Patrics Hand-out 3
Transcript of Patrics Hand-out 3
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Polymer Blends
- Homogeneous blends
- miscible on molecular scale,
mobility is averaged, consequently glass transition
temperatures are averaged
- Heterogeneous blends
p. 295
- not miscible but phase separated,
mobility of original phases present, consequently glass
transition temperatures of original phases are present
Miscibility and modulus
M
Purecomponents
Tg1 Tg2
Tg12
M
Miscibleblend
Tg1 Tg2
M
T
Immiscibleblend
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Phase Behaviour of Blends
Change of Gibbs free energy Gm should be negative and second derivativewith respect to volume fraction must be larger than zero for complete
Gm = Hm - TSm
.
- Complete miscibility seldom in highmolecular systems because of entropyeffects (Sm 0) favourable interactionsare necessary (0 > Hm)
p. 297
- Heterogeneous blends common
Phase Behaviour of Blends
Example: Polystyrene Polycarbonate blends shows LCST behaviour
Decreasing molecular
Lower Critical
Solution Temperature
weight of PS
p. 299
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Commercial Miscible Polymer Blends
p. 303
Glass Transition and Crystallisation in PVDF/PMMA
Poly(vinylidene fluoride) can crystallisedepending on composition andtemperature. PMMA serves like a diluent
and lowers the meltin tem erature.
p. 303
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Properties of Blends
p. 304
Toughened Plastics and Phase Separated Blends
Example: high-impact Polystyrene (HIPS)
Promotion ofextensive shearyielding or crazeformation
p. 306
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Interpenetrating Networks
Example: IPN of poly(ethyl acrylate) and polystyrene
p. 307
Properties of Fibers
p. 290
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Properties of Matrices
p. 309
Mechanical Properties
Modulus : in the fiber direction in uniaxial reinforced composite
EL = (1-f) Em + f Ef
Strength :
L = (1-f) m + f f
p. 310
Reinforcement in perpendicular direction much lower and dependent oninterfacial adhesion between fiber and matrix.
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Interfacial Adhesion and Coupling Agents
p. 312
Nanocomposites
p. 316
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Nanocomposites properties
p. 315
Nanocomposite Structure
Exfoliated nanoclay in a polymer matrix
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Polysulfone Nanocomposites
p. 317
Composite Processing: Filament Winding
Products: pipes,tanks, flagpoles
p. 318
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Composite Processing: Pultrusion
Continuous moulding process for profiles utilizing glassor other fibrous reinforcement in a polyester or otherresin matrix
p. 319
Polymer Processing and Rheology
Basic steps for processing thermoplastics and elastomers:
heating of material
Rheology is science of flow of materials
p. 427
transport of hot melt
shape realization
fixation of shape
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Extrusion Process
- Extrusion is a continuous process to produce:tubes, profiles, cables, plates, foils, fibers, bottles
tratt
silpaket
skruv
vrmeelement termoelement gngamatar-ficka
p. 429
matarzonkompressionszonskjuvzon
munstycke
mantel
Extrusion Process
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Molding Processes
Moldin : discontinuous rocess
- injection molding
- reaction injection molding
- compression molding
- transfer molding
- thermoforming termoformning, vacuumformning
formpressning
reaktiv formsprutning
formsprutning
sprutpressning
p. 429
- blow molding
- rotational molding
formblsning
rotationsgjutning
Injection Molding
un yc e
p. 432
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Injection Molding
Injection Molding
p. 433
inlopp frdelningskanal
formrumskanal
formrum
frgreningskanal
kallplugg
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Reaction Injection Molding
RIM process with two separate tanks for polymerisation reagents
Polyamides
Epoxies
Polyurethanes
p. 434
Compression Molding Process
A. View of open mold withmolding material in place
B. Closed mold showing formed partand flash formed from excess resin
p. 430
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Transfer Molding
A. Transfer potis loaded whilemold is in closed position
.into mold form
C. Mold opens and ejector pins pushout molded part
p. 431
Thermoforming
Also called vacuumforming
p. 435
A. Flat sheet is heated
B. Softened sheet is forcedto fit the mold contour byevacuating the spacebetween the sheet and themold
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Blow Molding
Extrusion blow-molding process in the production of plastic bottles
p. 436
PET preforms forinjection blow molding
Calendering
Production of plastic sheet of PVC, PVC blends and copolymers of PVC
Simplified representation ofa calendering process,usually several cylindersinvolved
p. 437
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Coating
A. Roll coating
B. Blade coating
p. 437
C. Curtain coating
Polymer Rheology
Shear stress is proportional to shear rate
The viscosit is
p. 440
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Viscosity of Polymer Melts
Typical behaviour of a polymeric melt
Zero-shear viscosity
-avarage molecular mass
p. 442
Rheometry
Measurement techniques:
Capillary rheometer
Couette rheometer
p. 461
Cone-and Plate rheometer
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Capillary Rheometer
Range : shear rates from 1 105 s-1
By measuring pressure drop over thecapillary and volumetric flow rate theshear stress and shear strain rate can becalculated and thus the viscosity.
p. 462
Couette Rheometer
The shear stress is determinedby measuring the torque, theshear rate is determined by theangular velocity and dimensions ofthe system.
p. 465
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Cone-and Plate Rheometer
Why using a cone ? Cone angle is very small, 1-3 degrees
Shear rate is independent on R !
p. 467
ear ra e
Shear stress is proportional to torque
Viscosity measurements
Polymer melts at 200 oC
HDPE
PP
PSPMMA
LDPE
p. 468
Cone-and-plate