Synthesis and Characterization of Novel Soybean-Oil-Based Elastomers with Favorable Processability and Tunable Properties

A new series of soybean-oil-based elastomers poly(epoxidized soybean oil-co-decamethylene diamine) (PESD) was synthesized by ring-opening polymerization from epoxidized soybean oil (ESO) and decamethylene diamine (DDA) in different molar ratios. The effect of the molar ratio on the structure and properties of PESD was identified by various methods. According to the results of Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (1H NMR) and thermogravimetry (TGA), the glycerol center of ESO was broken by ammonolysis as expected in the process of polymerization, which resulted in un-cross-linked elastomers with low glass transition temperatures (Tg) ranging from −30 to −17 °C. PESD-3 (molar ratio of DDA to ESO is 2:1) was found to have the highest molecular weight and was most suitable for further processing. Then, PESD-3 was successfully cross-linked through succinic anhydride by a general rubber processing method to obtain a cross-linked bioelastomer. The mechanism of chain growth, ammonolysis of ester group, and cross-linking of PESD-3 was studied. The tensile strength of cross-linked PESD could be flexibly adjusted from 0.8 to 8.5 MPa by using different amounts of succinic anhydride without reinforcing fillers. The final bioelastomer possesses good damping property, low water absorption, and low degradation rate in phosphate buffer solution. These properties indicate potential engineering applications.