MANU 3317-Notes 2

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Author:
mackoy
ID:
111724
Filename:
MANU 3317-Notes 2
Updated:
2011-10-24 10:31:25
Tags:
plastics
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Description:
Polymer Chemistry
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  1. hydrocarbon growing chain length (CnH2n+2)
    growing chain length = increasing molecular mass from gas to solid plastics
  2. polymerization
    • • Monomers plus additives and catalysts are added to the reactor
    • • Polymerization (chain formation) is initiated
    • • Chain growth is brought to a predetermined halt
    • • Not all molecules have the same molecular weight (length)
    • • product is a reactor bead (salt like)
  3. Molecular Weight
    • • Proportional to the length of the carbon backbone
    • • As MW increases, MI decreases: longer molecules do not flow around each other as easily when heated to the melting point
    • • Extrusion grades require low MI for melt strength
  4. MWD molecular weight distribution MWD


    narrow MWD = best properties but harder to process

    wide MWD = reduce properties but easier to process
  5. resin grades
    prime resin = resin w/c has been polymerized to rigid published spec (highly priced resins)

    virgin resin = prime resins that have undergone only one heat history before shipping

    • wide spec resin = polymerized but has fallen outside of rigid published spec (cheaper than prime resins)
  6. monomer (mer)
    =basic unit of the hydrocarbon
  7. Elemental Substitution
    • substituting "X" with different element/molecule
  8. copolymers / comonomers
    to complete chemical structure of copolymer, place two structures side by side, connecting the C
  9. copolymer types (arrangements)
  10. terpolymers
    • -3 separate mers combined
    • -also exhibit aternating, random and block structures
    • -ex. ABS
  11. amorphous vs crystalline polymers
    -crystalline = tightly packed orderly chains, therefore structure disrupts light, making themtranslucent (PE) or opaque; TM – melting temperature; when plastics go from rigid to viscous liquid

    -amorphous = loosely packed
    chains, therefore structure does not disrupt light, making them transparent (acrylic); TG – glass transition temperature; when plastics go from rigid to ‘leathery’
  12. melt index MI
    = the amount of thermoplastic extruded out in grams/min under specified temp and pressure

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