To get a better understanding of the curing process of multi-component ther
mosets differential scanning calorimetric (DSC) and temperature modulated D
SC (TMDSC) measurements were performed during isothermal curing of semi-int
erpenetrating polymer networks (semi-IPNs) with amounts of 10 or 20 wt.% of
linear polymer and of the corresponding pure networks at temperatures betw
een 333 and 393 K. The network component consists of diglycidylether of bis
phenol A (DGEBA) cross-linked with diaminodiphenyl methane (DDM) and the li
near polymer component is polysulfone (PSn) or polyethersulfone (PES). The
curing time dependence of conversion was estimated from time dependent heat
flow measurements during isothermal curing. The curing kinetics is discuss
ed in the framework of different models taking into account the catalytic e
ffects and the influence of diffusion. A lower reaction rate was found in t
he semi-IPNs compared with the pure networks which is related to a decrease
of the diffusion coefficient and/or the density of reacting units due to t
he linear polymer component. The final conversions were found to decrease w
ith an increasing amount of the linear polymer component and with decreasin
g curing temperature which corresponds to less perfect network structures.
The time evolution of the glass transition temperatures during isothermal c
uring was determined by the DSC and TMDSC. At the beginning of the reaction
only one glass transition-indicating a one phase system-was found whereas
at later stages of curing the two phase structure-consisting of a DGEBA/DDM
-rich and a PSn-or PES rich phase-was indicated by two glass transition tem
peratures. (C) 1999 Elsevier Science Ltd. All rights reserved.