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

Three C-21-based reactive polyamides were synthesized from tung oil and different polyamines. The thermal and mechanical properties of cured products of the C-21-based polyamides and diglycidyl ether of bisphenol A (DGEBA) were investigated. It was found that the cured materials were superior to those cured by C-36-based polyamides in tensile strength and flexural strength and had a better flexural modulus. The glass transition temperatures of the three cured C-21-based polyamides, determined by differential scanning calorimetry (DSC), were found to be 108, 109 and 116 degrees C, which were also higher than those of C-36-based polyamides. The curing kinetics of C-21-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 Malek. A two-parameter (m, n) autocatalytic model (the Sestak-Berggren equation) was found to be the most suitable to describe the curing kinetics of the studied curing agents. The activation energy (E-a) values of the three curing agents with DGEBA are dependent on the amine values of polyamides. The E-a 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. Polymer Journal (2010) 42, 51-57; doi: 10.1038/pj.2009.303