Polymer Morphology - Crystalline State

Question 1

What do polymer crystals similar to small molecules/metallic crystals have?

Answer 1

-three dimensional positional order
-first order transition

Question 2

What do polymer crystals different to small molecules/metallic crystals have?

Answer 2

• degree of crystallinity is less than 100%
• unit cell never contains the whole chain
• bonding differs greatly in different directions

Question 3

What temperatures is crystallization between?

Answer 3

Tg and Tm

Question 4

What is degree of crystallinity controlled by?

Answer 4

-structure of polymer chain
-thermal history

Question 5

What are some techniques for detecting polymer crystal melting point?

Answer 5

• simple visual observation
• quantitative evaluation (x-ray diffraction, raman spectroscopy, etc.)

Question 6

What are some factors that control the degree of crystallinity?

Answer 6

• crystallization conditions
• chain structure

Question 7

What happens during the primary stage of isothermal crystallization?

Answer 7

Nucleation and growth of spherulites

Question 8

What happens during the secondary state of isothermal crystallization?

Answer 8

New crystals or lamellar thickening

Question 9

What are the kinetics of polymer crystallization?

Answer 9

-increases linearly over time
- impacted by structure/composition