Polymers Flashcards
they are composed of hydrogen and carbon.
Hydrocarbons
Molecules that have double and triple covalent bonds
Unsaturated
all bonds are single ones, and no new atoms may be joined without the removal of others that are already bonded.
Saturated hydrocarbon
simple hydrocarbons belong to the
paraffin family;
hydrocarbons have relatively low melting and boiling points. However, boiling temperatures rise with increasing molecular weight
paraffin molecules
Hydrocarbon compounds with the same composition may have different atomic
arrangements, a phenomenon t
isomerism.
The molecules in polymers are gigantic in comparison to the
macromolecules.
These long molecules are composed of structural entities, which are successively repeated along the chain.
Repeat units
refers to the small molecule from which a polymer is synthesized. Hence
Monomer
When all of the repeating units along a chain are of the same type, the resulting polymer
homopolymer.
Chains may be composed of two or more different repeat units
copolymers.
The monomers discussed thus far have an active bond that
may react to form two covalent bonds with other monomers forming a two-dimensional chainlike molecular structure
bifunctional.
the number of bonds that a given monomer can form
functionality
they have three active bonds,
trifunctional;
repeat units are joined together end to end in single chains.
Linear polymers
Some of the common polymers that form with linear
are polyethylene, poly (vinyl chloride), polystyrene, poly (methyl methacrylate), nylon, and the fluorocarbons.
Polymers may be synthesized in which side-branch chains are connected to the main
branched polymer ones.
branched polymers
adjacent linear chains are joined one to another at various
positions by covalent bonds, crosslinking is achieved either during synthesis or by a nonreversible chemical reaction.
crosslinked polymer
Many of the rubber elastic materials are crosslinked; in rubbers,
vulcanization.
Multifunctional monomers forming three or more active covalent bonds make three
dimensional networks (Figure 10.6d) and are termed
Network Polymers
a polymer that is highly cross linked may also be classified as a
network polymer
These materials have distinctive mechanical and thermal properties;
These materials have distinctive mechanical and thermal properties;
Two isomeric subclasses
stereoisomerism and geometrical isomerism.
denotes the situation in which atoms are linked together in the same order (head-to-tail) but differ in their spatial arrangement. For
Stereoisomerism
one stereoisomer, all of the R groups are situated on the same side of the chain
an isotactic configuration.
the R groups alternate sides
syndiotactic configuration, the
random positioning
atactic configuration
sometimes called gutta percha, has properties that are distinctly different from those of natural rubber as a result of this configurational alteration.
Transpolyisoprene
soften when heated
Thermoplastics (or thermoplastic polymers)
and harden when cooled
Thermoplastics (or thermoplastic polymers)
network polymers.
Thermosetting polymers or thermosets
They become
permanently hard during their formation and do not soften upon heating. Network
Thermosetting polymers or thermosets
composed of two repeat units a
Copolymer
two different units are randomly dispersed along
the chain i
a random copolymer.
the two repeat units alternate
chain positions,
alternating copolymer
one in which identical repeat units are clustered in blocks along the
chain (Figure 10.8c).
A block copolymer is
may range from completely amorphous to almost entirely (up
to about 95%) crystalline;
degree of crystallinity
Fracture strengths of polymeric materials are
are low relative to those of metals and ceramics.
The crosslinking process in elastomera
vulcanization,
are perhaps the most widely used group of polymers and include the
following: polyethylene, polypropylene, poly(vinyl chloride), polystyrene, and the fluorocarbons, epoxies, phenolics, and polyesters. T
PLASTICS
most important synthetic elastomer
SBR,
are capable of being drawn into long filaments having at least a 100:1
length-to-diameter ratio
Fiber
frequently applied to the surface of materials to serve one or more of the
following functions: (1) to protect the item from the environment, which may produce corrosive or deteriorative reactions; (2) to improve the item’s appearance; and (3) to provide electrical insulation. M
Coatings
stable suspension of small, insoluble
polymer particles dispersed in water
Latex
is a substance used to bond together the surfaces of two solid materials
Adhesives
include low density, a high degree of flexibility, high tensile and tear strengths, resistance to attack by moisture and other chemicals, and low permeability to some gases, especially water vapor.
Films
are plastic materials that contain a relatively high volume percentage of small pores and trapped gas bubbles. Both
Foams
are commonly used as cushions in automobiles and furniture, as well as in packaging and thermal insulation
Foams
is a linear polyethylene that has
an extremely high molecular weight.
Ultra-high-molecular-weight polyethylene (UHMWPE
is highly aligned and has the trade name Spectra. Some
ra-high-molecular-weight polyethylene (UHMWPE) is
are a group of chemically complex and structurally
distinct materials that have unique properties and are used in diverse applications. Discussion
Liquid crystal polymers (LCPs
(TPEs or TEs) are a type of polymeric material that, at
ambient conditions, exhibits elastomeric (or rubbery) behavior yet is thermoplastic.
Thermoplastic elastomers (TPEs or TEs
monomer units are attached one at a time in chainlike fashion to form a linear molecule.
addition polymerization,
involves stepwise intermolecular chemical reactions that may include more than a single molecular species.
Condensation polymerization
are added to improve the strength, abrasion resistance, toughness, and or thermal/dimensional stability of polymers.
Fillers
Many films are simply extruded through a ___; this may be followed by a rolling
(calendering) or drawing operation that serves to reduce thickness and improve strength.
thin die slit
process by which fibers are formed from bulk polymer material is termed
spinning
The strength of fibers is improved by a post forming process called
drawing.
the polymer is dissolved in a volatile solvent
dry spinning
as when a molten plastic material is poured
into a mold and allowed to solidify.
Casting
the molding of a viscous thermoplastic under pressure through
an open-ended die, similar to the extrusion of metals. A
Extrusion
most widely
used technique for fabricating thermoplastic materials
Injection Molding
