Cure and Water Monitoring in Selected Polymers

摘要

The objective of the research under this contract was to develop in-situmonitoring technique for cure and water in selected polymers. The techniques explored are intrinsic fluorescence, phosphorescence and UV reflection The polymers studied are epoxy, polyimide and vinyl polymers (MMA and styrene). These techniques were also used to probe fiber/resin interphase. The intrinsic fluorescence spectral shift (25 nm) due to the cure of epoxy with the main curing agent, p,p'-diamino diphenyl sulfone (DDS) was related to the extent of cure and implemented by fiber-optic fluorimeter for in-situ cure characterization of epoxy/graphite composites. The phosphorescence lifetime due to DDS was found to be useful to measure the extent of cure in the prepregs. The external UV reflection technique was developed as an intrinsic cure monitoring technique for polymers such as polyimides exhibiting weak fluorescence. A bifurcated multifiber probe for UV reflection technique has been implemented for in-situ imidization studies. Polymerization of styrene and methyl methacrylate (MMA) were successfully monitored by UV and in-situ fluorescence techniques via fiber-optics. For water-uptake monitoring, the fluorescence intensity of DDS which shows sensitive decrease was correlated to the water-uptake measured by gravimetry in neat epoxy as well as in epoxy composites. The characterization of cure reactions in epoxy/fiber interphase has been probed by evanescent fluorescence due to an extrinsic cure sensor, p,p'-diamino azobenzene by using sapphire fiber due to its high refractive index of 1.78 in comparison to that of epoxy of 1.61.