Application of Modified Natural Oils as Reactive Diluents for Epoxy Resins

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 non‐Newtonian 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 °C were calculated from the Ostwald‐de Waele rheological model and were used to calculate the flow‐activation energy (Ea) 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.