thermoplastic_materials_and_processing by cuiliqing


									Moulding of Plastics
Thermoplastic Materials and
Classification of Plastics

Thermoplastic Materials
  Fluidic when subject to heat, harden when
  Usually rigid
Thermostatic Materials
  Fluidic or powder form before processing, cure
   permanently when subject to heat or mixed with
  Rigid or elastic
General Purpose Thermoplastic
 Polyethylene (PE)
 Polypropylene (PP)
  Microwavable food containers, electric kettles
 Polystyrene (PS)
  CD cases
 PolyVinylChloride (PVC)
  Sewage pipes, flexible hoists
Engineering Thermoplastic Materials
 Polyamides (PA, Nylon)
 Polymethylmethacrylate (PMMA, Acrylic)
 AcrylonitrileButadieneStyrene (ABS)
  Product casing
 Polycarbonate (PC)
  Outdoor screenings, Bullet-proof windows, Electric
 PolyethyleneTerephthalate (PET)
  Soft-drink bottles
Thermostatic Materials
 Melamine Formaldehyde, Urea Formaldehyde
  (MF, UF)
  Dishes, lamination
 Phenolics (PF)
  Ashtrays, Pot handles, plugs and switches
 Polyurethane
  Shoe heels
 Unsaturated Polyester (UP)
  Fibre-glass installations
 Epoxy (EP)
  Glue, filler
Injection Moulding
   The injection moulding machine
    consists of a heated barrel equipped
    with a reciprocating screw (usually
    driven by a hydraulic motor), which
    feeds the molten polymer into a
    temperature controlled split mould via a
    channel system of gates and runners.
    The screw melts (plasticises) the
    polymer, and also acts as a ram during
    the injection phase. The screw action
    also provides additional heating by
    virtue of the shearing action on the
    polymer. The pressure of injection is
    high, dependant on the material being
    processed; it can be up to one
    thousand atmospheres.
   Animation: Injection Moulding
Typical Injection Mould Job-shop
Typical Injection Moulding Plant
Rotational Moulding
 The Rotational Moulding process is
  essentially split into four operations:
      A pre-determined amount of polymer
       powder is placed in the mould. With the
       powder loaded, the mould is closed,
       locked and loaded into the oven.
      Once inside the oven, the mould is
       rotated around two axis. The ovens are
       heated by convection, conduction and,
       in some cases, radiation. As the mould
       becomes hotter the powder begins to
       melt and stick to the inner walls of the
      When the melt has been consolidated
       to the desired level, the mould is
       cooled either by air, water or a
       combination of both.
      When the polymer has cooled
       sufficiently to retain its shape and be
       easily handled, the mould is opened
       and the product removed.
 Animation: Rotational Moulding

                                          Adapted from:
Rotational Moulding

                      MT3 by Ron Arad
Blow Moulding
   The process is divided in to three.
      The injection blow moulding machine
        is based on an extruder barrel and
        screw assembly which melts the
        polymer. The molten polymer is fed
        into a manifold where it is injected
        through nozzles into a hollow, heated
        preform mould. The preform mould
        forms the external shape and is
        clamped around a mandrel (the core
        rod) which forms the internal shape of
        the preform.
      The preform mould opens and the
        core rod is rotated and clamped into
        the hollow, chilled blow mould. The
        core rod opens and allows
        compressed air into the preform,
        which inflates it to the finished article
      After a cooling period the blow mould
        opens and the core rod is rotated to
        the ejection position. The finished
        article is stripped off the core rod and
        leak-tested prior to packing.
   Animation: Extrusion Blow Moulding
   Animation: Injection Stretch Blow Moulding
   Animation: Injection Blow Moulding
Compression Moulding
   Compound or blend is placed in
    mould and heated under pressure.
    When reaction is complete,
    product is cooled and ejected.
   Animation: Compression Moulding
Plastic Resources
Plastic Resources

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