Lecture 4

Question 1

What are the two forces responsible for binding chains together?

Answer 1

• chain entaglement
• large number of weak van der walls forces combined together
• larger the chain the greater the strength

Question 2

What are semi crystalline polymers?

Answer 2

-polymers that are both amorphous and crystalline at the same time.

Question 3

What is the melting temp and glass transition temp.?

Answer 3

Melting temp: temp at which a polymer becomes viscoeleastic (solid to solid-liquid state)

Glass transition temp: Temp. where molecules gain enough energy to the point where they can slide and move (become amorphous)

Question 4

Two different types of polymers:

Answer 4

1. Natural polymers: natural
   - naturally occuring and come from biological sources and are biodegradable.
   - not as long lasting or customizable
2. Synthetic polymers-Man made
   - long lasting and customizable
   - not as biodegradable and made on petroleum which cause a drag on the environment
   - can add additives to improve properties
   - cheap to produce
3. semi synthetic polymers:
   - natural polymers with additives which enhance it’s properties

Question 5

Homopolymers vs. copolymers

Answer 5

• Homopolymers: A polymer that is made up of one monomer

- Co-polymer: Polymers that are made up of multiple monomers

Question 6

Different types of copolymers:

Answer 6

Alternating copolymers: One type of polymer after another

Block polymers- groups of polymers arranged together on a chain

Groft polymer-chains of polymers that are attached to a straight chain and stick out

Question 7

Why is thermoset often preferred over thermoplastic-

Answer 7

Thermoset is more rigid and better at holding shape than thermoplastic.

Question 8

Difference between crystalline and amorphous?

Answer 8

Crystalline-rigid and packed together

amorphous-flexible and freely moving around

Question 9

Three factors that affect crystallinity and how they are affected:

Answer 9

1. polarity-more
2. rate of cooling-cool faster not enough time to align in a structured manner»more
3. Flexibility-ability to move around which inhibits the degree to which crystalline molecules come together
4. Regularity of structure

Question 10

Thermoplastic vs. thermoset:

Answer 10

Thermoplastic refers to a type of plastic that can be