HIGH PERFORMANCE MATERIALS

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HIGH PERFORMANCE MATERIALS
Developments
1926- 1990 Synthetic rubber. Polyvinyl
chloride (PVC). New molding and extrusion
techniques for plastics. Polystyrene.
Polyethelene. continuous casting of steel,
Plexiglass. Nylon in 1938. Teflon discovered by
Roy Plunkett. Fiberglass. Foam glass insulating
material. Plastic contact lens. Vinyl floor
covering. Aluminum-based metallic yard. Ceramic
magnets. Basic oxygen process to refine steel
making. Karl Zeigler invents new process for
producing polyethelene. Dacron, plasticized PVC,
and silicones manufactured by Dow Corning.
Polypropylene (petroleum-based). Superpolymers
(heat resistant). 1964 - Acrylic paint . Carbon
fiber (used to reinforce materials in high
temperature environment). Beryllium (hard metal)
developed for heat shields in spacecraft, animal
surgery, aircraft parts, etc. Sialon (ceramic
material for high-speed cutting tools in metal
machining). Soft bifocal contact lens in 1983.
Synthetic skin.
New composites and lightweight steel
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• SMART MATERIALS- which adjust to the requirements
• "smart materials" also called intelligent
  materials or active materials describes a group
  of material systems with unique properties.
• The technological field of smart materials is
  not transparent or clearly structured. It has
  evolved over the past decades with increasing
  pace during the 1990s to become what it is today.
• Smart materials, Intelligent Materials, Active
  Materials, Adaptive Materials and to some extent
  actuators and sensors are almost always used
  interchangeably.
• Active materials - two groups.
• 1. The classical active materials as
  viewed by the academic community and is
  characterized by the type of response these
  materials generate.
• 2. Consists of materials that respond to
  stimuli with a change in a key material property,
  eg.electrical conductivity or viscosity
• Mention of medicines, packed items which will
  indicate the life with change in time,
  environment, decay etc dress materials which
  will adjust with the human conditions etc. etc.

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• Self diagnostic materials
• Optic fibres composite Smart
  composites Smart tagged composites
• Temperature changing materials
• Thermoelectric materials
• Thickness changing fluids
• Magneto-Rehological fluids (MRFs)
• References
• Intelligent MaterialsSmart materials workshop

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Smart Materials
Colour changing materials Light emitting Materials Moving materials Photochromic materialsThermochromic materials Electroluminescent materialsFluorescent materialsPhosphorescent materials Conducting polymersDielectric elastomersPiezoelectric materialsPolymer gelsShape memory alloys (SMA)
A smart material with variable viscosity may turn
from a fluid which flows easily to a solid. A
smart fluid developed in labs at the Michigan
Institute of Technology
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Smart Materials
Also termed as Responsive Materials

• "Smart" materials respond to environmental
  stimuli with particular changes in some
  variables. Also called responsive materials.
  Depending on changes in some external
  conditions, "smart" materials change either their
  properties (mechanical, electrical, appearance),
  their structure or composition, or their
  functions. Mostly, "smart" materials are
  embedded in systems whose inherent properties can
  be favorably changed to meet performance needs.

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• Self diagnostic materials
• Optic fibres composite Smart
  composites Smart tagged composites
• Temperature changing materials
• Thermoelectric materials
• Thickness changing fluids
• Magneto-Rehological fluids (MRFs)
• References
• Intelligent MaterialsSmart materials workshop

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Shape Memory Alloys (SMA)

• Shape memory alloys (SMA's) are metals, which
  exhibit two very unique properties,
  pseudo-elasticity, and the shape memory effect.
  Arne Olander first observed these unusual
  properties in 1938 (Oksuta and Wayman 1938), but
  not until the 1960's were any serious research
  advances made in the field of shape memory
  alloys. The most effective and widely used alloys
  include NiTi (Nickel - Titanium), CuZnAl, and
  CuAlNi

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Shape Memory Alloys (SMA)

• Shape memory alloys (SMA's) are metals, which
  exhibit two very unique properties,
  pseudo-elasticity, and the shape memory effect.
• The most effective and widely used alloys include
  NiTi (Nickel - Titanium), CuZnAl, and CuAlNi

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Applications of Shape Memory Alloys

• Aeronautical Applications
• Surgical Tools
• Muscle Wires

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SHAPE MEMORY EFFECT

• Implemented in
• Coffee pots
• The space shuttle
• Thermostats
• Vascular Stets
• Hydraulic Fittings (for Airplanes)

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SHAPE MEMORY EFFECT

• Implemented in
• Coffee pots
• The space shuttle
• Thermostats
• Vascular Stets
• Hydraulic Fittings (for Airplanes)

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Microscopic and Macroscopic Views of the Two
Phases of Shape Memory Alloys
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Microscopic Diagram of the Shape Memory Effect
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How Shape Memory Alloys Work
The Martensite and Austenite phases
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Applications of Shape Memory Alloys

• Aeronautical Applications
• Surgical Tools
• Muscle Wires

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The Dependency of Phase Change Temperature on
Loading
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Pseudo-elasticity
Applications in which pseudo-elasticity is used
are Eyeglass Frames Under garments Medical
Tools Cellular Phone Antennae Orthodontic
Arches
Load Diagram of the pseudo-elastic effect
Occurring
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Advantages and Disadvantages of SMAs

• Bio-compatibility
• Diverse Fields of Application
• Good Mechanical Properties (strong, corrosion
  resistant)

Relatively expensive to manufacture and machine.
Most SMA's have poor fatigue properties this
means that while under the same loading
conditions (i.e. twisting, bending, compressing)
a steel component may survive for more than one
hundred times more cycles than an SMA element
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Ferromagnetic Shape Memory Alloys (FSMA)

• Ferromagnetic Shape Memory Alloys (FSMA) Recently
  discovered class of actuator material,
  Magnetically driven actuation (field intensity
  varies, about 3KG and larger) and
• large strains (around 6).
• FSMA are still in the development phase
• Alloys in the Ni-Mn-Ga ternary.
• FSMAs are ferromagnetic alloys which also support
  the shape memory effect.

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OPTICAL FIBRE

• Made of extremely pure silica.
• Thinner than a human hair and stronger than a
  steel fibre of similar thickness. It can carry
  thousands of times more information than a copper
  wire!
• Optical fibre cables have the advantage of being
  lighter and taking less space than copper wire
  cables for the same information capacity.

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Fabrication of Optical Fibres

• The best cakes are made of the best ingredients.
• To make a good optical fibre, we need to start
  with good quality materials, that is highly
  purified materials.
• The presence of impurities alter the optical
  properties of the fibre.
• There are several ways to manufacture optical
  fibres
• Directly drawing the fibre from what is called a
  preform.
• The fibre is then drawn from the preform

• i) Direct Techniques
• Two methods can be used to draw a fibre directly
  
• Double Crucible method
• Rod in Tube method

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1. Double Crucible
The molten core glass is placed in the inner
crucible. The molten cladding glass is placed in
the outer crucible. The two glasses come
together at the base of the outer cucible and a
fibre is drawn. Long fibres can be produced
(providing you don't let the content of the
crucibles run dry!). Step-index fibres and
graded-index fibres can be drawn with this
method.
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2. Rod in Tube
A rod of core glass is placed inside a tube of
cladding glass. The end of this assembly is
heated both are softened and a fibre is drawn.
Rod and tube are usually 1 m long. The core rod
has typically a 30 mm diameter. The core glass
and the cladding glass must have similar
softening temperatures. This method is
relatively easy just need to purchase the rod
and the tube. However, must be very careful not
to introduce impurities between the core and the
cladding.
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ii) Deposition Techniques

• Most optical fibres are made from preforms. The
  preforms are made by deposition of silica and
  various dopants from mixing certain chemicals
  the fibre is then drawn from the preform.
• Many techniques are used to make preforms. Among
  them
• Modified Chemical Vapour Deposition or MCVD
• Plasma-Enhanced Modified Chemical Vapour
  Deposition or PMCVD
• Outside Vapour Deposition or OVD
• Axial Vapour Deposition or AVD

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The Chemicals

• Oxygen (O2) and silicon tetrachloride (SiCl4)
  react to make silica (SiO2).
• Pure silica is doped with other chemicals such as
  boron oxide (B2O3), germanium dioxide (GeO2) and
  phosphorus pentoxide (P2O5) are used to change
  the refractive index of the glass.

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Modified Chemical Vapour Deposition (MCVD)
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• The chemicals are mixed inside a glass tube that
  is rotating on a lathe.
• They react and extremely fine particles of
  germano or phosphoro silicate glass are deposited
  on the inside of the tube.
• A travelling burner moving along the tube
• causes a reaction to take place and then
  fuses the deposited material.
• The preform is deposited layer by layer starting
  first with the cladding layers and followed by
  the core layers.
• Varying the mixture of chemicals changes the
  refractive index of the glass.
• When the deposition is complete, the tube is
  collapsed at 2000 C into a preform of the purest
  silica with a core of different composition.
• The preform is then put into a furnace for
  drawing.

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Plasma-Enhanced Modified Chemical Vapour
Deposition (PMCVD)
Plasma-Enhanced Modified Chemical Vapour
Deposition is similar in principle to MCVD. The
difference lies in the use of a plasma instead of
a torch. The plasma is a region of electrically
heated ionised gases. It provides sufficient heat
to increase the chemical reaction rates inside
the tube and the deposition rate. This technique
can be used to manufacture very long fibres (50
km).It is used for both step index and graded
index fibres.
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Outside Vapour Deposition (OVD)
The chemical vapours are oxidised in a flame in a
process called hydrolysis. The deposition is
done on the outside of a silica rod as the torch
moves laterally.When the deposition is complete,
the rod is removed and the resulting tube is
thermally collapsed
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Axial Vapour Deposition (AVD)
The deposition occurs on the end of a rotating
silica boule as chemical vapors react to form
silica. Core preforms and very long fibres can
be made with this technique. Step-index fibres
and graded-index fibres can be manufactured this
w
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From Preform to Fibre

• All these deposition techniques produce preforms.
  These are typically 1 m long and have a 2 cm
  diameter but these dimensions vary with the
  manufacturer.
• The preform is one step away from the thin
  optical fibre. This step involves a process
  called drawing.

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Fibre Drawing and Spooling

• During this last step of the fabrication process,
  many things will happen to the fibre
• the fibre is drawn from the preform.
• it is quality checked
• it is coated for protection
• it is stored on a spool (just like a
  photographic film).

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• The tip of the preform is heated to about 2000C
  in a furnace. As the glass softens, a thin
  strand of softened glass falls by gravity and
  cools down.
• As the fibre is drawn its diameter is constantly
  monitored
• A plastic coating is then applied to the fibre,
  before it touches any components. The coating
  protects the fibre from dust and moisture.
• The fibre is then wrapped around a spool.

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Fabrication of an Optical Fibre
Heating the preform
Drawing the fibre
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Piezoelectric Materials
1. When a piezoelectric material is deformed, it
gives off a small but measurable electrical
discharge
2. When an electrical current is passed through a
piezoelectric material it experiences a
significant increase in size (up to a 4 change
in volume)
Most widely used as sensors in different
environments
To measure fluid compositions, fluid density,
fluid viscosity, or the force of an impact
Eg Airbag sensor in modern cars-
senses the force of an impact on the car and
sends and electric charge deploying the airbag.
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Electro-Rheostatic (ER) and Magneto-Rheostatic
(MR) materials
These materials are fluids, which can experience
a dramatic change in their viscosity
Can change from a thick fluid (similar to motor
oil) to nearly a solid substance within the span
of a millisecond when exposed to a magnetic or
electric field the effect can be completely
reversed just as quickly when the field is
removed.
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• THERMOPLASTICS
• THERMOSETTING PLASTICS
• ELASTOMERS
• printouts shall be supplied

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• ABOUT
• METALLIC COATINGS
• DIFFUSION COATINGS
• ANODISING
• POWDER COATING
• THERMOPLASTICS
• THERMOSETTING PLASTICS
• ELASTOMERS printouts shall be supplied

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• Self diagnostic materials
• Optic fibres composite Smart
  composites Smart tagged composites
• Temperature changing materials
• Thermoelectric materials
• Thickness changing fluids
• Magneto-Rehological fluids (MRFs)
• References
• Intelligent MaterialsSmart materials workshop

41
Ferromagnetic Shape Memory Alloys (FSMA)

• Ferromagnetic Shape Memory Alloys (FSMA) Recently
  discovered class of actuator material,
  Magnetically driven actuation (field intensity
  varies, about 3KG and larger) and
• large strains (around 6).
• FSMA are still in the development phase
• Alloys in the Ni-Mn-Ga ternary.
• FSMAs are ferromagnetic alloys which also support
  the shape memory effect.

42
Advantages and Disadvantages of SMAs

• Bio-compatibility
• Diverse Fields of Application
• Good Mechanical Properties (strong, corrosion
  resistant)

Relatively expensive to manufacture and machine.
Most SMA's have poor fatigue properties this
means that while under the same loading
conditions (i.e. twisting, bending, compressing)
a steel component may survive for more than one
hundred times more cycles than an SMA element
43

• THERMOPLASTICS
• THERMOSETTING PLASTICS
• ELASTOMERS
• printouts shall be supplied

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CAST IRON

• GRAY C.I.
• DUCTILE C.I
• WHITE C.I.
• MALLEABLE IRON
• COMPACTED GRAPHITE IRON
• Also by stress levels as
• ferritic, Pearlitic, Quenched and tempered,
  Austempered

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Unit Operations in Polymer Processing

• Thermoplastic and thermoset melt processes may be
  broken down into

• Preshaping
• Shaping
• Shape Stabilization

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Unit Operations in Polymer Processing

• Preshaping steps
• Solids handling and conveying most processes
  usually involve feed in particulate form
• Plastication The creation of a polymer melt from
  a solid feed.
• Mixing often required to achieve uniform melt
  temperature or uniform composition in compounds
• Pumping The plasticated melt must be
  pressurized and pumped to a shaping device
• Shaping
• The polymer melt is forced through the shaping
  devices to create the desired shape.
• The flow behavior (rheology) of polymer melts
  influences the design of the various shaping
  devices, the processing conditions and the rate
  at which the product can be shaped.
• Shape stabilization
• Involves the solidification of the polymer melt
  in the desired shape, through heat transfer

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The Single Screw Plasticating Extruder

• Regions 1, 2, 3 Handling of particulate solids
• Region 3 Melting, pumping and mixing
• Region 4 Pumping and mixing
• Regions 34 Devolatilization (if needed)

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Product Shaping / Secondary Operations
EXTRUSION
Final Product (pipe, profile)

• Secondary operation
• Fiber spinning (fibers)
• Cast film (overhead transparencies,
• Blown film (grocery bags)

Shaping through die

• Preform for other molding processes
• Blow molding (bottles),
• Thermoforming (appliance liners)
• Compression molding (seals)

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Annular (Tubular) Dies

• In a tubular die the polymer melt exits through
  an annulus. These dies are used to extrude
  plastic pipes. The melt flows through the annular
  gap and solidifies at the exit in a cold water
  bath.

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Profile dies

• Profiles are all extruded articles having
  cross-sectional shape that differs from that of a
  circle, an annulus, or a very wide and thin
  rectangle (such as flat film or sheet)
• To produce profiles for windows, doors etc. we
  need appropriate shaped profile dies. The
  cross-section of a profile die may be very
  complicated

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Secondary Shaping

• Secondary shaping operations occur immediately
  after the extrusion profile emerges from the die.
  In general they consist of mechanical stretching
  or forming of a preformed cylinder, sheet, or
  membrane. Examples of common secondary shaping
  processes include
• Fiber spinning
• Film Production (cast and blown film)

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Fiber Spinning

• Fiber spinning is used to manufacture synthetic
  fibers. A filament is continuously extruded
  through an orifice and stretched to diameters of
  100 mm and smaller. The molten polymer is first
  extruded through a filter or screen pack, to
  eliminate small contaminants. It is then extruded
  through a spinneret, a die composed of multiple
  orifices (it can have 1-10,000 holes). The fibers
  are then drawn to their final diameter,
  solidified (in a water bath or by forced
  convection) and wound-up.

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Fiber Spinning

• Melt spinning technology can be applied to
  polyamide (Nylon), polyesters, polyurethanes and
  polyolefins such as PP and HDPE.
• The drawing and cooling processes determine the
  morphology and mechanical properties of the final
  fiber. For example ultra high molecular weight
  HDPE fibers with high degrees of orientation in
  the axial direction have extremely high stiffness
  !!
• Of major concern during fiber spinning are the
  instabilities that arise during drawing, such as
  brittle fracture and draw resonance. Draw
  resonance manifests itself as periodic
  fluctuations that result in diameter oscillation.

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Cast Film Extrusion

• In a cast film extrusion process, a thin film is
  extruded through a slit onto a chilled, highly
  polished turning roll, where it is quenched from
  one side. The speed of the roller controls the
  draw ratio and final film thickness. The film is
  then sent to a second roller for cooling on the
  other side. Finally it passes through a system of
  rollers and is wound onto a roll.
• Thicker polymer sheets can be manufactured
  similarly. A sheet is distinguished from a film
  by its thickness by definition a sheet has a
  thickness exceeding 250 mm. Otherwise, it is
  called a film.

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Sheeting Dies

• One of the most widely used extrusion dies is
  the coat-hanger or sheeting die. It is used to
  extrude plastic sheets. It is formed by the
  following elements
• Manifold evenly distributes the melt to the
  approach or land region
• Approach or land carries the melt from the
  manifold to the die lips
• Die lips perform the final shaping of the melt.
• The sheet is subsequently pulled (and cooled
  simultaneously) by a system of rollers

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Blown Film Extrusion

• Film blowing is the most important method for
  producing Polyethylene films (about 90 of all PE
  film produced)
• In film blowing a tubular cross-section is
  extruded through an annular die (usually a spiral
  die) and is drawn and inflated until the frost
  line is reached. The extruded tubular profile
  passes through one or two air rings to cool the
  material.
• Most common materials LDPE, HDPE, LLDPE

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Coextrusion

• In coextrusion two or more extruders feed a
  single die, in which the polymer streams are
  layered together to form a composite extrudate.

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Molding Processes

• Molding techniques for polymers involve the
  formation of three-dimensional components within
  hollow molds (or cavities)
• Injection Molding
• Thermoforming
• Compression Molding
• Blow Molding
• Rotational Molding

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Injection Molding

• Injection molding is the most important process
  used to manufacture plastic products. It is
  ideally suited to manufacture mass produced parts
  of complex shapes requiring precise dimensions.
• It is used for numerous products, ranging from
  boat hulls and lawn chairs, to bottle cups. Car
  parts, TV and computer housings are injection
  molded.
• The components of the injection molding machine
  are the plasticating unit, clamping unit and the
  mold.

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Injection Molding Cycle

• Injection molding involves two basic steps
• Melt generation by a rotating screw
• Forward movement of the screw to fill the mold
  with melt and to maintain the injected melt under
  high pressure
• Injection molding is a cyclic process
• Injection The polymer is injected into the mold
  cavity.
• Hold on time Once the cavity is filled, a
  holding pressure is maintained to compensate for
  material shrinkage.
• Cooling The molding cools and solidifies.
• Screw-back At the same time, the screw retracts
  and turns, feeding the next shot in towards the
  front
• Mold opening Once the part is sufficiently cool,
  the mold opens and the part is ejected
• The mold closes and clamps in preparation for
  another cycle.

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Injection Molding Cycle

• The total cycle time is tcycletclosingtcooling
  tejection.

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Thermoforming

• Thermoforming is an important secondary shaping
  operation for plastic film and sheet. It consists
  of warming an extruded plastic sheet and forming
  it into a cavity or over a tool using vacuum, air
  pressure, and mechanical means. The plastic sheet
  is heated slightly above the glass transition
  temperature for amorphous polymers, or slightly
  below the melting point, for semi-crystalline
  polymers. It is then shaped into the cavity over
  the tool by vacuum and frequently by plug-assist.

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Thermoforming

• Thermoforming is used to manufacture refrigerator
  liners, shower stalls, bathtubs and various
  automotive parts.
• Amorphous materials are preferred, because they
  have a wide rubbery temperature range above the
  glass transition temperature. At these
  temperatures, the polymer is easily shaped, but
  still has enough melt strength to hold the
  heated sheet without sagging. Temperatures about
  20-100C above Tg are used.
• Most common materials are Polystyrene (PS),
  Acrylonitrile-Butadiene-Styrene (ABS), PVC, PMMA
  and Polycarbonate (PC)

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Compression Molding

• Compression molding is the most common technique
  for producing moldings from thermosetting
  plastics and elastomers.
• Products range in size from small plastic
  electrical moldings and rubber seals weighing a
  few grams, up to vehicle body panels and tires.
• A matched pair of metal dies is used to shape a
  polymer under the action of heat and pressure.

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Blow Molding

• Blow molding produces hollow articles that do
  not require a homogeneous thickness distribution.
  HDPE, LDPE, PE, PET and PVC are the most common
  materials used for blow molding. There are three
  important blow molding techniques
• Extrusion blow molding
• Injection blow molding
• Stretch-blow processes
• They involve the following stages
• A tubular preform is produced via extrusion or
  injection molding
• The temperature controlled perform is transferred
  into a cooled split-mould
• The preform is sealed and inflated to take up the
  internal contours of the mould
• The molding is allowed to cool and solidify to
  shape, whilst still under internal pressure
• The pressure is vented, the mold opened and the
  molding ejected.

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Extrusion Blow molding

• In extrusion blow molding, a parison (or tubular
  profile) is extruded and inflated into a cavity
  with a specified geometry. The blown article is
  held inside the cavity until it is sufficiently
  cool.

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Injection Blow Molding

• Injection blow molding begins by injection
  molding the parison onto a core and into a mold
  with finished bottle threads. The formed parison
  has a thickness distribution that leads to
  reduced thickness variations throughout the
  container. Before blowing the parison into the
  cavity, it can be mechanically stretched to
  orient molecules axially (Stretch blow molding).
  The subsequent blowing operation introduces
  tangential orientation. A container with biaxial
  orientation exhibits higher optical clarity,
  better mechanical properties and lower
  permeability.