1. Odian Book
2-12

2. Common Engineering Thermosets (Not elastomers)
Bismaleimides
Epoxies
Phenol / Formaldehyde
Sheet Molding Compound
Polyurethanes** **Also thermoplastics
Step & Chain Growth
Step & Chain Growth
Step Growth
Chain Growth
Step Growth

3. Epoxy Systems
f = 2 “Tube A”
f = 4 “Tube B”
Mechanism
Network

4. Epoxy Systems Advantageous Properties of epoxies
High chemical and solvent resistance
Outstanding adhesion to many substrates
Good impact resistance
Good electrical properties

5. Epoxy Systems
f = 2 “Tube A”
f = 4 “Tube B”
Network

6. Epoxy Systems
Diglycidal Ether of Bisphenol-A (DGEBA)

7. Epichlorohydrin: Background
Chlorine intensive
- 4 atoms of chlorine/epi
Yields:
- chlorination: 82%
- HOCl and closure: 92%
Byproducts:
- chlorinated organics
Hydraulic load:
- 47 lbs water/lb of epi

8. Epoxy Systems <Mn> ≈ 15,000 – 20,000 g/mol
Viscous liquid to solid

9. Polyurethanes and Polyureas
Thermoplastics
Thermosets

10. Important Starting Materials for Polyurethanes
Diisocyantes
Polymeric Glycols (aka polyols)
MW < 3,000 g/mol
Chain extenders
Catalysts
Trialkyl tin acetate
Dialkyl tin diacetate
Relative rates
30,000x

11. Diisocyanates Diphenylmethane diisocyanate (MDI)
Toluene diisocyanate (TDI)
Dicyclohexylmethane diisocyanate (H-MDI)
Hexamethylene diisocyanate (HDI)
Cycloaliphatics

12. Diisocyanates
Phosgenation

13. Chain Extenders
For urethanes
For ureas

14. Polyurethane Fibers
Excess
Pre-polymer
Chain extenders

15. Sheet Molding Compound

16. Sheet Molding Compound

17. Phenol Formaldehyde Resins
1872 – Invented by Bayer
1907 – First patent and commercial process by Baekeland
Success: First wholly synthetic polymer used commercially

18. Phenol Formaldehyde Resins
Excellent thermal stability
High char yield
Low smoke generation
Low smoke toxicity

19. Base-Catalyzed Phenol-Formaldehyde Resins (Resols)
Excess formaldehyde
Resols cure with heat alone

20. Base-Catalyzed Phenol-Formaldehyde Resins (Resols)

21. Base-Catalyzed Phenol-Formaldehyde Resins (Resols)
Excess formaldehyde
Resols cure with heat alone

23. Base-Catalyzed Phenol-Formaldehyde Resins (Resols)
Cure of resole prepolymer proceeds under neutral or acidic conditions and at elevated temperature.
Crosslinking occurs via the continued formation of methylene links and the formation of dibenzyl ether linkages.
Higher temperatures favor the formation of methylene bridges
Both are condensation reactions and produce water

24. Acid-Catalyzed Phenol-Formaldehyde Resins (Novolacs)

25. Acid-Catalyzed Phenol-Formaldehyde Resins (Novolacs)
Excess phenol
No hydroxy methyl groups
Tg = 40 C
MW = 1 – 3000 g/mol
Require second additive for cure
Hexamethylene tetraamine