Term
| Is the glass transition temperature an equilibrium transformation temperature? |
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Definition
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Term
| Which has a higher specific volume, at the same temperature? (Glass or Solid) |
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Definition
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Term
| How does cooling rate affect the glass transition temperature? |
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Definition
| Higher cooling rate = higher glass transition temperature |
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Term
| Why should there be a lower limit to the glass transition temperature? |
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Definition
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Term
| As temperature increases, viscosity _____. |
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Definition
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Term
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Definition
| Property of resistance to flow in a fluid or semifluid |
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Term
| Zacharisen's Rules for Oxide Glass Formation |
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Definition
1. Oxide glass networks are composed of oxygen polyhedra.
2. Coordination of each oxygen atom in the glass network should be 2.
3. Coordination number of each metal atom in the glass network should be 3 or 4.
4. Oxide polyhedra share corners, not edges or faces.
5. Each polyhedron should share at least 3 corners. |
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Term
| Network former examples vs. network modifier examples |
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Definition
SIO2 GeO2 P2O5 As2O5
LiO2 K2O Na2O Cs2O MgO BaO |
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Term
| 3 Classifications of Polymers |
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Definition
1. The degree of polymerization
2. Thermoplastic vs thermoset
3. Molecular weight |
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Term
| 5 factors affecting (increase) crystallinity in polymers |
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Definition
1. Size of the side groups (decrease)
2. The extend of chain branching (decrease)
3. Tacticity (isotactic is best)
4. The complexity of the repeat unit (decrease)
5. The degree of secondary bonding (increase) |
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Term
| As temperature increases, modulus _____. |
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Definition
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Term
| Contracted state of a rubber band has ______ entropy that stretched state. |
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Definition
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Term
| A rubber brand is more crystallized when it is ____. |
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Definition
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Term
| Is glass transition temperature a thermodynamic variable? |
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Definition
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Term
| What kind of polymers are good glass formers? |
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Definition
| Those with large unit cells, large monomers |
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Term
| Atactic polymers with large, bulky side groups and extensive branching will form into ____, and not _____. |
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Definition
Good glass former;
Crystallize |
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Term
| Below Tg, large-scale molecular position is _______. |
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Definition
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Term
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Definition
| The arrangement of the rotatable bonds within a molecule. |
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Term
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Definition
The ratio of the weight average molecular weight to the number average molecular weight
Mw/Mn |
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Term
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Definition
| The number of repeat units in a polymer |
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Term
| Decreasing cooling rate, _____ the glass transition temp |
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Definition
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Term
| Below Tg, entropy of the glass is ____ than entropy of crystalline form. |
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Definition
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Term
| Increasing # of side branches ______ ability to crystallize. |
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Definition
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Term
| Increasing degree of crystallinity, ____ the modulus at a temp above Tg but below Tm. |
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Definition
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Term
| Increasing the extent of chain branching tends to _____ the ratio of Tg/Tm. |
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Definition
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Term
| Increasing the amount of network modifiers in an oxide glass tends to _________ the viscosity at a particular temp. |
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Definition
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Term
| Increasing the extent of chain branching results in an ______ of the density of a polymer. |
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Definition
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Term
| Why do elastomers contract with increased temperature? |
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Definition
| When rubber is stretched, segments uncoil and entropy decreases. Rubbers shrink when their temp is raised b/c of increased mobility and ability to coil. |
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Term
| Wax is what kind of polymer? |
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Definition
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Term
| 2 properties of thermosets |
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Definition
1. Do not melt
2. Can stretch to hundreds of their length |
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