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Specialty Resins

Specialty Resins. A. Brent Strong. Vinyl Esters. Epoxy resins that have been modified so that they can be cured like a polyester The modification is usually a reaction with an acrylic ( acrylic modified epoxy )

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Specialty Resins

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  1. Specialty Resins A. Brent Strong

  2. Vinyl Esters • Epoxy resins that have been modified so that they can be cured like a polyester • The modification is usually a reaction with an acrylic (acrylic modified epoxy) • The modification must substitute a carbon-carbon double bond for the epoxy ring • The name, vinyl ester, comes from old chemistry because the carbon-carbon bond (called a vinyl bond) is on the end and next to a polyester group

  3. Vinyl Ester Structure C ( C C )n C Unsaturated end group C C Unsaturated end group

  4. Vinyl esters − specific molecules H C Epoxy Methyl Acrylic Acid H C Vinyl Ester

  5. Specialty Vinyl Esters ( )n Epoxy Novolac Vinyl Ester Resin Bisphenol-A Epichlorohydrin-based vinyl ester

  6. Vinyl esters − Properties • Almost all properties of vinyl esters (and cost) are intermediate between polyesters and epoxies • Some of the most important properties include: • Water and chemical resistance • Electrical stability • Thermal stability • Toughness • Low volatiles during manufacture • Low shrinkage

  7. Vinyl Esters

  8. Phenolics • Key properties determining most of the applications of phenolics • Very low flammability and low smoke • Very stiff and hard • Very low heat transfer • High thermal stability • Good electrical properties • Excellent adhesion • Resistance to chlorinated solvents • Moderately low price (10-15% above polyesters)

  9. Phenolics − polymerization and crosslinking +…. + + + Loss of Water Vapor Formaldehyde Phenol 3-D Phenolic Network

  10. Phenolics • Applications • Handles for cooking pans • Interiors of public transportation • Glue for laminates (such as plywood) • Electrical switches and other equipment • Molded parts in moderately hot environments (such as near the motor of an automobile) • Billiard balls • Conversion to epoxy or vinyl ester resins • Rocket exit nozzles and carbon-carbon composites (ablation)

  11. Phenolic Flammability Phenolic Flammability Specific Optical Density Flame Spread Index Vinyl Ester Vinyl Ester Epoxy Epoxy FR Polyester FR Polyester Phenolic Phenolic 10 20 40 30 200 300 400 500 600 100 (ASTM E-662 for thermoset composites) (ASTM E-162 for thermoset composites)

  12. NBS Smoke Chamber (Smoldering) 700- 600- 500- 400- 300- 200- 100- Epoxy Polyester Optical Density Phenolic 0 2 4 6 8 10 12 14 16 18 20 22 Time (min)

  13. Rocket exit nozzle Nose Cone Rocket Propellant Rocket Motor Ablative Material Rocket Exit Throat Exit Nozzle 10 oF 500 oF 4000 oF

  14. Phenolics − Processing

  15. Phenolics

  16. Carbon-Carbon Composites • Carbon matrix and carbon fibers • Carbon matrix is made from phenolic resins that have been repeatedly charred and infiltrated with new resin • Very long process (up to 6 months for a part) • Very costly • Extremely high thermal stability • Needs flammability coating (ceramic) at very high temperatures

  17. Production Flow Chart for Carbon-Carbon Composites Polymer or Pitch Binder Carbon Fiber Cured Carbon/Resin Part Carbonization (up to 1000 oC) Impregnation by Gas or Liquid Graphitization 2500-3000 oC Carbon/Carbon Composite 2500-3000 oC

  18. Carbon-Carbon Composites − Thermal Stability 106- 105- 104- 103- 102- 10- 1- Experimental Advanced Metalics Polyimides Carbon-Carbon Exposure Time (sec) Epoxy Composites Ablative Materials (such as phenolics) oF oC 0 1000 2000 3000 4000 -18 538 1093 1650 2204 Temperature

  19. Carbon-Carbon Brake Pads

  20. Polyimides • Very high thermal stability • Excellent solvent resistance • Excellent mechanical properties • Self-extinguishing • Processing • Standard composite techniques • Cures are much longer for polyimides than epoxies or polyesters • Bis-maleimide (BMI) processes like a polyester

  21. Polyimides − specific molecules Crosslinked Polyimide (PMR-15) Crosslink sites Bismaleimide (BMI)

  22. Polyimides

  23. Cyanate esters • Superior dielectric loss properties • Radomes • Skins covering antennae arrays • Low moisture absorption • Low off-gassing • Space applications

  24. Cyanate Esters R=

  25. Cyanate Esters

  26. Polyurethanes • Very common plastic type and just now finding applications in composites • Excellent for resin infusion processes (RIM, RTM, etc.) • Properties can be easily tailored for an application • Varying the amount of aromatic and non-aromatic (aliphatic) content in both polyol and isocyanate (the monomers) • Domains give additional selectivity (Spandex) • Moderate cost (about like epoxies) • Tough and abrasion resistant

  27. Polyurethanes O O = = + C=N N=C OH HO Di-isocyanate Polyol H O O = = N C O N=C HO Urethane linkage

  28. Polyurethane

  29. Silicones • Widely used as a mold release • Can be a contamination that makes bonding difficult with some adhesives • Silicone can be an adhesive itself • Not widely used in composites as a matrix but might be used as a matrix for special applications • Moderate thermal stability (Equivalent to a high-performance epoxy) • Low moisture absorption • Electrical applications • Low flammability • Tooling (flexible)

  30. Silicone Non-breakable insulators

  31. Thank you Brent Strong

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