Ch. 10- Polymers

Question 1

polymer

Answer 1

a molecule with a large molecular mass that is formed by repeating smaller units (monomers)

Question 2

monomer

Answer 2

a substance of relatively low molecular mass; the building blocks of polymers

Question 3

polymerization

Answer 3

a process by which monomers are made into polymers

Question 4

celluloid

Answer 4

cellulose nitrate, derived from natural cellulose by treating it with nitric acid; earliest synthetic attempt to improve on natural polymers

Question 5

what do we use celluloid for?

Answer 5

as a substitute for more expensive materials like ivory, amber, and tortoise shell; used to make billiards balls, movie film, & stiff shirt collars

Question 6

why don’t we use celluloid as much?

Answer 6

it’s highly flammable and difficult to preserve

Question 7

what was the first truly synthetic polymer?

Answer 7

Bakelite, made from phenol & formaldehyde

Question 8

what is the simplest and least expensive synthetic polymer?

Answer 8

polyethylene

Question 9

why was polyethylene so important for the Battle of Britain?

Answer 9

it was invented just before the war, and was used as an electric insulator; without it, the British would have had to use what they had at the time (cotton braid + rubber paint) for electric wires, which was very ineffective for their radar; if their radar wasn’t as effective as it was with polyethylene, they could’ve lost the battle

Question 10

what is the source of most synthetic polymers?

Answer 10

petroleum & natural gas

Question 11

copolymer

Answer 11

a polymer formed by the combination of two (or more) different monomers

Question 12

what are the 3 main types of polyethylene

Answer 12

• high-density polyethylene (HDPE)
• low-density polyethylene (LDPE)
• linear low-density polyethylene (LLDPE)

Question 13

properties of high-density polyethylene (HDPE)

Answer 13

• has mostly linear molecules that pack tightly in a crystalline structure
• rigid & strong plastics
• have densities of 0.94-0.96 g/cm3
• hold shape in boiling water

Question 14

how do we use HDPE?

Answer 14

• threaded bottle caps
• toys
• detergent bottles
• milk jugs

Question 15

properties of low-density polyethylene (LDPE)

Answer 15

• has many side chains branching off the polymer molecules, preventing the molecules to tightly pack & assume crystalline structure
• waxy, bendable plastics
• have densities of 0.91-0.94 g/cm3
• severely deform in boiling water

Question 16

how do we use LDPE?

Answer 16

• plastic bags & film
• squeeze bottles
• electric wire insulation
• common household products that require flexibility

Question 17

how do we make linear low-density polyethylene (LLDPE)?

Answer 17

by polymerizing ethylene with a branched-chain alkene

Question 18

how do we use LLDPE?

Answer 18

• plastic films for landfill liners
• trash cans
• tubing
• automotive parts

Question 19

thermosetting polymer

Answer 19

a polymer that cannot be softened and remolded; very high temperatures cause them to discolor and decompose

Question 20

thermoplastic polymer

Answer 20

a polymer that can be heated and reshaped

Question 21

addition polymerization (chain-reaction polymerization)

Answer 21

a polymerization reaction in which all the atoms of the monomer molecules are included in the polymer

Question 22

vulcanization

Answer 22

the process of making naturally soft rubber harder by reacting it with sulfur

Question 23

vulcanization

Answer 23

the process of making naturally soft rubber harder by reacting it with sulfur

Question 24

cross-linking

Answer 24

connecting long chains of molecules through covalently bonded atoms or small groups of atoms

Question 25

Charles Goodyear

Answer 25

discovered vulcanization & was issued a patent for it

Question 26

elastomer

Answer 26

a polymeric material that returns to its original shape after being stretched

Question 27

what is natural rubber a polymer of?

Answer 27

isoprene

Question 28

condensation polymerization (step-wise polymerization)

Answer 28

a polymerization reaction in which not all the atoms in the starting monomers are incorporated in the polymer because water (or other small) molecules are formed as by-products

Question 29

polyamide

Answer 29

a polymer that has monomer units joined by amide linkages

Question 30

polyester

Answer 30

a polymer that has monomer units joined by ester linkages

Question 31

thermosetting resins

Answer 31

polymeric materials that harden irreversibly

Question 32

polycarbonates

Answer 32

"clear as glass", tough polymers that have carbonate groups

Question 33

polyurethanes

Answer 33

polymers that are similar to nylon polymers in structure, but have (--NHCOO) bonds, which are formed by an isocyanate group (--N=C=O) reacting with an alcohol group (--OH)

Question 34

epoxies

Answer 34

polymers that are powerful adhesives due to cross-linking

Question 35

silicone

Answer 35

a polymer whose chain consists of alternating silicon and oxygen atoms

Question 36

important properties of silicone

Answer 36

- can be linear, cyclic, or cross-linked networks - heat-stable and resistant to most chemicals - excellent waterproofing materials

Question 37

crystalline polymers

Answer 37

polymers composed of molecules that line up neatly to form long, strong fibers

Question 38

amorphous polymers

Answer 38

polymers composed of molecules that are randomly oriented & intertwined with one another

Question 39

glass transition temperature (Tg)

Answer 39

the temperature of a polymer that states if the polymer measures above that temperature, it's rubbery & tough, and if the polymer measures below that temperature, it's hard, stiff, & brittle, like glass

Question 40

why do we use synthetic fibers instead of natural fibers for everyday use?

Answer 40

- synthetic fibers can replicate many liked properties of natural fibers, like appearance & how they feel - less expensive - easier to care for - last longer - more useful (i.e. microfibers' ability to either absorb or repel water)

Question 41

of the 55% of solid waste produced by the U.S. annually, how much of it is plastic?

Answer 41

about 13%

Question 42

name two degradable plastics & their sources

Answer 42

- polylactic acid (PLA) made from corn or sugar cane | - polyhydroxyalkanoates (PHAs) made from microorganisms

Question 43

which plastics are currently recycled on a large scale in the U.S.?

Answer 43

- polyethylene terephthalate - PET (28% recycled) | - high-density polyethylene - HDPE (29% recycled)

Question 44

how have we developed flame-retardant fibers? how do we use them?

Answer 44

- we add chlorine & bromine atoms to polymeric fibers which results in flame-retardant fibers (required for children's sleepwear) - development of Nomex (meta-aramid) which is a synthetic fiber that does not react with flames/high heat (used for protective clothing, like firefighting gear)

Question 45

plasticizer

Answer 45

a substance added to some plastics to make them more flexible and easier to work with by lowering their glass transition temperature

Question 46

how can plasticizers be harmful to the environment?

Answer 46

plasticizers get lost by diffusion & evaporation as a plastic ages, spilling into the environment & degrading very slowly, leading to their becoming concentrated in the food chain

Question 47

what used to be a popular plasticizer that is now banned, and why is it banned?

Answer 47

polychlorinated biphenyls (PCBs); derived from biphenyls, when PCBs are exposed to other compounds, the hydrogen atoms of biphenyl get replaced with chlorine atoms, creating substances that have similar psychological effects as DDT (insecticide)

Question 48

what is the most popular plasticizer currently & why?

Answer 48

- phthalate esters which are derived from phthalic acid | - they're safer to use & degrade rapidly