Mechanistic modeling, reaction kinetics, and on-line remote monitoring of epoxy resin cure

Accurate kinetic models and reliable on-line monitoring techniques are essential for intelligent processing of epoxy resin-based polymers and polymer matrix composites. Fundamental mechanistic kinetic models and in situ remote monitoring of the epoxy resin cure reactions have been systematically investigated in this dissertation.; In Part I, epoxy resin/amine cure mechanisms and fundamental cure kinetics were studied via near-infrared (NIR) spectroscopy. NIR spectroscopy was established as a quantitative technique for characterizing the epoxy resin/amine cure reactions. The advantages of NIR spectroscopy over mid-infrared (MIR) spectroscopy for monitoring the epoxy resin/amine cure were delineated. Several epoxy resin/aromatic amine model compound systems were studied including monofunctional epoxide/monofunctional aromatic amine, monofunctional epoxide/multifunctional aromatic amine, and multifunctional epoxide/monofunctional aromatic amine. It was found that the mechanisms for the epoxy resin/aromatic amine cure reactions consist of three steps with the second step, the formation of termolecular intermediates, being the rate determining step. The reaction rate and their associated Arrhenius relations were determined from the mechanistic kinetic equations. Some disputed issues were addressed in lieu of the experimental evidences, which include substitution effect, conditions for etherification reaction, and the importance of the non-catalyzed reaction path in modeling the kinetics of the cure process.; Part II concerns the development of reliable on-line remote process monitoring methods for the epoxy resin/amine cure reactions. Both NIR attenuated total reflection (ATR) and NIR external reflectance techniques were studied as possible tools for the non-destructive remote sensing of the cure reactions. Different epoxy resin/amine cure systems were monitored successfully in situ by these two techniques. The concept of using ATR contact sensors avoids the fiber embedding procedure generally adopted; thus the optic fiber sensors would not be retained within the composite laminate. External reflection sensors can be operated in both reflection-absorption or diffuse reflection modes, depending on the nature of sample. Direct physical contact of the sensing probe with the sample is not required.; Part III presents significant conclusions reached and future work recommended.