Kinetic Analysis and Characterization of Epoxy Resins ... - FedOA

Results and Discussion 114
In the field of microwave cure of thermosetting resins there is still an ongoing debate
about the existence of the specific microwave effect. It is a topic quite controversial
and there have been conflicting results from different authors, a review of the state
of art in this area is presented in a paper of Thostenson et al. [24].
Marand et al. [25], Wei et al. [26] and Jordan et al. [27] have studied the cure
kinetics of epoxy resin systems. In all of these investigations, the reaction rates
were enhanced and times to gelation and vitrification were reduced due to microwave
heating. Marand et al. [25] showed that the molecular structure and curing
agent affect the magnitude of the acceleration in microwave heating. Research
by Wei [26] and co-workers was conducted to determine the effects of microwaves
on the molecular structure, and it was shown that the molecular structure of some
polymers is different when cured using microwaves as compared with conventional
curing.
These results are in contrast to the work of Mijovic and co-workers [28, 29, 30],
who have noticed either no change in the cure kinetics or a retardation of the cure
kinetics, when cured by microwaves. In a more recent work, an in situ method was
used to investigate the crosslinking of several different materials and they assert
that the claims of accelerated cure kinetics are unfounded [31].
The conflicting results by different laboratories indicate the need for additional
work in this area.
3.3.2 Static Operative Conditions
Experiments have been performed on epoxy samples, prepared according to
the procedure, indicated in the section 2.1.3 on page 54, and using the microwave
oven as a static cavity. The PP vessel containing the epoxy mixture has been cut
at a height of about 4-5 cm in order to place it in the centre of the tray on a glass
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