Morphology
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Morphology
Studies of physical form
arrangement and structure of a
material is called morphology
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Polymer Morphology
• As applied to polymers, morphology involves the
study of the arrangement of polymer molecules in
crystalline and amorphous regions.
• This means “Morphology” refers to the physical
structure or form in which polymer molecules are
organized.
• Molecular shape and the way molecules are arranged
in solids are important factors in determining the
properties of polymers.
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•Micro – crystalline
•Macro – crystalline
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Micro – crystalline
•Micro – crystalline polymers are the most
frequent.
•Considerable portions of polymer’s bulk
contain of amorphous region, which may still
be in a rubbery state or a glass state according
to whether the segments rotate or not. There
are small orderly crystallites in embedded in
regions
•Interior of such crystalline contains unit cells.
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Macro – Crystalline Polymers
• Macro – crystalline polymers are built on a more massive scale,
often reaching dimensions of several mm and containing unit
cell of size 10-7 0A3.
• It is apparent from size consideration that one chain of a micro
– crystalline polymer will travel large no of unit cells, even many
different crystallites.
• A lower free energy is usually obtained when molecules are
packed together regularly and closely and the lowest energy
when the regularity is the highest.
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• Regular package usually means closer packing and
thus more matter per unit space (or unit volume).
• Closer packing gives the molecules a chance to treat
further their attractive dipole and vander Waals
forces, thus lowering the free energy, and this is
the most important force tending to produce
crystal.
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•The simplest element of the
structure of a crystalline polymer is
its crystalline cell, formed by several
atoms/part of chains.
•It is characterized by strictly defined
dimensions.
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A crystal may be classified into one of seven large sub
group’s refer to as a crystal system.
system.
• All crystal systems are described by lattice
parameters (a or b or c and three angles α, β, γ).
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Crystals are made of infinite number of unit cells
Unit cell is the smallest unit of a crystal, which, if repeated,
could generate the whole crystal.
A crystal’s unit cell dimensions are defined by six numbers, the
lengths of the 3 axes, a, b, and c, and the three interaxial angles, ,
 and .
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Crystal Systems
•All unit cells fall into one of the bravis
lattices typically, simple molecules and
atoms form highly symmetrical form unit
cells such as simple cubic or various such as
body centred cubic or face centred cubic.
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These cells are categories
into 14 bravis lattices.
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Isomerism/Polymer Tacticity
Isotactic
Sindiotactic
atactic
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Crystalline/ Amorphous Polymers
•Crystalline polymers have a reasonable
chain structure and specific preferred
chain conformation.
•The presence of chain defects i.e. atactic
sequences/ chain branching make
impossible for the polymer to crystallize
an on cooling they ultimately form of
fully amorphous polymer.
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Lamellar Crystal
A type of crystal with a large extension in two dimensions
and a uniform thickness.
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Polymer Single Crystals
Lamellars
•The polymer single crystals have a structure in which
polymer chain pass vertically through the thickness
of the plate, then turn sharply (1800) and turn along
side themselves.
•The thickness of the lamellar is very small (100 –
2000A) compare to the length of the polymer chain.
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Lamellars
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•Therefore, the outward appearance in
single crystal dimensions, shape and
regularity of structures depend on the
-Chemical structure of a chain
-Crystallization condition
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Extended chain/Folded chain
• Under condition of non equilibrium (relatively rapid
crystallization), a crystal forms more rapidly from
folded chains than from extended once.
• If crystallization were to follow the extended chain
type, all the loops would be inside crystal.
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Extended chain/Folded chain
• If crystallization is folded one, the part of molecules that have not been
included in a crystal from loops of various lengths.
• In extended chain crystal, there is long-range order in the arrangement of
segments and the macromolecules.
• In folded chain crystal long-range order observe only as regard the
arrangement of segments.
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