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Chemical and Physical Properties PowerPoint PPT Presentation


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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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Chemical and physical properties l.jpg

Chemical and Physical Properties

MFG 355


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Ultraviolet (UV) Light Degradation


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Oxidation

  • Plastic paint


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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


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Chemical Resistivity and Solubility

  • PS exposed to gasoline


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Chemical Nature and Solvent-solute Interactions

  • Polar effects

    • Like with like

  • Steric effects

    • Crystallinity

  • Physical property effects on solvent-solute interactions

    • Solvent size

    • Swelling


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Like to like – polar polymer


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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?


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Plasticizers

  • Increase swelling

    • Randomness

  • Plasticizers can migrate out


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Solvent Welding


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Water Repellent

  • Surface tension must be LOW

    • Silicones = 24 dyne/cm

    • PTFE = 19 dyne/cm

    • PVC = 37 dyne/cm

  • Water wicking


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Corrosion-Resistant

  • Availability of electrons

  • Polymers are better than metals

  • Fluoropolymers—tightly attached

    • Electron shielded

  • Chlorine attachment (blocks electron availability)


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Coatings

  • Decorative and protective

    • Adhesion

    • Weatherability

    • Water solubility


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Environmental Resistance and Weathering


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Environmental Stress Cracking

  • Hawaii Story

    • Crosslinked, LLDPE

  • Banana Plantation

    • Drawdown


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Crazing

  • Cracks at stress areas


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Permeability

  • Diffusion Coefficient

    • D = Doe-A/RT

  • Fick’s Laws of diffusion

    • J = -D dc/dx

  • Barrier Properties

    • dc/dt = D d2c/dx2


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Gas (vapor) Permeation

  • Polar groups (solubility) to solvent or gas

  • Intermolecular size (distance)

  • Crosslinking and crystallinity


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Electrical Properties

  • Resistivity (1018 – 10-6)

  • Dielectric Strength

  • Arc Resistance

  • Dielectric Constant

  • Dissipation Factor (heat up)


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Conductive Polymers


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Conductive Polymers


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Optical Properties

  • Light Transmission

    • Clear

    • Translucent

    • Opaque

  • Colorants

    • Dyes

    • Pigments

  • Surface Reflectance


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Transparency

  • Non-crystalline

  • Index of refraction – low

  • Total luminous transmittance – high


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Plastic Identification

  • Spectroscopy


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Flammability

  • Self-extinguishing

    • Halogen effects (oxygen)

    • Fillers (Al2O3·3H2O) (heat)

    • Aromatics (fuel)

    • Silicones (fuel)

Heat

Fuel

Oxygen


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Flammability Tests

  • Vertical and horizontal burn tests


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Chamber

Sample

Sample holder

Gas manifold

N2

O2

Limiting Oxygen Index


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Flammability Tests

  • Radiant panel

  • Cone calorimeter


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Flexibility

  • CH2, O are flexible

    • PE, Polyisoprene, PEO, Siloxanes

  • Polybutylene terephthalate is more flexible than PET

  • Pendant groups

  • Crystallinity – reduces flexibility

  • Copolymers

  • Plasticizers (soluble)


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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


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Insulating Polymers

  • Non-polar is better

  • Foams

    • Air is an insulator


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Toughness

  • Backbone Structure

  • Pendant Groups


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Thank You


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Flammability Tests

  • Limiting oxygen index (LOI)


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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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