Unit 3 – The Chemistry of Engineering Materials Polymers Flashcards
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A ___________ is a molecular compound that can be distinguished by a high molar mass, ranging into thousands and even millions of mass and they are made up of many repeating
units.
polymer
_____________ were first developed in the early 20th century, and these polymers remarkably transformed our world as different materials can be created with properties that are ideal for different applications.
Synthetic (man-made) polymers
Polymers that have been around
since life itself began.
Natural Polymers
Cellulose, starch, and other complex carbohydrates are examples of
Natural Polymers
It is a polymer obtained from rubber trees and even the code
for life itself, DNA, is a natural polymer.
Natural rubber
Fill in the blanks
Because of the _________, we might expect that molecules containing thousands of carbon and hydrogen atoms can form a massive number of structural and geometric
isomers (if C=C bonds are present).
size polymers
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___________are the small molecules that are used for synthesizing polymers and each of it is analogous
to a link in a chain.
monomers
Monomers (_____ meaning “one”; _____ meaning “unit”)
mono
meros
Monomers ( mono meaning “____”; meros meaning “______”)
one
unit
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They can be created from one monomer, of from
a combination of two or more different monomers.
polymers
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If a polymer is made up of only type of monomer (e.g. polyethylene), then it is known as __________.
homopolymer
Give three homopolymers that are synthesized by the radical mechanism
Teflon TM
polytetrafuoroethylene
poly(vinyl chloride) (PVC)
___________ can be made from many different starting materials which usually come from crude oil (raw material).
Synthetic polymers
___________ is the starting material for many
plastics, pharmaceuticals, fabrics, and other carbon-based products.
crude oil
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The molecules in polymers are gigantic and because of their size they are often referred to as __________.
macromolecules
The backbone of each of a carbon-chain polymer is a string
of carbon atoms and within each molecule, the atoms are bound together by___________ bonds.
covalent interatomic
Each of the two remaining valence electrons for every carbon atom may be involved in side bonding with atoms or radicals that are positioned adjacent to the chain. Of course,
both _____and __________ are also possible.
chain
side double bonds
is a gas at ambient temperature and pressure which
has the following molecular structure.
hydrocarbon ethylene (C2H4)
page 126 for figure
Under appropriate conditions, ethylene gas reacted and it will transform to ___________ which is a solid polymeric material.
polyethylene (PE)
It is a solid polymeric material.
polyethylene (PE)
transforming ethylene to polyethylene
This process begins when an active center is formed by the reaction between an __________ (R·) and the ethylene monomer.
initiator or catalyst species
Next, the polymer chain forms by the __________ of monomer units to this actively growing chain molecule
sequential addition
Other chemistry of polymer structure such as tetrafluoroethylene monomer to form
__________________ (PTFE)
polytetrafluoroethylene
Italicize
Polytetrafluoroethylene (having the trade name Teflon) belongs to a family of polymers called the _____________.
fluorocarbons
The ______________(CH2=CHCl) is a slight variant of that for ethylene, in which one of the four H atoms is replaced with a Cl atom.
vinyl chloride monomer
vinyl chloride monomer leads to ____________
poly (vinyl chloride)
enumerate the polymer structures
Linear
Branched
Crosslinked
Network
are those in which the repeat units are joined together end to end in single chains.
Linear Polymers
-These long chains are flexible where each circle
represents a unit.
linear
-There may be extensive van der Waals and
hydrogen bonding between the chains.
Linear
-Some of the common polymers that form with
________ structures are polyethylene, poly(vinyl
chloride), polystyrene, poly(methyl methacrylate),
nylon, and the fluorocarbons.
linear
-The chain packing efficiency is reduced with the
formation of side branches, which results in a
lowering of the polymer density.
Branched
-For example, high-density polyethylene (HDPE) is
primarily a linear polymer, whereas low-density
polyethylene (LDPE) contains short-chain
branches.
Branched
-Adjacent linear chains are joined one to another at various positions by covalent bonds.
crosslinked
-The process of __________ is achieved either
during synthesis or by a nonreversible chemical
reaction.
crosslinking
is accomplished by
additive atoms or molecules that are covalently
bonded to the chains.
crosslinked
-Many of the rubber elastic materials are
________.
crosslinked
-These are multifunctional monomers forming three or more active covalent bonds make three-
dimensional networks.
Network
-A polymer that is highly crosslinked may also be
classified as a _______ polymer.
network
-These materials have distinctive mechanical and
thermal properties; the epoxies, polyurethanes,
and phenol-formaldehyde belong to this group.
network
Presently, there are more than ___________ synthetic polymers known,
60,000
six types of polymers
polyethylene LDPE (4)
polyethylene HDPE (2)
polyvinyl chloride PVC or V (3)
polystyrene PS (6)
polypropylene PP (5)
polyethylene terephthalate PETE or PET (1)
-Translucent if not
pigmented.
-Soft and flexible.
-Unreactive to acids
and bases.
-Strong and tough.
polyethylene LDPE
Bags, films, sheets,
bubble wrap, toys,
wire insulation.
polyethylene LDPE
-Similar to LDPE
-More rigid, tougher,
slightly more dense.
polyethylene HDPE
Opaque milk, juice,
detergents, and
shampoo bottles.
Buckets, crates, and
fencing
polyethylene HDPE
-Variable. Rigid if
not softened with a
plasticizer. Clear
and shiny, but often
pigmented.
Resistant to most chemicals, including
oils, acids, and
bases.
polyvinyl chloride
Rigid: Plumbing
pipe, house siding,
charge cards, hotel
room keys.
Softened: Garden
hoses, waterproof boots, shower
curtains, IV tubing.
polyvinyl chloride
-Variable. “Crystal”
form transparent,
sparkling,
somewhat brittle.
-“Expandable” form
lightweight foam.
-Both forms rigid
and degraded in
many organic
solvents.
polystyrene
“Crystal” form: Food
wrap, CD cases,
transparent cups.
“Expandable” form:
Foam cups,
insulated
containers, food
packaging trays, egg
cartons, packaging
peanuts.
polystyrene
-Opaque, very
tough, good
weatherability. High
melting point.
-Resistant to oils.
polypropylene
Bottle caps. Yogurt,
cream, and
margarine
containers.
Carpeting, casual
furniture, luggage.
polypropylene
-Transparent,
strong, shatter-
resistant. -
Impervious to acids
and atmospheric
gases.
-Most costly of the
six.
Polyethylene
terephthalate
Soft-drink bottles,
clear food
containers,
beverage glasses,
fleece fabrics, carpet
yarns, fiber-fill
insulation.
Polyethylene
terephthalate
_______________ is an alternative way of expressing average chain size of a polymer.
Degree of Polymerization (DP)
The ______________ is obtained by dividing the chains into a series of size ranges and then determining the number fraction of chains within each size range
number-average
molecular weight Mn
A ____________is based on the weight fraction of molecules within the various size ranges.
weight-average molecular weight Mw
two subdivision of polymers
thermoplastics
thermosets
they soften upon heating and later liquefy, then it hardens when cooled.
This process is reversible and can be repeated.
thermoplastics
Examples of common ____________________ polymers are polyethylene, polystyrene,
poly(ethylene terephthalate), and poly(vinyl chloride).
thermoplastic
For ________________ polymers which are network polymers, they do not soften upon
heating and they become permanently hard during their formation.
thermosetting
Examples of these _______________ (crosslinked and
network polymers) are vulcanized rubbers, epoxies, phenolics, and some polyester resins.
thermosets
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A ___________ is composed of two repeat units
copolymer
____________ are usually copolymers.
Synthetic
rubbers
4 copolymer arrangement
Random
Alternating
Block
Graft
two different units are randomly dispersed along the chain
Random
two repeat units alternate chain positions
alternating
identical repeat units are clustered in
blocks along the chain
block
homopolymer side branches of one type
may be grafted to homopolymer main
chains that are composed of a different
repeat unit
graft
In ___________, the atomic arrangement in polymer materials are more complex
as compared to metals and ceramics because in polymers it involves molecules instead of
just atoms or ions.
crystalline state
____________ is the packing of molecular chains to produce an ordered atomic array.
Polymer crystallinity
