Poly (urethane fatty amide) resin from linseed oil—A renewable resource

Poly (urethane fatty amide) [PULFA] resin was synthesized by using a one-shot technique at room temperature from diol linseed fatty amide [DLFA; a monomer obtained from the aminolysis of renewable resource, such as linseed oil with diethanolamine and sodium methoxide used as a catalyst], 1.0 moles, and varying ratio of toluylene-2,4(6)-diisocyanate [TDI, 0.08–1.5 moles] in minimum amount of xylene without any chain extender and catalyst. In this process phthalic acid/anhydride which is normally used in the synthesis of polyesteramide was completely replaced by TDI as in case of uralkyd. The reaction mechanism of the same has been discussed here. The mode of reaction and structure of the resin was confirmed by physico-chemical tests and spectral analysis. The performance of the coatings on mild steel strips was tested by physico-mechanical and chemical/corrosion resistance tests. Thermo gravimetric analysis [TGA] and differential scanning calorimetry [DSC] techniques were used to investigate the thermal stability and curing behavior of the resin. The aforementioned properties of newly synthesized resin were compared with those of reported linseed oil-based polyesteramide urethane [Ur-LPEA, synthesized by partial replacement of phthalic anhydride by TDI] and uralkyd. The newly synthesized resin has shown improved physico-mechanical and corrosion resistance performance to Ur-LPEA and alkyd, whereas to those of uralkyd has comparable results. The PULFA resin exhibits not only superior properties to some of the reported resins, but also helps in the conservation of energy by being synthesized at room temperature as compared to other similar reported systems which were synthesized at reasonably high temperatures. The present study reveals that the PULFA resin can be used as a substitute to Ur-LPEA, alkyd and uralkyd in the field of corrosion protective paints and coatings.