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Proceedings Paper

Microwave heating and the acceleration of polymerization processes
Author(s): Fabrizio Parodi
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Paper Abstract

Microwave power irradiation of dielectrics is nowadays well recognized and extensively used as an exceptionally efficient and versatile heating technique. Besides this, it revealed since the early 1980s an unexpected, and still far from being elucidated, capacity of causing reaction and yield enhancements in a great variety of chemical processes. These phenomena are currently referred to as specific or nonthermal effects of microwaves. An overview of them and their interpretations given to date in achievements in the microwave processing of slow-curing thermosetting resins is also given. Tailored, quaternary cyanoalkoxyalkyl ammonium halide catalysts, further emphasizing the microwave enhancements of curing kinetics of isocyanate/epoxy and epoxy/anhydride resin systems, are here presented. Their catalytic efficiency under microwave irradiation, microwave heatability, and dielectric properties are discussed and interpreted by the aid of the result of semi-empirical quantum mechanics calculations and molecule dynamics simulations in vacuo. An ion-hopping conduction mechanism has been recognized as the dominant source of the microwave absorption capacities of these catalysts. Dipolar relaxation losses by their strongly dipolar cations, viceversa, would preferably be responsible for the peculiar catalytic effects displayed under microwave heating. This would occur through a well-focused, molecular microwave overheating of intermediate reactive anionic groupings, they could indirectly cause as the nearest neighbors of such negatively-charged molecular sites.

Paper Details

Date Published: 14 December 1999
PDF: 16 pages
Proc. SPIE 4017, Polymers and Liquid Crystals, (14 December 1999); doi: 10.1117/12.373685
Show Author Affiliations
Fabrizio Parodi, Saiag SpA (Italy)

Published in SPIE Proceedings Vol. 4017:
Polymers and Liquid Crystals
Andrzej Wlochowicz, Editor(s)

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