Chemical and Physical Properties

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
• ?G ?H T?S
• Negative ?G is favorable
• Negative ?H means bonds are forming
• Positive ?S is standard (increasing)
• When does each term dominate to give a negative
  ?G?

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
• Fluoropolymerstightly 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
• Ficks 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 (Al2O33H2O) (heat)
• Aromatics (fuel)
• Silicones (fuel)

Heat
Fuel
Oxygen
26
Flammability Tests

• Vertical and horizontal burn tests

27
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
• 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