Film blowing

• Blown film extrusion is that the method used to make plastic films particularly for the packaging industry.

• The process involves extruding a tube of molten polymer through a die and inflating to many times its initial diameter to form a thin film bubble.

• The majority of polymer films are manufactured by film blowing. A single screw extruder is used to melt the polymer and pump it into a tubular die.

• Air is blown into the center of the extruded tube and causes it to expand in the radial direction.

• Extension of the melt in both the radial and down-stream direction stops at the freeze line because of crystallization of the melt.

• The nip rolls collect the film, still as protection the top of the bubble to keep up the air pressure inside. This process is employed extensively with polyethylene and polypropylene.

ADVANTAGES :

• Produce tubein a single operation.

• Regulation of film width and thichness by control of the amount of air in the bubble, the output of the extruder and also the speed of the haul-off.

• Eliminate end effects such as edge bead trim and non uniform temperature that can result from flat die film extrusion.

• Capability of biaxial orientation.

• Blown Film Extrusion will be used for the manufacture of co-extruded, multi-layer films for high barrier applications such as food packaging.

APPLICATIONS :

• Industry packaging - shrink film, stretch film, bag film or container liners

• Consumer packaging - packaging film for frozen products, shrink film for transport packaging, food wrap film, packaging bags, or form, fill and seal packaging film),

• Laminating film - laminating of aluminium or paper used for packaging for example milk or coffee.

• Barrier film - film made of raw materials such as polyamides and EVOH acting as an aroma or oxygen barrier used for packaging food - cold meats and cheese

• Films for the packaging of medical products,

• Agricultural film - greenhouse film, crop forcing film, silage film, silage stretch film).