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PROCESSABILITY AND THERMAL CHARACTERIZATION OF ATARD EPOXY RTM RESIN

PROCESSABILITY AND THERMAL CHARACTERIZATION OF ATARD EPOXY RTM RESIN. Peter J. Joyce U.S. Naval Academy Robert F. Boswell and Neil A. Graf Naval Air System Command. Objective. Thermally characterize the selected SI- ZG-5A epoxy resin, formulated by A.T.A.R.D. Laboratories

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PROCESSABILITY AND THERMAL CHARACTERIZATION OF ATARD EPOXY RTM RESIN

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  1. PROCESSABILITY AND THERMAL CHARACTERIZATION OF ATARD EPOXY RTM RESIN Peter J. Joyce U.S. Naval Academy Robert F. Boswell and Neil A. Graf Naval Air System Command

  2. Objective • Thermally characterize the selected SI- ZG-5A epoxy resin, formulated by A.T.A.R.D. Laboratories • resin characterization • cure modeling • SI-ZG-5A selected by AMIPC partner Boeing • Anhydride curing epoxy resin system • Properties similar to leading epoxy systems • Low viscosity • Wide process flexibility ASC 16 Technical Conference

  3. Manufacturer’s Cure Cycle 176°C 6 hrs Temperature (C) 0.54°C/min. 65°C 4 hrs Time (hrs) ASC 16 Technical Conference

  4. Baseline Thermal Analysis • Differential scanning calorimetry (DSC), • TA Instrument Model 2920 • Thermogravimetric analysis (TGA), • Rheometric dynamic analysis (RDA) • Rheometrics Scientific RDA II analyzer • 25-mm aluminum parallel plates with a gap setting of 0.8 mm • Oscillated at 1.0 Hz frequency while a constant 10% strain was applied ASC 16 Technical Conference

  5. Differential Scanning Calorimetry (Manufacturer’s rec. cure cycle 50:50 mix ratio) HR = 350J/g Tg = 207°C ASC 16 Technical Conference

  6. Rheometric Dynamic Anaylsis ASC 16 Technical Conference

  7. Thermogravimetric Analysis • Measured an 8-10 % weight loss. • Reduced to ~6% with degassing. • Due to the volatility of the catalyst. • Part A - < 4% weight loss (25-180°C @ 3°C/min.) • Part B - ~ 98% weight loss ASC 16 Technical Conference

  8. Cure Cycle Modification Eliminating initial 65°C hold exhibited negligible effect. Reducing 176°C from 6 hrs to 3 hrs, little effect. ASC 16 Technical Conference

  9. Varying Mix Ratio ASC 16 Technical Conference

  10. Cure Kinetics Analysis • Variable heating rate method (Duswait, 1974) • Heating rates: • 0.2C/min. • 0.5C/min. • 1.0C/min. • 5.0C/min. • 10.0C/min. • 20.0C/min. ASC 16 Technical Conference

  11. Dynamic DSC(5°C/min.) ASC 16 Technical Conference

  12. HEATING RATE (º C/min) PEAK HEIGHT (º C) ENTHALPY (J/g) 0.2 86.8 272 0.5 100.1 298 1.0 113.5 316 2.0 127 373 5.0 143 393 10.0 158 362 20.0 175 288 Summary Dynamic DSC testing ASC 16 Technical Conference

  13. Cure Kinetics Analysis • To calculate the activation energy, • A plot of the log-heating rate versus the reciprocal of the absolute temperature at a constant conversion will have a slope of 0.457 E/R. • The constant conversion point was taken at the peak exotherm. ASC 16 Technical Conference

  14. Arrhenius Plot E = 64 kJ/mol ASC 16 Technical Conference

  15. Cure Kinetics Analysis • The Arrhenius frequency factor can be calculated from the equation: • A = 7.36 min-1 ASC 16 Technical Conference

  16. Cure Kinetics Analysis • Assuming a first order reaction, the rate constant, k, may be calculated from the equation ASC 16 Technical Conference

  17. Cure Kinetics Analysis ASC 16 Technical Conference

  18. Cure Kinetics Analysis • By utilizing the rate constant, percent conversions were calculated. ASC 16 Technical Conference

  19. Results • DSC • Tg = 207°C, HR = 325-375 J/g (3501-6/474 J/g) • RDA • hmin= 2.3 cP after 79 min. @ 65°C • Gel point ~ 4 hrs • Cure cycle modifications • Initial hold @ 65°C can be eliminated • 2nd hold @ 176°C can be reduced from 6 hrs to 3 hrs • Cure kinetics analysis • Activation Energy, E = 64 kJ/mol • Log frequency factor, A = 7.36 min-1 ASC 16 Technical Conference

  20. Cure Modelling • Lee, Loos, and Springer (1982) • Calculate total heat of reaction, • Calculate the amount of heat, H, released up to time, t ASC 16 Technical Conference

  21. Cure Modelling • The degree of cure, a, is defined as • Calculate the rate of degree of cure, da/dt ASC 16 Technical Conference

  22. Cure Modelling • Curve fit ASC 16 Technical Conference

  23. Cure Modelling Ongoing. . . ASC 16 Technical Conference

  24. Acknowledgements • ONR, Dr. Ignacio Perez • Mr. Roland Cochran • Mr. Stan Ng • Dr. Reza Malek-Madani ASC 16 Technical Conference

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