**5. PU from SO FAT**

CFAT on chemical reaction with TDI by one shot technique yields CFATU (Figure 10), with an additional crosslinking site (hydroxyl group) conferred by parent CO containing 89% ricinoleic acid. Contrary to LFADU and PFADU, where the permissible limit of TDI addition is 1.5 moles, in CFATU, at 1.2.moles of TDI addition, CFATU becomes highly viscous. The difference prevails due to the additional hydroxyl functionality in CFATU, which presumably makes possible higher inter and intra crosslinking sites relative to LFADU and PFADU. As also observed in LFADU and PFADU, the physico‐chemical characteristics such as specific gravity, inherent viscosity and refractive index increase, while hydroxyl and iodine values decrease on increasing the content of TDI in PU. The thermal degradation occurred in the temperature range of 150–390 oC. The decomposition observed at earlier temperature range may be attributed to the thermal degradation of urethane linkages followed by the volatilization of the decomposition products while that at higher temperatures is correlated to the degradation of amide bond, aromatic ring and aliphatic alkyl chain of the fatty acid, respectively, followed by the volatilization of the decomposition products [45, 46].

#### **5.1. PU as coatings**

CFATU coatings have been prepared and their physico‐mechanical, thermal as well as corrosion resistance behavior has also been investigated [31]. CFATU have been further modified for improvement in their performance as discussed in proceeding sections.

**Figure 10.** Chemical structure of CFATU

#### **5.2. PU as hybrids**

420 Polyurethane

biodegradable and eco‐friendly nature.

**Figure 9.** CO (87‐90 % Ricinoleic acid) derived FAT [CFAT)

**5. PU from SO FAT** 

products [45, 46].

**5.1. PU as coatings** 

(12‐ hydroxy ‐9‐ octadecenoic acid), hydroxyl containing fatty acid, is the major component of CO, and constitutes about 89% of the total fatty acid composition. Castor seed products have widespread applications in many industries like paints, lubricants, pharmaceuticals and textiles. Today, the importance of these products has grown manifolds because of their

Due to the inherent hydroxyl functionality, CO stands as an excellent natural raw material for the development of PU. CO derived PU are flexible due to long aliphatic triglyceride dangling chains [42]. CO has three hydroxyl moieties in one triglyceride molecule. On amidation, CO yields fatty amide triol or alkan‐triol‐amide [FAT], which bears two hydroxyl ethyl groups directly attached to amide nitrogen, as well as one hydroxyl group in the pendant fatty chain obtained from the parent CO. Thus, CO derived FAT [CFAT] acts as SO derived triol (Figure 9). Rao et al prepared acrylated CFAT as a multifunctional amide for photocuring [31, 43, 44].

CFAT on chemical reaction with TDI by one shot technique yields CFATU (Figure 10), with an additional crosslinking site (hydroxyl group) conferred by parent CO containing 89% ricinoleic acid. Contrary to LFADU and PFADU, where the permissible limit of TDI addition is 1.5 moles, in CFATU, at 1.2.moles of TDI addition, CFATU becomes highly viscous. The difference prevails due to the additional hydroxyl functionality in CFATU, which presumably makes possible higher inter and intra crosslinking sites relative to LFADU and PFADU. As also observed in LFADU and PFADU, the physico‐chemical characteristics such as specific gravity, inherent viscosity and refractive index increase, while hydroxyl and iodine values decrease on increasing the content of TDI in PU. The thermal degradation occurred in the temperature range of 150–390 oC. The decomposition observed at earlier temperature range may be attributed to the thermal degradation of urethane linkages followed by the volatilization of the decomposition products while that at higher temperatures is correlated to the degradation of amide bond, aromatic ring and aliphatic alkyl chain of the fatty acid, respectively, followed by the volatilization of the decomposition

CFATU coatings have been prepared and their physico‐mechanical, thermal as well as corrosion resistance behavior has also been investigated [31]. CFATU have been further

modified for improvement in their performance as discussed in proceeding sections.

Ahmad et al have reported the preparation and characterization of metal containing CFATU [47]. They treated CFAT with zinc acetate (5, 10 and 15 wt%) and TDI (25–75 wt%) to prepare metal containing CFATU [MCFADU] ''in situ'' by microwave [MW] assisted preparation method in a domestic MW oven. During the preparation, it was observed that MCFATU with > 5wt% zinc acetate formed gel. While the conventional preparation method of LFADU, CFATU, PFADU and NFADU requires 8‐12 hours, CFATU is obtained in 4 minutes by MW assisted preparation method. By molecular interactions with the electromagnetic field and heat generated by molecular collision and friction, the reaction is facilitated to occur in much reduced time periods under the influence of MW irradiations. In this reaction, hydroxyl groups of CFAT react with zinc acetate and TDI successively. Curing of MCFATU is a two step process occurring by solvent evaporation (physical phenomenon) followed by the second stage curing (a chemical process) where free –NCO groups of MCFATU react with the atmospheric moisture to form urethane and amino groups through addition reaction. MCFATU acted as good corrosion protective coatings for mild steel. The best physico‐mechanical properties (scratch hardness 3.5 kg, impact resistance

150lb/inch, and bending ability 1/8 inch) were achieved at 5wt% loading of zinc acetate and 55 wt% of TDI, when evaluated by standard methods and techniques. The corrosion protection efficiency of the same was evaluated by potentiodynamic polarisation measurements [PDP] in aqueous solution of 3.5wt% HCl (CR 4.51 × 10‐3 mm/year; IE% 96.23), 3.5wt% NaOH (CR 1.36 × 10‐3 mm/year; IE% 90.81); 3.5wt%NaCl (CR 2.25 × 10‐3 mm/year; IE% 94.50) and tap water (Cl‐ ion 63 mg/L; Conductivity 0.953 mS/A) (CR 3.56 × 10‐3 mm/year; IE% 98.35).

Seed Oil Based Polyurethanes: An Insight 423

**Figure 12.** TEM of CFATU/ZnO composite

hydrogenation bear hydroxyl groups at terminal position.

SO derived polyols serve as the most important oleochemicals for PU production. Some of the SO polyols are derived through various chemical reactions such as epoxidation followed by hydration, ring opening by methanol, acids such as HBr, HCl, hydroformylation, ozonolysis of SO, others are naturally available polyols such as *Ricinus communis* or CO and Lesquerella oil. As discussed previously, the properties of PU also depend upon the type of polyol and the method by which the polyol is derived. In SO polyols, in general, hydroxyl groups are present in the middle of the triglyceride chains. Due to this, in cross linked polyols, the pendant or dangling chains provide steric hindrance to cross‐linking, they do not support stress under load and act as plasticizers. In SO polyols, there is difference in the length of elastically active network chains (EANC) and elastically inactive network chains or dangling chains (DC). This variation is also passed onto their respective PU. The properties of PU thus also depend upon the content of EANC and DC, i.e., the number and position of hydroxyl groups. The number of hydroxyls on each chain in SO polyols and their stereochemistry are also variable depending upon the hydroxylating agents, hydroxylating method and other reaction conditions. For example, polyols obtained by ozonolysis and

**6. SO based polyols** 
