Polymer Forming Method

Extrusion

Calendering

Injection Molding

Compression Molding

Transfer Molding

Thermoforming

Filament Winding

Blown Film Extrusion

Rotational Molding

Blow Molding

Pultrusion

Type of product:


rubber sheets skin coating of fabrics including shower curtains, tablecloths and laminating film

Working Principle


Machine equipped with two,three or more heavy internally heated or cooled rollers,usually placed above each other. Rollers rotate in opposite directions and operate at even or uneven speeds
used essentially for producing rubber sheets of various lengths and thickness

Common Process:
In this process, the extrudate is extruded directly into the nip area between two rolls.The rollers have small gap between them, and plastics is forced through this gaps by the counter rotating of the rollers.The extrusion process comprises the forcing of molten material
through a shaped die by means of pressure

Type of products:
Tubes, sheets and film to complicated profiles

Type of Polymer:
thermosetting resins

Products:granules, putty like masses, or preforms

Step of Processing:


  1. The mould is held between the heated platens of the hydraulic press
  2. A prepared quantity of molding compound is placed in the mould
    3.The platen closes with sufficient pressure to minimize
    flash at mould parts line
    4.The compounds softens and flows to shape, chemical cure then occurs as the internal mould temperature becomes high enough
    5.The press is opened and the molding removed

Products:
Small parts of polymer

General Step:
-Reservoir of the molding compound is located in the mold
-Closure is transferred via runner to the cavities thus develop the compression molding

Working Principle:
Inject molten polymer into a closed mold where.It is solidifies to give the product.The molding is recovered by opening the mold to release it.

General step:

When the mould is closed a short of melt is ready in the injection unit. Injection occurs when the valve opens and the screw acting as a plunger forces the melt through the nozzle into the mold

The hold on stage when pressure is maintained during the early stages of cooling to counteract contraction

The valves closes and screw rotation starts .Pressure develops against the closed off nozzle and the screw moves backwards to accumulate a fresh shot of melt in front

Meanwhile the molding in the mould has continue to cool when the moulding is ready,the press and the mould open and the molding is removed

The mould closes again and the cycle repeats

Working Principle:
utilize air to shap e softened
polymer tubes


Product:
Thin film and bag

General step:


1.The extruded materials flow through a tubular die.
2.The melt flow around a mandrel and exits the die as a tube.
3.A cooling ring is placed at the exit of the die to give.4.the tube some dimensional stability
4.Air is introduced through the back of the die and flow upwards inside the middleof the tube of materials.
5.The tube or bubble, continues to expand, cool and crystallize until the radial (tensile) strength of the plastics equals the pressure of the air inside.
6.The bubble is then forced into a flat sheet by the collapsing guides, and moved into the nips rolls
7.Then it travels down over some rollers and it was sealed

Product:
Hollow items such as milk and soda bottles

General Step
1.Melting the resin done in extruder.
2.Form the molten resin into a cylinder or tube (this tube is called parison)
3.The parison is placed inside a mold, and inflated so that the plastic is pushed outward against the cavity wall.
4.The part is allowed to cool in the mold and is then ejected.
5.The part is trimmed

Type of Polymer:
thermoplastic polymers

Type of product:
more complex external geometries, larger parts, and lower production quantities product

1.A predetermined amount of polymer powder is loaded into the cavity of a split mold
2.The mold is then heated and simultaneously rotated on two perpendicular axes, so that the powder impinges on all internal surfaces of the mold, gradually forming a fused layer of uniform thickness.
3.While still rotating, the mold is cooled so that the plastic skin solidifies.
4.The mold is opened, and the part is
unloaded Rotational speeds used in the process are relatively slow It is gravity,not centrifugal force, that causes uniform coating of the mold surfaces

Working Principle:
Uses gravity inside a rotating mold to achieve a hollow form

Product:
large parts such as swimming pool or motor vehicle parts

Working Principle:
reshaping of plastics under the influence of heat and pressure or vacuum

General Step:
1.Heat a thermoplastic sheet until it softens.
2.Force the hot and pliable material against the contours of a mold by using either mechanical, airor vacuum pressure.
3.Held against mold and allow to cool, and plastics retains its shape

Product:
pressure vessel, storage tanks, and
aerospace parts such as helicopter blades.

General Step:
1.The fibers are passed through the resin bath.
2.Then continuously wound onto the mandrel.
3.After number of layers, curing is carried out in an oven or room temperature.
4.Mandrel is removed

General Step:
1.Continuous rovings of the reinforcement are impregnated with the resins (passing through a bath of resin)
2.Then pulled through the heated die (compact & give shape to the composites).
3.Curing takes place in the heated die & Oven
4.Puller used to pull the whole system with certain speed.Pultrusion pulling action

Product:
components with continuous lengths and constants cross sectional shape (rod,tubes, beam, etc)