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Chemical and Physical Properties

Chemical and Physical Properties. MFG 355. Ultraviolet (UV) Light Degradation. Oxidation. Plastic paint. Chemical resistivity and solubility. Dissolving. None. Reacting. Swelling/softening. Nylon and H 2 O PVC and ketone. PVOH and water. Cellulosics and acids. PE and H 2 O.

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Chemical and Physical Properties

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  1. Chemical and Physical Properties MFG 355

  2. Ultraviolet (UV) Light Degradation

  3. Oxidation • Plastic paint

  4. Chemical resistivity and solubility Dissolving None Reacting Swelling/softening Nylon and H2O PVC and ketone PVOH and water Cellulosics and acids PE and H2O Increasing Chemical Reactivity to Plastic

  5. Chemical Resistivity and Solubility • PS exposed to gasoline

  6. Chemical Nature and Solvent-solute Interactions • Polar effects • Like with like • Steric effects • Crystallinity • Physical property effects on solvent-solute interactions • Solvent size • Swelling

  7. Like to like – polar polymer

  8. Thermodynamics of Solvent Interactions • Equation ΔG = ΔH – TΔS • Negative ΔG is favorable • Negative ΔH means bonds are forming • Positive ΔS is standard (increasing) • When does each term dominate to give a negative ΔG?

  9. Plasticizers • Increase swelling • Randomness • Plasticizers can migrate out

  10. Solvent Welding

  11. Water Repellent • Surface tension must be LOW • Silicones = 24 dyne/cm • PTFE = 19 dyne/cm • PVC = 37 dyne/cm • Water wicking

  12. Corrosion-Resistant • Availability of electrons • Polymers are better than metals • Fluoropolymers—tightly attached • Electron shielded • Chlorine attachment (blocks electron availability)

  13. Coatings • Decorative and protective • Adhesion • Weatherability • Water solubility

  14. Environmental Resistance and Weathering

  15. Environmental Stress Cracking • Hawaii Story • Crosslinked, LLDPE • Banana Plantation • Drawdown

  16. Crazing • Cracks at stress areas

  17. Permeability • Diffusion Coefficient • D = Doe-A/RT • Fick’s Laws of diffusion • J = -D dc/dx • Barrier Properties • dc/dt = D d2c/dx2

  18. Gas (vapor) Permeation • Polar groups (solubility) to solvent or gas • Intermolecular size (distance) • Crosslinking and crystallinity

  19. Electrical Properties • Resistivity (1018 – 10-6) • Dielectric Strength • Arc Resistance • Dielectric Constant • Dissipation Factor (heat up)

  20. Conductive Polymers

  21. Conductive Polymers

  22. Optical Properties • Light Transmission • Clear • Translucent • Opaque • Colorants • Dyes • Pigments • Surface Reflectance

  23. Transparency • Non-crystalline • Index of refraction – low • Total luminous transmittance – high

  24. Plastic Identification • Spectroscopy

  25. Flammability • Self-extinguishing • Halogen effects (oxygen) • Fillers (Al2O3·3H2O) (heat) • Aromatics (fuel) • Silicones (fuel) Heat Fuel Oxygen

  26. Flammability Tests • Vertical and horizontal burn tests

  27. Chamber Sample Sample holder Gas manifold N2 O2 Limiting Oxygen Index

  28. Flammability Tests • Radiant panel • Cone calorimeter

  29. Flexibility • CH2, O are flexible • PE, Polyisoprene, PEO, Siloxanes • Polybutylene terephthalate is more flexible than PET • Pendant groups • Crystallinity – reduces flexibility • Copolymers • Plasticizers (soluble)

  30. Heat Resistance • Stiffening groups along the chain • Phenyl groups • Tggoes up since it takes more heat to move molecules • Strong intermolecular H-Bonding • Crystallinity increases heat resistance

  31. Insulating Polymers • Non-polar is better • Foams • Air is an insulator

  32. Toughness • Backbone Structure • Pendant Groups

  33. Thank You

  34. Flammability Tests • Limiting oxygen index (LOI)

  35. Adhesives • Bonding (chemical) between surfaces is best • Crosslinking agents (ie siloxanes) • Solvent based • Latex adhesives – good flow into crevices for mechanical attachment • Pressure-sensitive – polymer flow (mechanical) • Hot melt – polymer flow • Reactive – low molecular weight to get stronger • End Groups

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