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MET > Polymers > Flashcards

Polymers Flashcards

1
Q

they are composed of hydrogen and carbon.

A

Hydrocarbons

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2
Q

Molecules that have double and triple covalent bonds

A

Unsaturated

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3
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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4
Q

simple hydrocarbons belong to the

A

paraffin family;

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5
Q

hydrocarbons have relatively low melting and boiling points. However, boiling temperatures rise with increasing molecular weight

A

paraffin molecules

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6
Q

Hydrocarbon compounds with the same composition may have different atomic
arrangements, a phenomenon t

A

isomerism.

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7
Q

The molecules in polymers are gigantic in comparison to the

A

macromolecules.

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8
Q

These long molecules are composed of structural entities, which are successively repeated along the chain.

A

Repeat units

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9
Q

refers to the small molecule from which a polymer is synthesized. Hence

A

Monomer

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10
Q

When all of the repeating units along a chain are of the same type, the resulting polymer

A

homopolymer.

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11
Q

Chains may be composed of two or more different repeat units

A

copolymers.

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12
Q

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

A

bifunctional.

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13
Q

the number of bonds that a given monomer can form

A

functionality

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14
Q

they have three active bonds,

A

trifunctional;

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15
Q

repeat units are joined together end to end in single chains.

A

Linear polymers

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16
Q

Some of the common polymers that form with linear

A

are polyethylene, poly (vinyl chloride), polystyrene, poly (methyl methacrylate), nylon, and the fluorocarbons.

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17
Q

Polymers may be synthesized in which side-branch chains are connected to the main
branched polymer ones.

A

branched polymers

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18
Q

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.

A

crosslinked polymer

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19
Q

Many of the rubber elastic materials are crosslinked; in rubbers,

A

vulcanization.

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20
Q

Multifunctional monomers forming three or more active covalent bonds make three
dimensional networks (Figure 10.6d) and are termed

A

Network Polymers

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21
Q

a polymer that is highly cross linked may also be classified as a

A

network polymer

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22
Q

These materials have distinctive mechanical and thermal properties;

A

These materials have distinctive mechanical and thermal properties;

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23
Q

Two isomeric subclasses

A

stereoisomerism and geometrical isomerism.

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24
Q

denotes the situation in which atoms are linked together in the same order (head-to-tail) but differ in their spatial arrangement. For

A

Stereoisomerism

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25
Q

one stereoisomer, all of the R groups are situated on the same side of the chain

A

an isotactic configuration.

26
Q

the R groups alternate sides

A

syndiotactic configuration, the

27
Q

random positioning

A

atactic configuration

28
Q

sometimes called gutta percha, has properties that are distinctly different from those of natural rubber as a result of this configurational alteration.

A

Transpolyisoprene

29
Q

soften when heated

A

Thermoplastics (or thermoplastic polymers)

30
Q

and harden when cooled

A

Thermoplastics (or thermoplastic polymers)

31
Q

network polymers.

A

Thermosetting polymers or thermosets

32
Q

They become
permanently hard during their formation and do not soften upon heating. Network

A

Thermosetting polymers or thermosets

33
Q

composed of two repeat units a

A

Copolymer

34
Q

two different units are randomly dispersed along
the chain i

A

a random copolymer.

35
Q

the two repeat units alternate
chain positions,

A

alternating copolymer

36
Q

one in which identical repeat units are clustered in blocks along the
chain (Figure 10.8c).

A

A block copolymer is

37
Q

may range from completely amorphous to almost entirely (up
to about 95%) crystalline;

A

degree of crystallinity

38
Q

Fracture strengths of polymeric materials are

A

are low relative to those of metals and ceramics.

39
Q

The crosslinking process in elastomera

A

vulcanization,

40
Q

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

A

PLASTICS

41
Q

most important synthetic elastomer

A

SBR,

42
Q

are capable of being drawn into long filaments having at least a 100:1
length-to-diameter ratio

A

Fiber

43
Q

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

A

Coatings

44
Q

stable suspension of small, insoluble
polymer particles dispersed in water

A

Latex

45
Q

is a substance used to bond together the surfaces of two solid materials

A

Adhesives

46
Q

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.

A

Films

47
Q

are plastic materials that contain a relatively high volume percentage of small pores and trapped gas bubbles. Both

A

Foams

48
Q

are commonly used as cushions in automobiles and furniture, as well as in packaging and thermal insulation

A

Foams

49
Q

is a linear polyethylene that has
an extremely high molecular weight.

A

Ultra-high-molecular-weight polyethylene (UHMWPE

50
Q

is highly aligned and has the trade name Spectra. Some

A

ra-high-molecular-weight polyethylene (UHMWPE) is

51
Q

are a group of chemically complex and structurally
distinct materials that have unique properties and are used in diverse applications. Discussion

A

Liquid crystal polymers (LCPs

52
Q

(TPEs or TEs) are a type of polymeric material that, at
ambient conditions, exhibits elastomeric (or rubbery) behavior yet is thermoplastic.

A

Thermoplastic elastomers (TPEs or TEs

53
Q

monomer units are attached one at a time in chainlike fashion to form a linear molecule.

A

addition polymerization,

54
Q

involves stepwise intermolecular chemical reactions that may include more than a single molecular species.

A

Condensation polymerization

55
Q

are added to improve the strength, abrasion resistance, toughness, and or thermal/dimensional stability of polymers.

A

Fillers

56
Q

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.

A

thin die slit

57
Q

process by which fibers are formed from bulk polymer material is termed

A

spinning

58
Q

The strength of fibers is improved by a post forming process called

A

drawing.

59
Q

the polymer is dissolved in a volatile solvent

A

dry spinning

60
Q

as when a molten plastic material is poured
into a mold and allowed to solidify.

A

Casting

61
Q

the molding of a viscous thermoplastic under pressure through
an open-ended die, similar to the extrusion of metals. A

A

Extrusion

62
Q

most widely
used technique for fabricating thermoplastic materials

A

Injection Molding

MET (11 decks)

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