**4. SO based triol**

418 Polyurethane

also improved adhesion with the penal surface exhibiting good scratch hardness, bending ability (1/8 inch) and impact tests (150 lb/inch) correlated to the synergism showed by both the components, LFADU backbone imparting flexibility and gloss, while the inorganic

The corrosion rate (CR) of Si LFADU is much lower (3.08 × 10−4 mm per year) relative to LFADU (3.124 mm/year) In 3.5wt% HCl, with inhibition efficiency (IE%) 99.77. In 3.5% NaOH, CR and IE% were found as 1.26 × 10−3 mm per year and 99.34, respectively. Si LFADU formed uniform and well adhered coating over the metal substrate which prohibits the permeation of corrosive media. The protection mechanism is purely through barrier action attributed to the hydrophobic inorganic content [37, 38]. Coating remained intact when subjected to corrosive media for 192 h as supported by the constant value of polarization resistance (Rp = 1.22 × 104 Ohm in NaOH and 7.7 × 105 Ohm for HCl). Thermal studies showed four step degradation, thermal stability increasing with higher inorganic content, with two glass transition temperatures (Tg) as observed at 115 ◦C and 155 °C in

Composite materials from FADU have not been prepared yet. In their recent research, Zafar et al have developed composites from FADU using metal oxides and organo‐ montmorillonite clay [OMMT] (Cloisite 30B; modified by an alkyl ammonium cation bearing two primary hydroxyl functions, alkyl group is tallow containing ≈65% C18, ≈30% C16, and ≈5% C14, Southern Clay product) as modifiers added in very lower amounts to FADU matrix (unpublished work). The sole aim behind the development of these composites was the improvement in performance of FADU materials in terms of thermal stability, physico‐mechanical and corrosion or chemical resistance performance, and also antimicrobial behavior relative to the pristine material for high performance applications. MMT occurred as nano‐sized aggregates with size ranging from 37 to 100 nm as observed by Transmission Electron Micrography [TEM]. The thermal stability of FADU/ MMT was found to increase with increased MMT loading. These composites may be used as protective coatings in future. Zafar et al have also developed FADU/MnO composites, with good antifungal behavior. MnO occurred as needles self‐assembled in "lemon slices" morphology as observed in optical micrograph (Figure 8). The said composite material may find

PU composites were prepared by the dispersion of conducting polymer poly (1‐ naphthylamine) [PNA] in LFADU matrix in amount ranging from 0.5–2.5 wt% by conventional solution method as reported by Riaz et al [39]. At lower levels, the composites were very fragile in nature. The polymerization of PNA occurred through N–C(5) linkages of 1‐naphthylamine units as confirmed by FTIR spectra. PNA also reacted with free isocyanate groups of TDI forming urea linkages, as also supported by spectral analysis. UV visible spectra also confirmed the formation of urea linkages between LFADU and PNA. TEM micrographs showed the average particle size as 17–27 nm. Nanoparticles appeared as

domains conferring excellent adhesion and hardness [36].

DSC thermogram with safe usage upto 200 °C.

application as antimicrobial agent in coatings and paints.

**3.3. PU as composites** 

Castor oil (CO) is obtained from seeds of *Ricinus communis* or Castor belonging to the family *Euphorbiaceae*. It is non edible oil. The crop is cultivated around the world because of the commercial importance of its oil. India is the world leader in castor production and dominates the international CO trade. Worldwide castor production was about 1.4 million metric tons during the year 2009 with an average yield of about 956 kg ha‐1. Ricinoleic acid (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 biodegradable and eco‐friendly nature.

Seed Oil Based Polyurethanes: An Insight 421

**Figure 10.** Chemical structure of CFATU

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

**5.2. PU as hybrids** 

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].

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