High‐performance bio‐based thermosetting resins composed of dehydrated castor oil and bismaleimide

The reaction of dehydrated castor oil (DCO) and 1,1′‐(methylenedi‐4,1‐phenylene)bismaleimide (BMI) in 1,3‐dimethyl‐2‐imidazolidinone (DMI) at 130°C for 6 h and subsequent precipitation gave DCO/BMI prepolymer, which was cured at 200°C for 2 h gave DCO/BMI cured product. The FE‐SEM analysis revealed that the cured products with CC ratio 2/1 and 1/1 are homogeneous, whereas phase separation occurs for the 1/2 product. The glass transition temperature, 5% weight loss temperature, and tensile modulus of the cured DCO/BMI increased with increasing BMI content. Regarding the tensile strength, the cured DCO/BMI 1/1 product showed the highest value. To evaluate the reaction of DCO and BMI, the model reaction products of DCO and N ‐phenylmaleimide (PMI) in DMI were analyzed by 1 H NMR spectroscopy. The 1 H NMR data of DCO revealed that DCO has about 4.8 CHCH bonds per triglyceride and that the ratio of conjugated and nonconjugated diene moieties is about 41/59. The NMR data of the reaction products of DCO/PMI with the CC ratio 2/1 and 1/1 at 200°C for 24 h revealed that both Diels–Alder and ene reactions occurs in addition to radical polymerization.