Investigation of microwave irradiation as an energy source in polymerization reactions | Posted on:2000-09-20 | Degree:Ph.D | Type:Dissertation | University:The University of Connecticut | Candidate:Fang, Xiaomei | Full Text:PDF | GTID:1461390014464115 | Subject:Chemistry | Abstract/Summary: | | Variable frequency microwaves were investigated as an energy source to cure unidirectional carbon fiber reinforced phenylethynyl-terminated polyimide composites, and to synthesize the poly(-caprolactam), poly(-caprolactone) and copoly(amide-ester) via ring opening polmerization.; The mechanism of the thermal and microwave cure reactions of a phenylethynyl-terminated imide model compound, 3,4′-bis[(4-phenylethynyl)phthalimido]diphenyl ether (PEPA-3,4′-ODA) and a phenylethynyl-terminated imide oligomer PETI-5 (Mn ∼ 5000 g/mol) was studied by kinetics and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. Both the model compound and PETI-5 exhibited much lower activation energies and higher rate constants by the microwave cure process than by the thermal cure process. Solid-state 13C-NMR studies revealed that the major cure reaction in both the model compound and PETI-5 resin is an ethynyl to ethynyl addition reaction, with a minor reaction to further form carbon-carbon single bonded structures.; Microwave energy was successfully applied to fabricate carbon fiber reinforced phenylethynyl-terminated polyimide composites, PETI-5/IM7, with higher glass transition temperatures (by 11° to 16°C) and enhanced mechanical properties at both room temperature and 177°C and in one-half the time, compared to the standard thermal process. Equivalent physical and mechanical properties were obtained from microwave synthesized nylon-6 and poly(-caprolactone) in reduced time relative to the commercially produced thermal products. Anionic copolymerization of -caprolactam with -caprolactone via microwave irradiation produced poly(-caprolactam-co--caprolactone) with higher yield, higher amide content, and higher Tg's relative to the thermally produced copolymer. | Keywords/Search Tags: | Poly, Microwave, Energy, Cure, Higher, Reaction, Phenylethynyl-terminated | | Related items |
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