Study on mechanical properties of the crosslinked with isocyanates product of the reaction of modified soybean oil with epoxy resin

Abstract

The hydroxyl derivative of soybean oil (SDEG) was obtained as a result of the epoxidation of soybean oil followed by the opening of oxirane rings in the reaction with diethylene glycol (Scheme A). This derivative was used in the process of fusion with bisphenol A-based low-molecular-weight epoxy resin EPR 162 (Scheme B), carried out using triphenylphosphine as a catalyst. The as-synthesized materials were characterized using FT-IR (Fig. 1) and H-1 NMR (Fig. 2) spectroscopy and by determining the content of unsaturated bonds, epoxy and hydroxyl groups as well as the number and weight average molecular weights and polydispersity index (Table 1 and 2, Fig. 3). The hydroxyl derivative of soybean oil and the product of the fusion process were crosslinked using polyisocyanates of different structure [Formulae (I)-(VI)]: toluene-2,4-diisocyanate, hexamethylene diisocyanate and 4,4'-methylene diphenyl diisocyanate. The cured materials (Table 3) were characterized for selected mechanical properties (Table 4) and morphological structure using SEM method (Fig. 4). It has been found that the crosslinked product of the fusion process has a homogeneous structure and better mechanical properties than the hydroxyl derivative crosslinked using the same curing agents. Both groups of materials based on the modified soybean oil showed mechanical properties intermediate between those of epoxy resin EPR 162 crosslinked using isophoronediamine and the resin cured with methyltetrahydrophthalic anhydride.