Properties and curing kinetics of C21-based reactive polyamides as epoxy-curing agents derived from tung oil

Abstract

Three C21-based reactive polyamides were synthesized from tung oil and different polyamines. The thermal and mechanical properties of cured products of the C21-based polyamides and diglycidyl ether of bisphenol A (DGEBA) were investigated. It was found that the cured materials were superior to those cured by C36-based polyamides in tensile strength and flexural strength and had a better flexural modulus. The glass transition temperatures of the three cured C21-based polyamides, determined by differential scanning calorimetry (DSC), were found to be 108, 109 and 116 °C, which were also higher than those of C36-based polyamides. The curing kinetics of C21-based polyamides in the presence of DGEBA were studied by non-isothermal DSC at different heating rates. The kinetic parameters of the curing process were determined by the iso-conversional method given by Málek. A two-parameter (m, n) autocatalytic model (the Šesták–Berggren equation) was found to be the most suitable to describe the curing kinetics of the studied curing agents. The activation energy (Ea) values of the three curing agents with DGEBA are dependent on the amine values of polyamides. The Ea value of the curing reaction decreased as the primary amine values of curing agents increased. The experimental non-isothermal DSC curves show a good agreement with theoretical calculations. Three C21-based reactive polyamides with various amine values as epoxy-curing agents were synthesized from tung oil and different polyamines. It was found that the cured materials were superior to those cured by widely used C36-based polyamides with regard to mechanical properties. The glass transition temperatures of three cured C21-based polyamides were found to be higher than that of C36-based polyamides. The curing kinetics were studied and nonisothermal DSC curves show a good agreement with theoretically calculated ones.