1. PROCESSING OF POLYMERS and POLYMER COMPOSITES
PE335, Lecture 7
PROCESSING OF POLYMERS and POLYMER COMPOSITES

2. PE335_Lecture7_ Processing© Caroline Schauer 2008
Background
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3. Thermoplastics and Thermosets
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4. Thermoplastics and Thermosets
- can be reversibly cooled and reheated repeatedly, i.e. recycled
- ex: polyethylene, polypropylene, polystyrene, etc.
Thermoset
– forms a network
– degrades (not melts) when heated
– mold the prepolymer then allow further reaction
– ex: unsaturated polyester, urethane, epoxy
Viscoelastic
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Viscoelasticity
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6. Thermal Characteristics of Linear Polymers: Thermoplastics
Tg = glass transition temperature – glass to rubber transition
Tm = crystalline melting point – typically 1.5Tg if the polymer can crystallize
T = service or “operation” temperature
Processing Temperature
≥ Tg +100˚C amorphous polymers form a melt
≥ Tg + 50˚C semicrystalline polymers form a melt
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7. Thermal Characteristics of Linear Polymers: Thermosets
Tg = glass transition temperature – glass to rubber transition
T = service or “operation” temperature
Cure Temperature
Determined by the (curing) chemical reaction
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Thermal Transitions
Amorphous vs. Crystalline
Modulus
Amorphous
Crystalline
(Stiffness)
Amorphous TG
Crystalline TG
Crystalline TM
Temperature
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9. Thermal Transition: Calorimetery
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10. Service Temperature Tests
Vicat Softening Point
ASTM D is the temperature at which a .040" steel rod will penetrate into a solid sample.
Heat Deflection
ASTM D-648
is the temperature at which a center loaded bar deflects 0.010" under a stress of 66 psi or 264 psi.
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Thermal Transitions
As the side chain becomes “longer”,Tg becomes lower.
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Melt Flow Index
. . is defined as the mass of polymer, in grams, flowing in ten minutes through a capillary of a specific diameter and length by a pressure applied via prescribed alternative gravimetric weights for alternative prescribed temperatures. (ASTM D1238 and ISO 1133).
. . is inversely proportional to viscosity of the melt at the conditions of the test, though it should be borne in mind that the viscosity for any such material depends on the applied force (shear stress).
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13. Processing Temperature
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Polymers Processing
Converting raw plastics to useful final products with desirable properties
Plastics  Polymers
(Plastics = Polymer + Additives)
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15. PE335_Lecture7_ Processing© Caroline Schauer 2008
Additives
Fillers: to improve mechanical properties and reduce cost.
Plasticizers: to improve flexibility, ductility, and toughness of polymers. Their presence also produces reductions in hardness and stiffness.
Stabilizers: to protect against atmospheric oxidation or UV radiation.
Colorants: to classify application of materials.
Flame retardants: may function by interfering with the combustion process through the gas phase, or by initiating a chemical reaction that causes a cooling of the combustion region.
etc
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16. Compounding/ Master Batch
Compounding is the process by which colour or additives are added to the basic thermoplastics material.
It involves melting the thermoplastics material then mixing it with the required pigments and/or additive material in an extruder.
The melt is then extruded and chopped into pellets as it cools, which can then be used directly by the plastics processor.
An associated process is masterbatch. This is where a high concentration of pigment and/or additives are dispersed in a carrier medium which can then be used directly by the processor in small quantities to pigment or modify the virgin polymer material.
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17. Compounding Pelletizer
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Processing Methods
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Processing Overview
The molten plastic is forced through “channels” in order to be shaped into products.
The “formed” plastic is solidified by cooling, e.g.
EXTRUSION (80% of plastics processed by extrusion)
Pipes
Sheet
Film
Profile
INJECTION MOLDING
BLOW MOLDING
Blow Stretch-blow
THERMOFORMING
COMPRESSION MOLDING (tires)
FIBER SPINNING
etc
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Processing Methods
Thermoplastic
Injection Molding
Extrusion
Blow Molding
Injection-blow Molding
Compression Molding
Calendaring
Rotational Molding
Thermo-forming (Vacuum Forming)
Cold Drawing
Casting
Fiber Spinning
Themosets
Reaction Injection Molding (RIM)
Compression Molding
Casting
Elastomer
Extrusion
Short Fiber Composites
Hand Layout
Injection Molding
Sheet Molding (Compression)
Bulk Molding (Compression)
Continuous Fiber Composites
Pultusion
Filament Winding
Lamination
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Injection Molding
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Injection Molding *
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Process Cycle
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24. Simulated Process Cycle
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Compression Molding
Compression molding is almost exclusively used for thermosets, elastomers and short-fiber composites.
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Extrusion
Ancillary Equipment
i.e. Sizing, Cooling,
Cutting, Printing,…
Produces continuous lengths having constant cross-sectional geometries.
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Blow Molding
Injection-blow Molding
Extrusion Blow Molding
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Blown Film Extrusion
The extruder is fitted with an annular die, pointing (usually) upwards. The tube produced is inflated with air and at the same time is drawn upwards in a continuous process.
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Fiber Spinning
The strength of fibers is improved by a post forming process called drawing.
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FLAT FILM CASTING
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THERMOFORMING
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ROTATIONAL MOLDING
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CALENDERING
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COATING
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37. Processing of Thermosets and Composites
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Compression Molding
Compression molding is almost exclusively used for thermosets, elastomers and short-fiber composites.
PE335_Lecture7_ Processing© Caroline Schauer 2008

39. Reaction Injection Molding (RIM)
Polyol and Isocyanate liquids are injected into a closed mold and reacted to form a polyurethane.
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Polyurethane
Polyurethane can be made in a variety of densities and hardnesses by varying the type of monomer(s) used and adding other and other additives.
Diol
Diisocyanate
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41. Spray Coating of Liquid Epoxy
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Epoxy Resins
The most widely used epoxide monomer is the diepoxide prepared by treating
one mole of bisphenol A with two moles of epichlorohydrin
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43. Epoxy Cross-linking (Hardening)
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44. Unsaturated Polyesters − crosslinking (curing)
Unsaturated portion
Polyesters must have unsaturated portions to crosslink
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45. Polyesters − crosslinking (curing)
Initiator I ● C C C C
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46. Fiber Reinforced Composite Processing
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47. Fiber-Reinforced Composites
Processing of
Fiber-Reinforced Composites
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All-composite Jet
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Hand Lay-Up Method
mold is treated
with mold release agent;
(2) thin gel coat (resin)
is applied;
(3) when gel coat has
partially set,
layers of resin and fiber
are applied,
the fiber is in the form of
mat or cloth;
each layer is rolled to impregnate the fiber with resin and remove air;
(4) part is cured;
(5) fully hardened part is removed from mold.
(6) Parts are stored for full cure.
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Spray-Up Method
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SUNSEEKER 120
Built at Sunseeker International UK. She was successfully launched in Poole in 2006 before being transferred to the owner. Her hull was crafted from composite. The motor yacht main superstructure is made for the most part using composite.
PE335_Lecture7_ Processing© Caroline Schauer 2008

53. Reinforced Reaction Injection Molding
Reinforced reaction injection molding (RRIM) - similar to RIM but includes reinforcing fibers, typically glass fibers, in the mixture.
Advantages: similar to RIM (e.g., no heat energy required, lower cost mold), with the added benefit of fiber‑reinforcement
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Pultrusion Process
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55. Sheet Molding Compound
Polyester
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56. Resin Transfer Molding (Polyester or Epoxy)
Preform is inserted into a matched die mold.
The heated mold is closed and the liquid resin is injected
The part is cured in mold.
The mold is opened and part is removed from mold.
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57. Fiber Preform Architcture
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Filament Winding
Polyester or
Epoxy
Glass or
Carbon
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59. FILAMENT WINDING: Overview
FILAMENT WINDING is a continuous process for fabricating a composite structure in which
continuous reinforcements (filament, wire, yarn, tape, or other),
either previously impregnated with a matrix material or
impregnated during winding,
are placed over a rotating form or mandrel
in a prescribed way to meet certain strength conditions.
When the required number of layers is applied, the wound form is cured and the mandrel can be removed or left as part of the structure.
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Pipes
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Tanks
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