Chapter 14

Question 1

What are 6 examples of natural polymers?

Answer 1

wood, cotton, leather, rubber, wool, silk

Question 2

What are most polymers made up of? What is this called?

Answer 2

made up of H and C

Hydrocarbons

Question 3

What are the intramolecular bonds of hydrocarbons?

Answer 3

covalent

Question 4

What is a saturated hydrocarbon? What is an example?

Answer 4

Each carbon is singly bonded to four other atoms

C2H6S

Question 5

What are unsaturated molecules?

Answer 5

Molecules that have double and triple covalent bonds

Question 6

What are saturated molecules?

Answer 6

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

Question 7

What is a Paraffin compound chemical formula?

Answer 7

Question 8

What are the first four molecules of the Paraffin family?

Answer 8

Methane, ethane, propane, butane

Question 9

What is the composition, structure, and boiling point of the first four paraffin compounds?

Answer 9

Question 10

What kind of bonds do unsaturated hydrocarbons have? Give examples for each.

Answer 10

Double and triple bonds that are somewhat unstable

Double bond: ethylene or ethene- C2H4

Tripple bond: acetylene or ethyne- C2H2

Question 11

What is isomerism? What’s are two examples?

Answer 11

When two compounds have the same chemical formula but have different structures/atomic arrangements

C8H18: normal-octane and 2,4-dimethylhexane

butane and isobutane

Question 12

How big are polymer molecules in comparison to hydrocarbon molecules? What are they often called?

Answer 12

molecules in polymers are MUCH bigger. They are called macromoledules.

Question 13

What are the two steps of free radical polymerization?

Answer 13

Initiation and propagation

Question 14

What happens during initiation in free radical polymerization?

Answer 14

a free radical “R” is added to a monomer (ex: ethylene)

Question 15

What happens during propagation in free radical polymerization?

Answer 15

the R+monomer i added to another repeat unit, creating a dimer, which eventually creates a polymer

Question 16

What is an initiator? Give an example.

Answer 16

A substance that starts the polymerization reaction by generating free radicals

Benzoyl peroxide

Question 17

What is polyethylene? Give an example.

Answer 17

A long-chain hydrocarbon

Paraffin wax for candles is short-chain polyethylene

Question 18

What are the repeat units for the first 4/10 polymeric materials?

Answer 18

1) polyethylene (PE)
2) poly (vinyl chloride) (PVC)
3) polytetrafluoroethylene (PTFE)
4) polypropylene (PP)

Question 19

What are the repeat units for 5-7/10 polymeric materials?

Answer 19

5) polystyrene (PS)
6) poly (methyl methacrylate) (PMMA)
7) phenol-formaldehyde (Backelite)

Question 20

What are the repeat units for 8-10/10 polymeric materials?

Answer 20

8) poly (hexamethylene adipamide) (nylon 6,6)
9) poly (ethylene terepthalate) (PET, a polyester)
10) polycarbonate (PC)

Question 21

What is molecular weight?

Answer 21

M

The mass of a mole of chains

Question 22

What is a homopolymer?

Answer 22

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

Question 23

What is a copolymer?

Answer 23

A polymer the chain has two or more different repeat units

Question 24

Why are not all chains in a polymer the same length?

Answer 24

There’s a distribution of molecular weights

Question 25

What type of bonding is in a linear polymer structure?

Answer 25

secondary bonding

Question 26

What are copolymers?

Answer 26

Two or more monomers polymerized together

Question 27

What are the four categories of copolymers?

Answer 27

1) random 2) alternating 3) block 4) graft

Question 28

What does a random copolymer look like?

Answer 28

A and B are randomly positioned along chain

Question 29

What does an alternating copolymer look like?

Answer 29

A and B alternate in polymer chains

Question 30

What does a block copolymer look like?

Answer 30

large blocks of A units alternate with large blocks of B units

Question 31

What does a graft copolymer look like?

Answer 31

chains of B units grafted onto A backbone

Question 32

How do you identify crystallinity in polymers? How do you define a crystal structure? What's an example?

Answer 32

Ordered atomic arrangements involving molecular chains Crystal structures are in terms of unit cells Polyethylene

Question 33

What are crystalline regions? What is their structue?

Answer 33

Thin platelets with chain folds at faces Chain folded structure

Question 34

Are polymers ever 100% crystalline? Why?

Answer 34

No they're rarely 100% crystalline It's difficult for all regions of all chains to become aligned

Question 35

What is degree of crystallinity usually expressed as?

Answer 35

% crystallinity

Question 36

What do physical properties of polymers usually depend on? What can change this?

Answer 36

Properties depend on % crystallinity Heat treating causes crystalline regions to grow and % crystallinity to increase

Question 37

How do polymer single crystals form? What do they look like under electron micrographs?

Answer 37

Single crystals only occur for slow and carefully controlled growth rates They look like multilayered single crystals (chain-folded layers) of polyethylene

Question 38

What structure do some semicrystalline polymers form?

Answer 38

Spherulite structures

Question 39

What does spherulite structure look like?

Answer 39

Alternating (lamellar) chain-folded crystallites and amorphous regions They begin at the nucleation site Regions are divided by interspherulitic boundary

Question 40

What is the growth rate for spherulite structure?

Answer 40

Relatively rapid

Question 41

What happens when a cross-polarized light is used to photomicrograph spherulites in polyethylene?

Answer 41

a maltese cross appears in each spherulite

Question 42

What are some polymers that form with linear structures?

Answer 42

1) polyethylene 2) poly (vinyl chloride) 3) nylon 4) fluorocarbons