IT 111 Plastics

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IT 111 Plastics

• Lecture 6
• Thomas E. Scott

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• Famous movie line
• The Graduate Dustin Hoffman, recently a
  graduate of THE OHIO STATE UNIVERSITY is told by
  Mr. Robinson (Mrs. Robinsons husband) the field
  that young Dustin should pursue.

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• PLASTICS

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Plastic Materials(often called resins)

• Pliable Material
• Capable of being shaped or formed by Heat and/or
  Pressure

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Plastics

• Typically organic Came from living things
  coal products, oil products
• Typically hydrocarbon Chemical combination of
  hydrogen and carbon
• Synthetic (most) man made

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Plastic

• Made up of polymers long chains of repeating
  groups of molecules
• Poly (Greek) many
• Meros (Greek) - parts
• Atoms include Hydrogen, Carbon, Fluorine
• Each group is called a monomer
• Polymerization combining monomers into polymers

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Types of Plastics

• Thermoplastics (e.g., polyethylene, polystyrene)
• Can be melted and formed again and again
• Thermosets (e.g., polyurethane, epoxy)
• Once formed, are destroyed rather than melted by
  heating.
• Elastomers Flexible material (stretching)
• Resin - Organic compound
• The base making up the plastic
• Plastic often includes fillers that change
  properties

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Plastics

• Plastics are NOT biodegradable
• Recycling of plastics, especially thermoplastics,
  has become an important industry.
• Major industrial uses
• Cars, buildings, packaging, textiles, paints,
  adhesives, pipes, electrical and electronic
  components, prostheses, toys, brushes, and
  furniture, and about everything else.

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Common Plastics

• Polyethylene terephthalate, or PET
• Used, e.g., in beverage bottles
• Poly Vinyl Chloride, PVC (hoses)
• Styrofoam, foamed polystyrene
• Insulated food containers
• Lucite
• Shatterproof windows

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Major Types

• Thermoplastic
• Materials that become soft when heated and solid
  when cooled to room temperature.
• This can be repeated many times.

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Major Types

• Thermosetting
• Materials that become solid when heated may be
  heated and formed ONE time.

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Heat Reaction

• Thermoplastic
• Similar to candle wax.
• Can be heated and softened many times.
• Polyethylene, acrylic, nylon, polystyrene.

• Thermoset
• Similar to concrete, jello.
• Cannot be re-softened.
• Chemically cures once.
• Epoxy, silicone, phenolic.

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Light Penetration

• Transparent Light passes through clearly. May
  be colored
• Translucent Light passes through, but not clear
• Opaque Light does not pass through

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Elastomers

• Repeated stretching
• Neoprene closest like rubber
• Latex
• Buna rubber - butadiene

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Polymer Structure

• Crystalline
• Amorphous

• Non-transparent in solid state
• Good chemical resistance
• Sharp melting point
• Key to processes

• Examples
• Polyethylene
• Nylon
• Polypropylene

• Examples
• Polystyrene
• Acrylic

• Clarity - Transparent
• Chemical attack
• Wide softening range

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Polymer Structure

• Crystalline
• Crystal when solid
• Amorphous when heated
• Crystal when solidified
• Eample uncooked spaghetti
• Examples
• Polyethylene
• Polyester
• Nylon

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Polymer Structure

• Amorphous
• Polycarbonate
• ABS
• PVC

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Plastic - Advantages

• Chemical resistant
• Good strength/weight ratio
• Easy to process
• Capable of foaming
• Many colors
• Can be sterilized
• Light transmission capability

• Thermal insulating
• Light weight
• Variety of forms available
• Flexible or rigid
• Electrical insulating
• Human tissue acceptance

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Plastic - Disadvantages

• Dimensional Instability
• Fragility
• Will not decompose
• Processing Fumes
• Cost
• Material and processes
• Fumes when burned

• Thermal range
• Flammability
• Chemical attack
• Difficult to repair
• Absorb Moisture

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Addition polymerization

• See Figure 5-3 of Horath
• Monomer to polymer chain
• Ethan gas to Ethylene momomer
• Chaining using heat and pressure

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Chained Polymers

• Directional strength anisotropy
• Additives to aid properties (Fillers, reinforcing
  agents, plasticizers, stabilizers)
• Glass fibers
• Cloth fibers
• Wood flour
• Mica

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Examples of Plastics

• ABS Auto fenders
• Acrylic Plexiglass
• Epoxies Cements
• Fluorocarbon Teflon
• Melamine Table ware
• Phenolic Detergent bottles

• Polyamide Rope
• Polycarbonite Safety glass
• Polyethylene Bottle caps
• Polystyrene Styrofoam
• Vinyl Seat covers

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Extrusion
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Injection Molding
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Blow Molding
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Compression Molding