Type of Document Dissertation Author Sun, Liangfeng Author's Email Address email@example.com URN etd-0412102-135248 Title Thermal Rheological Analysis of Cure Process of Epoxy Prepreg Degree Doctor of Philosophy (Ph.D.) Department Chemical Engineering Advisory Committee
Advisor Name Title Arthur M. Sterling Committee Chair Su-Seng Pang Committee Co-Chair Armando B. Corripio Committee Member Elizabeth J. Podlaha Committee Member Michael A. Stubblefield Committee Member Thomas J. Cleij Committee Member Andrew W. Maverick Dean's Representative Keywords
- cure kinetics
- epoxy prepreg
Date of Defense 2001-11-06 Availability unrestricted AbstractThe cure process of epoxy prepreg used as composite pipe joints was studied by means of differential scanning calorimetry (DSC), Bohlin Rheometer and other techniques. Isothermal DSC measurements were conducted between 110 and 220 oC, at 10 oC intervals. The results show that the complete cure reaction could be achieved at oC. The isothermal cure process was simulated with the four-parameter autocatalytic model. Except in the late stage of cure reaction, the model agrees well with the experimental data, especially at high temperatures. To account for the effect of diffusion on the cure rate, a diffusion factor was introduced into the model. The modified model greatly improved the predicated data at the late stage of cure reaction.
The dynamic cure process was different from the isothermal cure process in that it is composed of two cure reactions. For dynamic cure process, a three-parameter autocatalytic model was used. The parameters in the model were determined by two methods. One was based on Kissinger and Ozawa approach. The whole curing process was modeled with two reactions. Another method was based on Borchardt and Daniels kinetic approach with whole curing process was modeled with one reaction. The fitting results by first and second method agreed well with experimental value in the late and early cure stage, separately.
Rheological properties of epoxy prepreg are closely related to the cure process. With the development of cure reaction, gelation occurs and epoxy prepreg becomes difficult to process. As temperature increases, the gel time decreases. Viscosity profiles were described by different models. Except the first and nth order viscosity models, new viscosity models were proposed The proposed new viscosity models are better than the old models for both isothermal and dynamic cure processes.
To graphically represent the phase changes of the cure process, the isothermal cure diagrams of time-temperature-transformation (TTT) and conversion-temperature-transformation (CTT) are constructed. Each region in TTT and CTT diagrams corresponds with the phase state of the cure process, so the cure mechanism is clearly shown in the diagrams.
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