Term
| describe the graph that represents the contribution to carbon black and its different regimes |
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Definition
log shear modulus v log shear strain
1.region du to interaggregate interaction (filler filler)
2.additional cross linkage due to filler rubber links
3. hydrodynamic effect due to carbon black
pure gum modulus |
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Term
| filler filler interactions |
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Definition
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Term
storage compliance v. frequency
what is the effect of temperature |
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Definition
compliance is ~1/E therefore the slopes are related to viscosity
J^ as T^
can use shift factors to find the curve at a fixed T (J v. log shift) |
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Term
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Definition
| a phantom chain with no excluded volume |
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Term
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Definition
C=R^2/na^2
a=ak, C=1 for Kuhn chain |
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Term
persistence length
contour length |
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Definition
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Term
| problem drawing chain folded crystals |
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Definition
there are amorphous and crystalline regions can be modelled in series
crystal stiffness>>>amorphous |
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Term
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Definition
high draw ratio therefore high stiffness
used for low MWT polymer
produces chain extended crystal
done with special heat treatments
poor strength because of low MWT |
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Term
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Definition
super saturated polyer solution, fibers get caught around stirrer then with accelerating flow, crystallizes straight
no need for low MWT
forms shish kebabs |
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Term
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Definition
the best method
1-dilute solution of polymer
2-extruded
3-solvent extracted, draw in oven
draw ratio nl/Sqrt(nl) |
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Term
| what can effect crystalline melting point |
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Definition
side groups
flexible spacer
random copolymer |
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Term
lyotropic routes
name a material processed like this |
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Definition
solvent addition to lower melting point
add solvent > process > remove solvent and fiber crystallizes again but teh solvents are nasty
Kevlar |
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Term
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Definition
modest flow gives very good alignment
no entanglements
high stiffness straight from spinning |
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Term
lytropic v. thermotropic
what is their Achilles Heel? |
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Definition
lyotropic: higher melting points therefore better for high temperature service
lytropic can handle stiffer molecules
thermotropic can mold in the bulk because no solvent needed to extra
thermotropic can avoid nasty solvents
unfortunately they're all useless in compression (usually kink bands or buckling due to low shear strength molecules sliding over each other) |
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Term
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Definition
a time temperature superposition method using shift factors from J v. frequency to find viscosity
can be justified using free volume as well |
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Term
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Definition
| based on some of the same principles as WLF with different constants |
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Term
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Definition
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Term
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Definition
| viscosity over young's modulus |
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Term
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Definition
| time it takes to move chain through contour |
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Term
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Definition
gibbs * L * l^2 = 2* surface energy * l^2
gibbs = undercooling * enthalpy / temperature |
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Term
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Definition
| derives conditions for necking in polymers |
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Term
diamter of microfibrils
size of crazy |
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Definition
100 angstroms
several microns |
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Term
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Definition
1-monomer of styrene (MS) in which rubber is dissolved (PB)
2-initiatior is added
3-at some point MS converts to PS, phase separation
there are regions of MS/PS gelPB is soluble in MS but not PS
you may get some grafting here
regions of rubber enclosing PS in a PS matrix |
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Term
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Definition
| volume fraction of free material |
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Term
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Definition
equal to young's modulus
N is the number of cross links |
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Term
| what is the multiple crazing theory |
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Definition
one that says in rubber toughened materials, multiple crazes will form upon stresses leading to something analogous to a 'plastic zone' about the crack
impact resistance |
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Term
| what are the criteria for crazing |
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Definition
hydrostatic stress
shear stress for fibril formation
critical elastic strain in polymer
therefore yield criteria also contains a hydrostatic component |
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Term
| how can fibrils scatter light? |
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Definition
| due to change in density in the material |
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