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A method of synthesis of liquid high‐molecular‐weight epoxy resins from modified vegetable oils as natural raw materials is proposed. The possibility of application of epoxidized soybean, rapeseed, linseed, and sunflower oils as well as hydroxylated soybean and rapeseed oils as raw materials in the fusion process was verified. Reactions of: (i) epoxidized oils, used as low‐molecular‐weight epoxy resins, with Bisphenol A, as well as, (ii) Bisphenol A‐based epoxy resin with hydroxylated natural oils, were carried out in the presence of different catalysts (i.e., LiCl, 2‐methylimidazole, triphenylphosphine, and triethanolamine) in the temperature range of 130–160°C (depending on the catalyst type), and under nitrogen for minimization of the oxidative degradation. The epoxy value, color, number/weight‐average molecular weight, and polydispersity of the products obtained were studied in relation to the reaction conditions. Finally, the possibility of curing of the increased‐molecular‐weight epoxy resins, synthesized from the modified natural oils, with 2‐methylimidazole, dicyanodiamide, hexahydrophthalic anhydride, and triethylenetetramine was checked. The results of this research should enable reducing the use of petrochemical raw materials for the syntheses of high‐molecular‐weight epoxy resins. Copyright © 2008 John Wiley & Sons, Ltd.

Summary: Bisphenol A based low-molecular-weight epoxy resin was modified with epoxidized soybean oil, which exhibit viscosity reducing ability comparable to commercial grade active diluents. The studied compositions showed a nonNewtonian rheological behavior, typical for Bingham liquids. The values of the flow index (n) and the consistency index (k) for the compositions tested in the temperature range 25-65 8C were calculated from the Ostwald-de Waele rheological model and were used to calculate the flow-activation energy (E a ) using the Arhenius equation. Studies of co-crosslinking of mixed oil-resin compositions using isophorone diamine showed essential decrease of the reaction heat and peak maximum temperature. Mechanical properties, thermal stability, water absorption and chemical resistance of the epoxy resin modified with natural oil, were also investigated. Compositions of epoxy resin Ruetapox 0162, modified with the oil diluent, preserved very good mechanical properties of the epoxy resins and demonstrated relatively low water absorption as well as high chemical resistance. The compositions displayed even higher impact strength than pure epoxy resin due to plasticizing effect of the built-in oil. Compositions with the high contents (up to 60 weight %) of the oil were flexible materials with fast elastic recovery.

Summary: Modified natural oils -epoxidized soybean and rapeseed oils were tested as reactive diluents for viscosity regulation of Bisphenol A-based low-molecularweight epoxy resin. Satisfactory viscosity reducing ability of epoxidized oils as well as non-Newtonian rheological behaviour of the resin diluted with modified oils were demonstrated. Co-crosslinking of mixed oil-resin compositions using isophorone diamine was studied showing essential decreasing of the reaction heat and slight increasing of the peak maximum temperature. Mechanical properties, thermal stability, water absorption and chemical resistance of the epoxy resin modified with natural oils were also investigated.

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