Polymers and Polymerization

Question 1

A high number of low MW molecules and a low number of high MW molecules may have the same average MW but have ___ properties.

Answer 1

different

Question 2

___ describes materials that undergo softening when heated and hardening when cooled.

Answer 2

Thermoplastic

Question 3

___ describes cross linked polymers that do not soften on heating.

Answer 3

Thermoset

Question 4

What are the 3 stages of Addition Polymerization (Free-Radical Polymerization)

Answer 4

Initiation Stage
Propagation Stage
Termination Stage

Question 5

Explain the initiation stage of Addition Polymerization (Free-Radical Polymerization)

Answer 5

Free radicals are created. They attack double bonds of monomer molecules. Unshared electrons are moved to the end of the monomer = activated monomer molecules

Question 6

Explain the propagation stage of Addition Polymerization (Free-Radical Polymerization)

Answer 6

Activated monomer molecules attack double bonds of other monomers. More monomer molecules are added to the free radicals. Chains grow in length.

Question 7

Explain the termination stage of Addition Polymerization (Free-Radical Polymerization)

Answer 7

Materials like hydroquinone, eugenol or large amounts of oxygen will inhibit or retard polymerization by reacting with free radicals. Decreases the rate of initiation or increases the rate of termination. Decreasing rate of polymerization decreases the degree of polymerization or molecular weight.