05 chemical and physical.ppt chemical and physical MFG355 Insulating Polymers

chemical and physical MFG355
Insulating Polymers

1. Chemical and Physical
Properties
MFG 355

2. Ultraviolet (UV) Light Degradation

3. Oxidation
•Plastic paint

4. Chemical resistivity and solubility
None Swelling/softening
Dissolving Reacting
PE and H
2O
Nylon and H
2
O
PVC and ketone
PVOH and water Cellulosics
and acids
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 = D
oe
-A/RT
•Fick’s Laws of diffusion
J = -D dc/dx
•Barrier Properties
 dc/dt = D d
2
c/dx
2

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

19. Electrical Properties
•Resistivity (10
18
– 10
-6
)
•Dielectric Strength
•Arc Resistance
•Dielectric Constant
•Dissipation Factor (heat up)

20. Conductive Polymers
H
H
H
H
C
n
C C C( )
H
H
H
H
C
n
C C C( )

21. Conductive Polymers
Material
Conductivity (Ohm-cm)
-1
Silver 6.25 x 10
5
Copper 5.85 x 10
5
Gold 4.44 x 10
5
Polyacetylene (doped) .6.0 x 10
4
- 1.5 x 10
5
Steel .6.0 x 10
4
Silicon 1.56 x 10
-3
Carbon, graphite .1.0 x 10
-3
Polyacetylene (unmodified) .1.0 x 10
-11
to .1.0 x 10
-15
Carbon, diamond .1.0 x 10
-14
Alumina ceramic .1.0 x 10
-15
Epoxy .1.0 x 10
-15
Polyethylene, medium density .1.0 x 10
-16
Teflon .1.0 x 10
-18

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 (Al
2
O
3
·3H
2
O) (heat)
–Aromatics (fuel)
–Silicones (fuel)
Fuel Oxygen
Heat

26. Flammability Tests
•Vertical
and
horizontal
burn tests

27. Limiting Oxygen Index

Chamber
Sample
Sample holder
Gas manifold
N
2O
2

28. Flammability Tests
•Radiant panel
•Cone calorimeter

29. Flexibility
•CH
2, 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
–Tg

goes 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