don't despair of standard dull textbooks. just close the book once in a while and think what...
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Don't despair of standard dull textbooks. Just close the book once in a while and think what they just said in your own terms as a revelation of the spirit and wonder of nature. The books give you facts, but your imagination can supply life.
– Feynman
Don't despair of standard dull textbooks. Just close the book once in a while and think what they just said in your own terms as a revelation of the spirit and wonder of nature. The books give you facts, but your imagination can supply life.
– Feynman
Tensile strengthTensile strength
Glass transition temperature (Tg)
Glass transition temperature (Tg)
Glass transition temperature (Tg)
Glass transition temperature (Tg)
Molecular wt.Molecular wt.
Glass transition temperature (Tg)
Glass transition temperature (Tg)
Chemical structure
Chemical structure
Glass transition temperature (Tg)
Glass transition temperature (Tg)
Chain stiffnessChain stiffness
Glass transition temperature (Tg)
Glass transition temperature (Tg)
Chain stiffnessChain stiffness
Glass transition temperature (Tg)
Glass transition temperature (Tg)
Bulky side groups
Bulky side groups
Viscous flow Viscous flow
Occurs only by shearOccurs only by shear
z
xyDescribe deformation under shear by angle
Describe deformation under shear by angle
tantan zzxyxy
xyxy ̇ ˙ xyxy
Most polymer melts are shear-thinning (pseudoplastic) - i.e., become thinner at high shear rates
Most polymer melts are shear-thinning (pseudoplastic) - i.e., become thinner at high shear rates
Zero Shear Rate Viscosity5
4
3
2
1
00 1 2 3 4-1-2-3
Log a
(Pa)
Log sec-
1).
CompressionMoldingCalenderingExtrusion
InjectionMolding
SpinDrawing
100
SHEAR RATES ENCOUNTERED IN PROCESSING
101 102 103 104 105
Strain Rate (sec-1)
Viscous flow Viscous flow
Viscosity increases with MW
Plot is for zero shear rate values
Viscosity increases with MW
Plot is for zero shear rate values
Viscous flow Viscous flow
54321
Poly(di-methylsiloxane)Poly(iso-butylene)Poly(ethylene)Poly(butadiene)
Poly(tetra-methyl p-silphenyl siloxane)Poly(methyl methacrylate)Poly(ethylene glycol)Poly(vinyl acetate)Poly(styrene)
Log M + constant
Log m + constant
Creep Creep
Relaxation
Relaxation
Creep of cellulose acetate
Creep of cellulose acetate
Relaxation in PMMA Relaxation in PMMA
10
9
8
7
0.001 0.01 0.1 1 10 100 1000
Stress relaxationof PMMA
Time (hours)
400C
Log E
(t),
(dynes/
cm2)
600C
800C920C
1000C
1100C
1120C
1150C1200C
1250C
1350C
Creep & recovery Creep & recovery
Some specific polymers Some specific polymers Polyvinyl chloride (PVC) {-C-C-}n Polyvinyl chloride (PVC) {-C-C-}n
Cl HCl H
Cl HCl H –– ––
––––
Very rigid and strong, Tg = 60-80 Csiding, pipe, conduit, usw.
Very rigid and strong, Tg = 60-80 Csiding, pipe, conduit, usw.
Presence of Cl gives rise to solubility in various organic solvents - allows "solvent welding"
Presence of Cl gives rise to solubility in various organic solvents - allows "solvent welding"
Some specific polymers Some specific polymers Polyvinyl chloride (PVC) {-C-C-}n Polyvinyl chloride (PVC) {-C-C-}n
Cl HCl H
Cl HCl H –– ––
––––
Presence of Cl gives rise to solubility in various organic solvents
Rigid PVC difficult to form by some techniques (e.g., calendaring)……so add solvent as "plasticizer"
Presence of Cl gives rise to solubility in various organic solvents
Rigid PVC difficult to form by some techniques (e.g., calendaring)……so add solvent as "plasticizer"
PVC sheet then roll-formed onto fabric backing and - voilá - "vinyl"!PVC sheet then roll-formed onto fabric backing and - voilá - "vinyl"!
Some specific polymers Some specific polymers Rigid PVC difficult to form by some techniques (e.g., calendaring)……so add solvent as "plasticizer"
Rigid PVC difficult to form by some techniques (e.g., calendaring)……so add solvent as "plasticizer"
PVC sheet then roll-formed onto fabric backing and - voilá - "vinyl"!PVC sheet then roll-formed onto fabric backing and - voilá - "vinyl"!
Problem: solvent slowly evaporates, exp. when (auto) vinyl seats & fascia heated by sun
Soln: Armorall! Periodically put solvent back into polymer
Problem: solvent slowly evaporates, exp. when (auto) vinyl seats & fascia heated by sun
Soln: Armorall! Periodically put solvent back into polymer
Assignment:
Review today's classnotesa. tensile strengthb. Tg
c. viscous flowd. yielding, relaxation, crazinge. creep, relaxation, recoveryf. PVCg. plasticizers
Assignment:
Review today's classnotesa. tensile strengthb. Tg
c. viscous flowd. yielding, relaxation, crazinge. creep, relaxation, recoveryf. PVCg. plasticizers