Thermogravimetric study and kinetic modeling of semi-interpenetrating polymer network protonic conductive membranes to PEMFC

This work aims at studying the thermal behavior of a group of semi-interpenetrating polymer network (SIPN) membranes used as a base of proton conductive polymeric membrane for Fuel Cells. SIPNDX membranes were obtained from the cure reaction of diglycidyl ether of bisphenol A (DGEBA) and 4.4'diaminodiphenyl-sulphone (DDS) in the presence of polyethyleneimine (PEI) in different concentrations. All samples were analyzed in a thermogravimetric analyzer (303–973 K) under nitrogen flow and heating rates at 5, 10, 15, and 20 K min−1. The classical isoconversional models of Ozawa–Flynn–Wall (OFW) and Kissenger–Akahira–Sunose (KAS) were used to obtain the kinetic parameters, activation energy (Ea), and pre-exponential factor (A). We used the Coats-Redfern model and the Criado masterplot procedure to determine the best fitting reaction mechanism. This approach showed that for DGEBA/DDS network and SIPNDX samples, with up to 40 mass % PEI, the chemical reaction mechanism (F2). For higher PEI contents, SIPND50, diffusion-related models (D1 and R2), gave the most relevant mechanisms. Atomic force microscopy (AFM) images correlated with kinetic analysis endorses that in the SIPND50 the degradation reaction progress from the interface to the center of the phase, more reactive than the bulk. These SIPNs showed good potential as a solid electrolyte in fuel cells based on the thermal properties.