Lecture 11 Flashcards
What structure will a high density PE have?
linear crystalline (used for prosthesis)
What structure will a low density PE have?
branched amorphous (used for bottles/bags)
What does amorphous mean in regards to the order of the polymer?
no order or orientation
What does semi- crystalline mean in regards to the order of the polymer?
some order to structure
How do you get the Youngs Modulus on a stress vs strain graph?
the slope of the linear region is the youngs modulus
How do you get the yield strength on a stress vs strain graph?
the highest y value of the linear region
How do you get the ultimate strength on a stress vs strain graph?
the maxima of the curved region
How do you get the fracture point on a stress vs strain graph?
The last point of the line
What does the linear region of a stress vs strain curve represent?
elastic/recoverable (change in bond spacing)
What does the nonlinear region of a stress vs strain curve represent?
plastic deformation (slip of atoms/molecules)
What would the graph of a brittle material look like on a stress vs strain curve?
very steep slope that stops
What would the graph of an elastomer look like on a stress vs strain curve?
very shallow slope and long
What are the three types of polymer degradation?
hydrolysis, oxidation, enzymatic, and dissociation
What is polymer hydrolysis?
polymer bonds react with water molecules, break up, and produce new chain ends
What is polymer oxidation?
a chemical reaction that breaks down polymers when they are exposed to oxygen
What is enzymatic polymer degradation?
a process that uses enzymes to break down polymer chains
True/False: polymers are highly tunable.
True
What polymer structures dissolve?
linear and branched
What polymer structures do not dissolve?
crosslinked
- linear, branched based on __________
- crosslinked based on __________
- linear, branched based on polymer entanglement
- crosslinked based on introduced crosslinks
What does polymer chemistry impact?
cell interactions, mechanics, degradation/erosion
What polymer properties does MW affect?
viscosity, toughness, degradation, Tg/Tm, and crystallinity
