CHE 411 POLYMER TECHNOLOGY

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CHE 411POLYMER TECHNOLOGY

• Prof. AbdulAziz A. M. Wazzan

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CHAPTER ONE

• Polymer Chemistry

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INTRODUCTION

• Polymer (Poly ? many) (meros ? part)
• Polymer is a long molecule consisting of many
  small units (monomers) joined end to end
  (together).

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Example

• where
• n ? number of ethylene monomers which join
  together to form a molecules. Usually of order 10
  4 up to 106
• ?1 , ?2 ? The end group at very small
  concentration, they have no effect on the
  mechanical properties of the polymer but it give
  a chemical stability. (Initiate a degradation
  process) (Unzips).

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• There are two molecular factors that affect the
  mechanical properties of a polymer.
• 1. The length of the molecules which is ? to n
  which is ? to molecular size or relative molar
  mass
• 2. The shape of the molecules. (Branches),
  branching affected by the polymerization
  conditions. Branching can affect the toughness,
  creep resistance and the modulus.

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CLASSIFICATION OF POLYMERS
This classification based on the molecular
structure of the polymers.
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STRUCTURE

• Polymer macromolecules have a linear structure
  which represented with a chain with two ends.

• or nonlinear structure such as branched and
  Network

• Branched polymer have side chains or branches
  of significant length which are bonded to the
  main chain at branch point.

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• Example
• Heating ethylene gas at ? 200 oC and high
  pressure of ? 2000 atmosphere in the presence
  of suitable polymerization initiation will result
  in LDPE used for film packaging.

Low pressure process give linear PE or HDPE Used
for pipe, bottles.
There is also LLDPE made with copolymerization
of ethylene with suitable butane co-monomens
using ziegler - Natta type catalysis.
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CROSS LINKED POLYMERS

• A three dimensional structures in which each
  chain is connected to all others by a sequence of
  junction points. They are characterize by their
  crosslink density or degree of crosslinking.

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THERMOPLASTICS (Plastics)

• Linear or branched which can be melt upon the
  application of heat.
• They can be moulded in different shape using
  different techniques. Such as injection moulding
  and extrusion.
• Crystallization is not easily obtained upon
  cooling to the solid state because it required a
  considerable ordering of the highly coiled and
  entangled macromolecules.
• These which crystallize do not form perfectly
  crystalline materials but (sime-crystalline) with
  both crystalline and amorphous regions.
• Crystalline can be characterized by Tm (melting
  temperature). where as Tg (Glass Transition
  Temperature) characterize the amorphous required
  for both (amorphous polymer and sime crystalline)
• Tg is the temperature at which the material
  transform from the glassy state (hard) to the
  rubbery state (soft). (On set of chain motion)
  below Tg chain are not moving and frozen.
• Both Tg and Tm increases with increasing the
  chain stiffness and force of intermolecular
  attraction

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ELASTOMERS

• Crosslinked rubbery polymers which can be
  stretched easily to high extensions (3 to 10
  times there original length) and rapidly recover
  to the original dimension when the applied stress
  is released.

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THERMOSETS

• Normally rigid materials and net-work polymer
  where chain motion is restricted by a high degree
  of crosslinking .
• example (eggs).

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HOMOPOLYMERS

• Definition of a homopolymer is a polymer derived
  from one species of monomer (one type of Repeat
  Unit R.U.)
• ---- A-A-A-A-A-A----
• or A n
• where
• n is the number of R.U. linked together to form
  the macromolecule.
• See table 1.1 slight difference in chemical
  structure can lead to very significant difference
  in properties.

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COPOLYMERS

• Definition is a polymer derived from more than
  one species of monomer (two or more type of
  repeat unit R.U.).

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CATEGORIES OF COPOLYMERS

• 1. Statistical copolymer are copolymers which the
  sequential distribution of the R.U. obeys known
  statical laws.
•  ----A-A-B-B-B-A-A-B-B-B-A-A-A----
• 2. Random copolymer it is one typed statistical
  copolymer in which the distribution of R.U is
  truly random.
•  ----B-A-A-A- B-B-A-A-B-A-A-A-----
• 3. Alternating copolymer have only two different
  types of R.U. and these are arranged alternately
  along the polymer chain.
• -----A-B-A-B-A-B-----
• The above three have a properties which are
  intermediate to those of the desirable
  properties. Of the homopolymer in one single
  materials.

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• 4. Block copolymers a linear copolymers in which
  the R.U. exist only in long sequences. Or blocks
  of the same type.
•  Di block -----A-A-A-A-A-B-B-B-B-B-B-B-B----
•  Tri block ----A-A-A-A-B-B-B-B-B-A-A-AA------
• 5. Graft copolymers are branched polymers in
  which the branches have a different Chemical
  structure to that of the main chain.

Block Graft properties characteristic of each
of the constituent homopolymers. Example Rubber
toughened particles
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Thank You

• See You Next Lecture