Blow molding.

Blow molding

Polystyrene was the first synthetic polymer used for blow molding during second world war.
Blow molding is a process in which heated hollow thermoplastic tube (parison) is inflated into a closed mold confirming the shape of the cavity of the mold.
Blow molding is a manufacturing process by which hollow plastic parts are formed.
There are three principle techniques of blow molding based on the method by which parison is formed and these are

a) Extrusion blow molding (EBM)

b) Injection blow molding (IBM)

c) Stretch blow molding (SBM)

Extrusion blow molding

Extrusion blow molding is the simplest type of blow molding.
A hot plastic material, called parison is dropped from the extruder and captured in water cooled mold.
Once the mold are closed,air is injected through the top of the container as if one were blowing up a balloon.

Injection blow molding

Here Parison is injected molded .
Injection mold is opened and parison is transferred to a blow mold.
Soft polymer is inflated and it takes the shape of the mold.
Blow mold is opened and blown product is removed.

Stretch blow molding

Here parison is injected molded.
Injection mold is opened and parison is transferred to a blow mold.
Soft polymer is stretched and inflated so that it takes the shape of the mold.
Blow mold is opened and blown product is removed.

Blow Molding.

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