General Aviation Epoxy Curing And Phase Behavior Studies

A time-temperature-transition (TTT) diagram of a two component epoxies blends system was established by cure kinetic model and gelation model, which can give a full-scale description of the cure process. A chem-rehology model was added to the diagram to form a new TTT diagram with iso-viscosity curves, which was defined as TTT-ηdiagram. A TTT-ηdiagram shows various informations when the system was cured, so it can be used as a tool to produce and optimize the cure procedure. Phase separation behavior was studied to link the micro-structure and macro-properties, which was considered as an assistant to explain the optimized results and method.The cure kinetics was studied by dynamic DSC analysis, and the parameters of the cure reaction were obtained to establish a phenomenological model. The relationship between glass transition temperature (Tg) and cure degree (α) was analyzed with isothermal plus dynamic DSC method based on DiBenedetto equation, a mathematical description of Tg as a function of both time and temperature was suggested. Round disk compression mode DMA was employed to study the gelation at different temperatures, the relationship between gel-time and temperature was obtained. The conversion at gelation was turned out to beα=0.4539, while the temperature at which vitrification line and gelation line transected was found to be Tggel =70.18℃. The TTT diagram was plotted based on the works above, which served as a tool for process optimization in advanced composites manufacture.A rheometer was employed to determine the chem-rehology behavior at different isothermal temperature. A new six-parameters model was founded based on the experimental data. Several iso-viscosity curves was plotted on TTT diagram to form TTT-ηdiagram. A TTT-ηdiagram gives various curing informations and details, so it can be widely used to emit and improve the cure route.The results of SEM determination with different TP content indicated that phase reverse occurred when the TP was added 20~25 phr. As TP content ramping up, the phase structure changed from dispersive TP particle to TP enwrapping epoxy globe as a continuous phase. The spherical particle dimension was did statistic, showing that smaller dimension and little dispersion at higher content. An experimental expression was given to establish the relationship between the TP content and the particle dimension. The upper and lower limits of particle dimension were 1.838μm and 0.925μm, corresponding 19phr and 64phr of TP, the former had determined in experiment while the latter had not approved because of sample preparation handicap.The liqud nitrogen brittle SEM graph of two different stamping processing were analyzed, illuminating pre-cure degree was a key factor to control the phase structure on the interface, that was because that proper viscosity at the cure degree slowed the diffuse velocity forming a shallow inter-phase, and the TP film almost kept their desired position. A typical"Ex-situ"SEM graph was measured, the content of TP firstly keep a higher level and then dramatically descending because the transition layer approach, and the appropriate was needed.Optimized routines of three different composite manufacture processing were claimed from TTT-ηdiagram, also pointing the working area. The optimized"Ex-situ"processing was explained detailed using the results of cure kinetic model, chem-rehology model and SEM graph analysis, pointing out that the key orientation was to finding the proper viscosity or pre-cure degree through correct design of cure schedule on TTT-ηdiagram.