Extrusion

Our Blown Film Extrusion capability is up to 3 layers, includes LDPE, LLDPE, HDPE, EVA, Ionomer & PP.

One of the most common methods of film manufacture is Blown Film (also referred to as Tubular Film) Extrusion. The process involves extrusion of a plastic through a circular die, followed by 'bubble-like' expansion.

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

The Process

Plastic melt is extruded through an annular slit die, usually vertically, to form a thin walled tube. Air is introduced via a hole in the centre of the die to blow up the tube like a balloon. Mounted on top of the die, an air ring blows air onto the hot film to cool it. The tube of film then continues upwards, continually cooling, until it passes through nip rolls where the tube is flattened to create what is known as a 'lay flat' tube of film. This lay-flat or collapsed tube is then taken back down the extrusion 'tower' via more rollers.

The lay-flat film is then either kept as such or the edges of the lay-flat are slit off to produce two flat film sheets and wound up onto reels. If kept as lay-flat, the tube of film is made into bags by sealing across the width of film and cutting or perforating to make each bag.

Materials

Polyethylenes (HDPE, LDPE, LLDPE and PVC) are the most common resins in use, but a wide variety of other materials can be used as blends with these resins or as single layers in a multi-layer film structure.