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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
MMiscibleblend
Tg1 Tg2
M
T
Immiscibleblend
2
Phase Behaviour of Blends
Change of Gibbs free energy Gm should be negative and second derivative with respect to volume fraction must be larger than zero for complete miscibility
Gm = Hm - TSm
miscibility.
- Complete miscibility seldom in high molecular systems because of entropy effects (Sm≈ 0) favourable interactions are 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
g
weight of PS
p. 299
3
Commercial Miscible Polymer Blends
p. 303
Glass Transition and Crystallisation in PVDF/PMMA
Poly(vinylidene fluoride) can crystallise depending on composition and temperature. PMMA serves like a diluent and lowers the melting temperature.
p. 303
and lowers the melting temperature.
4
Properties of Blends
p. 304
Toughened Plastics and Phase Separated Blends
Example: high-impact Polystyrene (HIPS)
Promotion of extensive shear yielding or craze formation
p. 306
5
Interpenetrating Networks
Example: IPN of poly(ethyl acrylate) and polystyrene
p. 307
Properties of Fibers
p. 290
6
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
f m f f
Reinforcement in perpendicular direction much lower and dependent on interfacial adhesion between fiber and matrix.
7
Interfacial Adhesion and Coupling Agents
p. 312
Nanocomposites
p. 316
8
Nanocomposites properties
p. 315
Nanocomposite Structure
Exfoliated nanoclay in a polymer matrix
9
Polysulfone Nanocomposites
p. 317
Composite Processing: Filament Winding
Products: pipes, tanks, flagpoles
p. 318
10
Composite Processing: Pultrusion
Continuous moulding process for profiles utilizing glass or other fibrous reinforcement in a polyester or other resin 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
11
Extrusion Process
- Extrusion is a continuous process to produce:
tubes, profiles, cables, plates, foils, fibers, bottles
tratt
silpaket
skruv
värmeelement termoelement gängamatar-ficka
p. 429
matarzonkompressionszonskjuvzon
munstycke
mantel
Extrusion Process
12
Molding Processes
Molding: discontinuous processMold ng d scont nuous process- injection molding
- reaction injection molding
- compression molding
- transfer molding
- thermoforming termoformning, vacuumformning
formpressning
reaktiv formsprutning
formsprutning
sprutpressning
p. 429
- blow molding
- rotational molding
formblåsning
rotationsgjutning
Injection Molding
m st k värmeelementmunstycke värmeelement
p. 432
13
Injection Molding
Injection Molding
p. 433
inlopp fördelningskanal
formrumskanal
formrum
förgreningskanal
kallplugg
14
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 with molding material in place
B. Closed mold showing formed part and flash formed from excess resin
p. 430
15
Transfer Molding
A. Transfer potis loaded while mold is in closed position
B Plunger pushes molding material B. Plunger pushes molding material into mold form
C. Mold opens and ejector pins push out molded part
p. 431
Thermoforming
Also called vacuum forming
p. 435
A. Flat sheet is heated
B. Softened sheet is forced to fit the mold contour by evacuating the space between the sheet and the mold
16
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 of a calendering process, usually several cylinders involved
p. 437
17
Coating
A. Roll coating
B. Blade coating
p. 437
C. Curtain coating
Polymer Rheology
Newton’s law of viscosity:Newton s law of viscosity:
Shear stress is proportional to shear rate
The viscosity is
p. 440
The viscosity is
18
Viscosity of Polymer Melts
Typical behaviour of a polymeric melt
Zero-shear viscosityis directly related to the weightis directly related to the weight-avarage molecular mass
p. 442
Rheometry
Measurement techniques:
Capillary rheometer
Couette rheometer
p. 461
Cone-and Plate rheometer
19
Capillary Rheometer
Range : shear rates from 1 – 105 s-1
By measuring pressure drop over the capillary and volumetric flow rate the shear stress and shear strain rate can be calculated and thus the viscosity.
p. 462
Couette Rheometer
The shear stress is determined by measuring the torque, the shear rate is determined by the angular velocity and dimensions of the system.
p. 465
20
Cone-and Plate Rheometer
Why using a cone ? Cone angle is very small, 1-3 degrees
Shear rate is independent on R !
Shear rate
p. 467
Shear rate
Shear stress is proportional to torque
Viscosity measurements
Polymer melts at 200 oC
HDPE
PP
PS PMMA
LDPE
p. 468
Cone-and-plate