Test 3 Flashcards
Contrast thermoplastic and thermosetting materials.
thermoplastics have little crosslinking thermosets have significant crosslinking thermoplastics soften with heating thermosets do not soften with heating thermosets are hard and brittle
List some thermoplastic materials
polyethylene
polypropylene
polycarbonate
polystyrene
List some thermosets
vulcanized rubber
epoxies
polyester resin
phenolic resin
For an ionic ceramic compound, what are the characteristics that determine the crystal structure?
relative ion size and ion valence
What is the coordination number and rc/ra range for the rock salt (NaCl) crystal structure?
6
0.414-0.732
What is the coordination number and rc/ra range for the Cesium Chloride (CsCl) crystal structure?
8
0.732-1.000
What is the coordination number and rc/ra range for the Zinc Blende (ZnS) crystal structure?
4
0.225-0.414
What kind of bonds are found in ceramics?
ionic and covalent
What is the formula for an aromatic ring?
C6H4
What does tau_c represent?
fiber matrix bond strength or matrix shear yield strength
sigma_cd’ represents what?
Longitudinal tensile strength for discontinuous
and aligned fibrous composite and l < lc
What does sigma’m represent?
Stress in matrix at composite failure
What does sigma*f represent?
fiber tensile strength
What does K represent?
fiber-efficiency parameter?
What is the value of K if all fibers are parallel and the stress is parallel to the fibers?
1
What is the value of K if all fibers all parallel and the stress is perpendicular to the fibers?
0
What is the value of K if the fibers are randomly and uniformly distributed within a specific plane and the stress is in any direction in the plane of the fibers??
3/8
What is the value of K if the fibers are randomly and uniformly distributed within three dimensions in space and the stress is in any direction?
1/5
List the three kinds of tacticity in order of decreasing regularity.
isotactic, syndiotactic, atactic
Describe the Rock Salt (NaCl) crystal structure.
Both Na and Cl are arranged in FCC pattern. Na+ is in the shifted pattern.
Describe the Cesium Chloride (CsCl) crystal structure.
Octahedral with Cs+ in the middle. Looks like BCC.
Describe the Zinc Blende (ZnS) crystal structure.
The sulfur looks like FCC. Zinc is in the tetrahedral sites.
What causes Tg and Tm to increase?
increasing chain stiffness
What increases chain stiffness?
- bulky sidegroups
- polar groups or sidegroups
- chain double bonds or aromatic chain groups
What affects Tm only?
The regularity of repeat units