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Polymer engineering > Molecular origin of Polymer Properties > Flashcards

Molecular origin of Polymer Properties Flashcards

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1
Q

is a macromolecule
(long molecules) built of small
covalently bonded units called
monomers

A

polymer

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2
Q

These small units are repeated
throughout the macromolecule
chain.

A

mer/monomers

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3
Q

The macromolecules are bonded
together by

A

weak Van der Waals
and hydrogen (secondary) bonds,
or additional covalent crosslinks

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4
Q

Most polymers are

A

organic

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5
Q

Each C atom has _____ electrons that participate in covalent bonding, each H atom
has _______ bonding electron

A

4, 1

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6
Q

exists when each of the two bonding atoms contributes one
electron

A

single bond

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7
Q

between two carbon atoms involve the sharing of two and
three pairs of electrons, respectively

A

double, triple bhond

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8
Q

▪ Molecules that have double, and triple covalent bonds are termed

A

unsaturated

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9
Q

each carbon atom is not bonded to the maximum (four) other atoms

A

unsaturated

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10
Q

all bonds are single ones, and no new atoms may be
joined without the removal of others that are already bonded

A

saturated hydrocarbon

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11
Q

molecule that combines with other molecules of the
same or different type to form a polymer

A

monomer

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12
Q
A
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12
Q

The structure of the repeating unit of a polymer is __________to that of the monomer molecule(s

A

essentially that or
closely related

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13
Q

low-molecular-weight polymer

A

oligomer

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14
Q

If the ethylene gas is reacted under appropriate conditions, it will transform to

A

polyethylene (PE)

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15
Q

specifies the length of the polymer molecule.

A

degree of polymerization

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16
Q

indicates the number of repeating units strung
together in the polymer chain (molecule)

A

The subscript designation, n

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17
Q

The subscript designation, n, is known as

A

degree of polymerization

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18
Q

normally required for a material to
develop useful properties and before it can be appropriately described as a
polymer

A

A high degree of polymerization

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19
Q

dimensionless quantity given by the sum of the atomic
weights in the molecular formula.

A

Molecular weight

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20
Q

The relation between degree of polymerization and molecular weight M of
the same macromolecule

A

M= (DP)Mo

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21
Q

CLASSIFICATION OF POLYMERS BASED ON ORIGIN

A

Natural and synthetic

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22
Q

Wood, rubber, cotton, leather, wool, silk,
protein, enzymes, starches, cellulose

A

Natural polymers

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23
Q

Fibers, elastomers, plastics, adhesives

A

synthetic polymers

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24
CLASSIFICATION BASED ON POLYMER STRUCTURE
LINEAR, BRANCHED OR CROSS-LINKED, NETWORK VS. FUNCTIONALITY
25
its interlinking capacity, or the number of sites it has available for bonding with other molecules under the specific polymerization conditions.
functionality of a molecule
26
A molecule may be classified as ______________ depending on whether it has one, two, or greater than two sites available for linking with other molecules.
monofunctional, bifunctional, or polyfunctional
27
those in which the repeat units are joined together end to end in single chains.
Linear polymers
28
Some of the common examples of linear polymers
polyethylene, PVC, polystyrene, and polyamides.
29
Linear polymers are generally more
rigid
30
have side chains or branches growing out from the main chain
Branched polymers
31
The side chains or branches in branched polymers are made of the ______repeating units as the main polymer chains
same
32
For a polymer to classify as branched polymer the side chains or branches should comprise of a minimum
one complete monomer unit
33
One of the most common example of branched polymer
LDPE
34
adjacent linear chains are joined one to another at various positions by covalent bonds
Crosslinked polymers
35
tend to be permanent in nature.
crosslinks
36
Once the crosslinks between the chains develop the polymer then becomes
thermoset
37
Common examples of crosslinked polymers
Bakelite, melamine, epoxies, bulk molding compounds, rubber, and various adhesives
38
Multifunctional monomers forming three or more active covalent bonds make three dimensional networks and are termed
network polymers.
39
the epoxies, polyurethanes, and phenol-formaldehyde belong to t
network polymers
40
CLASSIFICATION BASED ON POLYMER STRUCTURE
AMORPHOUS OR CRYSTALLINE
41
material exhibits organized and tightly packed molecular chains.
crystalline polymer
42
In terms of properties, they have good strength & wear, and good chemical resistance, but they typically lack in impact resistance
crystalline polymer
43
Examples of crystalline polymers include
polyethylene, polyacrylonitrile, poly(ethylene terephthalate), and polytetrafluoroethylene.
44
polymers that have no crystalline regions and no uniformly packed molecules
Amorphous polymers
45
polymers that are composed of amorphous regions where molecules are randomly arranged.
Amorphous polymers
46
good examples of amorphous polymers
Natural rubber latex and styrene-butadiene rubber
47
measure of the degree of order or orientation in a crystal.
degree of crystallinity
48
CLASSIFICATION BASED ON POLYMER STRUCTURE
HOMOPOLYMER OR COPOLYMER
49
When all of the repeating units along a chain are of the same type, the resulting polymer is called a
homopolymer
50
produce a polymer that has increased mechanical properties
homopolymers
51
a polymer made up of more than one type of monomer unit.
copolymer
52
produced by polymerizing two or more types of monomer together in a process referred to as copolymerization.
copolymers
53
Copolymers produced are sometimes also referred
biopolymers
54
The purpose of creating a copolymer is to
manufacture a polymer with more desirable properties
55
There are three other copolymer structures, other than random
alternating, block, and graft copolymer structures
56
the two mers alternate in a regular fashion along the polymer chain
alternating copolymer
57
linear polymer with one or more long uninterrupted sequences of each mer in the chain
block copolymer
58
a branched copolymer with a backbone of one type of mer and one or more side chains of another mer
graft copolymer
59
linear polymers with high symmetry and high intermolecular forces that result usually from the presence of polar groups.
fibers
60
They are characterized by high modulus, high tensile strength, and moderate extensibilities
fibers
61
molecules with irregular structure, weak intermolecular attractive forces, and very flexible polymer chains.
elastomers
62
polymers that have viscosity and elasticity and therefore are known as viscoelasticity.
elastomers
63
They inherit the unique property of regaining their original shape and size after being significantly stretched
elastomers
64
polymer, typically modified with additives, which can be molded or shaped under reasonable conditions of pressure and temperature.
plastic
65
CLASSIFICATION BASED ON POLYMERIZATION MECHANISM
CONDENSATION POLYMERS ADDITION POLYMERS
66
formed from a series of reactions, often of condensation type, in which any two species can react at any time leading to a larger molecule.
Condensation polymers
67
form of a step-growth polymerization where smaller molecules or monomers react with each other to form larger structural units (usually polymers) while releasing by-products such as water or methanol molecule
Condensation polymers
68
The by-products of condensation are normally referred to as
condensate
69
produced by reactions in which monomers are added one after another to a rapidly growing chain.
Addition polymers
70
CLASSIFICATION OF POLYMERS ACCORDING TO THERMAL PROCESSING BEHAVIOR
THERMOPLASTICS THERMOSETS
71
Plastics that soften when heated and become firm again when cooled
THERMOPLASTICS
72
This is the more popular type of plastic because the heating and cooling may be repeated and the thermoplastic may be reformed
THERMOPLASTICS
73
Most linear polymers and those having some branched structures with flexible chains are
thermoplastic
74
these are plastics that soften when heated and can be molded but harden permanently. They will decompose when reheated.
THERMOSETS
75
heated, undergoes a chemical change to produce a cross-linked, solid polymer.
A thermoset
76
Thermosets usually exist initially as liquids called
prepolymers
77
CLASSIFICATION BASED ON PREPARATIVE TECHNIQUE
BULK POLYMERIZATION SOLUTION POLYMERIZATION SUSPENSION POLYMERIZATION EMULSION POLYMERIZATION
78
only the monomer (and possibly catalyst and initiator, but no solvent) is fed into the reactor
bulk polymerization
79
The monomer undergoes polymerization, at the end of which a solid mass is removed as the polymer product
bulk polymerization
80
involves polymerization of a monomer in a solvent in which both the monomer (reactant) and polymer (product) are soluble
Solution polymerization
81
refers to polymerization in an aqueous medium with the monomer as the dispersed phase. Consequently, the polymer resulting from such a system forms a solid dispersed phase.
Suspension polymerization
82
similar to suspension polymerization, but the initiator is located in the aqueous phase (continuous phase) in contrast to the monomer (dispersed phase) in suspension polymerization.
Emulsion polymerization
83
BULK PROPERTIES OF POLYMERS
TENSILE STRENGTH YOUNG’S MODULUS OF ELASTICITY TRANSPORT PROPERTIES PURE COMPONENT PHASE BEHAVIOR
84
quantifies how much stress the material will endure before failing
tensile strength of a material
85
Tensile strength ___________ with polymer chain length
increases
86
Quantifies the elasticity of the polymer.
YOUNG’S MODULUS OF ELASTICITY
87
defined as the ratio of rate of change of stress to strain.
YOUNG’S MODULUS OF ELASTICITY
88
relate to how rapidly molecules move through the polymer matrix
Transport properties
89
Transport properties are very important in many applications of polymers for
films and membranes.
90
PURE COMPONENT PHASE BEHAVIOR
➢MELTING POINT ➢ GLASS TRANSITION
91
suggests not a solid-liquid phase transition but a transition from a crystalline or semi-crystalline phase to a solid amorphous phase
melting point
92
crucial physical parameter for polymer manufacturing, processing, and use
glass-transition temperature (Tg)
93
molecular motions are frozen, and polymers are brittle and glassy
Below Tg
94
molecular motions are activated, and polymers are rubbery and viscous
Above Tg

Polymer engineering (5 decks)

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