Polyethylene Monomer: Ethylene High Density Polyethylene (HDPE) - - PowerPoint PPT Presentation

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Polyethylene Monomer: Ethylene High Density Polyethylene (HDPE) - - PowerPoint PPT Presentation

Mar 22, 2024 339 likes •530 views

Polyethylene Monomer: Ethylene High Density Polyethylene (HDPE) Low Density Polyethylene (LDPE) Linear Low Density Polyethylene (LLDPE) 1 Low Density Polyethylene (LDPE) High Density Polyethylene (HDPE ) High degree of

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SLIDE 1

Polyethylene

Monomer: Ethylene

  • High Density Polyethylene (HDPE)
  • Low Density Polyethylene (LDPE)
  • Linear Low Density Polyethylene (LLDPE)

1

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SLIDE 2
  • Low Density Polyethylene (LDPE)
  • High degree of short and long chain

branching

  • Density - 0.910–0.940 g/cm3
  • Lower tensile strength and increased

ductility

  • Free radical polymerization
  • Plastic bags and film wrap
  • High Density Polyethylene (HDPE)
  • Low degrees of branching (essentially

linear)

  • Density > 0.940 g/cm3
  • High tensile strength
  • Various catalysts (ZN, Metallocene)
  • Milk jugs, detergent bottles, garbage

containers and water pipes

Long chain branching (HDPE) Short chain branching (LLDPE) Hyperbranched (LDPE)

2

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SLIDE 3

Timeline of Polyethylene

  • 1898
  • Synthesized by accident while heating diazomethane (Called

Poly-“methylene” due to repeating –CH2 group)

  • 1930-35
  • First polymerization of ethylene at Imperial Chemical

Industries.

  • Advent of the free radical process to produce LDPE

3

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SLIDE 4

Free Radical Polymerization

  • 1. INITIATION (You need Initiators)

AIBN

Benzoyl Peroxide

4

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SLIDE 5

Free Radical Polymerization

  • 2. PROPAGATION

High pressure is needed during the propagation step in order to bring the ethylene monomer closer to the free radicals

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SLIDE 6

Free Radical Polymerization

  • 3. TERMINATION (Many ways)
  • a. COUPLING

6

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SLIDE 7

Free Radical Polymerization

  • 3. TERMINATION (Many ways)
  • b. DISPROPORTIONATION

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SLIDE 8

Free Radical Polymerization

  • 3. TERMINATION (Many ways)
  • c. CHAIN TRANSFER (Hydrogen Abstraction)

8

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SLIDE 9

Free Radical Polymerization

SIDE REACTIONS (Causes Branching)

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SLIDE 10

Disadvantages

  • 1. Uncontrolled Process
  • Structure,

Molecular weight

  • 2. Requires high pressure
  • 3. Reactions are highly

exothermic

  • 4. Inefficient process (20%

ethylene polymerized)

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SLIDE 11

Timeline of Polyethylene

  • 1898
  • Synthesized by accident while heating diazomethane (Called

Poly-“methylene” due to repeating –CH2 group)

  • 1930-35
  • First polymerization of ethylene at Imperial Chemical

Industries.

  • Advent of the free radical process to produce LDPE
  • 1950’s
  • Ziegler-Natta Catalyst (Inorganic Catalyst for HDPE)

11

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SLIDE 12

Zieglar-Natta Catalyst

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SLIDE 13

Zieglar-Natta Catalyst

Mechanism

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SLIDE 14

Timeline of Polyethylene

  • 1898
  • Synthesized by accident while heating diazomethane (Called

Poly-“methylene” due to repeating –CH2 group)

  • 1930-35
  • First polymerization of ethylene at Imperial Chemical

Industries.

  • Advent of the free radical process to produce LDPE
  • 1950’s
  • Ziegler-Natta Catalyst (Inorganic Catalyst for HDPE)
  • 1970’s
  • Metallocene Catalyst (Organic-Inorganic Hybrid Catalyst for

HDPE)

14

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SLIDE 15

Metallocene Catalyst

Zirconium Sandwich The Bread is Cyclopentadiene The Filling is Zr bonded to Chlorine

15

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SLIDE 16

Timeline of Polyethylene

  • 1898
  • Synthesized by accident while heating diazomethane (Called

Poly-“methylene” due to repeating –CH2 group)

  • 1930-35
  • First polymerization of ethylene at Imperial Chemical

Industries.

  • Advent of the free radical process to produce LDPE
  • 1950’s
  • Ziegler-Natta Catalyst (Inorganic Catalyst for HDPE)
  • 1970’s
  • Metallocene Catalyst (Organic-Inorganic Hybrid Catalyst for

HDPE) What is next ?

  • Organic Routes (biological enzymatic reactions)

16

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SLIDE 17

Zieglar-Natta Catalyst

Mechanism

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