2.  Polymer family
 Large size molecules-long chain molecules
formed by polymerization
 Low cost
 Low density
 Low electrical and thermal conductivity
 ……
 ……

3.  Thermoplastic
 Thermosetting

4. Bond between adjacent long chain molecules (secondary bond)
Covalent bond between mers (primary bond)
•The overall strength of plastic depend on the secondary bond
•Increased temperature (Tm and Tg) weaken secondary bond (thermal vibration of
long molecules) and the chain are easily move by external shaping.

5.  Also known as thermosoftening plastic
 Can be remelted, recycled and remoulded.
 More elastic and flexible
 Example: vinyl ,acrylic, polycarbonate,
Polyamide, polyethylene and polypropylene.
 Application : lense, bubble top, windshield,
zipper.

6.  Cannot be melted and re-shaped after it is
cured
 Cannot be recycled
 Better suited to high-temperature applications
 Generally stronger than thermoplastic
materials due to this 3-D network of bonds
 Example : Polyester, Bakelite, Vulcanized
rubber, epoxy, melamine, polyamides
 Application : Electrical insulators and plastic
ware, car parts, body parts of modern airplanes
and printed circuit boards

9.  Raw material (pellet, granules, powder) are placed into hopper
and fed into the barrel of screw extruder.
 Helical screw blend the pellet and convey them down the barrel
toward the die
 Barrel heater and the screw internal friction heat the pellet and
liquidizes them.
 Molten plastic was then forced through the die.
 Extruded part was then cooled by exposing it to blowing air or
pass through water-filled chanel

10.  Parts- Solid rod, sections, channel, sheet,
tubing, pipe, architectural parts.
 Defects- surfaces fractures (uneven die shapes),
bambooing and sharkskin effect ( friction at
die-polymer interface and elastic recovery and
non-uniform deformation of product outer
layer.

11.  Control parameters- extruder screw rotational
speed, barrel wall temperature, die design, rate
of cooling, drawing speed.
 The flowrate- control by the shape, pitch and
flight angle of helical screw
 Cooling rate and uniformity – control by
cooling medium such as air and water
 Design of die and extruder
 Pressure and heat rate
 Continuous supply of raw material

15.  Has high production rates (fast cycle time)
 Good dimensional control
 Complex shapes with good dimensional
accuracy
 Parts generally weigh 100g-600g (small parts)
or heavier ( automobile components)
 High tooling cost (die)

18.  Product - Cup, container, housing, knob, toy,
electrical and telecommunication devices
Examples of product

21. Design capabilities
 Proper control of temperature and pressure
 Mold design modifications
 Good control of flowrate in the die cavities
Defect
 Weld lines- molten plastic flows in from 2 opposite
runners and meet in the middle of cavities
 Void/Porosity-runner section too small, premature
solidification, preventing full filling of mold cavity
 Flash- die do not close completely
 Sink marks/ Pull in- thick molded section

24.  Extrusion blow moulding
 Injection blow moulding
 Multilayer blow moulding
 Modified/ combined extrusion and injection
moulding process.
 Product : hollow container, water bottle,
drinking cup, pharmaceutical and cosmetic
containers.

25.  A tube or pre form (parison) is first extruded.
 It is clamped into the mold with cavity much
larger than the parison diameter
 It is then blown upward to fill the mould
cavity
 The pieces was then cooled and ejected from
mold

26.  Short tubular pieces (parison) is injection molded in
cool dies.
 The dies then open and the parison is transferred by
an indexing mechanism.
 Hot air is injected from the blow pin into the parison,
expanding to the wall of mold cavity
 The pieces was then cooled and ejected from mold
after the blow pin is removed

28.  Parts produces are hollow tubing and
containers
 Sufficient blowing pressure
 Strong and rigid die ( typical material : steel,
aluminum, beryllium copper)
 Improper filled molds
 The blow pressure of hot blasting ranging from
350 to 700 kPa depending on the material types
 Blow ratio can be up to 7:1.
 Drum with volume up to 2000 liters can be
made through this process

29.  Process of forming thermoplastic sheet/film
over a mold through the application of heat
and pressure.
 Sheet is clamp and heated to sag point ( above
Tg) by radiant heating.
 It was then force using vacuum or pressurized
air against the mold surfaces.

31.  Typical parts- tray, house appliances, panel for
shower stall, etc
 Cannot made part with holes/opening due to
unable to maintain pressure during forming
 Material had to exhibit high and uniform
elongation.
 The molds is made from aluminum due to low
strength and low cost requirement
 The mold has small holes (<0.5mm) to help
vacuum forming

32.  Tearing of sheet during forming
 Non-uniform wall thickness
 Improper filled molds
 Poor part definition
 Lack of surfaces details

33.  Made through roll method or doctor blade
method.
 In roll method, the polymer coating material is
squeeze against the substrate (fabric, paper,
cardboard, metal foil), by mean of opposing rolls.
This cause the polymer to uniformly cover the base
material and the take-up reel will roll and gather
the coated material
 In doctor blade method, a sharp knife edge control
the amount of polymer melt that is coasted in the
substrate. Similarly, the coated material will be
collected through a take up reel.