Curing studies on the epoxides of carbono‐ and thiocarbonohydrazones

Abstract

SYNOPSISThe curing behavior of a new class of N -N bonded epoxy resins has been analyzed using the simultaneous DTA-TG, dynamic mechanical analysis (DMA) , and thermomechanical analysis (TMA ) techniques. The resin systems, viz, diglycidyl ether of furfuraldehydecarbonohydrazone ( DGFCH ) , diglycidyl ether of furfuraldehydethiocarbonohydrazone (DGFTCH) , and tetraglycidyl ether of vanillinthiocarbonohydrazone (TGVTCH) with the curative, diaminodiphenylmethane (DDM) , taken in stoichiometric amounts have been examined. The curing exotherm could be resolved from the decomposition exotherm qualitatively using DTA-TG analysis. The DMA has been carried out in both the dynamic and isothermal mode to follow the curing process of the systems DGFCH/DDM and TGVTCH/ DDM. The storage modulus (G'), loss modulus (G"), complex viscosity (7) and creep factor (tan 6 ) were measured simultaneously. The crossover point of G' and G", taken as the gelation point in isothermal runs, was determined to obtain time to gelation at that temperature. The isothermal runs a t different temperatures have been used to calculate activation energy of the curing process up to gelation. For the difunctional resin DGFTCH, the activation energy value was found to be 18.7 kcal/mol. The thermomechanical analysis (TMA) has been used to find the glass transition ( Tgo), and melt transition ( T,) temperatures. The cured tetrafunctional TGVTCH /DDM system as expected, has higher T, than those of the two difunctional resin systems.