A polymer (/ˈpɒlɪmər/; Greek poly-, "many" + -mer, "parts")
is a large molecule, or macromolecule, composed of many repeated
subunits. Because of their broad range of properties, both
synthetic and natural polymers play essential and ubiquitous roles in
everyday life. Polymers range from familiar synthetic plastics such
as polystyrene to natural biopolymers such as
DNA and proteins that
are fundamental to biological structure and function. Polymers, both
natural and synthetic, are created via polymerization of many small
molecules, known as monomers. Their consequently large molecular mass
relative to small molecule compounds produces unique physical
properties, including toughness, viscoelasticity, and a tendency to
form glasses and semicrystalline structures rather than crystals.
The term "polymer" derives from the ancient Greek word πολύς
(polus, meaning "many, much") and μέρος (meros, meaning "parts"),
and refers to a molecule whose structure is composed of multiple
repeating units, from which originates a characteristic of high
relative molecular mass and attendant properties. The units
composing polymers derive, actually or conceptually, from molecules of
low relative molecular mass. The term was coined in 1833 by Jöns
Jacob Berzelius, though with a definition distinct from the modern
IUPAC definition. The modern concept of polymers as covalently
bonded macromolecular structures was proposed in 1920 by Hermann
Staudinger, who spent the next decade finding experimental
evidence for this hypothesis.
Polymers are studied in the fields of biophysics and macromolecular
science, and polymer science (which includes polymer chemistry and
polymer physics). Historically, products arising from the linkage of
repeating units by covalent chemical bonds have been the primary focus
of polymer science; emerging important areas of the science now focus
on non-covalent links.
Polyisoprene of latex rubber is an example of a
natural/biological polymer, and the polystyrene of styrofoam is an
example of a synthetic polymer. In biological contexts, essentially
all biological macromolecules—i.e., proteins (polyamides), nucleic
acids (polynucleotides), and polysaccharides—are purely polymeric,
or are composed in large part of polymeric components—e.g.,
isoprenylated/lipid-modified glycoproteins, where small lipidic
molecules and oligosaccharide modifications occur on the polyamide
backbone of the protein.
The simplest theoretical models for polymers are ideal chains.
1 Common examples
2.1 Biological synthesis
2.2 Modification of natural polymers
3.1 Monomers and repeat units
3.2.2 Chain length
Monomer arrangement in copolymers
3.3.2 Chain conformation
3.4 Mechanical properties
3.4.1 Tensile strength
Young's modulus of elasticity
3.5 Transport properties
3.6 Phase behavior
3.6.1 Melting point
Glass transition temperature
3.6.3 Mixing behavior
3.6.4 Inclusion of plasticizers
3.8 Optical properties
4 Standardized nomenclature
6.1 Product failure
7 See also
10 External links
Polymers are of two types:
Natural polymeric materials such as shellac, amber, wool, silk and
natural rubber have been used for centuries. A variety of other
natural polymers exist, such as cellulose, which is the main
constituent of wood and paper.
The list of synthetic polymers, roughly in order of worldwide demand,
includes polyethylene, polypropylene, polystyrene, polyvinyl chloride,
synthetic rubber, phenol formaldehyde resin (or Bakelite), neoprene,
nylon, polyacrylonitrile, PVB, silicone, and many more. More than 330
million tons of these polymers are made every year (2015). 
Most commonly, the continuously linked backbone of a polymer used for
the preparation of plastics consists mainly of carbon atoms. A simple
example is polyethylene ('polythene' in British English), whose
repeating unit is based on ethylene monomer. However, other structures
do exist; for example, elements such as silicon form familiar
materials such as silicones, examples being
Silly Putty and waterproof
Oxygen is also commonly present in polymer
backbones, such as those of polyethylene glycol, polysaccharides (in
glycosidic bonds), and
DNA (in phosphodiester bonds).
Main article: Polymerization
The repeating unit of the polymer polypropylene
Polymerization is the process of combining many small molecules known
as monomers into a covalently bonded chain or network. During the
polymerization process, some chemical groups may be lost from each
monomer. This is the case, for example, in the polymerization of PET
polyester. The monomers are terephthalic acid (HOOC-C6H4-COOH) and
ethylene glycol (HO-CH2- CH2-OH) but the repeating unit is
-OC-C6H4-COO-CH2-CH2-O-, which corresponds to the combination of the
two monomers with the loss of two water molecules. The distinct piece
of each monomer that is incorporated into the polymer is known as a
repeat unit or monomer residue.
Laboratory synthetic methods are generally divided into two
categories, step-growth polymerization and chain-growth
polymerization. The essential difference between the two is that
in chain growth polymerization, monomers are added to the chain one at
a time only, such as in polyethylene, whereas in step-growth
polymerization chains of monomers may combine with one another
directly, such as in polyester. However, some newer methods such
as plasma polymerization do not fit neatly into either category.
Synthetic polymerization reactions may be carried out with or without
a catalyst. Laboratory synthesis of biopolymers, especially of
proteins, is an area of intensive research.
Main article: Biopolymer
Microstructure of part of a
DNA double helix biopolymer
There are three main classes of biopolymers: polysaccharides,
polypeptides, and polynucleotides. In living cells, they may be
synthesized by enzyme-mediated processes, such as the formation of DNA
DNA polymerase. The synthesis of proteins involves
multiple enzyme-mediated processes to transcribe genetic information
DNA to RNA and subsequently translate that information to
synthesize the specified protein from amino acids. The protein may be
modified further following translation in order to provide appropriate
structure and functioning. There are other biopolymers such as rubber,
suberin, melanin and lignin.
Modification of natural polymers
Naturally occurring polymers such as cotton, starch and rubber were
familiar materials for years before synthetic polymers such as
polyethene and perspex appeared on the market. Many commercially
important polymers are synthesized by chemical modification of
naturally occurring polymers. Prominent examples include the reaction
of nitric acid and cellulose to form nitrocellulose and the formation
of vulcanized rubber by heating natural rubber in the presence of
sulfur. Ways in which polymers can be modified include oxidation,
cross-linking and end-capping.
Especially in the production of polymers, the gas separation by
membranes has acquired increasing importance in the petrochemical
industry and is now a relatively well-established unit operation. The
process of polymer degassing is necessary to suit polymer for
extrusion and pelletizing, increasing safety, environmental, and
product quality aspects. Nitrogen is generally used for this purpose,
resulting in a vent gas primarily composed of monomers and
Polymer properties are broadly divided into several classes based on
the scale at which the property is defined as well as upon its
physical basis. The most basic property of a polymer is the
identity of its constituent monomers. A second set of properties,
known as microstructure, essentially describe the arrangement of these
monomers within the polymer at the scale of a single chain. These
basic structural properties play a major role in determining bulk
physical properties of the polymer, which describe how the polymer
behaves as a continuous macroscopic material.
Chemical properties, at
the nano-scale, describe how the chains interact through various
physical forces. At the macro-scale, they describe how the bulk
polymer interacts with other chemicals and solvents.
Monomers and repeat units
The identity of the repeat units (monomer residues, also known as
"mers") comprising a polymer is its first and most important
Polymer nomenclature is generally based upon the type of
monomer residues comprising the polymer. Polymers that contain only a
single type of repeat unit are known as homopolymers, while polymers
containing two or more types of repeat units are known as
copolymers. Terpolymers contain three types of repeat units.
Poly(styrene), for example, is composed only of styrene monomer
residues, and is therefore classified as a homopolymer. Ethylene-vinyl
acetate, on the other hand, contains more than one variety of repeat
unit and is thus a copolymer. Some biological polymers are composed of
a variety of different but structurally related monomer residues; for
example, polynucleotides such as
DNA are composed of four types of
A polymer molecule containing ionizable subunits is known as a
polyelectrolyte or ionomer.
Main article: Microstructure
The microstructure of a polymer (sometimes called configuration)
relates to the physical arrangement of monomer residues along the
backbone of the chain. These are the elements of polymer structure
that require the breaking of a covalent bond in order to change.
Structure has a strong influence on the other properties of a polymer.
For example, two samples of natural rubber may exhibit different
durability, even though their molecules comprise the same monomers.
Branch point in a polymer
An important microstructural feature of a polymer is its architecture
and shape, which relates to the way branch points lead to a deviation
from a simple linear chain. A branched polymer molecule is
composed of a main chain with one or more substituent side chains or
branches. Types of branched polymers include star polymers, comb
polymers, brush polymers, dendronized polymers, ladder polymers, and
dendrimers. There exist also two-dimensional polymers which are
composed of topologically planar repeat units. A polymer's
architecture affects many of its physical properties including, but
not limited to, solution viscosity, melt viscosity, solubility in
various solvents, glass transition temperature and the size of
individual polymer coils in solution. A variety of techniques may be
employed for the synthesis of a polymeric material with a range of
architectures, for example Living polymerization.
The physical properties of a polymer are strongly dependent on the
size or length of the polymer chain. For example, as chain length
is increased, melting and boiling temperatures increase quickly.
Impact resistance also tends to increase with chain length, as does
the viscosity, or resistance to flow, of the polymer in its molten
state. Melt viscosity
displaystyle eta ,
is related to polymer chain length Z roughly as
displaystyle eta ,
~ Z3.2, so that a tenfold increase in polymer chain length results in
a viscosity increase of over 1000 times. Increasing chain length
furthermore tends to decrease chain mobility, increase strength and
toughness, and increase the glass transition temperature
(Tg). This is a result of the increase in chain
interactions such as Van der Waals attractions and entanglements that
come with increased chain length. These interactions
tend to fix the individual chains more strongly in position and resist
deformations and matrix breakup, both at higher stresses and higher
A common means of expressing the length of a chain is the degree of
polymerization, which quantifies the number of monomers incorporated
into the chain. As with other molecules, a polymer's size may
also be expressed in terms of molecular weight. Since synthetic
polymerization techniques typically yield a polymer product including
a range of molecular weights, the weight is often expressed
statistically to describe the distribution of chain lengths present in
the same. Common examples are the number average molecular weight and
weight average molecular weight. The ratio of these two values
is the polydispersity index, commonly used to express the "width" of
the molecular weight distribution. A final measurement is contour
length, which can be understood as the length of the chain backbone in
its fully extended state.
The flexibility of an unbranched chain polymer is characterized by its
Monomer arrangement in copolymers
Main article: copolymer
Monomers within a copolymer may be organized along the backbone in a
variety of ways. A copolymer containing a controlled arrangement of
monomers is called a sequence-controlled polymer. Alternating,
periodic and block copolymers are simple examples of
Alternating copolymers possess two regularly alternating monomer
residues: [AB]n (structure 2 at right). An example is the
equimolar copolymer of styrene and maleic anhydride formed by
free-radical chain-growth polymerization. A step-growth copolymer
Nylon 66 can also be considered a strictly alternating
copolymer of diamine and diacid residues, but is often described as a
homopolymer with the dimeric residue of one amine and one acid as a
Periodic copolymers have monomer residue types arranged in a repeating
sequence: [AnBm...] m being different from n.
Statistical copolymers have monomer residues arranged according to a
statistical rule. A statistical copolymer in which the probability of
finding a particular type of monomer residue at a particular point in
the chain is independent of the types of surrounding monomer residue
may be referred to as a truly random copolymer (structure 3).
For example, the chain-growth copolymer of vinyl chloride and vinyl
acetate is random.
Block copolymers have long sequences of different monomer
units (structure 4). Polymers with two or three blocks of two
distinct chemical species (e.g., A and B) are called diblock
copolymers and triblock copolymers, respectively. Polymers with three
blocks, each of a different chemical species (e.g., A, B, and C) are
termed triblock terpolymers.
Graft or grafted copolymers contain side chains or branches whose
repeat units have a different composition or configuration than the
main chain. (structure 5) The branches are added on to a preformed
main chain macromolecule.
Main article: Tacticity
Tacticity describes the relative stereochemistry of chiral centers in
neighboring structural units within a macromolecule. There are three
types: isotactic (all substituents on the same side), atactic (random
placement of substituents), and syndiotactic (alternating placement of
Polymer morphology generally describes the arrangement and microscale
ordering of polymer chains in space.
When applied to polymers, the term crystalline has a somewhat
ambiguous usage. In some cases, the term crystalline finds identical
usage to that used in conventional crystallography. For example, the
structure of a crystalline protein or polynucleotide, such as a sample
prepared for x-ray crystallography, may be defined in terms of a
conventional unit cell composed of one or more polymer molecules with
cell dimensions of hundreds of angstroms or more.
A synthetic polymer may be loosely described as crystalline if it
contains regions of three-dimensional ordering on atomic (rather than
macromolecular) length scales, usually arising from intramolecular
folding and/or stacking of adjacent chains. Synthetic polymers may
consist of both crystalline and amorphous regions; the degree of
crystallinity may be expressed in terms of a weight fraction or volume
fraction of crystalline material. Few synthetic polymers are entirely
The crystallinity of polymers is characterized by their degree of
crystallinity, ranging from zero for a completely non-crystalline
polymer to one for a theoretical completely crystalline polymer.
Polymers with microcrystalline regions are generally tougher (can be
bent more without breaking) and more impact-resistant than totally
Polymers with a degree of crystallinity approaching zero or one will
tend to be transparent, while polymers with intermediate degrees of
crystallinity will tend to be opaque due to light scattering by
crystalline or glassy regions. Thus for many polymers, reduced
crystallinity may also be associated with increased transparency.
The space occupied by a polymer molecule is generally expressed in
terms of radius of gyration, which is an average distance from the
center of mass of the chain to the chain itself. Alternatively, it may
be expressed in terms of pervaded volume, which is the volume of
solution spanned by the polymer chain and scales with the cube of the
radius of gyration.
A polyethylene sample that has necked under tension.
The bulk properties of a polymer are those most often of end-use
interest. These are the properties that dictate how the polymer
actually behaves on a macroscopic scale.
The tensile strength of a material quantifies how much elongating
stress the material will endure before failure. This is very
important in applications that rely upon a polymer's physical strength
or durability. For example, a rubber band with a higher tensile
strength will hold a greater weight before snapping. In general,
tensile strength increases with polymer chain length and crosslinking
of polymer chains.
Young's modulus of elasticity
Young's modulus quantifies the elasticity of the polymer. It is
defined, for small strains, as the ratio of rate of change of stress
to strain. Like tensile strength, this is highly relevant in polymer
applications involving the physical properties of polymers, such as
rubber bands. The modulus is strongly dependent on temperature.
Viscoelasticity describes a complex time-dependent elastic response,
which will exhibit hysteresis in the stress-strain curve when the load
Dynamic mechanical analysis
Dynamic mechanical analysis or DMA measures this complex
modulus by oscillating the load and measuring the resulting strain as
a function of time.
Transport properties such as diffusivity relate to how rapidly
molecules move through the polymer matrix. These are very important in
many applications of polymers for films and membranes.
The term melting point, when applied to polymers, suggests not a
solid–liquid phase transition but a transition from a crystalline or
semi-crystalline phase to a solid amorphous phase. Though abbreviated
as simply Tm, the property in question is more properly called the
crystalline melting temperature. Among synthetic polymers, crystalline
melting is only discussed with regards to thermoplastics, as
thermosetting polymers will decompose at high temperatures rather than
Glass transition temperature
A parameter of particular interest in synthetic polymer manufacturing
is the glass transition temperature (Tg), at which amorphous polymers
undergo a transition from a rubbery, viscous liquid, to a brittle,
glassy amorphous solid on cooling. The glass transition temperature
may be engineered by altering the degree of branching or crosslinking
in the polymer or by the addition of plasticizer.
Phase diagram of the typical mixing behavior of weakly interacting
In general, polymeric mixtures are far less miscible than mixtures of
small molecule materials. This effect results from the fact that the
driving force for mixing is usually entropy, not interaction energy.
In other words, miscible materials usually form a solution not because
their interaction with each other is more favorable than their
self-interaction, but because of an increase in entropy and hence free
energy associated with increasing the amount of volume available to
each component. This increase in entropy scales with the number of
particles (or moles) being mixed. Since polymeric molecules are much
larger and hence generally have much higher specific volumes than
small molecules, the number of molecules involved in a polymeric
mixture is far smaller than the number in a small molecule mixture of
equal volume. The energetics of mixing, on the other hand, is
comparable on a per volume basis for polymeric and small molecule
mixtures. This tends to increase the free energy of mixing for polymer
solutions and thus make solvation less favorable. Thus, concentrated
solutions of polymers are far rarer than those of small molecules.
Furthermore, the phase behavior of polymer solutions and mixtures is
more complex than that of small molecule mixtures. Whereas most small
molecule solutions exhibit only an upper critical solution temperature
phase transition, at which phase separation occurs with cooling,
polymer mixtures commonly exhibit a lower critical solution
temperature phase transition, at which phase separation occurs with
In dilute solution, the properties of the polymer are characterized by
the interaction between the solvent and the polymer. In a good
solvent, the polymer appears swollen and occupies a large volume. In
this scenario, intermolecular forces between the solvent and monomer
subunits dominate over intramolecular interactions. In a bad solvent
or poor solvent, intramolecular forces dominate and the chain
contracts. In the theta solvent, or the state of the polymer solution
where the value of the second virial coefficient becomes 0, the
intermolecular polymer-solvent repulsion balances exactly the
intramolecular monomer-monomer attraction. Under the theta condition
(also called the Flory condition), the polymer behaves like an ideal
random coil. The transition between the states is known as a
Inclusion of plasticizers
Inclusion of plasticizers tends to lower Tg and increase polymer
flexibility. Plasticizers are generally small molecules that are
chemically similar to the polymer and create gaps between polymer
chains for greater mobility and reduced interchain interactions. A
good example of the action of plasticizers is related to
polyvinylchlorides or PVCs. An uPVC, or unplasticized
polyvinylchloride, is used for things such as pipes. A pipe has no
plasticizers in it, because it needs to remain strong and
heat-resistant. Plasticized PVC is used in clothing for a flexible
quality. Plasticizers are also put in some types of cling film to make
the polymer more flexible.
The attractive forces between polymer chains play a large part in
determining polymer's properties. Because polymer chains are so long,
these interchain forces are amplified far beyond the attractions
between conventional molecules. Different side groups on the polymer
can lend the polymer to ionic bonding or hydrogen bonding between its
own chains. These stronger forces typically result in higher tensile
strength and higher crystalline melting points.
The intermolecular forces in polymers can be affected by dipoles in
the monomer units. Polymers containing amide or carbonyl groups can
form hydrogen bonds between adjacent chains; the partially positively
charged hydrogen atoms in N-H groups of one chain are strongly
attracted to the partially negatively charged oxygen atoms in C=O
groups on another. These strong hydrogen bonds, for example, result in
the high tensile strength and melting point of polymers containing
urethane or urea linkages. Polyesters have dipole-dipole bonding
between the oxygen atoms in C=O groups and the hydrogen atoms in H-C
Dipole bonding is not as strong as hydrogen bonding, so a
polyester's melting point and strength are lower than Kevlar's
(Twaron), but polyesters have greater flexibility.
Ethene, however, has no permanent dipole. The attractive forces
between polyethylene chains arise from weak van der Waals forces.
Molecules can be thought of as being surrounded by a cloud of negative
electrons. As two polymer chains approach, their electron clouds repel
one another. This has the effect of lowering the electron density on
one side of a polymer chain, creating a slight positive dipole on this
side. This charge is enough to attract the second polymer chain. Van
der Waals forces are quite weak, however, so polyethylene can have a
lower melting temperature compared to other polymers.
Polymers such as PMMA and HEMA:MMA are used as matrices in the gain
medium of solid-state dye lasers that are also known as polymer
lasers. These polymers have a high surface quality and are also highly
transparent so that the laser properties are dominated by the laser
dye used to dope the polymer matrix. These type of lasers, that also
belong to the class of organic lasers, are known to yield very narrow
linewidths which is useful for spectroscopy and analytical
applications. An important optical parameter in the polymer used
in laser applications is the change in refractive index with
temperature also known as dn/dT. For the polymers mentioned here the
(dn/dT) ~ −1.4 × 10−4 in units of K−1 in the 297 ≤ T ≤ 337
There are multiple conventions for naming polymer substances. Many
commonly used polymers, such as those found in consumer products, are
referred to by a common or trivial name. The trivial name is assigned
based on historical precedent or popular usage rather than a
standardized naming convention. Both the American
(ACS) and IUPAC have proposed standardized naming conventions;
the ACS and
IUPAC conventions are similar but not identical.
Examples of the differences between the various naming conventions are
given in the table below:
Poly(ethylene oxide) or PEO
Poly(ethylene terephthalate) or PET
In both standardized conventions, the polymers' names are intended to
reflect the monomer(s) from which they are synthesized rather than the
precise nature of the repeating subunit. For example, the polymer
synthesized from the simple alkene ethene is called polyethylene,
retaining the -ene suffix even though the double bond is removed
during the polymerization process:
The characterization of a polymer requires several parameters which
need to be specified. This is because a polymer actually consists of a
statistical distribution of chains of varying lengths, and each chain
consists of monomer residues which affect its properties.
A variety of laboratory techniques are used to determine the
properties of polymers. Techniques such as wide angle X-ray
scattering, small angle X-ray scattering, and small angle neutron
scattering are used to determine the crystalline structure of
Gel permeation chromatography
Gel permeation chromatography is used to determine the
number average molecular weight, weight average molecular weight, and
polydispersity. FTIR, Raman and NMR can be used to determine
composition. Thermal properties such as the glass transition
temperature and melting point can be determined by differential
scanning calorimetry and dynamic mechanical analysis. Pyrolysis
followed by analysis of the fragments is one more technique for
determining the possible structure of the polymer.
a useful technique to evaluate the thermal stability of the polymer.
Detailed analysis of TG curves also allow us to know a bit of the
phase segregation in polymers. Rheological properties are also
commonly used to help determine molecular architecture (molecular
weight, molecular weight distribution and branching) as well as to
understand how the polymer will process, through measurements of the
polymer in the melt phase. Another polymer characterization technique
is Automatic Continuous Online Monitoring of
(ACOMP) which provides real-time characterization of polymerization
reactions. It can be used as an analytical method in R&D, as a
tool for reaction optimization at the bench and pilot plant level and,
eventually, for feedback control of full-scale reactors. ACOMP
measures in a model-independent fashion the evolution of average molar
mass and intrinsic viscosity, monomer conversion kinetics and, in the
case of copolymers, also the average composition drift and
distribution. It is applicable in the areas of free radical and
controlled radical homo- and copolymerization, polyelectrolyte
synthesis, heterogeneous phase reactions, including emulsion
polymerization, adaptation to batch and continuous reactors, and
modifications of polymers.
A plastic item with thirty years of exposure to heat and cold, brake
fluid, and sunlight. Notice the discoloration, swelling, and crazing
of the material
Polymer degradation is a change in the properties—tensile strength,
color, shape, or molecular weight—of a polymer or polymer-based
product under the influence of one or more environmental factors, such
as heat, light, chemicals and, in some cases, galvanic action. It is
often due to the scission of polymer chain bonds via hydrolysis,
leading to a decrease in the molecular mass of the polymer.
Although such changes are frequently undesirable, in some cases, such
as biodegradation and recycling, they may be intended to prevent
environmental pollution, even though is widely known the fact that
fossil-based high density plastics and biodegradation are inversely
proportional and opposing concepts. Degradation can also be useful in
biomedical settings. For example, a copolymer of polylactic acid and
polyglycolic acid is employed in hydrolysable stitches that slowly
degrade after they are applied to a wound.
The susceptibility of a polymer to degradation depends on its
structure. Epoxies and chains containing aromatic functionalities are
especially susceptible to
UV degradation while polyesters are
susceptible to degradation by hydrolysis, while polymers containing an
unsaturated backbone are especially susceptible to ozone cracking.
Carbon based polymers are more susceptible to thermal degradation than
inorganic polymers such as polydimethylsiloxane and are therefore not
ideal for most high-temperature applications. High-temperature
matrices such as bismaleimides (BMI), condensation polyimides (with an
O-C-N bond), triazines (with a nitrogen (N) containing ring), and
blends thereof are susceptible to polymer degradation in the form of
galvanic corrosion when bare carbon fiber reinforced polymer CFRP is
in contact with an active metal such as aluminium in salt water
The degradation of polymers to form smaller molecules may proceed by
random scission or specific scission. The degradation of polyethylene
occurs by random scission—a random breakage of the bonds that hold
the atoms of the polymer together. When heated above 450 °C,
polyethylene degrades to form a mixture of hydrocarbons. Other
polymers, such as poly(alpha-methylstyrene), undergo specific chain
scission with breakage occurring only at the ends. They literally
unzip or depolymerize back to the constituent monomer.
The sorting of polymer waste for recycling purposes may be facilitated
by the use of the Resin identification codes developed by the Society
of the Plastics Industry to identify the type of plastic.
Chlorine attack of acetal resin plumbing joint
In a finished product, such a change is to be prevented or delayed.
Failure of safety-critical polymer components can cause serious
accidents, such as fire in the case of cracked and degraded polymer
fuel lines. Chlorine-induced cracking of acetal resin plumbing joints
and polybutylene pipes has caused many serious floods in domestic
properties, especially in the USA in the 1990s. Traces of chlorine in
the water supply attacked vulnerable polymers in the plastic plumbing,
a problem which occurs faster if any of the parts have been poorly
extruded or injection molded. Attack of the acetal joint occurred
because of faulty molding, leading to cracking along the threads of
the fitting which is a serious stress concentration.
Ozone-induced cracking in natural rubber tubing
Polymer oxidation has caused accidents involving medical devices. One
of the oldest known failure modes is ozone cracking caused by chain
scission when ozone gas attacks susceptible elastomers, such as
natural rubber and nitrile rubber. They possess double bonds in their
repeat units which are cleaved during ozonolysis. Cracks in fuel lines
can penetrate the bore of the tube and cause fuel leakage. If cracking
occurs in the engine compartment, electric sparks can ignite the
gasoline and can cause a serious fire. In medical use degradation of
polymers can lead to changes of physical and chemical characteristics
of implantable devices.
Fuel lines can also be attacked by another form of degradation:
Nylon 6,6 is susceptible to acid hydrolysis, and in one
accident, a fractured fuel line led to a spillage of diesel into the
road. If diesel fuel leaks onto the road, accidents to following cars
can be caused by the slippery nature of the deposit, which is like
Wikimedia Commons has media related to Polymers.
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Solid-state dye lasers
Thermal diffusivity in rubber
^ Roiter, Y.; Minko, S. (2005). "AFM Single
Molecule Experiments at
the Solid-Liquid Interface: In Situ Conformation of Adsorbed Flexible
Polyelectrolyte Chains". Journal of the American
Chemical Society. 127
(45): 15688–15689. doi:10.1021/ja0558239. PMID 16277495.
^ "polymer – definition of polymer". The Free Dictionary. Retrieved
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^ "Define polymer". Dictionary Reference. Retrieved 23 July
^ Painter, Paul C.; Coleman, Michael M. (1997). Fundamentals of
polymer science : an introductory text. Lancaster, Pa.: Technomic
Pub. Co. p. 1. ISBN 1-56676-559-5.
^ McCrum, N. G.; Buckley, C. P.; Bucknall, C. B. (1997). Principles of
polymer engineering. Oxford ; New York: Oxford University Press.
p. 1. ISBN 0-19-856526-7.
^ http://goldbook.iupac.org/M03667.html; accessed 7 October 2012. Per
IUPAC Gold Book and PAC sources referenced therein, "In many
cases, especially for synthetic polymers, a molecule can be regarded
as having a high relative molecular mass if the addition or removal of
one or a few of the units has a negligible effect on the molecular
properties." However, they note that the "statement fails in the case
of certain macromolecules for which the properties may be critically
dependent on fine details of the molecular structure."
^ IUPAC, Compendium of
Chemical Terminology, 2nd ed. (the "Gold Book")
(1997). Online corrected version: (2006–) "macromolecule
^ If two substances had empirical formulae that were integer multiples
of each other – e.g., acetylene (C2H2) and benzene (C6H6) –
Berzelius called them "polymeric". See: Jöns Jakob Berzelius (1833)
"Isomerie, Unterscheidung von damit analogen Verhältnissen"
(Isomeric, distinction from relations analogous to it), Jahres-Bericht
über die Fortschitte der physischen Wissenschaften …, 12 :
63–67. From page 64: "Um diese Art von Gleichheit in der
Zusammensetzung, bei Ungleichheit in den Eigenschaften, bezeichnen zu
können, möchte ich für diese Körper die Benennung polymerische
(von πολυς mehrere) vorschlagen." (In order to be able to denote
this type of similarity in composition [which is accompanied] by
differences in properties, I would like to propose the designation
"polymeric" (from πολυς, several) for these substances.)
Originally published in 1832 in Swedish as: Jöns Jacob Berzelius
(1832) "Isomeri, dess distinktion från dermed analoga
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Look up polymer in Wiktionary, the free dictionary.
How to Analyze Polymers Using X-ray Diffraction
Polymer Chemistry Hypertext, Educational resource
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