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Evaluation and design of polymer systems for enhanced microwave heating
Microwave heating of different polymer systems (epoxy-amine.
polypropylene-iron, carbon-black-filled perfiuoroelastomer) was evaluated using
dielectric testing and monitored processing in a multimode microwave cavity.
Dielectric measurements were made using a field perturbation technique and a
transmission/reflection technique. The electric loss factor of the epoxy system
continuously decreased during cure. Results for the microwave heating of the
polypropylene-iron composites show that heating is enhanced with increased iron
concentration and smaller iron particle size, although the penetration depth of the
microwaves Is decreased, especially after the onset of percolation. A novel solidstate
processing technique for thermoset systems was also evaluated. By milling
the reactants to a fine powder, and mixing them completely, the extent to which
diffusion limited the process was significantly reduced: increased milling resulted
in higher activation energies. In addition to the inherent advantages of solid-state
processing. it Is possible that processing times for solid-state processing could
approach processing times for traditional melt processing.