Polymers

Question 1

they are composed of hydrogen and carbon.

Answer 1

Hydrocarbons

Question 2

Molecules that have double and triple covalent bonds

Answer 2

Unsaturated

Question 3

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

Answer 3

Saturated hydrocarbon

Question 4

simple hydrocarbons belong to the

Answer 4

paraffin family;

Question 5

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

Answer 5

paraffin molecules

Question 6

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

Answer 6

isomerism.

Question 7

The molecules in polymers are gigantic in comparison to the

Answer 7

macromolecules.

Question 8

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

Answer 8

Repeat units

Question 9

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

Answer 9

Monomer

Question 10

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

Answer 10

homopolymer.

Question 11

Chains may be composed of two or more different repeat units

Answer 11

copolymers.

Question 12

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

Answer 12

bifunctional.

Question 13

the number of bonds that a given monomer can form

Answer 13

functionality

Question 14

they have three active bonds,

Answer 14

trifunctional;

Question 15

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

Answer 15

Linear polymers

Question 16

Some of the common polymers that form with linear

Answer 16

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

Question 17

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

Answer 17

branched polymers

Question 18

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.

Answer 18

crosslinked polymer

Question 19

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

Answer 19

vulcanization.

Question 20

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

Answer 20

Network Polymers

Question 21

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

Answer 21

network polymer

Question 22

These materials have distinctive mechanical and thermal properties;

Answer 22

These materials have distinctive mechanical and thermal properties;

Question 23

Two isomeric subclasses

Answer 23

stereoisomerism and geometrical isomerism.

Question 24

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

Answer 24

Stereoisomerism

Question 25

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

Answer 25

an isotactic configuration.

Question 26

the R groups alternate sides

Answer 26

syndiotactic configuration, the

Question 27

random positioning

Answer 27

atactic configuration

Question 28

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

Answer 28

Transpolyisoprene

Question 29

soften when heated

Answer 29

Thermoplastics (or thermoplastic polymers)

Question 30

and harden when cooled

Answer 30

Thermoplastics (or thermoplastic polymers)

Question 31

network polymers.

Answer 31

Thermosetting polymers or thermosets

Question 32

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

Answer 32

Thermosetting polymers or thermosets

Question 33

composed of two repeat units a

Answer 33

Copolymer

Question 34

two different units are randomly dispersed along the chain i

Answer 34

a random copolymer.

Question 35

the two repeat units alternate chain positions,

Answer 35

alternating copolymer

Question 36

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

Answer 36

A block copolymer is

Question 37

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

Answer 37

degree of crystallinity

Question 38

Fracture strengths of polymeric materials are

Answer 38

are low relative to those of metals and ceramics.

Question 39

The crosslinking process in elastomera

Answer 39

vulcanization,

Question 40

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

Answer 40

PLASTICS

Question 41

most important synthetic elastomer

Answer 41

SBR,

Question 42

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

Answer 42

Fiber

Question 43

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

Answer 43

Coatings

Question 44

stable suspension of small, insoluble polymer particles dispersed in water

Answer 44

Latex

Question 45

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

Answer 45

Adhesives

Question 46

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.

Answer 46

Films

Question 47

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

Answer 47

Foams

Question 48

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

Answer 48

Foams

Question 49

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

Answer 49

Ultra-high-molecular-weight polyethylene (UHMWPE

Question 50

is highly aligned and has the trade name Spectra. Some

Answer 50

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

Question 51

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

Answer 51

Liquid crystal polymers (LCPs

Question 52

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

Answer 52

Thermoplastic elastomers (TPEs or TEs

Question 53

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

Answer 53

addition polymerization,

Question 54

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

Answer 54

Condensation polymerization

Question 55

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

Answer 55

Fillers

Question 56

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.

Answer 56

thin die slit

Question 57

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

Answer 57

spinning

Question 58

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

Answer 58

drawing.

Question 59

the polymer is dissolved in a volatile solvent

Answer 59

dry spinning

Question 60

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

Answer 60

Casting

Question 61

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

Answer 61

Extrusion

Question 62

most widely used technique for fabricating thermoplastic materials

Answer 62

Injection Molding