Cast Film Line

Cast Film line: The Melt emerging out of the die lips strikes the chrome plated chill roll where it solidifies. Subsequently the film is pulled through nip rolls. Trimming blades trims-off the thicker edges. Then the film is wound on the winder.

Tubular-quench: It involves the downward extrusion of a tubular extrudate from an annular die.

Followed by Quenching on water–covered converging boards

1. Which causes rapid crystallization which enhances the optical property.

2. The tube is inflated with air to give a film of required lay-flat width and thickness. 

3. It is widely recommended for PP film.

Orientation of films: Orientation of film by stretching it under heat is widely applied to films such as PP,PS, PA and PET to improve clarity, impact strength, and (particularly of PP) barrier properties. 

1. Basic PS film in its non-oriented form is brittle and has only a limited use as a dielectric in capacitors. When biaxially oriented, the film is tough and can be thermoformed into crystal clear tubs, trays and larger items such as cake covers.

2. The largest application of orientation techniques, however, is in the manufacture of PP films and the various processes will be illustrated mainly with respect to this film. 

3. The main processes can be divided into linear and tubular. 

4. The principle of the linear type can be illustrated by considering the two-stage process.

Multi-layer film: The process is carried out by Co-extrusion.

It involves the extrusion of two or more layers of different or similar materials using two or more extruders and Input combining adapter. 

Multilayer Film Dies: Two types of dies:

1. Feed Block         2.Multimanifold

In Feed Block the melt streams are brought    together and flow out the die

In Multimanifold the melt spreads independently and meet at the die exit  

Two types of process 

   1. Oscillating Platform 2. Oscillating Haul-Off

Advantages of Multi-layer Film: 

1. Two to seven layers depending on the application.

2. It possesses good barrier properties against gas and moisture.

3. High tensile, impact and tear strength.

4. Good stiffness, optical, carrier and printing properties.

E.g. LDPE/HDPE/LDPE, LLDPE/LDPE..etc.