**3.2. PU as hybrids**

Organic‐inorganic hybrid materials have been developed with FADU as organic constituent and metal/metalloid as inorganic component to improve the performance and broaden the applications of PU (Figure 6).

**Figure 6.** PU as hybrids

In one report, Zafar et al. have prepared organic‐inorganic hybrids by using boric acid as inorganic content and PFADU as organic matrix [B‐PFADU] [34]. B‐PFADU was characterized by standard spectral techniques and physico‐chemical methods. B‐PFADU performed well as protective coatings in terms of physico‐mechanical and chemical resistance tests. B‐PFADU showed no change in water and xylene upto 15 days. However, slight deterioration in performance was observed in alkali and acid media, correlated to the presence of ‐O‐B‐O‐ which is susceptible to hydrolysis on exposure to these media. B‐

PFADU showed high activity against *E. coli* (Zone of inhibition: 21‐30 mm) and moderate activity against *S. aureus* (Zone of inhibition: 16‐20 mm). The reason can be the presence of urethane, amide, and hydroxyl groups in the polymer backbone, which can presumably interact with the surface of microbes, causing antibacterial action. B‐PFADU can be used as an antibacterial agent as well as coating material.

In another work, Ahmad and co‐workers developed LFADU hybrid material with tetraethoxy orthosilane [TEOS] as inorganic constituent in the hybrid material [Si LFADU] by in situ silylation of LFAD with TEOS (at 80 ◦C) followed by urethanation with TDI (at room temperature) [35]. Along with the typical absorption bands for LFADU, additional absorption bands were observed at 484 cm−1 (Si–O–Si bending), 795 cm−1 (Si–O–Si sym str) and 1088 cm−1 (Si–O–Si assym str) in FTIR due to the presence of ‐Si–O–Si‐ bond in the hybrid backbone. Hydroxyl value decreases while refractive index and specific gravity increase with the loading of TEOS in Si LFADU, supporting the formation of the hybrid materials by insitu siylation and urethanation reaction. Optical micrograph of Si LFADU showed the presence of SiO2 particles surrounded by LFADU (Figure 7).

**Figure 7.** Optical micrograph of Si LFADU

416 Polyurethane

**3.1. PU as coatings** 

rich in linolenic acid).

**3.2. PU as hybrids** 

**Figure 6.** PU as hybrids

applications of PU (Figure 6).

(Figure 5)[32].

LFADU has free –OH, –NCO, aliphatic hydrocarbon chains (from parent LO), amide and urethane groups, which make it an excellent candidate for application in protective coatings (Figure 4). LFADU coatings undergo curing at ambient temperature (28‐30oC) by three stage curing phenomenon, (i) solvent evaporation (physical process), (ii) reaction of free –NCO groups of LFADU with atmospheric moisture, and (iii) auto‐oxidation. These coatings show good scratch hardness (2.5kg), impact resistance (200lb/inch), bending ability (1/8inch) and chemical resistance to acid and alkali. PU from PGO [PFADU] has shown moderate antibacterial behavior against *Salmonella* sp. with good scratch hardness (1.9kg), impact resistance (150lb/inch), bending ability (1/8inch), and gloss (46 at 45o) [33]. LFADU coatings have shown superior coating properties than PFADU owing to the fatty acid composition of parent oils (PGO, a non‐drying oil has higher content of oleic acid while LO, a drying oil, is

Karak and Dutta have reported the use of NFADU coatings with very good alkali resistance

Organic‐inorganic hybrid materials have been developed with FADU as organic constituent and metal/metalloid as inorganic component to improve the performance and broaden the

In one report, Zafar et al. have prepared organic‐inorganic hybrids by using boric acid as inorganic content and PFADU as organic matrix [B‐PFADU] [34]. B‐PFADU was characterized by standard spectral techniques and physico‐chemical methods. B‐PFADU performed well as protective coatings in terms of physico‐mechanical and chemical resistance tests. B‐PFADU showed no change in water and xylene upto 15 days. However, slight deterioration in performance was observed in alkali and acid media, correlated to the presence of ‐O‐B‐O‐ which is susceptible to hydrolysis on exposure to these media. B‐

Si LFADU formed hybrid coatings by simple curing route at ambient temperature, over mild steel panels of standard sizes with improved gloss and scratch hardness. SiO2 domains 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 domains conferring excellent adhesion and hardness [36].

Seed Oil Based Polyurethanes: An Insight 419

smaller aggregates which later on formed larger aggregates. XRD analysis revealed purely amorphous nature of composites. With the increase in the loading of PNA in the composites, the distortion and torsional strain increased in the composites due to higher urea linkages. It was found that as the percent loading of PNA in the composites increased, their electrical conductivity values also increased; however, these values fell in the semi‐conducting range, which was much higher relative to the conductivity values obtained with very high loading of PNA in previously reported composites. The improved electrical conductivity values of LFADU/PNA composites can be correlated to the hydrogen bonding and urea type linkages formed between the two polymers, which provide the path to charge conduction [40,41].

**Figure 8.** Optical micrographs of FADU/MnO (a) 100 X, (b) 200 X, (c) 500 X

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

**4. SO based triol** 

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 DSC thermogram with safe usage upto 200 °C.
