1. Growing More Ductile Epoxies: An Essential Work of Fracture Study Frederick A. Pfaff Stonhard A Division of the StonCor Group, Inc.

2. Twofold Goal of This Study Feasibility of Using Difunctional Amines as Chain Extenders in Amine-Cured Epoxy Formulations Feasibility of Using Difunctional Amines as Chain Extenders in Amine-Cured Epoxy Formulations Suitability of the Method of Essential Work to Determine Fracture Toughness of Thermoset Epoxy Compositions Suitability of the Method of Essential Work to Determine Fracture Toughness of Thermoset Epoxy Compositions

3. OUTLINE Amine-Cured Epoxy Formulation Considerations Amine-Cured Epoxy Formulation Considerations Fracture Toughness Test Methods Fracture Toughness Test Methods Experimental Details Experimental Details Tensile Test Results Tensile Test Results Fracture Toughness Results Fracture Toughness Results Solvent Uptake Solvent Uptake Conclusions Conclusions

4. Formulation Perspectives Amine – Cured Epoxies

5. Formulation Trends Lower VOC  Lower MWt. Resins Lower VOC  Lower MWt. Resins Liquid Epoxy Liquid Epoxy Amidoamine, Aliphatic & Cycloaliphatic Amine Hardeners Amidoamine, Aliphatic & Cycloaliphatic Amine Hardeners Diluents & Plasticizers Diluents & Plasticizers High Crosslink Density High Crosslink Density Tend to be Relatively Brittle Tend to be Relatively Brittle

6. Cure & Glass Transition Temperature (T g ) Two Components – Epoxy & Amine Two Components – Epoxy & Amine Cures to Solid Crosslinked Mass Cures to Solid Crosslinked Mass T g of Reacting Mixture Increases as Cure Proceeds T g of Reacting Mixture Increases as Cure Proceeds T g ≤ Cure Temperature + 30 º C T g ≤ Cure Temperature + 30 º C Vitrification Effect Vitrification Effect Properties of Epoxies Used Within Approx. 30 º C of T g Are Not Completely Glass-like Properties of Epoxies Used Within Approx. 30 º C of T g Are Not Completely Glass-like

7. Managing Formula T g Most Unmodified Amines Cure Liquid Epoxy To a High T g Most Unmodified Amines Cure Liquid Epoxy To a High T g Ultimate T g 80 - 150ºC or Greater Ultimate T g 80 - 150ºC or Greater Will Not Cure to Completion Under Normal Ambient Conditions Will Not Cure to Completion Under Normal Ambient Conditions T g Reduced by Inclusion of Plasticizing Modifiers T g Reduced by Inclusion of Plasticizing Modifiers Term Includes All Non-Fugitive Diluents & Plasticizers Term Includes All Non-Fugitive Diluents & Plasticizers

8. Plasticizing Modifiers Reactive Reactive Mono-epoxide Diluents Mono-epoxide Diluents Stoichiometric Excess Stoichiometric Excess Non-Reactive Non-Reactive Benzyl Alcohol, Ester & Hydrocarbon Plasticizers Benzyl Alcohol, Ester & Hydrocarbon Plasticizers Lower Tg Lower Tg Reduce Viscosity Reduce Viscosity Important Impact on Cured Properties Important Impact on Cured Properties Proper Choice Critical to Performance!

9. Side-Effects in Cured State Stoichiometric Excess & Monofunctional Diluents Stoichiometric Excess & Monofunctional Diluents Dangling Chain Ends Dangling Chain Ends Non-Reactive Plasticizers Non-Reactive Plasticizers Not Chemically Bound − Extractable Not Chemically Bound − Extractable Plasticizer Migration Plasticizer Migration Sometimes Count as VOC Sometimes Count as VOC Can Result in Lower Strength & Poorer Chemical Resistance Can Result in Lower Strength & Poorer Chemical Resistance A Fresh Approach Could Be Helpful

10. Chain Extension Reactants With Functionality = 2 Reactants With Functionality = 2 Amines with Two Active Hydrogens Would be Chain Extenders Amines with Two Active Hydrogens Would be Chain Extenders Mono-Primary Amines Mono-Primary Amines Di-Secondary Amines Di-Secondary Amines “Grow” Higher MWt. Simultaneous With Crosslinking Reaction “Grow” Higher MWt. Simultaneous With Crosslinking Reaction

11. Goals Partial Replacement for Traditional Plasticizing Modifiers Partial Replacement for Traditional Plasticizing Modifiers Viscosity & T g Reduction Viscosity & T g Reduction Better Cured Property Balance Better Cured Property Balance Reduced Brittleness Reduced Brittleness Minimal Negative Effect on Other Mechanical Properties & Chemical Resistance Minimal Negative Effect on Other Mechanical Properties & Chemical Resistance

12. Fracture Toughness Testing

13. Need For a New Method Linear Elastic Fracture Method for Brittle Break Materials Linear Elastic Fracture Method for Brittle Break Materials Example: ASTM D5045 Example: ASTM D5045 ASTM E1820 for Ductile Materials ASTM E1820 for Ductile Materials J-Integral Method J-Integral Method Successive Loadings & Unloadings Successive Loadings & Unloadings Careful Measurement of Crack Length After Each Loading Cycle Careful Measurement of Crack Length After Each Loading Cycle Inconvenient For Most Industrial Coatings Labs

14. Method of Essential Work First Proposed by Cotterell & Reddel First Proposed by Cotterell & Reddel Basically a Tensile Test on Notched Specimens Basically a Tensile Test on Notched Specimens LigamentNotches “DENT” Configuration

15. Method of Essential Work, cont’d. W f = W e + W i (1) w f = W f / l*t = w e + βw i *l (2)

16. EWF Constraints Dimensional Requirements Dimensional Requirements Full Yielding Before Failure Full Yielding Before Failure Self-Similarity of Load Curves at All Ligament Lengths Self-Similarity of Load Curves at All Ligament Lengths Plastic Zone Constraint Plastic Zone Constraint l < 2r p

17. Experimental Details

18. Primary Materials IPDABzOH Bis A Epoxy

19. Epoxy Materials n Bisphenol A Epoxy C13 Epoxy Diluent

20. Amine Chain Extenders N-Dodecyl Amine N-Amyl Amine N, N’-Dimethyl Ethylene Diamine

21. Chain Extension Scenarios

22. Experimental Formulations IDDESCRIPTION TgTgTgTgSG MOD 1 Control651.137 MOD 2 30% Excess Epoxy 391.192 MOD 3 Hi BzOH 281.116 MOD 4 Mono-Epoxide471.135 MOD 5 Hi MWt Liquid Epoxy 641.14 MOD 6 n-Amyl Amine 561.133 MOD 7 DM-EDA481.195 MOD 8 n-Dodecyl Amine 531.139

23. Parallel Glass Plate Casting Arrangement

24. Solvent Uptake Testing Weight Change After 6 Hour RT Immersion Weight Change After 6 Hour RT Immersion Weight Change After 24 Hour 90ºC Immersion Weight Change After 24 Hour 90ºC Immersion Weight Change After Dry Bake Weight Change After Dry Bake Final Weight Change Final Weight Change %Δm f = 100 * [(m w – min(m i, m d ) ) / m i ]

25. Tensile Test Results

26. Tensile Load Curves

27. Tensile Yield Stress vs. T g

28. Essential Work of Fracture Test Results

29. EWF Median Load Curves

30. MOD 1 EWF Results

31. MOD 2 EWF Results

32. MOD 3 EWF Results

33. MOD 4 EWF Results

34. MOD 5 EWF Results

35. MOD 6 EWF Results

36. MOD 7 EWF Results

37. MOD 8 EWF Results

38. EWF vs. Yield Stress

39. EWF vs. T g

40. Mechanical Properties Summary Chain Extension Via Difunctional Amines Provides: Chain Extension Via Difunctional Amines Provides: Reduction of Viscosity & T g with Less Plasticizer Reduction of Viscosity & T g with Less Plasticizer Tensile Strength Comparable to Strength Obtained With Higher MWT. Epoxy Tensile Strength Comparable to Strength Obtained With Higher MWT. Epoxy Superior to Mono-Epoxide Modification Superior to Mono-Epoxide Modification Superior Balance of Tensile Strength & Fracture Toughness Combined with T g Reduction Superior Balance of Tensile Strength & Fracture Toughness Combined with T g Reduction

41. Solvent Uptake Test Results

42. Solvent Exposure % Weight Changes

43. Conclusions Method of Essential Work Appears to be Applicable to Ductile Thermoset Epoxy Compositions Method of Essential Work Appears to be Applicable to Ductile Thermoset Epoxy Compositions Plastic Zone Requirement Not Met Plastic Zone Requirement Not Met More Work Needed More Work Needed Chain Extension Via Difunctional Amine Insertion Provides: Chain Extension Via Difunctional Amine Insertion Provides: Superior Balance of Mechanical Properties Superior Balance of Mechanical Properties Little to No Adverse Effect on Solvent Uptake Little to No Adverse Effect on Solvent Uptake

44. Conclusions Solvent Uptake Excessive With Large Stoichiometric Excess of Epoxy Solvent Uptake Excessive With Large Stoichiometric Excess of Epoxy Best Overall Properties Obtained From Non- Pendant Chain Extender, DM-EDA Best Overall Properties Obtained From Non- Pendant Chain Extender, DM-EDA