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. Sept. 12, 2001ASC 16 Technical Conference 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

3. Sept. 12, 2001ASC 16 Technical Conference Manufacturer’s Cure Cycle Time (hrs) Temperature (C) 176°C 65°C 4 hrs 6 hrs 0.54°C/min.

4. Sept. 12, 2001ASC 16 Technical Conference 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

5. Sept. 12, 2001ASC 16 Technical Conference Differential Scanning Calorimetry (Manufacturer’s rec. cure cycle 50:50 mix ratio) T g = 207°C H R = 350J/g

6. Sept. 12, 2001ASC 16 Technical Conference Rheometric Dynamic Anaylsis

7. Sept. 12, 2001ASC 16 Technical Conference 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

8. Sept. 12, 2001ASC 16 Technical Conference Cure Cycle Modification Eliminating initial 65°C hold exhibited negligible effect. Reducing 176°C from 6 hrs to 3 hrs, little effect.

9. Sept. 12, 2001ASC 16 Technical Conference Varying Mix Ratio

10. Sept. 12, 2001ASC 16 Technical Conference 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.

11. Sept. 12, 2001ASC 16 Technical Conference Dynamic DSC (5°C/min.)

12. Sept. 12, 2001ASC 16 Technical Conference Summary Dynamic DSC testing HEATING RATE (º C/min) PEAK HEIGHT (º C) ENTHALPY (J/g) 0.286.8272 0.5100.1298 1.0113.5316 2.0127373 5.0143393 10.0158362 20.0175288

13. Sept. 12, 2001ASC 16 Technical Conference 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.

14. Sept. 12, 2001ASC 16 Technical Conference Arrhenius Plot E = 64 kJ/mol

15. Sept. 12, 2001ASC 16 Technical Conference Cure Kinetics Analysis  The Arrhenius frequency factor can be calculated from the equation:  A = 7.36 min -1

16. Sept. 12, 2001ASC 16 Technical Conference Cure Kinetics Analysis  Assuming a first order reaction, the rate constant, k, may be calculated from the equation

17. Sept. 12, 2001ASC 16 Technical Conference Cure Kinetics Analysis

18. Sept. 12, 2001ASC 16 Technical Conference Cure Kinetics Analysis  By utilizing the rate constant, percent conversions were calculated.

19. Sept. 12, 2001ASC 16 Technical Conference Results  DSC  T g = 207°C, H R = 325-375 J/g (3501-6/474 J/g)  RDA   min = 2.3 cP after 79 min. @ 65°C  Gel point ~ 4 hrs  Cure cycle modifications  Initial hold @ 65°C can be eliminated  2 nd 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

20. Sept. 12, 2001ASC 16 Technical Conference Cure Modelling  Lee, Loos, and Springer (1982)  Calculate total heat of reaction,  Calculate the amount of heat, H, released up to time, t

21. Sept. 12, 2001ASC 16 Technical Conference Cure Modelling  The degree of cure, , is defined as  Calculate the rate of degree of cure, d  /dt

22. Sept. 12, 2001ASC 16 Technical Conference Cure Modelling  Curve fit

23. Sept. 12, 2001ASC 16 Technical Conference Cure Modelling Ongoing...

24. Sept. 12, 2001ASC 16 Technical Conference Acknowledgements  ONR, Dr. Ignacio Perez  Mr. Roland Cochran  Mr. Stan Ng  Dr. Reza Malek-Madani