Curing behavior and thermal properties of TGDDM copolymerized with a new pyridine-containing diamine and with DDM or DDS

• A pyridine containing diamine (PDD) was used as a curing agent for TGDDM.
• The curing kinetics, DMTA and TGA were compared with DDS and DDM and their blends.
• The curing Ea values were in-between those for DDS and DDM.
• The Tgs of the TGDDM thermosets increased in the order PDD < DDM < DDS.
• PDD had the best thermal stability.

A new pyridine-containing diamine, 4,4′-(pyridine-2,6-diylbis(oxy)) dianiline (PDD) was used as curing agent for a tetra-epoxy resin, N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM). The chemical reactivity of the diamine was evaluated using Friedman's method, and compared with traditional diamine curing agents, 4,4′-diaminodiphenylmethane (DDM) and diaminodiphenylsulphone (DDS). PDD was found to be more reactive with the epoxy groups of TGDDM than DDS but less reactive than DDM. The dynamic mechanical thermal analysis showed all materials had Tgs above 250 °C and thermosets formed from TGDDM with blends of PDD with either DDM or DDS had Tgs which increased linearly with composition. Thermogravimetric analysis (TGA) of TGDDM/PDD under argon atmosphere gave a distinctive two-stage decomposition curve compared with the approximately single step observed when TGDDM was cured by the traditional amines. When carried out under air atmosphere, the TGA mass loss occurred in multiple stages and the rate of degradation for the PDD-cured TGDDM was slower than that for DDM- and DDS-cured epoxy resin. This suggests PDD enhances the flame retardancy of the cured thermosets when compared to the more traditional diamine curing systems.

TGA thermograms of cured epoxy in air.Figure optionsDownload as PowerPoint slide