPNs showed good mechanical
properties.
CO TDI, HMDI, MDI BA, BMA, EA,
EMA
Synthesis of IPNs and
determination of their
physicochemical properties
IPNs decomposed at a very
high temperature.
[77]
CO HMDI HEMA Using of HEMA in the
IPNs preparation and
determination of chemical,
mechanical and thermal
properties of IPNs
IPNs were partly soluble in
some of the solvents.
Interpenetration of PU as a
separate phase in polyviniyl
brough about the enhanced
modification in mechanical
properties. There was a rapid
weight loss from 40% to 90%
in the temperature range of
400–500 1C and almost all the
IPNs decomposed completly
around 600 1C.
[78]
CO IPID BA Investigation of the effect
of NCO/OH molar ratio
on morphology, chemical
resistance and thermal,
dielectric and mechanical
properties
IPNs were elastomers and
exhibited good mechanical
properties. They behaved like
insulators.
[79]
CO MDI AN Investigation of the effect
of PU/poylacrylonitrile
ratio on physical, chemical,
optical and mechanical
properties of IPNs
With increase in content of
AN the tensile and tear
strengths, and tensile modulus
increased. The crystal size
distribution changed
significantly with increase of
concentration of AN
monomer. Optical properties
showed improvement with
increase of AN content.
[80]
CO TDI BA Syntesis of IPNs and
determination of their
resistance to chemical
reagents, thermal stabilities
and mechanical properties
IPNs were stable in all
standart reagents but became
brittle and lose their gloss in
methyl ketone, toluene snd
CCl4. Tg’ s of all IPNs were
determined around 40 1C. All
IPNs exhibited good
mechanical properties.
[81]
CO TDI 2-Hydroxyethyl
methacrylate
Investigation of the effect
of PU content, activator,
acrylic cross-linker on the
kinetics of formation for
IPN
The rate of formation of the
IPN was found faster than
were the rates of the individual
network formation.
[82]
CO TDI, HMDI 2-Hydroxy-4-
methacryloyloxy
acetophenone
Investigation of the effect
of NCO/OH ratio on
Increasing the NCO/OH
ratios in the IPNs, the thermal
stability increased because of
[83]
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 649
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Table 10 (continued )
Polyurethane component Vinyl/Acrylic
component
Aim of study Comment Reference
Polyol Isocyanate
morphology and thermal
behavior
more crosslinking. With
increase in the monomer
content, nature of
homogeneity of the phase
increased.
CO IPDI Cardanyl
methacrylate
Synthesis of IPNs and
determination of the
kinetic parameters
involved in the thermal
degradation, by using the
computerised LOTUS
package method
IPN decomposed in three
distinct steps. The activation
energy for the second step is
higher, which suggests that the
recrosslinking occurs at a
lower rate. The activation
energy for the second step is
lower, which suggests that the
depolymerisation occurs at a
faster rate.
[84]
CO TDI Mixture of EA
and EGDMA
Determination of thermal,
mechanical,
mechanothermal,
morphological and
dielectric properties of
IPNs
IPNs are tough materials
having synergistic properties
of their corresponding
homopolymers.
[85]
CO
TDI Various
monomers
Investigation of the effect
of vinyl/acrylic monomer
type, and NCO/OH molar
ratio on mechanical and
thermal properties of IPNs
AN was the best monomer in
the formulation of one type of
IPNs. The apparent crosslink
density and tensile strength of
the IPNs increased with NCO/
OH molar ratio.
[86]
CO NCO-terminated
polyether, NCO-
terminated
polybutadiene
AN, BMA, EMA,
MMA, St
Investigation of the effect
of synthesis conditions on
mechanical properties of
IPNs
AN is a good monomer for
synthesizing (polyether-castor
oil) PU/vinyl or methacrylic
polymer, but is a poor
monomer for preparing
(polybutadiene-castor oil) PU/
vinyl or methacrylic polymer.
Both polyether-based and
polybutadiene-based behaved
as elastomers at optimum
conditions of the synthesis.
[87]
CO TDI PVP Investigation of the
structure of semi-IPNs by
associated dynamic
mechanical and dielectric
spectroscopies.
Dynamic mechanical and
dielectric spectroscopies can
be used for stuying semi-IPNs.
Each method has shed light on
different aspect of the
molecular motions.
[88]
CO Isocyanatoethyl
methacrylate
Preparation of
UV-curable IPNs
Semi- and full IPNs were
prepared with similar
composition by swelling
the base networks with the
appropriate methacrylate
monomers.
[89]
TDI MMA [90]
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670650
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 651
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C(COO
O CH2 CH CH2OCOR
O)n
OCN (CH2 )6 NCO
Uralkyd resin (UAR)
UAR + CHCH2 IPN
CO
CO
O
C(COO
OO CH2CH2 CHCH CH2CH2 O)n)mOOOCOCORR
CONH(CH2 )6CO(NH
Triglyceride oil + Glycerol Partial glycerides
Scheme 16. Synthesis of IPN based on uralkyd resin/polystyrene.
Scheme 17. Preparation of an oil-based polyamide.
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670652
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Scheme 18. Hydrogen bonding causing thixotropy.
Amide Urea Urethane
C-CN-H
OH
N-CN-H
OH
O-CN-H
O
Scheme 19. Potential hydrogen bonding structures.
Scheme 20. Styrenation of conjugated
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 653
preparation of styrenated-oil products. DCO, tungand oiticica are the ideal oils for styrenation due totheir conjugation. Other oils are used after applyingsome modifications, such as blowing, isomerization,or blending with conjugated oils, in order to gethomogeneous product.
Thermosetting oil-based polymers were alsoobtained by cationic copolymerization of regularsoybean oil, low saturation soybean oil andconjugated low saturation soybean oil with divinyl-benzene [117]. Conjugated low saturation soybeanoil-based polymers exhibited the highest moduli andthermal stabilities, because of their low unreactedfree oil content.
and non-conjugated fatty acids.
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Although vinyl modified triglyceride oils aremainly used in paint industry, in recent years therehas been increasing trend towards their use asbiopolymers [118,119]. For example, Li and Larock[120–123] reported the preparation of tung oil-styrene-divinylbenzene copolymers by thermal poly-merization. The resulting polymers were light yellowcolor, transparent, rigid, tough and thermally stablebelow 300 1C. The same research group preparedthermosetting polymers by cationic polymerizationof tung, soybean and fish oils. The polymerizationwas initiated by boron trifluoride diethyl etherate.
3.5.2. Macroinitiator/macromonomer method
An alternative method, macroinitiator method,was suggested for styrenation of oils [124]. First, alow molecular weight azo initiator incorporated tooil part into two steps, and then in the presence ofstyrene free radicals were generated by the thermaldecomposition of the azo groups and the oil-styrenecopolymers was obtained (Scheme 21). This processdoes not require an additional initiator and allowsstyrenation of drying and semidrying oils withoutany pre-treatment. Since active radical sites weredirectly generated on the oil backbone, homopolys-
Scheme 21. Styrenation of triglycerid
tyrene did not form as a by-product. By using thistechnique, coating polymers were prepared usingthermally splitted secondary esters of castor oil(Scheme 22) and interesterification product oflinseed and castor oils (Scheme 23) [125,126]. Thestyrenated products obtained by the macroinitiatormethod showed good film properties.
Another method, namely the macromonomer(macromer) technique, has been reported[127,128]. In this case, first the macromer of thefollowing structure (Scheme 24) was preparedthrough the reaction of hydroxyl containing oilspecimens with a vinyl monomer such as acrylic acidand methyl methacrylate. Then this monomer washomopolymerized and copolymerized with styrene.In another study, first, transesterification product oflinseed oil and castor oil was used to obtain amacromer. Subsequently, the macromer was sub-jected to homo- and copolymerization reactions inthe same manner (Scheme 25) [129].
In some studies, styrenated samples were pre-pared via hydroxymethylation, followed by malei-nization, of soybean and sunflower oils [130–132].The resulting maleate half esters were copoly-merized with styrene by free radical initiation
e oil via macroinitiator method.
ARTICLE IN PRESS
Scheme 22. Modification of castor oil.
Scheme 23. interesterification of castor oil and linseed oil.
Scheme 24. Styrenation of triglyceride oil via macromonomer
method.
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 655
(Scheme 26). Another method involving epoxida-tion and ring opening processes for styrenation oftriglyceride oils was suggested. In the first step,
epoxidation of double bonds in fatty acid chain wasachieved. Subsequently, ring opening of epoxygroups with acrylic acid yielded hydroxyl acrylatedtriglyceride oils [130,133]. As shown in Scheme 27,free radical polymerization of hydroxyl acrylatedmacromonomer gave the desired polymers. Simul-taneous addition of bromine and acrylate to thetriglyceride double bonds was achieved by Eren andKusefoglu [134]. By this way, soybean and sun-flower oils were bromoacrylated by a one-steproute. Soybean oil gave a higher acrylate substitu-tion than the other. The bromoacrylation yields forsoybean and sunflower oils were 75% and 55%,respectively. Homopolymers and copolymers ofbromoacrylated sample were obtained by thermaland photopolymerization techniques. While soy-bean oil-based polymer was a rigid, bromoacrylatedsunflower oil-styrene copolymer-exhibited semi-ri-gid properties. The authors suggested that by
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mixing bromoacrylated soybean- and sunflower oilswith small amount of antimony oxide or hydratedzinc borate, polymers having good flame-retardantproperties could be prepared. An improved methodwas also described for hydroxybromination oftriglycerides and fatty acid methyl esters in onestep, with good conversion, using NBS/acetone/water mixture (Scheme 28) [135]. After preparingacrylated hydrobromide derivative of sunflower oil
Scheme 25. Styrenation of castor oil and linseed oil mixture via
macromonomer method.
O
O
O
EtAlCl2
0°C, 2 hr
ParaformaldehyCH2-O-CO
CH -O-CO
CH2-O-CO
CH2-O-CO
CH -O-CO
CH2-O-CO
CH2-OH
Scheme 26. Stynthesis and polymerization of
it was successfully homo- and copolymerized in thepresence of thermal or photo initiator.
3.5.3. Fatty acid- or oil-grafted polymers
The blending of immiscible two or more polymershas become increasingly important way for devel-oping new materials having good properties[50,136]. Since it is difficult to obtain goodmechanical properties and stable morphology viasimple blend, some preformed graft or blockcopolymers are usually added as compatibilizers.Moreover, these copolymers are synthesized duringthe blending through polymer–polymer graftingreactions using functionalized polymers. Acrylicacid, methacrylic acid, glycidyl methacrylate, etc.are the most commonly used monomers for prepar-ing functionalized polymers obtained by graftcopolymerization. Additionally, a number of studieson long-chain unsaturated fatty acids as graftmonomer have been reported. In these studies, themechanism, reactivity and kinetics of grafting oflong-chain carboxylic acids onto acrylonitrile-buta-diene-styrene (ABS) terpolymer were investigated[136–138].
For biomedical applications, graft copolymerswere prepared from linseed and soybean oils andmethyl methacrylate, styrene or n-butyl methacry-late [139,140]. Oils were firstly converted to poly-meric peroxide under atmospheric conditions or O2
gas at room temperature. Then, it was used toinitiate the graft copolymerization of vinyl mono-mer. It was found that poly(methyl methacrylate)-based graft copolymers can be used for biomedicalapplications.
CH2-OH
CH2-O-CO-CH
Styrene
Polymer Network
de CH2-O-CO
CH -O-CO
CH2-O-CO
CH2-O-CO
CH -O-CO
CH2-O-CO
HOOC-CH
maleate half ester-based triglyceride oil.
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O
O
O
O
O
O
O
O
O
O
O
O
O
COOHO
O
O
O
O
OOH
O
O
RPolymer
Scheme 27. Synthesis of macromonomers by ring opening of epoxy groups and subsequent polymerization.
CH2-O-CO
CH -O-CO
CH2-O-CO
CH2-O-CO
CH -O-CO
CH2-O-CO
OHBr
NBS/Acetone/H2O
CH2-O-CO
CH -O-CO
CH2-O-CO
O-CO-CH=CH2Br
CH2=CH-COCl
Scheme 28. Hydroxybromination and acrylation of triglycerides.
O
CH3(CH2)7CH = CH (CH2)7 COOH + CH3CO3H
(oleic acid)
CH3(CH2)7CH - CH (CH2)7 COOH + CH3CO2H
(9,10-Epoxystearic acid)
Scheme 29. Epoxidation of oleic acid.
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 657
3.6. Epoxy resins
Epoxidized oils are important plasticizers andstabilizers for PVC. Mono- and di-unsaturated fattyacids and their esters can be converted to epoxy(oxirane) derivatives by chemical oxidation [3]. Thereaction occurred at the double bonds on the fattyacid chains. Oxidation of oleic acid in the presenceof peracetic acid is given in Scheme 29. Enzymaticepoxidation of unsaturated fatty acids was alsoachieved by Uyama et al. [141].
Epoxidized oils can be used for obtaining varioustypes of polymers by taking advantage of thereaction of the active hydrogen such as thosepresent in alcohol, amine and carboxylic acid. Inthis approach, polymer preparation is achieved intwo steps. Typically, an intermediate product
having hydroxyl groups was prepared in the firststep (Scheme 30) and subjected to subsequentcondensation to yield desired polymers, such as
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polyurethane, polyester, etc. Linseed oil based-polyurethanes can be obtained from the reactionof hydoxylated linseed oil prepared from epoxidizedlinseed oil, and diisocyanate (Scheme 31) [142]. In
RC H CH R
O
+ R' COOH RC H CH R
OH
OC O R'
RC H CH R
O
+
RC H CH R
O
+
R' NH2
R' OH
R CH R
NH
OH
R'
RC H CH R
OH
OH R'
CH
Scheme 30. Reaction of epoxides with active hydrogen contain-
ing compounds.
CH3COOH + H2O2 CH3COOOHH+
CH=CH + CH3COO
CH - CH
CH - CH
O
+ CH3CO
H+
H2O2, H
-H+
O
CH - CH
OH
OH2
Scheme 31. Preparation of polyuretha
another study, epoxidized linseed oil was polymer-ized with anhydrides in one-step in the presencetertiary amines or imidazoles catalysts [143]. Epox-idized oils can undergo homopolymerization as well[144].
Vernonia seed oil contains naturally epoxy acidsin its structure (Scheme 32). A UV-curable resin wassynthesized via transesterification of vernonia fattyacids with a hyperbranched hydroxy functionalpolyether [145]. The resin was cationically polymer-ized in the presence of vernolic acid methyl ester asdiluents. Epoxidized seed oils are widely used forthe synthesis of cationic UV-curable coatings [146–154]. Interestingly, epoxynorbornene oils showedhigher photopolymerization rate than epoxidizedoils [155]. Epoxynorbornene oils were prepared viaDiels–Alder reaction of dicyclopentadiene with oilat high pressure, followed by epoxidation. Addi-tionally, epoxynorbornene oils were successfully
+ H2O
OH
CH - CH
CH - CH
CH - CH
OH
+ OH
OH2
OH
OH
CH3
NCO
NCO
ONH-CO
O
NH
CH3
n
(
)
ne prepared from epoxidized oil.
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Scheme 32. Structure of vernonia seed oil.
Scheme 33. Half esters of dicarboxylic short oil epoxy esters.
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 659
used in the formulation of UV-curable organic–inorganic hybrid films [156].
From the sunlight-cured methacrylate of verno-nia oil, IPNs were prepared in combination with acured epoxy resin [157].
For the preparation of water-soluble polymers,epoxy resins are reacted with drying oils/drying oilfatty acids [158,159]. The obtained polymers wereeither half esters of dicarboxylic epoxy esters, ormaleinised epoxy esters of unsaturated fatty acids.All polymers become water soluble on neutraliza-tion with dimethyl ethanolamine. The former typeof polymers was prepared by a two-step procedure.In the first step, preparation of epoxy resin estersfrom drying oil fatty acids and epoxy resin wasachieved. In the second step, the free hydroxylgroups present in the epoxy resin esters weresemi-esterified with polybasic acid anhydrides(Scheme 33). Maleinised fatty acid epoxy resinesters are also prepared in two stages (Scheme 34).Drying oil fatty acids were reacted with epoxy resin,followed by the reaction with MA. The product hasvery good hydrolytic stability when compared withhalf esters of dicarboxylic epoxy esters, andmaleinised epoxy resin fatty acid esters.
3.7. Polyesteramides
Alternating polyesteramides are regular copoly-mers and combine the good properties of polyesterand polyamide [160]. 1,4-Diaminebutane terephtha-late is a typical example for polyesteramide family(Scheme 35(a)). If the alkyl chain (R1) is longenough, the Tg of the polymer is below roomtemperature, so the material shows thermoplasticelastomer behavior. If the R1 is a short chain alkyl,the Tg is above room temperature and the polymerscan be used as an engineering plastic.
Oil-modified polyesteramide resins are amide-modified alkyds that have improved properties overnormal alkyds (Scheme 35(b)). A number of linseedoil-based polyesteramides were obtained for using
as surface coating materials [161–163]. Polymerswere synthesized into two steps; preparation of N,
N’-bis(2 hydroxyethyl) linseed oil (HELA) from oiland diethanolamine, and preparation of polyester-amide from HELA and phthalic acid (Scheme 36).
In order to improve film properties, linseed oil-based polyesteramid was modified with TDI. Thepresence of urethane linkage in the polymerimproves adhesion, toughness, and water andchemical resistances [164,165].
Nahar (Mesua ferrea) seed, soybean and Ponga-
mia glabra oils were also used in the preparation ofpolyesteramides [166–168]. Soybean oil-based poly-esteramide urethane was suggested for biomedicalapplications after filling with boron, because itexhibited anti-microbial properties.
3.8. Polynaphthols
In the preparation of artificial urushi, triglycerideoils were used. Urushi is a typical Japanesetraditional lacquer extensively used in art andhousehold materials. The main components ofurushi are urushiols and catechol derivatives bear-ing a C15 unsaturated hydrocarbon chain. For thepreparation of artificial urushi, C18 unsaturated
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Scheme 34. Maleinised epoxy ester of unsaturated fatty acids.
(a)
(b)
Scheme 35. Structure of polyesteramides.
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hydrocarbon chain derived from plant oils wasconnected with the catechol group through as esterlinkage [169–172]. Cross-linkable polyphenols wereobtained from triglyceride oils [173–175].
4. Metathesis of oils
Catalytic metathesis of olefins was first investi-gated by Banks and Bailey [176]. In metathesisreactions, olefins are converted into new olefins viaan exchange of alkylidene groups (Scheme 37(a)).The catalytic metathesis of fatty acid esters wasfirst described by Van Dam et al. [177]. Methyloleate was converted into equimolar amountsof 9-octadecene and dimethyl ester of 9-octa-decene dioic acid in the presence of WCl6(CH3)4Sn(Scheme 37(b)). Boelhouwer discussed the meta-thesis of fatty acid esters in detail [178]. Usingthe same catalyst system, Erhan et al. [179] achi-eved metathesis of soybean oil. The olefin meta-thesis of vegetable oils has been suggested toproduce an improved drying oil. Chlorinated
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(a)
(b)
(c)
(d)
Scheme 37. Catalytic metathesis reactions.
Scheme 36. Synthesis of polyesteramides from triglyceride oils.
F. Seniha Guner et al. / Prog. Polym. Sci. 31 (2006) 633–670 661
solvent or chlorobenzene is used as a solvent in thiscatalyst system.
It should be pointed out that WCl6(CH3)4Snsystem is extremely sensitive to moisture andoxygen, and has disposal problem because of thesolvent. Alternative effective catalyst system,Grubbs’ ruthenium catalyst (Cy3P)2Cl2Ru ¼ CHPhwas used in the metathesis of oils [180]. Notably, thepreparation process in the case of this catalyst isenvironmentally friendly.
Olefin metathesis has a variety of polymerpreparation through ring-opening metathesis poly-merization (ROMP) (Scheme 37(c)) and acrylicdiene metathesis polymerization (ADMET)(Scheme 37(d)). Grubbs’ ruthenium catalyst hasbeen employed in ADMET polymerization ofsoybean oil [181]. In this work, after evaluation ofADMET polymerization catalysts, Mo-based and
Ru-based catalysts, ethylene glycol dioleate andglyceryl trioleate were prepared as a model reactantand their ADMET polymerization was investigated(Scheme 38). Then, ADMET polymerization ofsoybean oil was succeeded and a variety ofpolymers, from sticky oils to rubbers, were pre-pared.
Olefin metathesis was applied to triglyceride oilsin order to prepare various types of polymers, suchas polyolefins, polyesters, polyethers (Scheme 39)[182,183]. For this purpose, unsaturated fatty acidmethyl esters were obtained from oils, followed byconversion of methyl esters to o-unsaturated estersand a-olefins by metathesis with ethylene. In thereaction, heterogeneous rhenium or homogeneousruthenium catalysts were used. To prepare poly-olefins, o-unsaturated esters were copoly-merized with ethylene. Polyesters were obtained by
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(a)
(b)
Scheme 38. ADMET polymerization of fatty acid esters.
Scheme 39. Preparation of various polymers via metathesis reaction.
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metathetical dimerization of o-unsaturated esters,followed by alcoholysis with diols or by acidictransesterification with diols, followed by ADMET.In order to synthesize polyether, o-unsaturatedesters first were achieved enzymatic epoxidation,and then they were polymerized.
Refvik and Larock [184] synthesized a newmaterial by thermal polymerization of metathesized
soybean oil in the presence of air. The product wasyellow and brittle.
5. Composites from oil-based polymers
Polymer composites are used in a wide range ofapplication areas, such as aerospace, military,construction, electrical and electronics, medicine,
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Organic-rich region Inorganic-rich region
Fig. 4. A theoretical inorganic–organic hybrid material prepared
with sol–gel process.
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marine, transportation etc. [50]. It is known thatcomposites consist of two or more materialsforming separate phase. Some of the fillers usedfor composite preparation are carbon or graphite,glass, boron, steel, aromatic polyamide.
In recent years, composites prepared from oil-based polymers have become a special interest inmany areas. Polyurethane resin prepared fromcastor oil, for example, was used to obtain graphitecomposite as an electrode material [185]. The 60%(graphite, w/w) composite exhibited good mechan-ical and appropriated electric resistance, easypreparation and surface renovation. The most usingoil in the preparation of durable and strongcomposite material is soybean oil [186].
In another study, epoxidized soybean oil-basedcomposite was prepared and their viscoelasticproperties were investigated [187]. Authors sug-gested that new material prepared exhibited strongviscoelastic solid properties similar to syntheticrubbers. Dweib et al. [188,189] manufacturedmaterials from soybean oil-based resin and naturalfibers for using as the roof, floors or walls of a houseor low-rise commercial buildings. For preparingsoybean oil-based resin, first, soybean oil wasepoxidized and then vinylated by styrene or acrylicacid.
Husic et al., [190] first, synthesized polyurethaneswith soybean oil-based polyol or petrochemical-based polyol, and then prepared glass-reinforcedcomposites from them. Investigation of theirmechanical behaviors revealed that properties ofthe soybean oil-based composites were comparablewith those based on petrochemical polyol. Addi-tionally, oxidative, thermal and hydrolytic stabilityof soybean oil-based composites were superior tothose of the latter. All results indicated thatpolyurethane matrix based on soybean oil is apreferable alternative to the petrochemical polyur-ethanes in glass-reinforced composites. In anotherstudy, modified soybean oil matrix material wasused in the preparation of composites with differentglass/flax ratios and different fiber arrangements[191].
In recent years, nanocomposites has become oneof the most important area in polymer scienceBiodegradable nanocomposites obtained from nat-ural oil-based polymers led to plant oil silica hybridcoatings endowed with excellent flexibility [192,193].Epoxy-exfoliated clay nanocomposites were pre-pared using long-chain alkylammonium-exchangedsmectite clay [194].
6. Oil-based inorganic–organic hybrid materials
Hybrids are composites formed or composed ofheterogeneous elements. Inorganic–organic hybridscan be classified in different morphological combi-nations; (i) the inorganic matrix, where organicmaterials are embedded in an inorganic polymer, (ii)the organic matrix, where inorganic materials areembedded in an organic polymer, (iii) the inter-penetrating network, where inorganic and organicpolymeric networks are independently formedwithout mutual chemical bonds, and (iv) truehybrids, where inorganic and organic polymericsystems with mutual chemical bonds are formed[195,196].
The primary goal is to combine the best proper-ties of the inorganic phase with the best propertiesof the organic phase. The properties of newmaterials are showing in many cases surprisingimprovements. The inorganic–organic hybrid mate-rials, for example, provide improved the durability,the mechanical and chemical resistances, and adhe-sion of composites.
During the last decades the use of sol–gel processhas gradually increased for preparing inorganic–or-ganic hybrid products and materials. In this method
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inorganic macro-molecular sol–gel networks incor-porate into organic polymer structures (Fig. 4). Thisprocess is also used for preparing triglyceride-basedinorganic–organic hybrid coatings known as cer-amers [144,156,197–215]. Depending on the amountand type of sol–gel precursors, final properties ofthe ceramer coatings could be adjusted within awide range.
7. Conclusion
As far as the environmental and energytical issuesare considered, triglyceride oils are expected toplay a key role during the 21st century as enablingto synthesize polymers from renewable sources.Polymers form triglyceride oils may be preparedby using various strategies. The choice of thestrategy is important to succeed the polymeri-zation and related to the structure of the oiland monomer. The presence of oil/fatty acid chainin the polymer structure improves some physicalproperties of polymer in terms of flexibility,adhesion, resistances of water and chemicals.Because of their source and structural nature,triglyceride oils can widely be used as themselves.In bio-applications their biocompatibility and/orbiodegradability play an important role. Even onlythese factors make triglyceride oils as essential rawmaterials to be used in various applications in thefuture.
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