Electron-spin-resonance investigations and surface characterization of TGDDM-DDS epoxy and T-300 graphite fiber exposed to ionizing radiation

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:5027330

Seo, K S

In an effort to elucidate the changes in molecular structural and mechanical properties of epoxy/graphite fiber composites upon exposure to ionizing radiation in a simulated space environment, spectroscopic and surface properties of tetraglycidyl-4,4'-diamino diphenyl methane (TGDDM) cured with diamino diphenyl sulfone (DDS) and T-300 graphite fiber were investigated following exposure to gamma radiation and electrons. The system was studied using electron spin resonance (ESR) spectroscopy, infrared absorption spectroscopy, contact angle measurements, and electron spectroscopy for chemical analysis. Two kinetically-distinguishable (fast-decaying and slow-decaying) radical species are produced in TGDDM-DDS epoxy upon irradiation, and their decay behavior is strongly affected by the crosslinking density distribution in the cured epoxy. The fraction of fast-decaying radicals increases with increasing decay temperature while the decay rate constant of slow-decaying radicals does not depend on the decay temperature. Unirradiated T-300 graphite fibers have a large concentration of free radicals (10/sup 19/-10/sup 20/ spins/g), thus overshadow any change in ESR spectra of irradiated composites. The surface energy of epoxy increases monotonically with radiation dose up to 1000 Mrad and leveled off. This increase in the surface energy is mainly due to the increased concentration of polar groups, mostly carbonyl groups as confirmed by absorption at 1720 cm/sup -1/. The increase in the surface energy was accelerated by the presence of oxygen. The surface energy of graphite fiber changes slightly with radiation dose. Both the interaction of free radicals at the graphite fiber/epoxy interface and the increase in the surface energy would be possible factors which increase the interfacial strength of the composite after irradiation.

• Research Organization: North Carolina State Univ., Raleigh (USA)
• OSTI ID: 5027330
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360406* -- Materials-- Polymers & Plastics-- Radiation Effects-- (-1987)
360605 -- Materials-- Radiation Effects
CARBON
CHEMICAL RADIATION EFFECTS
CHEMISTRY
ELECTROMAGNETIC RADIATION
ELECTRON SPIN RESONANCE
ELECTRONS
ELEMENTAL MINERALS
ELEMENTARY PARTICLES
ELEMENTS
EPOXIDES
FERMIONS
FIBERS
GAMMA RADIATION
GRAPHITE
IONIZING RADIATIONS
LEPTONS
MAGNETIC RESONANCE
MINERALS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
POLYMERS
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RESONANCE