**1. Introduction**

Seed oils [SO] are cost‐effective, eco‐friendly and biodegradable in nature. They bear functional groups such as carboxyls, esters, double bonds, active methylenes, hydroxyls, oxirane rings and others, amenable to several derivatization reactions. Their abundant availability, non‐toxicity and rich chemistry has established SO as focal point of polymer production, e.g., production of polyesters, alkyds, epoxies, polyols, polyethers, polyesteramides, polyurethanes and others. The escalating prices of petro‐based chemicals, environmental and health concerns have further beckoned the enhanced utilization of SO as polymer precursors. SO have attracted enormous attention as potential source of platform chemicals, at both laboratory and industrial scale. Today, oil‐seed bearing crop plants are being raised and modified for uses in areas covering biodiesel, lubricants, folk medicines, cosmetics, plastics, coatings and paints.

SO based polyurethanes [PU] occupy an important position due to their simple preparation methods, outstanding properties and versatile applications in foams, coatings, adhesives, sealants, elastomers and others [1‐4]. In general, PU are prepared by chemical reaction of a diol, polyol or any oligomer or polymer containing hydroxyl groups, with an aliphatic, cycloaliphatic or aromatic isocyanate. SO serve as green precursors to diols, polyols and other –OH containing polymers offering greener raw materials in PU synthesis, replacing their petro‐based counterparts. The choice of SO polyol or isocyanate is governed by the end‐use application of SO PU ranging from soft and flexible to rigid PU foams, thermoplastic to thermosetting PU, flexible films to tough, scratch‐resistant, impact resistant coatings and paints. It is well known that the structure of a triglyceride is very complex. Every SO has a characteristic fatty acid profile. Amongst the same species, the composition of triglycerides in a particular SO varies by weather conditions of crops and soil. Triglycerides vary by their fatty acid chain lengths, presence as well as the position of double bonds and degree of unsaturation of the constituent fatty acids. The structures of

© 2012 Sharmin et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 Sharmin et al., licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

natural SO and their derivatives, i.e., epoxies, diols, polyols, polyesters and alkyds are complex. Thus, the properties of PU obtained from SO derivatives depend on a number of factors such as (i) the type, composition and distribution of fatty acid residues in the constituent triglycerides, (ii) the number, distribution, site of hydroxyls (in the middle or closer to the end of the triglyceride chain) and level of unsaturation in the fatty triester chains of the parent diol or polyol, (iii) the type, position and structure of isocyanates used and (iv) the urethane content of the final PU [5‐8].

Seed Oil Based Polyurethanes: An Insight 411

more stable PU than their counterparts with secondary hydroxyls. PU with high crosslink density show higher thermal stability. Hydrolytic stability of PU also depends on the degree of crosslinking, temperature, and physical state of PU. In SO based PU, although SO have ester groups susceptible to hydrolysis, long hydrophobic fatty acid chains cause shielding effect. Under highly humid conditions, urethane bonds undergo hydrolysis producing

SO are rich in various functional groups such as double bonds, active methylenes, esters, hydroxyls and others. These undergo several chemical transformations yielding numerous derivatives with versatile applications as inks, plasticizers, lubricants, adhesives, coatings and paints. Amongst various SO derivatives, those containing hydroxyl groups are used in the production of PU. These include SO based diols, triols, polyols, polyesters, alkyd,

**Figure 1.** SO derivatives used in the production of PU (a) polyol, (b) triol, (c) fatty amide triol, (d) fatty

The chemistry of SO based PU is very vast, governed by several factors such as the type of diol or polyol, type of isocyanate, preparation method of diols or polyols, type of chain

amide diol, (e) monoglyceride, (f) polyesteramide, (g) polyetheramide, and (h) alkyd.

amine and carbon dioxide [1, 19].

polyesteramide, polyetheramide and others (Figure 1).

The ingredients for the preparation of SO based PU generally comprise of a diol or polyol (containing active hydrogens) derived from SO and an isocyanate, aliphatic and aromatic such as 1,6‐hexamethylene diisocyanate [HMDI], isophorone diisocyanate [IPDI], cyclohexyl diisocyanate [CHDI], L‐Lysine Diisocyanate [LDI], toluylene 2,4‐diisocyanate or toluylene 2,6‐diisocyanate [TDI], 4,4'‐ methylenediphenyl diisocyanate [MDI], naphthylene 1,5‐ diisocyanate [ND]. PU are prepared by polyaddition reaction between the two components, often in presence of a chain extender, cross‐linker or a catalyst. Today, several environment friendly routes for the production of PU have cropped up. Research has been focussed on the preparation of PU from non‐isocyanate routes, and also on the use of fatty acid based isocyanates for PU production, considering the persisting challenges of polymer industry and immediate attention sought towards environmentally benign chemicals and chemical routes for the same [9‐18].

SO based PU are generally flexible in nature. Generally, these PU show low Tg due to the presence of long aliphatic chains and also poor mechanical properties (owing to the presence of dangling chains). The thermal stability of SO based PU is also lower since the decomposition of urethane bonds starts at 150‐200oC. Javni et al have studied the decomposition of PU from Olive, Peanut, Canola, Corn, Soybean, Sunflower, Safflower and Castor oils [7]. The decomposition involves the dissociation of urethane bonds to isocyanate, alcohol, amine, olefin and carbon dioxide. The properties of PU depend upon their crosslinking density as well as chemical composition. In an execellent review, Petrovic has highlighted the different properties of PU prepared from polyols obtained by different methods. As the properties of polyols depend upon the methods of preparation, so also the properties of PU derived therefrom. He has presented a brief outline of the effect of polyols prepared by epoxidation, hydroformylation, ozonolysis, effect of crosslinking density, and type of isocyanate on the properties of PU. He described the effect of the structure of polyols prepared by epoxidation followed by ring opening with methanol, HCl, HBr, and by hydrogenation of epoxidized Soybean oil, and showed that PU obtained from these polyols showed relatively higher glass transition temperatures and improved mechanical properties. Halogenated polyols obtained via ring opening by HCl and HBr gave PU that were less stable than ones without halogens, and had higher Tg (70oC –80oC) than the latter. Polyols obtained via hydroformylation crystallize below room temperature while those derived through hydrogenation reveal crystallization at temperature higher than room temperature. PU from non‐halogenated polyols had higher thermal stability than brominated (100oC) or chlorinated polyols (160oC). Polyols with primary hydroxyls give more stable PU than their counterparts with secondary hydroxyls. PU with high crosslink density show higher thermal stability. Hydrolytic stability of PU also depends on the degree of crosslinking, temperature, and physical state of PU. In SO based PU, although SO have ester groups susceptible to hydrolysis, long hydrophobic fatty acid chains cause shielding effect. Under highly humid conditions, urethane bonds undergo hydrolysis producing amine and carbon dioxide [1, 19].

410 Polyurethane

natural SO and their derivatives, i.e., epoxies, diols, polyols, polyesters and alkyds are complex. Thus, the properties of PU obtained from SO derivatives depend on a number of factors such as (i) the type, composition and distribution of fatty acid residues in the constituent triglycerides, (ii) the number, distribution, site of hydroxyls (in the middle or closer to the end of the triglyceride chain) and level of unsaturation in the fatty triester chains of the parent diol or polyol, (iii) the type, position and structure of isocyanates used

The ingredients for the preparation of SO based PU generally comprise of a diol or polyol (containing active hydrogens) derived from SO and an isocyanate, aliphatic and aromatic such as 1,6‐hexamethylene diisocyanate [HMDI], isophorone diisocyanate [IPDI], cyclohexyl diisocyanate [CHDI], L‐Lysine Diisocyanate [LDI], toluylene 2,4‐diisocyanate or toluylene 2,6‐diisocyanate [TDI], 4,4'‐ methylenediphenyl diisocyanate [MDI], naphthylene 1,5‐ diisocyanate [ND]. PU are prepared by polyaddition reaction between the two components, often in presence of a chain extender, cross‐linker or a catalyst. Today, several environment friendly routes for the production of PU have cropped up. Research has been focussed on the preparation of PU from non‐isocyanate routes, and also on the use of fatty acid based isocyanates for PU production, considering the persisting challenges of polymer industry and immediate attention sought towards environmentally benign chemicals and chemical

SO based PU are generally flexible in nature. Generally, these PU show low Tg due to the presence of long aliphatic chains and also poor mechanical properties (owing to the presence of dangling chains). The thermal stability of SO based PU is also lower since the decomposition of urethane bonds starts at 150‐200oC. Javni et al have studied the decomposition of PU from Olive, Peanut, Canola, Corn, Soybean, Sunflower, Safflower and Castor oils [7]. The decomposition involves the dissociation of urethane bonds to isocyanate, alcohol, amine, olefin and carbon dioxide. The properties of PU depend upon their crosslinking density as well as chemical composition. In an execellent review, Petrovic has highlighted the different properties of PU prepared from polyols obtained by different methods. As the properties of polyols depend upon the methods of preparation, so also the properties of PU derived therefrom. He has presented a brief outline of the effect of polyols prepared by epoxidation, hydroformylation, ozonolysis, effect of crosslinking density, and type of isocyanate on the properties of PU. He described the effect of the structure of polyols prepared by epoxidation followed by ring opening with methanol, HCl, HBr, and by hydrogenation of epoxidized Soybean oil, and showed that PU obtained from these polyols showed relatively higher glass transition temperatures and improved mechanical properties. Halogenated polyols obtained via ring opening by HCl and HBr gave PU that were less stable than ones without halogens, and had higher Tg (70oC –80oC) than the latter. Polyols obtained via hydroformylation crystallize below room temperature while those derived through hydrogenation reveal crystallization at temperature higher than room temperature. PU from non‐halogenated polyols had higher thermal stability than brominated (100oC) or chlorinated polyols (160oC). Polyols with primary hydroxyls give

and (iv) the urethane content of the final PU [5‐8].

routes for the same [9‐18].

SO are rich in various functional groups such as double bonds, active methylenes, esters, hydroxyls and others. These undergo several chemical transformations yielding numerous derivatives with versatile applications as inks, plasticizers, lubricants, adhesives, coatings and paints. Amongst various SO derivatives, those containing hydroxyl groups are used in the production of PU. These include SO based diols, triols, polyols, polyesters, alkyd, polyesteramide, polyetheramide and others (Figure 1).

**Figure 1.** SO derivatives used in the production of PU (a) polyol, (b) triol, (c) fatty amide triol, (d) fatty amide diol, (e) monoglyceride, (f) polyesteramide, (g) polyetheramide, and (h) alkyd.

The chemistry of SO based PU is very vast, governed by several factors such as the type of diol or polyol, type of isocyanate, preparation method of diols or polyols, type of chain extender, cross‐linker, reaction temperature and other reaction conditions. In this chapter we have focussed on the preparation, structure and properties of PU obtained from diols, triols and polyols derived by amidation of SO termed as "SO alkanolamides". In the proceeding sections, we have also discussed the modifications of the said SO alkanolamides based PU at the forefront of PU chemistry such as SO based metal containing PU, PU hybrids, composites for applications mainly in coatings, paints and foams.

Seed Oil Based Polyurethanes: An Insight 413

The reaction proceeds by nucleophilic acyl substitution bimolecular (SN2) reaction mechanism. As the name suggests, FAD contains an amide group, with two hydroxyl ethyl groups directly attached to amide nitrogen along with the pendant aliphatic chain of SO. FAD is derived from different SO such as Linseed (*Linum ussitassimum*), Soybean (*Glycine max*), Karanj (*Pongamia glabra*), Nahor (*Mesua ferrea*), Jatropha (*Jatropha Curcus*), Olive (*Olea europea*), Coconut (*Cocos nucifera*) and others [20‐30] (Figure 2). FAD is used as raw material

FAD can be treated with an isocyanate such as TDI, IPDI, HMDI, MDI, ND, CHDI and LDI

**Figure 3.** FADU from (a) Linseed, (b) Soybean (c) Karanj, Nahor, Jatropha, Olive and (d) Castor

technique to prepare PU [LFADU] as introduced by Ahmad et al [32] (Figure 4).

For the first time, Linseed oil [LO] derived FAD [LFAD] was treated with TDI by one‐shot

for various polymers such as PU, poly (esteramide) and poly (ether amide).

forming poly (urethane fatty amide) (Figure 3) [FADU] [31].

**3. PU from SO FAD** 
